Determination of antibiotic resistance pattern in bacteria isolated from municipal wastewater treatment plant

Abstract

Background and purpose: Wastewaters are the most important sources of antibiotics entrance into the aqueous environments. Conventional wastewater treatments cannot eliminate these micropollutants and antibiotic resistant bacteria. The aim of this study was to determine the antibiotic resistance pattern in bacteria isolated from untreated sewage and effluent of municipal wastewater treatment plant in Tabriz. Materials and methods: In this cross sectional study, in addition to counting the number of different types of bacteria in raw sewage and municipal wastewater effluent, various bacteria including Enterobacteriaceae and Staphylococcus, Bacillus and Pseudomonas were identified using specific mediums, API E20 kits and biochemical tests. Susceptibility test of bacteria to antibiotics was determined by Kirby-Bauer's disc diffusion. Results: The results showed lower than one log removal efficiency for coliforms bacteria by the wastewater treatment plants. The difference in the number of colonies apart from staphylococci was not significant in wastewater influent and effluent. Aeromonas and staphylococci were the most frequent bacteria in wastewater influent and effluent, respectively. Enterobacteriaceae were generally more sensitive than other bacteria. Resistance to antibiotics was found to be higher in the penicillin member of antibiotics. Resistant to four antibiotics including cephalexin, ampicillin, methicillin and amoxicillin were between 60 to 100%. The resistance of all species increased in the effluent of wastewater treatment plant. Conclusion: Growth and survival of antibiotic resistant bacteria increases in wastewater treatment plants and conventional treatment processes do not demonstrate enough efficiency for removal of these strains. é 2015, Mazandaran University of Medical Sciences. All rights reserved.