Occurrence and antibiotic-resistance of Pseudomonas species isolated from drinking water in southern Greece.

A total of 194 samples of drinking waters consisting of 88 tap waters and 106 non-carbonated bottled waters were processed for isolation of Pseudomonas species during a 4-month period according to standard methods. Pseudomonas aeruginosa was the predominant isolated Pseudomonas species. Twenty-eight (14.4%) P. aeruginosa were isolated from 194 samples. Eight (9%) were isolated from 88 tap water samples and 20 (18.8%) from 106 bottled water samples. Eight (9%) tap waters yielded non-P. aeruginosa strains while bottled waters yielded 22 (20.7%) non-P. aeruginosa strains (P < 0.05). Antibiotic-resistant strains of Pseudomonas species have been isolated from the drinking waters. All but Pseudomonas stutzeri species had a multiple chloramphenicol-erythromycin resistance phenotype. Streptomycin and tetracycline resistance for P. aeruginosa was invariably accompanied by chloramphenicol, tetracycline, erythromycin and nalidixic acid resistance. The susceptibility of Pseudomonas species to newer antimicrobial agents (beta lactams, aminoglycosides, third generation cephalosporins and quinolones) was also evaluated. Ceftazidime and ciprofloxacin seemed to be the most active molecules. There were no resistant P. aeruginosa and P. stutzeri strains to all newer antibiotics tested while Pseudomonas maltophilia was the most resistant among the tested species (69.2% resistance for the newer antibiotics).