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Applied and Environmental Microbiology, May 2008, p. 3094-3098, Vol. 74, No. 10
0099-2240/08/$08.00+0 doi:10.1128/AEM.02009-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Department of Thoracic Medicine, The Prince Charles Hospital, Rode Road, Chermside 4032, Australia,1 Queensland Mycobacterial Reference Laboratory, Brisbane 4000, Australia,2 Queensland University of Technology, Brisbane, Australia3
Received 2 September 2007/ Accepted 11 March 2008
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°C, at 35°C, and at 35°C with CO2 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.
Published ahead of print on 21 March 2008.
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