Comparison of the bacteriological quality of tap water and bottled mineral water.

The bacteriological quality of tap water from municipal water supplies, 20-L bottles of mineral water from water dispensers and samples collected from new 20-L bottles of mineral water were comparatively studied. Total coliforms, termotolerant coliforms, Escherichia coli, fecal streptococci, Pseudomonas aeruginosa, Staphylococcus spp. and heterotrophic plate count were enumerated. The results showed that 36.4% of the tap water samples from municipal water systems and 76.6% of the 20-L bottles of mineral water from water dispensers were contaminated by at least one coliform or indicator bacterium and/or at least one pathogenic bacterium. The bacteriological quality of municipal tap water is superior when compared with the 20-L bottles of mineral water collected from water dispensers and samples collected from new 20-L bottles of mineral water before installation in the dispensers. This highlights the need for an improved surveillance system for the bottled water industry. For the municipal water systems, it is recommended to perform the Pseudomonas enumeration periodically, in addition to the routine data collected by most systems.

Characterisation of potential virulence markers in Pseudomonas aeruginosa isolated from drinking water.

Pseudomonas aeruginosa isolates from tap water, mineral water, and artesian well water were investigated for their ability to produce different potential virulence factors or markers such as hemolysins, hemaglutinins, cytotoxins and their ability to adhere to epithelial cells and to abiotic surfaces. The susceptibility to antibiotics, human serum sensitivity and the survival of P. aeruginosa isolates in a chlorinated environment were also examined. Of the 30 isolates tested, 16 possessed the capacity to adhere to abiotic surfaces, and 28 to adhere to epithelial cells; 30 were capable of producing hemolysins, 27 produced cytotoxins, 9 hemagglutinins, and 18 were classified as serum-resistant. For the lowest concentration of chlorine (0.2 mg/l) tested, no killing of biofilm bacteria could be discerned, even after prolonged exposure to the agent. Although all the drinking water isolates were susceptible to aztreonam, cefepime, ceftazidime, ciprofloxacin, imipenem, meropenem, piperacillin-tazobactam, and polymyxin, the P. aeruginosa isolates were resistant to one or more antibiotics. The increasing prevalence of resistance in the isolates from environmental sources may have important therapeutic implications. A notable proportion of the P. aeruginosa isolates from drinking water were able to develop virulence factors, and the incidence of virulence properties was not statistically different among the three sources. A more extensive study of the virulence properties of this bacterium by toxic assays on animals should be explored. Still more interesting would be toxicity assays on immuno-deficient animals with isolates from drinking water in order to better understand the health risk these bacteria may present.