Antibiotic Resistance and Phenotypic and Genotypic Detection of Colistin Resistance among Enterobacter Species Isolated from Patients of a Tertiary Care Hospital, Bangladesh

Abstract

The prevalence of antimicrobial resistance among Enterobacter species is alarmingly high. