Journal of Water and Health Vol 5 No 2 pp 219–227 © IWA Publishing 2007 doi:10.2166/wh.2007.004
Prevalence of bacterial pathogens in biofilms of drinking water distribution systems
S. M. September, F. A. Els, S. N. Venter and V. S. Brözel
Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, 0002, South Africa
NPB 252B, Department of Biology and Microbiology, Box 2140DSouth Dakota State University, Brookings, SD 57007, USA Tel: 605 688 6483Fax: 605 688 5624volker.brozel@sdstate.edu
ABSTRACT
Water for human consumption is required to be free from any bacteria that might pose a health risk. The presence of biofilms in the drinking water distribution system may play a role in the presence of potential pathogens in the drinking water supply. Ninety-five biofilm samples from various parts of South Africa were tested for the presence of Escherichia coli, Aeromonas, Pseudomonas, Salmonella, Shigella and Vibrio spp. Members of these genera were quantified by the three-tube most probable number (MPN) approach using enrichment broths and plating on selective agars. The heterotrophic culturable counts were determined for both the planktonic and biofilm phases of the samples. Biofilm density varied between 10 and 1.9 × 109 colony forming units cm-2. The 16S rRNA identity of the putative pathogenic isolates revealed that high numbers of Aeromonas, Pseudomonas, Klebsiella and Enterobacter were present, but no putative Salmonella and Shigella could be confirmed. None of the Pseudomonas isolates belonged to the pathogenic Pseudomonas aeruginosa or Pseudomonas mendocina while the Aeromonas isolates showed relatedness to known pathogenic members of this group.
Keywords: biofilm; distribution system; drinking water; pathogen
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