United States
Environmental Protection
Agency
Office of Science and Technology
Office of Water
Washington, DC 20460
EPA-822-B-01-007
August 1999
vwwv.epa.gov
&EPA
Mycobacteria:
Health Advisory
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I. INTRODUCTION
The Health Advisory Program, sponsored by the Office of Water (OW), provides
information on the health effects, analytical methodology and treatment technology that would
be useful in dealing with the contamination of drinking water. Most of the Health Advisories
(HAs) prepared by the Office of Water are for chemical substances. This Health Advisory
however, addresses contamination of drinking water by a microbial pathogen, examines
pathogen control, and addresses risk factors for exposure and infection.
Health Advisories serve as informal technical guidance to assist Federal, State and local
officials responsible for protecting public health when emergency spills or contamination
situations occur. They are not to be construed as legally enforceable Federal standards. The
HAs are subject to change as new information becomes available.
This Health Advisory is based on information presented in the Office of Water's Criteria
Document (CD) forMycobacteria. Individuals desiring further information should consult the
CD. This document will be available from the U.S. Environmental Protection Agency, OW
Resource Center, Room M6099; Mail Code: PC-4100, 401 M Street, S.W., Washington, D.C.
20460; the telephone number is (202) 260-7786. The document can also be obtained by calling
the Safe Drinking Water Hotline at 1-800-426-4791.
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II. GENERAL INFORMATION
History
• Mycobacteria were one of the first types of bacteria recognized to cause disease
(tuberculosis and leprosy).
• The name Mycobacterium, which means fungus-bacterium, was introduced in 1896. The
name does not imply that Mycobacterium are fungi; rather it describes the way that the
tubercle bacillus grows on the surface of liquid media as mold-like pellicles
(Gangadharam & Jenkins, 1998).
• In the 1940s and 1950s, it became apparent that there were many other species of
mycobacteria (in addition to those which cause tuberculosis and leprosy) which could
contribute to disease, based on their isolation from clinical patients.
Taxonomy
• Mycobacteria belong to the Order Actinomycetales, Family Mycobacteriaceae and
Genus Mycobacterium.
• One of the early techniques used to classify mycobacteria was the system of Adansonian
taxonomy (Grange, 1996b). This system was based on the use of cultural and
biochemical properties to group related strains. Although this system is rarely used
today, this approach facilitated the use of discriminative identification tests for use in
diagnostic mycobacteriology.
• Dr. Ernest Runyon performed the initial work and grouping classifications on the
taxonomy of Mycobacterium in the mid-1950s. In Runyon's classification,
mycobacteria, excluding those in the M. tuberculosis complex and noncultivable taxa
(e.g., M. leprae), were divided into four groups based on growth rates and pigmentational
properties.
• In 1980, 41 species of mycobacteria were included in the Approved Lists of Bacterial
Names (Grange, 1996b). Today, there are 71 recognized or proposed species of
mycobacteria (Shinnick and Good, 1994). Over 20 of these species are known to cause
disease in humans.
• Mycobacteria not identified as tuberculosis or leprosy complex, have been addressed by a
variety of nomenclature including; 'atypical mycobacteria', 'mycobacteria other than
tubercle' bacilli (MOTT), 'environmental mycobacteria' or 'non-tuberculous
mycobacteria' (NTM) (Wolinsky, 1979). This document uses the NTM nomenclature.
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Morphologic and Taxonomic Characteristics
• Aerobic, asporogenous rods, which tend to be acid-fast at some stage of their growth
cycle.
• Have been referred to as the 'ducks of the microbial world' due to their thick, waxy,
outer coating which enables them to thrive in aquatic environments.
• Have cell walls with very low permeability, contributing to their resistance to therapeutic
agents. The mycobacterial cell wall is highly complex and has a lipid content that
approximates 60% of the structure (Brennan and Nikaido, 1995). The cell wall
characteristics allow the mycobacterial species to survive in different environments (e.g.,
in biofilms in water habitats or particulate matter in soils and water) and resist
disinfection procedures.
Lifecycle
Most studies have revealed that mycobacteria exist as non-sporing acid-fast rods and
replicate by binary fission (Grange, 1996b). However, some investigators have
hypothesized that a more complex life cycle (possibly involving cell-wall-free forms or
microspores) exists. Several authors have produced evidence for unusual forms and life
cycles of mycobacteria.
Unusual life cycles may explain the phenomenon of mycobacterial dormancy and
persistence (Grange, 1996b). Wayne (1994) reviewed the mechanism of dormancy seen
inM tuberculosis. There is ample evidence that these organisms are capable of adapting
to prolonged periods of dormancy in tissues, and that this dormancy is responsible for the
latency of disease. Wayne (1994) indicates that there may be two or more stages
involved in the process leading from active replication to dormancy. One of these steps
involves a shift from rapid to slow replication, the second involves complete shutdown of
replication, but does not result in death of the cell.
Host Range
In addition to human, tuberculosis infection also occurs in a wide range of domesticated
and wild animals. M. bovis, which causes tuberculosis in animals, has one of the widest
host ranges of all pathogens. Hosts include the African buffalo, baboon, badger, bison,
opossum, cat, elk, Fallow deer, goat, horse, Leche antelope, maral, pig and wild boar,
Rock hyrax, and seal (Morris et al., 1994; Grange, 1996b).
Leprosy is a disease that is primarily transmitted from person to person. Humans were
thought to serve as the only reservoir of M leprae until 1974, when scientists discovered
nine-banded armadillos in Louisiana with leprosy in an advanced stage. It is now
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thought that the nine-banded armadillo is the primary animal reservoir forM leprae and
may serve as a vector for transmission of leprosy to humans either by direct or indirect
contact (Jenkins, 1991). M. leprae has also been found to infect chimpanzees and sooty
mangabey monkeys in Africa (Grange, 1996a).
Several of the NTM species have been isolated from animals, birds and fish. These
include: M. avium complex, M. marinum., M. ulcerans, M. paratuberculosis, M. simiae,
M.fortuitum andM smegmatis. Most of the NTM agents that cause human and animal
diseases have demonstrated very little person-to-person contagiousness (Wayne &
Sramek, 1992).
III. OCCURRENCE
No evidence was found that water serves as a source of infection for tuberculosis or leprosy.
Because the bacterial species that cause these diseases have not been recovered from water
sources, the remaining sections of this health advisory will focus only on NTM species.
NTM are ubiquitous in nature and consist of a large number of species which vary in
pathogenicity. These infections are more likely transmitted from environmental sources by
ingestion, inhalation and inoculation of Mycobacterium bacilli. These environmental sources
may include aerosols, water, soil, dust, food products and contaminated medical equipment
(Gangadharam & Jenkins, 1998).
