Qom University of Medical Sciences Journal

Background and Objectives: Antibiotics are among the most effective drugs used to treat humans. These materials enter in different ways into sewage and known as important biological contaminants in aquatic and agricultural environment. The availability of conditions for antibiotic resistance gene transfer to sewage bacteria, converted human environmental wastes to an important source of antibiotic resistant bacteria. Considering the spread of antibiotic resistant strains in treatment centers of Qom province, the aim of this study is to investigate the frequency and antibiotic resistance pattern in coliform bacteria isolated from wastewater treatment system of Qom city in different seasons.

Methods: This study was carried out on 120 samples of municipal wastewater treatment plant (incoming and outgoing) in Qom. After sampling, transport of samples to the laboratory, isolation and phenotypic identification of bacteria, and Determination of antibiotic resistance pattern, were performed according to CLSI standards. The frequency of bacteria was determined using most probable number (MPN) method.

Results: In this study, of 384 strains of bacteria (isolated in spring, summer, and winter), Escherichia coli (50%), Citrobacter (30%), Enterobacter (11%), Klebsiella (1%) and non-coliform bacteria (Proteus sp.) 8%, were identified. The most antibiotic resistance was observed in Citrobacter and Enterobacter bacteria (isolated in summer) to penicillin G with a frequency of 94%.

Conclusion: Due to the high frequency of antibiotic resistance in Citrobacter and Enterobacter strains in the sewage treatment plant in Qom province, especially in the summer, this ecosystem can be reported as an important source of spread of antibiotic-resistant strains.