Occurrence of mycobacteria in water treatment lines and in water distribution systems

The frequency of recovery of atypical mycobacteria was estimated in two treatment plants providing drinking water to Paris, France, at some intermediate stages of treatment. The two plants use two different filtration processes, rapid and slow sand filtration. Our results suggest that slow sand filtration is more efficient for removing mycobacteria than rapid sand filtration. In addition, our results show that mycobacteria can colonize and grow on granular activated carbon and are able to enter distribution systems. We also investigated the frequency of recovery of mycobacteria in the water distribution system of Paris (outside buildings). The mycobacterial species isolated from the Paris drinking water distribution system are different from those isolated from the water leaving the treatment plants. Saprophytic mycobacteria (present in 41.3% of positive samples), potentially pathogenic mycobacteria (16.3%), and unidentifiable mycobacteria (54.8%) were isolated from 12 sites within the Paris water distribution system. Mycobacterium gordonae was preferentially recovered from treated surface water, whereas Mycobacterium nonchromogenicum was preferentially recovered from groundwater. No significant correlations were found among the presence of mycobacteria, the origin of water, and water temperature.     

Persistence of Nontuberculous Mycobacteria in a Drinking Water System after Addition of Filtration Treatment

There is evidence that drinking water may be a source of infections with pathogenic nontuberculous mycobacteria (NTM) in humans. One method by which NTM are believed to enter drinking water distribution systems is by their intracellular colonization of protozoa. Our goal was to determine whether we could detect a reduction in the prevalence of NTM recovered from an unfiltered surface drinking water system after the addition of ozonation and filtration treatment and to characterize NTM isolates by using molecular methods. We sampled water from two initially unfiltered surface drinking water treatment plants over a 29-month period. One plant received the addition of filtration and ozonation after 6 months of sampling. Sample sites included those at treatment plant effluents, distributed water, and cold water taps (point-of-use [POU] sites) in public or commercial buildings located within each distribution system. NTM were recovered from 27% of the sites. POU sites yielded the majority of NTM, with >50% recovery despite the addition of ozonation and filtration. Closely related electrophoretic groups of Mycobacterium avium were found to persist at POU sites for up to 26 months. Water collected from POU cold water outlets was persistently colonized with NTM despite the addition of ozonation and filtration to a drinking water system. This suggests that cold water POU outlets need to be considered as a potential source of chronic human exposure to NTM.     

Persistence of nontuberculous mycobacteria in a drinking water system after addition of filtration treatment

There is evidence that drinking water may be a source of infections with pathogenic nontuberculous mycobacteria (NTM) in humans. One method by which NTM are believed to enter drinking water distribution systems is by their intracellular colonization of protozoa. Our goal was to determine whether we could detect a reduction in the prevalence of NTM recovered from an unfiltered surface drinking water system after the addition of ozonation and filtration treatment and to characterize NTM isolates by using molecular methods. We sampled water from two initially unfiltered surface drinking water treatment plants over a 29-month period. One plant received the addition of filtration and ozonation after 6 months of sampling. Sample sites included those at treatment plant effluents, distributed water, and cold water taps (point-of-use [POU] sites) in public or commercial buildings located within each distribution system. NTM were recovered from 27% of the sites. POU sites yielded the majority of NTM, with >50% recovery despite the addition of ozonation and filtration. Closely related electrophoretic groups of Mycobacterium avium were found to persist at POU sites for up to 26 months. Water collected from POU cold water outlets was persistently colonized with NTM despite the addition of ozonation and filtration to a drinking water system. This suggests that cold water POU outlets need to be considered as a potential source of chronic human exposure to NTM.     

Factors Influencing Numbers of Mycobacterium avium, Mycobacterium intracellulare, and Other Mycobacteria in Drinking Water Distribution Systems

Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on mycobacterial numbers. Overall, mycobacterial recovery from the systems was low (15% of samples). Numbers of mycobacteria ranged from 10 to 700,000 CFU liter⁻¹. The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that mycobacteria grow in the distribution system. The increase in mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r² = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm²). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.     

