Are antibiotic-resistant Pseudomonas aeruginosa isolated from hospitalised patients recovered in the hospital effluents?

Previous reports have studied the presence of antibiotic-resistant Pseudomonas aeruginosa strains in hospital wastewater without determination of their clonal relationship with the clinical strains of this species. The objectives of this study were to quantify the presence of P. aeruginosa in wastewater of our hospital, to determine their antibiotic-resistance profile and to potentially trace clinical antibiotic-resistant strains from patients to wastewater. Specimens were taken at the end of the wastewater network of our hospital just before the reject in the collective network of the town. Two specimens were taken each Monday during 12 weeks. All P. aeruginosa isolates recovered from hospitalised patients during the study period were collected. Genotyping of both clinical and wastewater isolates was determined by using pulsed-field gel electrophoresis (PFGE). The antibiotic-resistance profile of wastewater isolates was different from that of clinical isolates. The mechanisms involved in antibiotic resistance were different according to the origin of the isolates (wastewater versus human isolates). There was no common PFGE pattern in antibiotic-resistant P. aeruginosa from humans and wastewater. This study suggests that the risk of spread of antibiotic resistance in hospital wastewater is limited.