Because routine environmental monitoring for NTM is not a common practice, the occurrence of
these bacteria is often only indicated by outbreaks or sporadic cases of mycobacterial infection.
Therefore, this section considers the worldwide occurrence or incidence of mycobacterial
infections as well as the occurrence of NTM in water, soil, and air. Environmental factors
influencing NTM survival also are discussed.
Occurrence in Water
Environmental mycobacterial species have been repeatedly isolated from natural and municipal
waters. They occur in surface water, notably ponds, streams, and estuaries. Piped water supplies
are readily colonized by mycobacteria which can thereby lead to more frequent exposure of
humans. Mycobacterial characteristics such as surface hydrophobicity and charge, as well as
certain physiochemical factors like salinity, temperature, humidity and wind currents can
influence the distribution of mycobacteria in water systems (Falkinham, 1996).
Waste Water
• In 1980, a survey conducted in Korea found that both slow- and rapid-growing
environmental mycobacteria (EM) were isolated from 67% of the sewage samples
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collected. Slow growers constituted 49% of sewage isolates. The isolates from sewage
samples included: M gordonae, M. scrofulaceum, M.flavescens, M. phlei, M. terrae (,
M.fortuitum, M. chelonei andM smegmatis (Won Jin et al., 1984).
In Czechoslovakia, environmental mycobacteria have been isolated from waste water in
the North-Movarian Region (Kaustova, 1981). Between 1985 and 1991, the reference
laboratory in the Czech Republic reported that 8.2% (102) of 1244 waste water samples
tested were positive for mycobacterial species (Slosarek et al., 1994).
Surface Waters
Mycobacterium-avium-intracellulare-scrofulaceum (MAIS) organisms were recovered
from so-called acid-brown swamps and lake water samples collected in Georgia,
Virginia, and West Virginia. The high rate of recovery of MAIS organisms in these
regions was attributed to the combination of higher temperatures, low oxygenated waters,
low pH soils, higher zinc, and fulvic and humic acids (Kirschner et al., 1992).
In a study in Finland, MAIS complex organisms were detected in 40% of surface water
samples collected from streams. Concentrations of these organisms were found to range
from 50 to 1,400 CFU/L (mean 370 CFU/L). Additionally, M. malmoense was detected
in two stream waters at concentrations of 320 and 750 CFU/L. In all surface water
samples (not limited to streams), mycobacteria were detected at a mean of 1,500 CFU/L
(Katila et al., 1995).
In Valencia, Spain, 15 strains ofM gordonae and 10 strains of MAC were identified in a
variety of surface water samples (Sabater and Zaragoza, 1993).
Swimming Pools/Hot Tubs
Mycobacterial species including, M. marinum, M. chelonei, M. scrofulaceum andM
gordonae were isolated from swimming pool samples collected in Araraquara, Sao
Paulo, Brazil (Falcao et al., 1993). The number of isolates ranged from 1-3 per site.
A survey was made of water quality of swimming pools in semi-public areas (hotels,
recreational parks and camping grounds) and whirlpools (in sauna institutes and fitness
clubs) that were not yet subject to water quality standards under Dutch legislation
(Havelaar et al., 1985). Mycobacteria were detected in all water samples. Water
temperatures in pools and whirlpools ranged from 18-25'C and 35-40'C, respectively.
The mycobacterial numbers in whirlpools on the average were about ten times higher
than those in swimming pools, with M. gordonae being the predominant species
recovered. M. marinum was not detected in any of the samples and M. kansasii was
recovered three times from whirlpools. Only M avium andM fortuitum-M. chelonei
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complex were found in both types of pool samples, but the highest densities were seen in
whirlpools.
Species in theM avium complex have been recovered from hot tubs (Embil et al., 1997;
Kahana et al., 1997). Aerosols generated by the hot tub action are linked to case reports
of disease in humans.
Ground Water
An investigation was conducted to determine whether ground water could be a natural
source of NTM, particularly the MAIS group, in order to explain the geographic bias for
infected people in the southeastern U.S. The samples that were tested originated in three
geographic regions characterized by different human reactivity to PPD-B. These regions
included the Georgia coastal plain, the Virginia coastal plain, and the Valley and Ridge
Region of Montgomery Co. Virginia. Relatively low numbers of mycobacterial isolates
and very low numbers of MAIS isolates were recovered in the selected regions and were
not found to correlate with the distribution of PPD-B reactivity or the incidence of MAIS
infection. The data strongly suggest that clean ground waters are not sources of human
infection by MAIS or other mycobacteria (Martin et al., 1987).
Environmental mycobacteria were isolated from 27 out of 63 well water samples
examined during a nationwide tuberculosis prevalence survey in Korea in 1980. M.
fortuitum, M. terrae, andM gordonae were the predominant species. (Won Jin et al.,
1984).
Water reservoirs constructed of concrete or steel tanks, located below and above ground
in a small town in Texas were reported to contain M. kansasii and M. gordonae
(Steadham, 1980). The investigators postulated that the NTM species could have entered
the reservoirs and passed into the water distribution system from deep water wells or
through seepage of water and soil which accumulate in both concrete and steel reservoirs.
Drinking Water
von Reyn et al. (1993) investigated mycobacterial recovery from water supply samples
from wells, hot and cold municipal water supplies, showers and stand pipes. M. avium
complex organisms were recovered from 1/6 and 2/8 of samples collected in New
Hampshire and Boston, respectively.
Tap water samples from both hot and cold outlets in a French hospital contained NTM.
The predominant species included M. kansasii, M. gordonae, and M. fortuitum (Dailloux,
1991).
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Scarlata et al. (1985) reported detection of NTM in 37% of tap water samples collected in
Palermo, Italy.
Kubalek and Mysak (1995) investigated the prevalence of environmental mycobacteria
collected from a drinking water supply system in the North Moravian region of the Czech
Republic during 1984 to 1989. Samples were obtained from 16 localities by tap swabs,
tap scrapings or collecting running water. The most commonly identified species of
NTM wereM gordonae (20.4%), M.flavescem (13.8%), rapidly growing mycobacteria
(5%) and occasionally M. fortuitum, M. terrae andM. scrofulaceum.
von Reyn et al. (1994) investigated mycobacteria in water collected from hospital taps.
They found concentrations ofM avium ranging from none to 5.2 CFU/mL.
Falsely reported outbreaks of nosocomial infections by NTM species have been traced to
the use of tap water, used on medical devices and equipment during certain surgical and
lab procedures, which is contaminated withM xenopi (Sniadack et al., 1993), M
gordonae (Stine et al., 1987) and M. fortuitum (Jacobsen et al., 1996).