Biodiversity of amoebae and amoebae-resisting bacteria in a drinking water treatment plant

The complex ecology of free-living amoebae (FLA) and their role in spreading pathogenic microorganisms through water systems have recently raised considerable interest. In this study, we investigated the presence of FLA and amoebae-resisting bacteria (ARB) at various stages of a drinking water plant fed with river water. We isolated various amoebal species from the river and from several points within the plant, mostly at early steps of water treatment. Echinamoeba- and Hartmannella-related amoebae were mainly recovered in the drinking water plant whereas Acanthamoeba- and Naegleria-related amoebae were recovered from the river water and the sand filtration units. Some FLA isolates were recovered immediately after the ozonation step, thus suggesting resistance of these microorganisms to this disinfection procedure. A bacterial isolate related to Mycobacterium mucogenicum was recovered from an Echinamoeba-related amoeba isolated from ozone-treated water. Various other ARB were recovered using co-culture with axenic Acanthamoeba castellanii, including mycobacteria, legionella, Chlamydia-like organisms and various proteobacteria. Noteworthy, a new Parachlamydia acanthamoebae strain was recovered from river water and from granular activated carbon (GAC) biofilm. As amoebae mainly multiply in sand and GAC filters, optimization of filter backwash procedures probably offers a possibility to better control these protists and the risk associated with their intracellular hosts.     

Diversity of Nontuberculoid Mycobacterium Species in Biofilms of Urban and Semiurban Drinking Water Distribution Systems

Nontuberculous mycobacteria (NTM) are ubiquitous and have been isolated from a variety of environmental sources, including water. Various NTM were isolated from biofilms in drinking water distribution systems in two urban and two semiurban areas in South Africa. Most of the isolates belonged to opportunistic pathogenic species of the NTM group, but none belonged to the Mycobacterium avium complex.     

Cooccurrence of Free-Living Amoebae and Nontuberculous Mycobacteria in Hospital Water Networks,and Preferential Growth of Mycobacterium avium in Acanthamoeba lenticulata

The incidence of lung and other diseases due to nontuberculous mycobacteria (NTM) is increasing. NTM sources include potable water, especially in households where NTM populate pipes, taps, and showerheads. NTM share habitats with free-living amoebae (FLA) and can grow in FLA as parasites or as endosymbionts. FLA containing NTM may form cysts that protect mycobacteria from disinfectants and antibiotics. We first assessed the presence of FLA and NTM in water and biofilm samples collected from a hospital, confirming the high prevalence of NTM and FLA in potable water systems, particularly in biofilms. Acanthamoeba spp. (genotype T4) were mainly recovered (8/17), followed by Hartmannella vermiformis (7/17) as well as one isolate closely related to the genus Flamella and one isolate only distantly related to previously described species. Concerning mycobacteria, Mycobacterium gordonae was the most frequently found isolate (9/17), followed by Mycobacterium peregrinum (4/17), Mycobacterium chelonae (2/17), Mycobacterium mucogenicum (1/17), and Mycobacterium avium (1/17). The propensity of Mycobacterium avium hospital isolate H87 and M. avium collection strain 104 to survive and replicate within various FLA was also evaluated, demonstrating survival of both strains in all amoebal species tested but high replication rates only in Acanthamoeba lenticulata. As A. lenticulata was frequently recovered from environmental samples, including drinking water samples, these results could have important consequences for the ecology of M. avium in drinking water networks and the epidemiology of disease due to this species.     

Factors influencing numbers of Mycobacterium avium, Mycobacterium intracellulare, and other Mycobacteria in drinking water distribution systems

Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on mycobacterial numbers. Overall, mycobacterial recovery from the systems was low (15% of samples). Numbers of mycobacteria ranged from 10 to 700,000 CFU liter(-1). The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that mycobacteria grow in the distribution system. The increase in mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r(2) = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm(2)). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.     

Isolation and automated ribotyping of Mycobacterium lentiflavum from drinking water distribution system and clinical specimens

Automated ribotyping as a tool for identifying of nontuberculous mycobacteria was evaluated. We created a database comprising of riboprints of 60 strains, representing 32 species of nontuberculous mycobacteria. It was shown that combined ribopatterns generated after digestion with EcoRI and PvuII were distinguishable between species of both slow-growing and rapid-growing mycobacteria. The findings were in good agreement with the 16S rRNA gene sequencing results, allowing correct identification of Mycobacterium lentiflavum isolated from clinical specimens and from biofilms growing in public water distribution system. The automated ribotyping was powerful in discriminating between M. lentiflavum and closely related species M. simiae and M. palustre. Mycobacterium lentiflavum strains from drinking water biofilms were resistant to two to four antimycobacterial drugs. The drinking water distribution system may, thus, be a source of nontuberculous mycobacteria resistant to multiple drugs.     

