Prevalence of amoxicillin resistance by Enterococci found in the hospital wastewater

Document Type : Original Article


1 Department of Microbiology, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran

2 Department of Environmental Health and Engineering, School of Health, Alborz University of Medical Sciences, Karaj, Iran

3 Department of Environmental Health Engineering, Environmental Health Research Center, Kurdistan University of Medical Sciences, Sanandaj, Iran

4 Diagnostic laboratory, Rajaei Hospital, Alborz University of Medical Sciences, Karaj, Iran

5 Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran


Enterococci are found worldwide and are considered to be opportunistic pathogens. Antimicrobial resistance in these bacteria is increasing and is associated with their capability to sustain in the wastewater. We, therefore, aimed to determine the antimicrobial resistance of Enterococcus spp. that are isolated from the wastewater and clinical specimens. Isolation, identification, and determination of the antibiotic susceptibility patterns in the Enterococcus isolates were performed according to the standard procedures. The concentration of amoxicillin in the wastewater was determined by high-performance liquid chromatography (HPLC). A total of 20 Enterococci were isolated and identified in this study. Of all the Enterococcus spp. isolates, 85 and 70% were resistant to tetracycline and ciprofloxacin, respectively. Surprisingly, the antimicrobial susceptibility tests revealed that the wastewater isolates had a higher rate of resistance than the clinical isolates. Amoxicillin concentrations in both the teaching hospitals were analyzed to be 8.6 and 6.8 ppm, respectively. The results of this study revealed that the hospital wastewater, which mixes with the environment, usually comprises resistant Enterococci. The use of HPLC allows the detection of amoxicillin concentrations in the wastewater samples of the teaching hospitals.


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