Occurrence in Other Media
Soil
• Mycobacterial species that have been shown to be normal inhabitants of soil include M.
kansasii (Jones, 1965), MAIS complex (Brooks et al., 1984a; Kirschner et al., 1992) M.
malmoense (Saito et al., 1994) and rapidly growing species M. smegmatis and M.
fortuitum (Jones, 1965; Wolinsky and Rynearson, 1968).
• Katila et al. (1995) investigated the occurrence of mycobacteria in soils from unpolluted
areas of Finland. Mycobacteria were detected in all soil samples with a mean of 3.6 x 105
CFU/g dry weight.
• The presence of M avium of the same serotype in tuberculous lesions in pigs and in sputa
of swine workers led Reznikov and Robinson (1970) to postulate that dusts from M.
avium contaminated soil generated in the swine facility were the source of transmission
for both pigs and man.
• Potting soil samples collected from the homes of HIV patients were found to contain
serotypes of MAC that were similar to the isolates from the HIV patients of the study
group. Although a relationship of exposure to potting soil and acquisition of MAC could
not be demonstrated, the data suggest that potting soil may be a potential reservoir of
organisms causing MAC infection in San Francisco (Yajko et al., 1995).
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Air
Shelton et al. (1999) recently investigated aerosolized NTM as a possible cause of
hypersensitivity pneumonitis in three machine workers. Water-based coolants are
typically recycled and may frequently become colonized by microorganisms. In one case
study, mycobacteria from theM chelonae complex were identified in concentrations
ranging from non-detectable to 6.6 x 106 CFU/mL in bulk coolant samples. Air samples
collected in the area around the colonized machines revealed concentrations ranging from
56 to 2,256 CFU/m3. In the second case study, Shelton et al. (1999) found mycobacterial
counts of 102 to 107 CFU/mL in machine fluid samples. Air samples collected near the
colonized machines yielded concentrations exceeding the limits of the sampler (greater
than 9,424 CFU/m3). The mycobacteria detected in this case were rapid-growers which
were identical to a newly proposed mycobacterial species M. immunogen. In the third
case study, concentrations of mycobacteria in metal removal fluids were found to range
from non-detectable to greater than 106 CFU/mL. Again, the mycobacteria were identical
toM immunogen.
Some evidence suggests that some forms of NTM infection may be associated with heavy
occupational exposures to dust (Oldham et al., 1975). An apparent association was found
between infection withM kansasii and exposure to dusts in the metal grinding trades.
The association between dust exposure and mycobacterial infection may have two
complementary mechanisms: (1) dust may act as a pulmonary irritant or toxin, resulting
in increased susceptibility to mycobacterial infection; and (2) dust serves as a vehicle for
mycobacterial exposure.
Surfaces
In a model system, the accumulation of NTM in biofilms resulted in mycobacterial
densities of more than 106 colony-forming units per square centimeter (CFU/cm2) within
10 weeks (Schulze-Robbecke et al., 1991) providing evidence that biofilms may serve as
reservoirs for these organisms.
In a study conducted in Bonn, Germany, 90% of biofilm samples from piped water
systems contained mycobacteria at average densities ranging between 103 andlO4
CFU/cm2 with a maximum density of 5.6 x 106 CFU/cm2. Samples collected from
organic substances such as plastic and rubber typically had higher concentrations of
mycobacteria than did inorganic substances such as copper or glass. The opportunistic
pathogens identified in this study included M. chelonae, M. fortuitum, M. gordonae and
M. kansasii (Schulze-Robbecke et al., 1992).
Food
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Studies of risk factors for MAC infection among AIDS patients in San Francisco did not
support the hypothesis that food was a likely source of organisms that cause MAC
infection in AIDS patients (Yajko et al., 1995).
Worldwide Distribution of Mycobacterial Infection
• NTM are generally found in the environment as free-living organisms, but many are also
known opportunistic human pathogens. NTM diseases are not notifiable or required to
be reported; therefore, information on the occurrence of disease is likely to be
underestimated. However, human infections due to NTM appear to be increasing at a
significant rate across the United States.
• With the emergence of the AIDS pandemic, it is estimated that 25% - 50% of HIV-
patients in the United States and Europe are infected with NTM, the primary species of
which isM avium (Horsburg, 1991). Presently, the use of highly active anti-retroviral
therapy (HAART) has led to a decrease in this estimated risk and rate of infection of
NTM in AIDS patients.
• In non-AIDS patients, the occurrence of NTM diseases is also on the rise. This is
suggested by the frequency with which MAC has been isolated from clinical samples in
regional reference laboratories in the state of Massachusetts from 1972 to 1983 (du
Moulin et al., 1985). Reports from Milwaukee, Philadelphia and Portland indicate that
the prevalence of pulmonary disease due to MAC in the general population has begun to
approach and exceed that of tuberculosis (Iseman, 1998). The Centers for Disease
Control and Prevention (CDC) estimates that rates for non-AIDS NTM diseases in the
United States are 1.8 per 100,000 per year, of which 1.3 are due to the M. avium complex
(MAC) (O'Brien, 1989).
• The incidence of mycobacterial disease may be influenced by exposure to dusty
conditions. Among 154 patients in Great Britain with pulmonary M kansasii disease, 33
had pneumoconiosis and another 31 were coal miners, steel workers or worked in dusty
conditions (Jenkins, 1981). In a study of 12 patients withM kansasii pulmonary
infections in southern California, seven had pre-existing pulmonary disease and three
reported previous exposures to dust (Gorse et al., 1983 ).
• M. marinum has been well established as a human pathogen, based on clusters of cases
observed between 1930 and 1970 (Dobos et al., 1999). Infections in humans have been
reported in coastal areas of the Middle East (Evan-Paz et al., 1976), in the Far East
(Iredell et al., 1992) and in several countries in Europe (Collins et al., 1984) as well as in
the United States (Zeligman, 1972).
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In some developing countries, M. ulcerous disease is a problem, with hundreds of
individuals afflicted with disabling lesions and only limited therapy available (Marston et
al., 1995). Although endemic occurrence of the disease has been reported mostly in
tropical and subtropical areas of the world (Hayman, 1991), a large outbreak ofM
ulcercms infection on a temperate southern Australian island was reported by Veitch et al.
(1997).
From the time thatM haemophilum was first described as a human pathogen in 1978 up
until 1989, only 18 cases of infection had been reported: seven patients were from the
United States, and 11 were from Australia, Canada and France (MMWR, 1991). From
1989 to 1991, CDC identified M haemophilum in eight patients from Connecticut,
Florida, Georgia, Pennsylvania, Texas and Virginia.