Pyrosequence Analysis of the hsp65 Genes of Nontuberculous Mycobacterium Communities in Unchlorinated Drinking Water in the Netherlands

Studies have shown that certain opportunistic pathogenic species of nontuberculous mycobacteria (NTM) can be present in distributed drinking water. However, detailed information about NTM population composition in drinking water is lacking. Therefore, NTM communities in unchlorinated drinking water from the distribution system of five treatment plants in the Netherlands were characterized using 454 pyrosequencing of the hsp65 gene. Results showed high diversities in unchlorinated drinking water, with up to 28 different NTM operational taxonomic units (OTUs) in a single sample. Each drinking water sample had a unique NTM community, and most (81.1%) OTUs were observed only once. One OTU was observed in 14 of 16 drinking water samples, indicating that this NTM species is well adapted to unchlorinated drinking water conditions. A clear influence of season, source type (groundwater, surface water), easily assimilable organic carbon (AOC) concentration, biofilm formation rate, and active biomass in treated water on the establishment of an NTM community in drinking water was not observed. Apparently, local conditions are more important for the development of a specific NTM community in the drinking water distribution system. A low (4.2%) number of hsp65 gene sequences showed more than 97% similarity to sequences of the opportunistic pathogens M. avium, M. genavense, and M. gordonae. However, most (95.8%) NTM hsp65 gene sequences were related to not-yet-described NTM species that have not been linked to disease, indicating that most NTM species in unchlorinated drinking water from distribution systems in the Netherlands have a low public health significance.     

Diversity of nontuberculoid Mycobacterium species in biofilms of urban and semiurban drinking water distribution systems

Nontuberculous mycobacteria (NTM) are ubiquitous and have been isolated from a variety of environmental sources, including water. Various NTM were isolated from biofilms in drinking water distribution systems in two urban and two semiurban areas in South Africa. Most of the isolates belonged to opportunistic pathogenic species of the NTM group, but none belonged to the Mycobacterium avium complex.     

Biodiversity of Amoebae and Amoeba-Resisting Bacteria in a Hospital Water Network

Free-living amoebae (FLA) are ubiquitous organisms that have been isolated from various domestic water systems, such as cooling towers and hospital water networks. In addition to their own pathogenicity, FLA can also act as Trojan horses and be naturally infected with amoeba-resisting bacteria (ARB) that may be involved in human infections, such as pneumonia. We investigated the biodiversity of bacteria and their amoebal hosts in a hospital water network. Using amoebal enrichment on nonnutrient agar, we isolated 15 protist strains from 200 (7.5%) samples. One thermotolerant Hartmannella vermiformis isolate harbored both Legionella pneumophila and Bradyrhizobium japonicum. By using amoebal coculture with axenic Acanthamoeba castellanii as the cellular background, we recovered at least one ARB from 45.5% of the samples. Four new ARB isolates were recovered by culture, and one of these isolates was widely present in the water network. Alphaproteobacteria (such as Rhodoplanes, Methylobacterium, Bradyrhizobium, Afipia, and Bosea) were recovered from 30.5% of the samples, mycobacteria (Mycobacterium gordonae, Mycobacterium kansasii, and Mycobacterium xenopi) were recovered from 20.5% of the samples, and Gammaproteobacteria (Legionella) were recovered from 5.5% of the samples. No Chlamydia or Chlamydia-like organisms were recovered by amoebal coculture or detected by PCR. The observed strong association between the presence of amoebae and the presence of Legionella (P < 0.001) and mycobacteria (P = 0.009) further suggests that FLA are a reservoir for these ARB and underlines the importance of considering amoebae when water control measures are designed.     

