Evaluation of Antibiotic Resistance Pattern of Pathogenic Bacteria in the Yasooj Municipal Wastewater Treatment Plant

Background & objectives: Wastewater treatment plants represent one of the most important approachs for water conservation. On the other hand, wastewaters can act as a source of antibiotics in aquatic environments. The aim of this study was to evaluate the performance of the Yasooj municipal wastewater treatment plant for removal of Escherichia coli, Pseudomonas aeruginosa and Listeria monocytogenes and also the antibiotic resistance pattern of these bacteria. Methods: In this cross sectional study, samples of inlet, outlet aerated lagoon, outlet settlement lagoon and outlet effluent were collected from the wastewater treatment plant in order to count, isolate, and identify E. coli, P. aeruginosa and L. monocytogenes. Antibiotic resistance pattern was investigated using disk diffusion method for 6 different antibiotics according to CLSI reference method. Results: E. coli, P. aeruginosa and L. monocytogenes were isolated and identified in all levels of purification of wastewater treatment plants. The effectiveness of sewage treatment processes to remove E. coli, P. aeruginosa and L. monocytogenes was 54.17-99.33 in the outlet effluent. The bacterial isolates showed high rate of resistance against cefixime and trimethoprim-sulfamethoxazole and low resistance to imipenem. Multidrug resistance pattern (double and triple) was observed in bacterial isolates. Conclusions: This study showed that antibiotic-resistant bacteria in the outlet effluent are discharged into the environment. Further research needs to be undertaken to improve sewage treatment technologies, thereby producing a better quality treated sewage effluent.