Co-existence of [i]Legionella[/i] and other Gram-negative bacteria in potable water from various rural and urban sources
Journal Title: Annals of Agricultural and Environmental Medicine - Year 2011, Vol 18, Issue 2
Abstract
A total of 320 potable water samples were collected from various rural and urban sources located in the Lublin region of eastern Poland. They comprised: 55 samples of treated (chlorinated) tap water from rural dwellings distributed by the municipal water supply system (MWSS), 111 samples of treated tap water from urban dwellings distributed by the MWSS, 45 samples of untreated well water from household wells and 109 samples from private water supply systems (PWSS) distributing untreated well water. Water samples were examined for the presence and species composition of [i]Legionella, Yersinia[/i], Gram-negative bacteria belonging to family Enterobacteriaceae (GNB-E) and Gram-negative bacteria not belonging to the family Enterobacteriaceae (GNB-NE), by filtering through cellulose filters and culture on respectively GVPC, CIN, EMB and tryptic soya agar media. The occurrence of[i] Legionella [/i]in the samples taken from the outlets of the urban MWSS was high (77.5%), and significantly greater compared to frequencies noted in rural MWSS (7.3%), and samples of well water from household wells (28.9%) and PWSS (13.8%) (p<0.001). Strains [i]L. pneumophila[/i] serogroups 2-14, [i]L. pneumophila[/i] serogroup 1 and [i]Legionella spp[/i]. (species other than [i]L. pneumophila[/i]) formed respectively 64.3%, 17.5%, and 18.2% of total isolates from urban MWSS, 100%, 0, and 0 of those from rural MWSS, 69.2%, 7.7%, and 23.1% of those from household wells, and 66.7%, 0, and 33.3% of those from PWSS. The concentration of Legionella strains in the positive samples from urban MWSS exceeded the threshold limit value of 100 cfu/100 ml in 86.1%, while in the other sources this value was not exceeded. No [i]Yersinia[/i] strains were isolated from the examined water samples. Altogether 8 species or genera of Gram-negative bacteria belonging to Enterobacteriaceae family (GNB-E) and 10 species or genera of Gram-negative bacteria not belonging to the Enterobacteriaceae family (GNB-NE) were found in the examined samples. In the MWSS samples, an inverse relationship was found between [i]Legionella[/i] and GNB-E and the numbers of [i]Enterobacter[/i] spp. and[i] Serratia [/i]spp. strains were signifi cantly more common in the samples without [i]Legionella[/i]. By contrast, in the PWSS samples, the numbers of [i]Enterobacter[/i] spp., [i]Klebsiella[/i] spp. and [i]Salmonella [/i]spp. were distinctly and significantly greater (p<0.01-p<0.001) in the samples containing[i] Legionella[/i]. Among GNB-NE, Pseudomonas aeruginosa strains occurred significantly more frequently in samples containing [i]Legionella [/i](for MWSS and well water separately p<0.05, for total samples p<0.001). Similarly, strains of [i]Flavobacterium breve[/i] and [i]Xanthomonas [/i]spp. occurred significantly more often in the samples with [i]Legionella[/i], while the numbers of [i]Aeromonas[/i] spp. and [i]Vibrio[/i] spp. strains were significantly greater in the samples not containing [i]Legionella[/i]. In conclusion, a health risk could be associated with exposure to the water from urban MWSS because of the high prevalence and concentration of [i]Legionella[/i], and with exposure to well water from PWSS because of the correlation of occurrence of [i]Legionella[/i] and potentially pathogenic Enterobacteriaceae strains, and the possibility of synergistic effects. The adverse effects could be also due to the significant correlation of [i]Legionella [/i]and [i]Pseudomonas[/i] aeruginosa that occured in water from various sources.
Authors and Affiliations
Nimfa Maria Stojek, Jacek Dutkiewicz
Keywords
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