Distribution of Environmental Mycobacteria in Karonga District, Northern Malawi

The genus Mycobacterium includes many species that are commonly found in the environment (in soil and water or associated with plants and animals), as well as species that are responsible for two major human diseases, tuberculosis (Mycobacterium tuberculosis) and leprosy (Mycobacterium leprae). The distribution of environmental mycobacteria was investigated in the context of a long-term study of leprosy, tuberculosis, Mycobacterium bovis BCG vaccination, and the responses of individuals to various mycobacterial antigens in Karonga District, northern Malawi, where epidemiological studies had indicated previously that people may be exposed to different mycobacterial species in the northern and southern parts of the district. A total of 148 soil samples and 24 water samples were collected from various locations and examined to determine the presence of mycobacteria. The detection method involved semiselective culturing and acid-fast staining, following decontamination of samples to enrich mycobacteria and reduce the numbers of other microorganisms, or PCR with primers specific for the mycobacterial 16S rRNA gene, using DNA extracted directly from soil and water samples. Mycobacteria were detected in the majority of the samples, and subsequent sequence analysis of PCR products amplified directly from soil DNA indicated that most of the products were related to known environmental mycobacteria. For both methods the rates of recovery were consistently higher for dry season samples than for wet season samples. All isolates cultured from soil appeared to be strains of Mycobacterium fortuitum. This study revealed a complex pattern for the environmental mycobacterial flora but identified no clear differences between the northern and southern parts of Karonga District.     

Diversity,Community Composition,and Dynamics of Nonpigmented and Late-Pigmenting Rapidly Growing Mycobacteria in an Urban Tap Water Production and Distribution System

Nonpigmented and late-pigmenting rapidly growing mycobacteria (RGM) have been reported to commonly colonize water production and distribution systems. However, there is little information about the nature and distribution of RGM species within the different parts of such complex networks or about their clustering into specific RGM species communities. We conducted a large-scale survey between 2007 and 2009 in the Parisian urban tap water production and distribution system. We analyzed 1,418 water samples from 36 sites, covering all production units, water storage tanks, and distribution units; RGM isolates were identified by using rpoB gene sequencing. We detected 18 RGM species and putative new species, with most isolates being Mycobacterium chelonae and Mycobacterium llatzerense. Using hierarchical clustering and principal-component analysis, we found that RGM were organized into various communities correlating with water origin (groundwater or surface water) and location within the distribution network. Water treatment plants were more specifically associated with species of the Mycobacterium septicum group. On average, M. chelonae dominated network sites fed by surface water, and M. llatzerense dominated those fed by groundwater. Overall, the M. chelonae prevalence index increased along the distribution network and was associated with a correlative decrease in the prevalence index of M. llatzerense, suggesting competitive or niche exclusion between these two dominant species. Our data describe the great diversity and complexity of RGM species living in the interconnected environments that constitute the water production and distribution system of a large city and highlight the prevalence index of the potentially pathogenic species M. chelonae in the distribution network.     

The Tracing of Mycobacteria in Drinking Water Supply Systems by Culture, Conventional, and Real Time PCRs

Mycobacteria are widely present in diverse aquatic habitats, where they can survive for months or years while some species can even proliferate. The resistance of different mycobacterial species to disinfection methods like chlorination or ozonation could result in their presence in the final tap water of consumers. In this study, the culture method, Mycobacterium tuberculosis complex conventional duplex PCR for detection of non-tuberculous mycobacteria (NTM) and quantitative real-time PCR (qPCR) to detect three subspecies of M. avium species (M. a. avium, M. a. hominissuis, and M. a. paratuberculosis) were used to trace their possible path of transmission from the watershed through the reservoir and drinking water plant to raw drinking water and finally to households. A total of 124 samples from four drinking water supply systems in the Czech Republic, 52 dam sediments, 34 water treatment plant sludge samples, and 38 tap water household sediments, were analyzed. NTM of 11 different species were isolated by culture from 42 (33.9 %) samples; the most prevalent were M. gordonae (16.7 %), M. triplex (14.3 %), M. lentiflavum (9.5 %), M. a. avium (7.1 %), M. montefiorenase (7.1 %), and M. nonchromogenicum (7.1 %). NTM DNA was detected in 92 (76.7 %) samples. By qPCR analysis a statistically significant decrease (P < 0.01) was observed along the route from the reservoir (dam sediments), through water treatment sludge and finally to household sediments. The concentrations ranged from 10⁰ to 10⁴ DNA cells/g. It was confirmed that drinking water supply systems (watershed–reservoir–drinking water treatment plant–household) might be a potential transmission route for mycobacteria.     

