Background: Beta-lactams are the largest group of antibiotics used by hospitals to treat infections caused by Gram-negative bacteria. Enterobacteriaceae, natural microbiota of the human gastrointestinal tract, represent a large part of bacterial communities colonizing hospital effluents, and they could be a source of genes encoding extended-spectrum-beta-lactamases (ESBLs). Those genes may be transmitted to other bacteria present in sewage and the environment.

Materials and methods: In this descriptive study, the isolated strains were identified by biochemical methods in accordance with Bergey's manual of systematic bacteriology. Screening and phenotypic confirmatory test for ESBL production were performed using standard double disc diffusion methods. Each initial ESBL screening test isolate was investigated for the presence of bla _CTX-M genes via polymerase chain reaction (PCR) using gene-specific primers.

Results: Of 108 bacterial isolates, 52 (48%) were phenotypically ESBL-positive, but only 32 (29.63%) isolates harbored bla _CTX-M gene. Escherichia coli and Citrobacter spp. were the most frequently identified ESBL-positive strains.

Conclusion: The results showed that ESBL-genes were presented in the hospital wastewater and could be threat for public health.

Keywords: Extended-spectrum-beta-lactamases, bla _CTX-M, Hospital sewage.