There is a lack of information on the occurrence of NTM in animals; however, reports
raise the possibility that certain animals may represent a natural reservoir for these
mycobacteria (Gangadharam and Jenkins, 1998). Strains of disease-causing M avium
have been recovered from ducks, geese and swans in an English wildlife reserve. NTM
species such asM marinum andM scrofulaceum which are normally associated with
water as a habitat, have been found in fish.
Epidemiology and Disease Outbreaks
• NTM diseases are not reportable; therefore, information regarding the occurrence of
disease outbreaks is likely to be underestimated. Many infections caused by these
organisms are episodic and sporadic (e.g.,M kamasii, M. marinum, andM ulcerans
infections).
• Waterborne NTM have been associated with a large number of nosocomial and pseudo-
outbreaks worldwide. Nosocomial disease outbreaks usually involve sternal wound
infections, plastic surgery wound infections or postinjection abscesses. Falsely reported
outbreaks are usually related to contaminated hospital equipment and water supplies.
• Outbreaks of mycobacterial disease have been reported after exposures in public
swimming areas. In 1954, an outbreak of 80 cases of M marinum were reported due to
exposure in a contaminated swimming pool. An additional outbreak involving at least
290 cases occurred in children who swam in a warm mineral water pool in Glenwood
Springs, Colorado (Wolinsky, 1979).
Factors Affecting Environmental Survival
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• The survival of environmental mycobacteria in habitats that are potential reservoirs or
sources of infection may be influenced by certain physiochemical factors which include
temperature, pH, organic matter salinity and humidity.
• du Moulin et al. (1988) reported that temperatures between 52° and 57°C encouraged the
proliferation of M. avium in hospital water supplies and recommended raising the
temperature of hot-water systems to reduce exposure of patients to organisms of the
MAIS complex.
• Other investigators have found thatM kansasii colonized cold water systems and mixer
taps, whereas M. xenopi predominated in hot water systems and mixer taps (McSwiggan
and Collins, 1974; Wright et al., 1985).
• An investigation was conducted to measure the heat susceptibility of opportunistic
mycobacteria frequently isolated from domestic water supply systems versus the heat
susceptibility of L. pneumophila (Schulze-Robbecke and Buchholtz, 1992). It was
concluded thatM kansasii is more susceptible to heat than L. pneumophila, whereas M
fortuitum,M. intracellulare andM marinum are equally susceptible to temperatures
between 55° and 60° C. However, M. avium, M. chelonae, M. phlei, M. scrofulaceum
and M. xenopi were found to be more heat resistant than L. pneumophila.
• A study designed to evaluate the efficiency of ozone as a disinfectant in secondary
wastewater effluent under different environmental conditions, showed that the survival of
M.fortuitum increased with an increase in pH from 5.7 to 10.1 (Farooq et al., 1977)
• Humic and fulvic acids are known to affect the survival of environmental mycobacteria
either directly (Brooks et al., 1984b) or indirectly in combination with other
physiochemical variables such as temperature, oxygen content, pH and inorganic
substances (Kirschner et al., 1992). The combination of higher temperatures, low
oxygenated waters low soil pH, and waters high in zinc, humic and fulvic acids from
swamp waters most likely favor the growth and survival of MAIS organisms (Flaig et al.,
1975; Schnitzer, 1982).
IV. HEALTH EFFECTS IN HUMANS
Clinical Symptoms
• The clinical symptoms seen following infection with NTM depend greatly on the
mycobacterial species and site of the infection. NTM diseases in immunocompetent
hosts are relatively rare even though exposure to organisms is common based on their
ubiquitous nature in the environment.
• Common clinical syndromes include:
• • Pulmonary infection
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• • Lymph infection (lymphadenitis)
• • Ear infection
• • Skin & soft tissue infection
• • Catheter-associated infection
• • Disseminated Infection
Pulmonary Infection
In adults, pulmonary infection is the most commonly recognized form of NTM
infections. These infections often present clinically as chronic cough, sputum production
and fatigue. Older adults are generally the population in which chronic lung disease due
to NTM is observed (ATS, 1997).
Two forms of pulmonary disease are recognized: apical cavitary disease that is best
recognized with MAC and M. kansasii infection in middle aged male smokers, and
modular bronchiectasis that is best recognized in MAC and M. abscessus infection and is
most commonly seen in elderly non-smoking women (ATS, 1997).
Members of the M avium complex orM kansasii are the NTM species most commonly
associated with pulmonary infection in the U.S. However, other species known to
occasionally cause pulmonary disease include; M. xenopi, M. fortuitum, M. abscessus, M.
szulgai, M. malmoense, M. simiae, M. celatum, M. asiaticum and M. shimodii (ATS,
1997).
Lymph Infection (Lymphadenitis)
Lymphadenitis occurs predominantly in young children, between 1 and 5 years old, and
typically affects the cervical, submaxillary, submandibular and preauricular lymph nodes
(ATS, 1997; Jenkins, 1991). In the absence of HIV infection, this disease rarely affects
adults. Historically, the classical cause of cervical lymphadenitis wasM scrofulaceum
whereas today, the species most commonly involved is theM avium complex. M.
malmoense., M. scrofulaceum, M. kansasii and M. fortuitum have been implicated to a
lesser extent.
Ear Infection
M. abscessus has recently been implicated in causing sporadic ear (otologic) infections
after placement of tympanotomy tubes. This infection is characterized by nonspecific
otorrhea and abundant granulation tissue which has lasted over 3 months and is
unresponsive to standard antibiotic therapy (Correa and Starke, 1996).
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Skin & Soft Tissue Infection
Multiple species of mycobacteria have been identified as causative agents of skin and
soft tissue infections. These include; M. marinum, M. ulcerans, M. haemophilum, M.
fortuitum, M. abscessus, M. chelonae and species within the M. avium complex. These
infections can be either community acquired or nosocomial infections.
M. marinum is the species of Mycobacterium most commonly associated with skin
infections. Most often, infection from this species occurs following an exposure of cut or
abraded skin to organisms present in aquariums, pools, natural water supplies and salt
water (Feldman, 1974; Wolinsky, 1979; ATS, 1997). The incubation period can range
from two weeks to several months (Dobos et al., 1999). The typical outcome of infection
is the development of a localized skin lesion on the arms or legs. Occasionally, synovial
involvement or development of subcutaneous nodules along lymph channels will occur.