Mycobacteria in water and loose deposits of drinking water distribution systems in Finland

Drinking water distribution systems were analyzed for viable counts of mycobacteria by sampling water from waterworks and in different parts of the systems. In addition, loose deposits collected during mechanical cleaning of the main pipelines were similarly analyzed. The study covered 16 systems at eight localities in Finland. In an experimental study, mycobacterial colonization of biofilms on polyvinyl chloride tubes in a system was studied. The isolation frequency of mycobacteria increased from 35% at the waterworks to 80% in the system, and the number of mycobacteria in the positive samples increased from 15 to 140 CFU/liter, respectively. Mycobacteria were isolated from all 11 deposits with an accumulation time of tens of years and from all 4 deposits which had accumulated during a 1-year follow-up time. The numbers of mycobacteria were high in both old and young deposits (medians, 1.8 x 10(5) and 3.9 x 10(5) CFU/g [dry weight], respectively). Both water and deposit samples yielded the highest numbers of mycobacteria in the systems using surface water and applying ozonation as an intermediate treatment or posttreatment. The number and growth of mycobacteria in system waters correlated strongly with the concentration of assimilable organic carbon in the water leaving the waterworks. The densities of mycobacteria in the developing biofilms were highest at the distal sites of the systems. Over 90% of the mycobacteria isolated from water and deposits belonged to Mycobacterium lentiflavum, M. tusciae, M. gordonae, and a previously unclassified group of mycobacteria. Our results indicate that drinking water systems may be a source for recently discovered new mycobacterial species.     

Ammonia-Oxidizing Bacteria and Archaea in Groundwater Treatment and Drinking Water Distribution Systems

The ammonia-oxidizing prokaryote (AOP) community in three groundwater treatment plants and connected distribution systems was analyzed by quantitative real-time PCR and sequence analysis targeting the amoA gene of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Results demonstrated that AOB and AOA numbers increased during biological filtration of ammonia-rich anoxic groundwater, and AOP were responsible for ammonium removal during treatment. In one of the treatment trains at plant C, ammonia removal correlated significantly with AOA numbers but not with AOB numbers. Thus, AOA were responsible for ammonia removal in water treatment at one of the studied plants. Furthermore, an observed negative correlation between the dissolved organic carbon (DOC) concentration in the water and AOA numbers suggests that high DOC levels might reduce growth of AOA. AOP entered the distribution system in numbers ranging from 1.5 × 10³ to 6.5 × 10⁴ AOPs ml⁻¹. These numbers did not change during transport in the distribution system despite the absence of a disinfectant residual. Thus, inactive AOP biomass does not seem to be degraded by heterotrophic microorganisms in the distribution system. We conclude from our results that AOA can be commonly present in distribution systems and groundwater treatment, where they can be responsible for the removal of ammonia.Ammonia can be present in source water used for drinking water production or added to treated water with chlorine to form chloramines as a disinfectant. However, the presence of ammonia in drinking water is undesirable because nitrification might lead to toxic levels of nitrite (29) or adverse effects on water taste and odor (4) and might increase heterotrophic bacteria, including opportunistic pathogens (29). Two-thirds of the drinking water in The Netherlands is produced from groundwater. Most of the groundwater used for drinking water production is anoxic with relatively high concentrations of methane, iron, manganese, dissolved organic carbon (DOC), and ammonia. Treatment of anoxic groundwater aims at achieving biologically stable water, because drinking water in The Netherlands is distributed without a disinfectant residual. As a result, a highly efficient nitrification process during rapid medium filtration is required.Nitrification is the microbial oxidation of ammonia to nitrate and consists of two processes: the oxidation of ammonia to nitrite by ammonia-oxidizing prokaryotes (AOP) and the oxidation of nitrite to nitrate by nitrite-oxidizing bacteria (NOB). Recently it was shown that in addition to bacteria, archaea also are capable of ammonia oxidation (13). Since then, ammonia-oxidizing archaea (AOA) have been found in many different ecosystems, including wastewater treatment systems (10, 20, 24). However, it is currently unknown if AOA are present in drinking water treatment processes and distribution systems. Recent studies have focused on nitrification in drinking water treatment (16, 28). In those studies, AOB and NOB were enumerated by traditional most-probable-number (MPN) methods using selective liquid media. However, MPN methods are time-consuming and underestimate the numbers of AOP and NOB (3). Quantitative real-time PCR has been used to quantify AOB in drinking water (12) and might be a useful tool for quantifying AOB and AOA in drinking water.In our study, a real-time PCR method targeting the amoA gene of AOB or AOA was developed to quantify numbers of AOP in drinking water. This real-time PCR method was used together with a phylogenetic analysis of the amoA gene of AOB and AOA to do the following: (i) determine the treatment steps where AOP dominates in the groundwater treatment train of three drinking water production plants in The Netherlands, (ii) quantify the AOP entering the distribution system and determine the fate of AOP during transport in the distribution system, and (iii) elucidate the role of AOA in nitrification during drinking water treatment and in distribution systems.     

