Terry C. Covert

Detection of Mycobacterium avium subsp. paratuberculosis in Drinking Water and Biofilms by Quantitative PCR

ABSTRACT It has been suggested that Mycobacterium avium subspecies paratuberculosis has a role in Crohns disease. The organism may be acquired but is difficult to culture from the environment. We describe a quantitative PCR (qPCR) method to detect M. avium subsp. paratuberculosis in drinking water and the results of its application to drinking water and faucet biofilm samples collected in the United States.

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

ABSTRACT 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.

Isolation of the genome sequence strain Mycobacterium avium 104 from multiple patients over a 17-year period

ABSTRACT The genome sequence strain 104 of the opportunistic pathogen Mycobacterium avium was isolated from an adult AIDS patient in Southern California in 1983. Isolates of non-paratuberculosis M. avium from 207 other patients in Southern California and elsewhere were examined for genotypic identity to strain 104. This process was facilitated by the use of a novel two-step approach. In the first step, all 208 strains in the sample were subjected to a high-throughput, large sequence polymorphism (LSP)-based genotyping test, in which DNA from each strain was tested by PCR for the presence or absence of 4 hypervariable genomic regions. Nineteen isolates exhibited an LSP type that resembled that of strain 104. This subset of 19 isolates was then subjected to high-resolution repetitive sequence-based PCR typing, which identified 10 isolates within the subset that were genotypically identical to strain 104. These isolates came from 10 different patients at 5 clinical sites in the western United States, and they were isolated over a 17-year time span. Therefore, the sequenced genome of M. avium strain 104 has been associated with disease in multiple patients in the western United States. Although M. avium is known for its genetic plasticity, these observations also show that strains of the pathogen can be genotypically stable over extended time periods.

Molecular Comparison of Mycobacterium avium Isolates from Clinical and Environmental Sources

ABSTRACT We collected Mycobacterium avium isolates from clinical and drinking-water sources and compared isolates among themselves and to each other using molecular methods. Four clinical isolates were related to water isolates. Groups of indistinguishable clinical isolates were identified. The groups of identical clinical isolates suggest a common source of exposure.

Electrophoretic mobility of Mycobacterium avium complex organisms

ABSTRACT The electrophoretic mobilities (EPMs) of 30 Mycobacterium avium complex organisms were measured. The EPMs of 15 clinical isolates ranged from −1.9 to −5.0 μm cm V−1 s−1, and the EPMs of 15 environmental isolates ranged from −1.9 to −4.6 μm cm V−1 s−1 at pH 7.

Comparative resistance of escherichia coli and enterococci to chlorination

Abstract Pure cultures of Escherichia coli and Enterococcus faecium were inactivated by free chlorine and monochloramine. Indigenous E. coli and enterococci in wastewater effluents were also inactivated. Selective bacteriological media specifically designed for the enumeration of the target microbes were utilized in the study. Results show that enterococci are more resistant than E. coli to chlorine disinfection.

Detection of Escherichia coli in water using a colorimetric gene probe assay

Abstract A commercially available DNA hydribization assay (Gene‐trak(R), Framingham, MA, USA) was compared with the EC‐MUG procedure for the detection of Escherichia coli in water. The gene probe gave positive responses for pure cultures of E. coli, E. coli 0157:H7, E. fergusonii. Shigella sonnei, S. dysenteriae and S. boydii. The hybridization assay was capable of detecting E. coli in environmental samples and survivors among chlorine exposed cells.