M. ulcerans causes distinctive, often severe, skin lesions. It is thought that the primary
mode of infection with this species is through cuts from vegetation (e.g., grass) which
allow the organisms to enter the skin. Lesions develop as small, palpable, painless,
subcutaneous swellings approximately 4 to 10 weeks after infection. The growing
nodule, which is firm and attached to the skin, remains superficial and extends laterally
involving fat and fascia around muscle bundles or the muscles themselves. The skin
overlying the lesion loses pigmentation, becomes filled with fluid and necrotic and often
ulcerates. The ulceration typically has undermined edges and enlarges over many months
(Feldman, 1974). M. ulcerans has not been found in the United States, but is well
recognized in Australia and Africa.
M. haemophilum has been observed to cause joint and skin infections in
immunocompromised patients and lymphadenitis and skin lesions in healthy children.
The lesions frequently occur on the arms or legs as raised violaceus nodules, which often
may become erythematous and ulcerated (Dobos et al., 1999). Recurrence of ulcers may
occur in patients who have not undergone a complete excision of the lesion.
The rapidly growing mycobacterial species M. abscessus, M. fortuitum and M. chelonae
are also a common cause of skin and soft tissue infections following local trauma.
Catheter-Associated Infection
Although infrequent, catheter-associated mycobacterial infections have most often been
associated with long-term central venous catheters and are linked to rapidly growing
mycobacterial species. The disease may include exit site infections, tunnel infections or
catheter-related bacteremia (Correa and Starke, 1996). Exit site infection is characterized
by white to green purulent drainage. Tunnel tract infection is accompanied by erythema
and induration of the surrounding tissues.
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The most common NTM species associated with catheter-associated infections are M.
fortuitum, M. chelonae, M. abscessus andM mucogenicum (Wallace et al., 1993).
Rarely, other species may be seen, including M avium complex. Infections may also
follow use of other types of catheters, including peritoneal catheters, ventriculostomy
tubes and nasolacrimal duct tubes.
Disseminated Infection
Disseminated NTM infection in HIV patients appears to originate from a primary
infection of either the respiratory or gastrointestinal tracts (Correa and Starke, 1996).
These infections may involve any organ, but most commonly occur in the lungs, liver,
spleen, lymph nodes or bone marrow (Correa and Starke, 1996). Common symptoms
include prolonged fevers (often accompanied by night sweats), weight loss and
occasional abdominal pain or diarrhea. This disease is most commonly seen in patients
with less than 50 CD4 cells (ATS, 1997). The primary Mycobacterium species
associated with disseminated infections in HIV infected patients isM avium. However,
M. kansasii, M. haemophilum and M. genavense have also been implicated.
Prior to the HIV epidemic, disseminated infection caused by MAC was rare, occurring
primarily in patients with underlying malignancy or immunodeficiency. M. avium
complex, M kansasii, M. chelonae, M. scrofulaceum, M. abscessus andM haemophilum
have all been observed to cause disease in individuals without HIV infection. The typical
symptom of disseminated infection withM avium complex is a fever of unknown origin,
whereas symptoms caused by the other species consist of multiple subcutaneous nodules
or abscesses that drain spontaneously (ATS, 1997).
In immune-suppressed individuals other than those with HIV, dissemination of disease
from a cutaneous infection is the most common form of NTM disease. These infections
are usually due toM chelonae, M. abscessus, M. haemophilum and rarely other species
such as M. kansasii.
Dose Response
An organism is pathogenic for a specific host if it can infect that host and produce signs
and symptoms of disease. Some pathogens, such asM tuberculosis, can successfully
infect and cause disease in a completely normal host in whom all defenses are intact.
Other organisms have a more limited pathogenicity and cause disease almost exclusively
in hosts with one or more defense defects. Such organisms are thus termed
"opportunistic". Almost all of the NTM fit into this latter category.
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The dose-response relationship is dependent on the host's immune status, presence of
predisposing factors (e.g., broken skin), and the species of NTM. Therefore, a dose of
organisms that results in infection in an immunocompromised individual, may have no
apparent effect in a healthy host.
At least one study has shown that inhalation of MAC is more likely to cause infection
than oral exposure (Gangadharam et al. 1989; cited in Rusin et al., 1997). In this study,
beige mice were exposed once via either the intranasal or oral route to MAC. Via the
intranasal route, lung infections were seen within one day and lymph node, liver and
spleen infections were seen within 8 weeks. The oral exposure did not result in systemic
infection; however, MAC organisms were isolated from spleen and lung tissue samples 6
to 8 weeks post-exposure.
Bermudez et al. (1992) (cited in Rusin et al., 1997) found that when beige mice were
challenged to five oral doses of 104 CPU of M. avium given on alternate days of
exposure, bacteremia was detected in 26.9% and mortality occurred in 11.5% of mice
within 4 weeks. By 8 weeks, all of the animals had disseminated disease and as many as
70% had bacteremia caused by MAC strains. After exposure to five doses of 108 CPU of
MAC, bacteremia occurred in 45% of the dosed animals and mortality was seen in 25%.
Immunity
The stages of immune response seen in mycobacterial disease are similar to those in other
infections and consist of recognition, response and reaction. The first stage consists of
'recognizing' the invading mycobacteria as 'foreign'. In the second stage, the host
defense mechanisms are triggered. The last stage represents the interaction between the
Mycobacterium and the host.
Cell-mediated immunity is thought to be the host immune response which is mainly
responsible for protection against NTM infection. However, some mycobacteria can
survive within macrophages.
Treatment
Treatment of NTM infection depends on the location and extent of disease involvement, status of
the host's immune system, and the mycobacterial species. Since there are a variety of disease
manifestations for the NTM species, a variety of treatment options exist. A statement reviewing
treatment of NTM disease has been issued by the American Thoracic Society (ATS, 1997).
Pulmonary Infection
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Recent studies have shown that the macrolides clarithromycin and azithromycin have
strong activity against MAC (ATS, 1997). According to a recent statement by the
American Thoracic Society (ATS, 1997), initial therapy for this MAC-associated
pulmonary disease in adult HIV-negative patients should consist of a minimum three
drug regimen, consisting of clarithromycin or azithromycin, and rifabutin or rifampin,
and ethambutol. On this regimen, patients should show clinical improvement within 3 to
6 months. For patients whose disease has failed to respond to the regimen, an alternative
four drug regimen, consisting of isoniazid, rifampin, ethambutol and streptomycin, has
been recommended (ATS, 1997).
In adult patients with pulmonary infection caused by M. kansasii, a three drug treatment
regimen consisting of isoniazid, rifampin and ethambutol is recommended (ATS, 1997).
In cases where no treatment is provided, there is progression of clinical and radiographic
disease.