Variations of bacterial 16S rDNA phylotypes prior to and after chlorination for drinking water production from two surface water treatment plants

We examined the variations of bacterial populations in treated drinking water prior to and after the final chlorine disinfection step at two different surface water treatment plants. For this purpose, the bacterial communities present in treated water were sampled after granular activated carbon (GAC) filtration and chlorine disinfection from two drinking water treatment plants supplying the city of Paris (France). Samples were analyzed after genomic DNA extraction, polymerase chain reaction (PCR) amplification, cloning, and sequencing of a number of 16S ribosomal RNA (rRNA) genes. The 16S rDNA sequences were clustered into operational taxonomic units (OTUs) and the OTU abundance patterns were obtained for each sample. The observed differences suggest that the chlorine disinfection step markedly affects the bacterial community structure and composition present in GAC water. Members of the Alphaproteobacteria and Betaproteobacteria were found to be predominant in the GAC water samples after phylogenetic analyses of the OTUs. Following the chlorine disinfection step, numerous changes were observed, including decreased representation of Proteobacteria phylotypes. Our results indicate that the use of molecular methods to investigate changes in the abundance of certain bacterial groups following chlorine-based disinfection will aid in further understanding the bacterial ecology of drinking water treatment plants (DWTPs), particularly the disinfection step, as it constitutes the final barrier before drinking water distribution to the consumer’s tap.     

Environmental mycobacteria in Korea. I. Distribution of the organisms

Environmental mycobacteria in Korea have been investigated by examining 54 soil, 111 house dust, 63 well water, and 98 sewage samples collected from 123 randomly selected areas in Korea during the fourth nationwide tuberculosis prevalence survey in 1980. A variety of mycobacteria were isolated from 76% of soil, 67% of sewage, 43% of well water, and 7% of house dust samples. Some samples yielded more than one species; thus 56 strains were obtained from soil, 107 strains from sewage, 48 strains from well water and 8 strains from house dust. Mycobacterium fortuitum was the most common species of environmental mycobacteria in Korea and the species was distributed equally in all types of samples tested. The M. terrae complex was also one of the common species of environmental mycobacteria and it seemed to be more abundant in water samples than in soil. Scotochromogenic slow growers M. scrofulaceum and M. gordonae were common microbes in soil and water samples, although the latter was more frequently detected in water samples. Scotochromogenic rapid growers M. flavescens and M.phlei, and photochromogenic rapid grower M. vaccae were isolated more frequently from sewage or water samples than from soil. Nonphotochromogenic rapid growers M. chelonei (chelonae) and M. smegmatis were isolated mostly from sewage and the former was rarely found in soil and well water samples. The clinically important species M. avium-intracellulare complex was found less frequently in all types of test samples.     

Rapid Assay for In Situ Identification of Coagulase-Positive Staphylococci Recovered by Membrane Filtration from Swimming Pool Water

A rapid, in situ thermonuclease test that identifies colonies of Staphylococcus aureus among staphylococci isolated from swimming pool water by membrane filtration recovery on various selective and differential media is described.