Comparison of methods for processing drinking water samples for the isolation of Mycobacterium avium and Mycobacterium intracellulare.
Several protocols for isolation of mycobacteria from water exist, but there is no established standard method. This study compared methods of processing potable water samples for the isolation of Mycobacterium avium and Mycobacterium intracellulare using spiked sterilized water and tap water decontaminated using 0.005% cetylpyridinium chloride (CPC). Samples were concentrated by centrifugation or filtration and inoculated onto Middlebrook 7H10 and 7H11 plates and Lowenstein-Jensen slants and into mycobacterial growth indicator tubes with or without polymyxin, azlocillin, nalidixic acid, trimethoprim, and amphotericin B. The solid media were incubated at 32 degrees C, at 35 degrees C, and at 35 degrees C with CO(2) and read weekly. The results suggest that filtration of water for the isolation of mycobacteria is a more sensitive method for concentration than centrifugation. The addition of sodium thiosulfate may not be necessary and may reduce the yield. Middlebrook M7H10 and 7H11 were equally sensitive culture media. CPC decontamination, while effective for reducing growth of contaminants, also significantly reduces mycobacterial numbers. There was no difference at 3 weeks between the different incubation temperatures.
Thomson
Rachel
R
Department of Thoracic Medicine, The Prince Charles Hospital, Rode Rd., Chermside 4032, Australia. R.Thomson@mailbox.uq.edu
Carter
Robyn
R
Gilpin
Chris
C
Coulter
Chris
C
Hargreaves
Megan
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001431:Bacteriological Techniques / Q000379:methods*; D002498:Centrifugation; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D005374:Filtration; D009162:Mycobacterium avium / Q000302:isolation & purification*; D015269:Mycobacterium avium Complex / Q000302:isolation & purification*; D013696:Temperature; D013885:Thiosulfates / Q000494:pharmacology; D014871:Water Microbiology
D000900:Anti-Bacterial Agents; D003470:Culture Media; D013885:Thiosulfates; C017717:sodium thiosulfate