Although there are multiple other species of NTM that are known to cause pulmonary
infection, treatment recommendations are only available for four species; M. malmoense,
M. simiae, M. szulgai andM xenopi. Treatment durations typically last between 18 to 24
months (ATS, 1997). MostM malmoense isolates are susceptible to ethambutol, and
many are also susceptible to rifampin and streptomycin. In most cases, favorable
responses have been seen using the alternative four-drug treatment regimen for MAC.
For patients requiring treatment of M simiae infection, initial therapy may be
implemented using the alternative four-drug treatment regimen for MAC. Based on
susceptibility tests, this regimen can be modified as needed (ATS, 1997). M. szulgai is
typically susceptible to rifampin and higher concentrations of isoniazid, streptomycin and
ethambutol (ATS, 1997). Most patients treated with these drugs in combination respond
favorably to therapy. In vitro tests have shown that the susceptibility of M xenopi to
antituberculosis drugs is variable (ATS, 1997). It is recommended that for initial therapy,
patients should be administered a macrolide, rifampin or rifabutin, and ethambutol with
or without initial streptomycin. If treatment fails or patients show signs of relapse,
surgery may be a consideration.
Skin and Soft Tissue Infection
Cutaneous lesions caused by NTM may spontaneously regress over a few week period,
but the deeper lesions can persist or advance, often requiring treatment (Rosenzweig,
1996). Guidelines for drug therapy of disease caused by rapidly growing mycobacteria
have been developed; however, susceptibility testing of isolates is recommended prior to
beginning a treatment regimen.
For serious infection caused by M. fortuitum and M. abscessus, an initial therapy of
amikacin combined with high-dose cefoxitin given intravenously is recommended (ATS,
1997). Surgery may be required in cases of extensive disease, abscess formation or
where drug therapy is difficult.
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Several treatment strategies have been identified for cutaneous infection caused by M.
marinum. These include observation, surgical excision, use of antituberculosis agents
and use of single antibiotic agents. The American Thoracic Society (ATS, 1997) has
indicated that acceptable treatment regimens for adults include clarithromycin,
minocycline or doxycycline, trimethoprim-sulfamethoxazole, or rifampin plus
ethambutol daily. Each of these regimens should be administered for a minimum of three
months.
Drugs for treatment of infection by M ulceram are considered ineffective. Surgical
removal is generally considered the treatment of choice for this disease.
Disseminated Infection
Treatment of disseminated M avium infection requires multi-drug therapy due to
problems with drug resistance. Recommendations for treatment, based on currently
available data, advise a minimum of three drugs, one of which should be clarithromycin
or azithromycin (ATS, 1997). Ethambutol is often used as the second agent and rifabutin
as the third. In patients with AIDS, adverse effects resulting from NTM treatment drugs
may necessitate frequent changes to the therapeutic regimen.
Sensitive Subpopulations
• In many patients with mycobacterial disease, there are predisposing factors present.
These factors include, traumatic breaches of the skin, pre-existing pulmonary disease or
damage, lung architectural defects, bronchiectasis and generalized congenital and
acquired immunosuppressive disorders (such as HIV) (Grange, 1996a; Dawson, 1990).
• NTM has been recovered frequently in patients with cystic fibrosis, particularly in the
southeastern United States.
Several species of NTM are generally seen only or primarily in patients with suppressed
immune status. These species include M genavense andM haemophilum.
Children
It is difficult to estimate the true incidence of disease caused by NTM in children. These
infections are typically underestimated due to a lack of mandatory reporting and the fact
that NTM disease is seldom a cause of death in children.
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• In general, symptoms seen in children are similar to those presented in adults. The
superficial lymph nodes of the head and neck are the most common sites of clinically
significant NTM infection in children, with onset occurring more rapidly in younger
children. Of the mycobacteria isolated from children under 12 years of age with
lymphadenitis, 65% to 80% are MAC, and 10% to 20% areM scrofulaceum (Correa and
Starke, 1996). Pulmonary disease is relatively rare in the pediatric age group.
• Symptoms of disseminated NTM infection in pediatric patients include recurrent fever,
failure to thrive, neutropenia, night sweats, abdominal pain, anemia and anorexia (Correa
and Starke, 1996).
• Mycobacterial lymphadenitis in children most commonly occurs as a lump in the neck of
a child who is otherwise healthy (Colville, 1993). The involved nodes are typically high
in the neck, just under or near the jaw. There is little or no associated pain or tenderness
(Wolinsky, 1979). The nodes typically progress rather rapidly to softening, rupture, sinus
formation and prolonged drainage. The most common treatment for lymphadenitis
caused by NTM is complete surgical excision. This treatment has a greater than 95%
cure rate.
• Therapy for otologic infections consists of surgical debridement, removal of foreign
material, and long-term antimicrobial therapy determined by susceptibility testing. This
disease is almost invariably due toM abscessus. Clarithromycin is the treatment drug of
choice for this infection.
• The primary treatment for skin and soft tissue infection in children is antimicrobial drug
therapy, often accompanied by surgical debridement if necessary (ATS, 1997).
V. HEALTH EFFECTS IN ANIMALS
Several of the NTM species have been known to cause disease in animals. These
include: M. avium complex, M. marinum, M. ulcemns, M. paratuberculosis, M. simiae,
M. fortuitum and M. smegmatis.
Strains of the M avium complex have been recovered from numerous animals including
pigs, ducks, geese, swans, and monkeys (Gangadharam and Jenkins, 1998). Most are
presumed to beM avium. Most strains of MAC are non-pathogenic in guinea pigs and
mice, although some have been shown to be virulent in chickens (Gangadharam and
Jenkins, 1998). Progressive disease in laboratory mice has been seen after infection with
several strains of M avium-intracellulare.
The causative agent of Johne's disease isM paratuberculosis. This disease is a slow,
progressive infection of the intestine which can result in diarrhea and wasting of the
infected animal. The disease is usually associated with cattle, sheep and goats.
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However, other ruminants, both domestic and wild, have been affected (Power et al.,
1993).
It is estimated that approximately 10% of dairy cattle and 33% of dairy herds in the state
of Wisconsin are infected with M. paratuberculosis (Falkinham, 1996). Since the
principal routes of infection are from infected to uninfected cattle and from infected
mothers to their young, removal of infected animals from herds or of newborns calves
from their mothers has been successful in reducing the incidence of the disease.
Some investigators have observed that paratuberculosis in cattle may be transmitted in
utero. In fetuses from cows with clinical signs of paratuberculosis, prevalence of fetal
paratuberculosis ranged from 21% to 37%.
