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GENETIC FINGERPRINTING OF MYCOBACTERIUM AVIUM COMPLEX (MAC) ORGANISMS ISOLATED FROM HOSPITAL PATIENTS AND THE ENVIRONMENT
Pfaller, S L. AND T C. Covert. GENETIC FINGERPRINTING OF MYCOBACTERIUM AVIUM COMPLEX (MAC) ORGANISMS ISOLATED FROM HOSPITAL PATIENTS AND THE ENVIRONMENT. Presented at American Society for Microbiology, Washington, DC, May 18-22, 2003.
1)Develop an improved method(s) for isolating and/or detecting nontuberculous mycobacteria from potable water. 2)Determine the best DNA fingerprinting method to use to determine genetic relatedness with clinical and environmental isolates.
A particularly pathogenic group of mycobacteria belong to the Mycobacterium avium complex (MAC), which includes M. avium and M. intracellulare. MAC organisms cause disease in children, the elderly, and immuno-compromised individuals. A critical step in preventing MAC infections is identifying the source of infection and preventing exposure to that source. The standard method for tracking MAC infection outbreaks is long restriction fragment length polymorphism analysis using pulsed-field gel electrophoresis (PFGE). The method is labor-intensive and may lack sensitivity. The purpose of this study was to develop a rapid, reproducible, and efficient method for fingerprinting mycobacteria at the strain level. Mycobacteria isolates were obtained from AIDS and non-AIDS patients, as well as drinking water and food sources. The strains were identified as M. avium, M. intracellulare, or "MX" using AccuProbe (GenProbe). One hundred and sixty-six isolates were typed using Amplified Fragment Length Polymorphism (AFLP) analysis. Phylogenetic analysis using maximum parsimony was utilized to determine the genetic relatedness of the isolates. AFLP was able to distinguish between MAC species and differentiate between strains within each species. Furthermore, the method was rapid and highly reproducible. None of the isolates were genetically identical. Several "MX" strains clustered with M. intracellulare, and their identities were confirmed with 16S sequence analysis. For both species of Mycobacterium, most drinking water isolates clustered more closely with each other than with patient or food isolates, suggesting that the harsh decontamination procedures used to isolate mycobacteria from the environment select for a subset of the organisms present. Patient isolates were more genetically diverse.