Manning et al. (1998) investigated an epizootic of paratuberculosis in farmed elk. Elk
infected withM paratuberculosis have clinical signs (e.g., weight loss and diarrhea) and
histologic lesions which are similar to those in cattle.
M. marinum is known to infect fish and serve as an important cause of morbidity,
mortality and economic loss. Some reports indicate that the prevalence of M marinum
infection in fish may be as high as 15% (Gangadharam and Jenkins, 1998). Clinical signs
of M marinum infection in fish include emaciation, poor growth and retarded sexual
maturation. Infection rates reportedly range from 10% to 100% when there is an infected
fish present in the population. Mycobacterial infections in fish are considered non-
treatable. It is recommended that infected stocks be destroyed and that disinfection occur
prior to restocking (Reed and Francis-Floyd, 1995).
Cases of disease from infection withM ulcerous have been reported in koala bears
inhabiting Australia (Grange, 1996a).
In 1965, M. simiae was described as a new species of mycobacteria upon its isolation
from monkeys. Data suggest that transmission occurs from animal to animal as shown by
a case study in which 26% of healthy monkeys caged in groups with infected monkeys
developed M simiae infection over a 13 to 90 day contact period (Falkinham, 1996).
M.fortuitum andM smegmatis are known to cause mastitis in sheep and cattle and skin
and soft tissue infection in domestic house cats. M.fortuitum has also been noted to be
pathogenic for mice, producing distinctive abscesses in the kidneys and the syndrome of
spinning disease as a result of lesions in the cochlea (Wolinsky, 1979). Additionally, M
fortuitum may produce localized abscesses, but not progressive disease, when inoculated
subcutaneously or intraperitoneally in rabbits and guinea pigs (Wolinsky, 1979).
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VI. RISK ASSESSMENT
Pathogen Characterization and Occurrence
NTM species have been recovered from waste waters, surface waters and ground waters
as well as from aerosols associated with water sources. Mycobacteria can multiply in
water that is essentially devoid of nutrients, and they are relatively resistant to
disinfection with many water treatment chemicals, including chlorine. Although there
are data on the occurrence of NTM species in water sources, the data are often not
quantitative.
Exposure
The Centers for Disease Control and Prevention (CDC) conducted a surveillance study of
NTM disease from 1981 to 1983. Based on this study, the annual case rate estimates for
non-AIDS related NTM diseases was 1.8 per 100,000 individuals, of which
approximately 1.3 were attributable to MAC (O'Brien, 1989). In 1996, the rate of NTM
infection in the United States population based on reported data was 7.7 per 100,000
individuals (CDC, 1999a).
There are three primary pathways of exposure to mycobacteria in water by which humans
are known or suspected to become infected: ingestion, inhalation and entry through
abraded skin. For water ingestion, USEPA (1993) recommends a value of 2 L/day be
used as an estimate of a reasonable maximum exposure in adults. Based on this ingestion
rate of 2 L/day and concentrations of mycobacteria ranging from 0.01 to 5.2 CFU/mL in
municipal water systems, adults could be expected to ingest from <20 to 10,400 CPU on
a daily basis. No information was located on the amount of aerosolized water which is
inhaled daily, nor the amount of water which can potentially enter through broken or
abraded skin, but the exposure rate is presumably much lower than for ingestion.
Human Health Effects
In many patients with mycobacterial disease, there are often predisposing factors present,
including pre-existing pulmonary disease or damage, and generalized congenital and
acquired immunosuppressive disorders (Grange, 1996a).
The most common clinical syndromes are pulmonary infection, lymphadenitis, otologic
infection, skin and soft tissue infection, catheter-associated infection and disseminated
infection.
Dose Response
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Little is known regarding the Dose-Response relationship between mycobacterial
exposure and infection in humans by either ingestion, inhalation or dermal exposure
pathways. Some oral ingestion studies have been conducted in animal models (Rusin et
al., 1997), however, these studies are limited in that they did not test responses at a range
of doses, but instead tested the health effects after oral ingestion of a single
concentration.
Risk Characterization
NTM are opportunistic pathogens with widespread distribution in the environment but a
very low rate of infection in the general population.
Sufficient information is not available to support a quantitative characterization of the
threshold infective dose (i.e., the dose required to produce infection) of NTM species.
Despite the lack of data on factors necessary to perform a risk assessment, there are direct
observations which can be utilized to provide a rough overview of risks in the United
States. As mentioned above, NTM infections are not required to be reported, therefore
the following rates may be underestimated. The annual case rate estimates from 1981 to
1983 for non-AIDS related NTM diseases are 1.8 per 100,000 individuals. This is
equivalent to an annual risk of 1.8 x 10"5 for developing NTM disease as a result of
exposure to NTM organisms from all sources (including non-water sources) in the United
States.
The goal of the Surface Water Treatment Rule (SWTR) is to reduce risk to less than one
infection per year per 10,000 people (risk = 1 x 10"4) based on exposure to a
microorganism in drinking water. Assuming that case rates have not increased
dramatically over the last two decades, the population average risk of developing disease
associated with NTM organisms from any exposure source is probably below the goal
identified by the SWTR. Risks to individuals may be higher.
It has been estimated that in the United States, 25% to 50% of individuals with AIDS
will develop NTM diseases (Pozniak et al., 1996; Falkinham, 1996). In 1998, the annual
rate of AIDS in the United States was 17.1 cases per 100,000 population. However,
some states have case rates as high as 189 per 100,000 population, as seen in 1998 in the
District of Columbia. If it is expected that 25% to 50% of AIDS patients will develop
NTM disease, this would be equivalent to a prevalence of approximately 4.3 to 8.6 per
100,000 across the United States and 47.3 to 95 per 100,000 in the District of Columbia.
The recent use of highly active anti-retroviral therapy (HAART) has led to a decrease in
risk/rate of NTM infiction in AIDA patients.
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VII. METHODOLOGY
Sampling and Recovery
• Because the majority of mycobacterial species grow slowly, some method of
decontamination is necessary to kill the other bacteria and fungi present in the water. If
this decontamination step does not occur, these other microorganisms will overgrow the
culture medium and often cause its breakdown by proteolysis. Acids, alkalis and
detergents are often used during the decontamination process since mycobacteria are
generally more resistant to these chemicals than are other bacteria (Jenkins, 1991).
• Carson et al. (1988) found that sodium hypochlorite (0.2 ug/mL of free chlorine)
appeared to be the most effective in reducing gram-negative bacterial populations
stemming from background contamination while still allowing good recovery of NTM in
test samples.
• livanainen et al. (1997) compared two decontamination methods for the isolation of
mycobacteria from brook waters. The decontaminates were 0.7 mol/L NaOH followed
by 50 g/L oxalic acid and 0.9 mol/L H2SO4 combined with 0.5 g/L cycloheximide. The
authors reported that in general, the NaOH-oxalic acid method resulted in lower
contamination and higher isolation of mycobacteria than the H2SO4-cycloheximide
method.
• In addition to decontamination methods, recovery of mycobacteria is often dependent on
the culture medium. Some media favor rapid-growing mycobacteria and may result in
obscured growth of the slower growing species. One of the most common media used in
culturing mycobacteria, the Lowenstein-Jensen medium, contains eggs, asparagine,
glycerol and some mineral salts.
Detection, Quantification and Identification
Numerous methods have been developed for the detection of mycobacteria in samples.
Although the majority of these methods have been developed for the analysis of clinical
specimens (e.g., blood, sputum), they can also be applied to detection in water sources.
These methods include:
• • Polymerase chain reaction (PCR)
Radiometric methods (BACTEC)
GC/MS
• • Nucleic acid probes
• • Cultural and biochemical tests
Overall, the most common and reliable method for the detection and identification of
mycobacteria is culture isolation.
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Polymerase chain reaction (PCR) techniques take a small quantity of bacterial DNA and
enzymatically produce multiple (as many as a billion) copies of the target DNA segment.
These segments can then be separated via gel electrophoresis. This technique can be
used to identify, the disease-causing bacteria. One drawback of PCR techniques is that
they can result in a positive reading even if the bacteria have been inactivated, due to the
presence of residual genetic material in the water source. This may lead to inappropriate
assertions that a drinking water source is contaminated, when the detected genetic
material may in fact be from non-viable cells (Cormican et al., 1992).
Radiometric detection of mycobacteria, also known as BACTEC methods, is becoming
widely used. The BACTEC TB460 system can distinguish between M tuberculosis and
NTM via the use of a selective growth inhibitor called NAP (ATS, 1997). The average
time for performing this test is five days. Although the BACTEC system can detect
growth of mycobacteria; it is not quantitative. Additionally, this system can not be used
for species identification.
Gas chromatography-mass spectrometry (GC/MS) has been used for the detection and
quantificiation of various mycobacterial strains in drinking water.
Species of mycobacteria can also be identified via High Performance Liquid
Chromatography (HPLC) analysis of species-specific mycolic acids (Butler et al., 1991,
1992; CDC, 1999b). Most commonly reported species can be rapidly identified using
this method. CDC has developed a document entitled "Mycolic Acid Pattern Standards
for HPLC Identification of Mycobacteria" (CDC, 1999b) to serve as a resource in species
identification.
Nucleic acid probes are a tool which can be used for rapid identification of pure cultures
of mycobacteria (Gangadharam and Jenkins, 1998). Probes have been developed for the
following species:M tuberculosis complex, M avium,M. intracellulare^M. avium
complex, M kansasii, andM gordonae.
In addition to the above methods, identification of mycobacteria is often performed by
evaluating both cultural and biochemical characteristics (Grange, 1996; Gangadharam
and Jenkins, 1998). Until more methods are developed for species identification, the
conventional methods based on morphology, growth rates and biochemical parameters
will continue to be the most utilized.
VIII. ANALYSIS AND TREATMENT
Drinking Water Treatment Methods
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In general, drinking water treatment methods can be separated into two modes of action:
removal and disinfection. Removal methods typically are physical rather than chemical
techniques. Disinfection is defined as the destruction or inactivation of pathogenic
microorganisms including bacteria, amoebic cysts, algae, spores and viruses
(Montgomery, 1985).
The quality of the raw or source water and the measures that are taken to improve water
quality prior to disinfection will have a significant effect on the efficacy of any treatment
method.
Water quality factors that influence disinfection efficiency include particulates or
aggregates (suspended solids or turbidity), dissolved organic matter, inorganic
constituents, pH and temperature (Sobsey, 1989).
Physicochemical treatment methods are generally used prior to disinfection to 'clarify'
the source or raw waters for improvement of water quality. These treatment methods are
also used to improve the efficiency of disinfection (called disinfection demand) by
reducing the inorganic and organic loads present in source water prior to drinking water
treatment. These methods include:
• • Sedimentation
• • Flocculation and coagulation
• • Filtration
• • Adsorption
Disinfection/Inactivation
Disinfection treatment methods consist of a number of different processes that are used to
destroy or inactivate pathogenic microorganisms. These include treatment with: chlorine
(free chlorine), chloramines, chlorine dioxide, bromine, iodine, ozone and ultraviolet
radiation.
Many species of mycobacteria have proven resistant to chlorine treatment. This is of
concern, since most waters that are intended for human use are treated with chlorine. In
fact, it is estimated that 98% of municipal water suppliers in the United States use
chlorine for water treatment.
The susceptibility of mycobacterial strains to chloramines has not been fully evaluated
(Pelletier et al., 1988).
Preliminary studies have shown that M. fortuitum is more resistant to ozonation than is E.
coli. Farooq et al. (1977) concluded that ozone residual is the controlling factor in the
inactivation of M. fortuitum.
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No information was located regarding the disinfection efficacy of bromine, iodine or
hydrogen peroxide against NTM species.
Inactivation by UV radiation is believed to act through direct absorption of UV energy by
the microorganism, causing molecular rearrangement and disruption of unsaturated
chemical bonds. Studies have shown that UV radiation can be effective for disinfecting
water contaminated with pathogenic mycobacteria (Kubin et al., 1982).
IX. RESEARCH NEEDS
NTM are an important cause of community- and hospital-acquired illness, and they can
be associated with morbidity and mortality when an infection is not rapidly diagnosed and
treated. In addition, NTM are widely distributed in the environment, including treated water
supplies. Additional information is needed to institute optimal prevention and control measures
and to minimize the morbidity and mortality associated with these organisms. Specific
information gaps include the following:
• More information is required on the latency and dormancy periods of NTM diseases.
This information will facilitate the identification of environmental sources which lead to
disease outbreaks and may help identify species-specific transmission factors.
• More comprehensive data on the concentration of NTM species in water sources is
needed, especially as it relates to potable water supplies in order to accurately estimate
exposures to these organisms.
• Further information is needed regarding the nature of the dose-response relationship for
NTM species, particularly for exposures from potable water. More specifically, research
is needed to establish the minimal infectious dose for high-risk and general populations.
This information will help support development of acceptable levels of these organisms
in water supplies.
• Identification of the most effective (and most cost-effective) biocidal treatments for
NTM species in water sources.
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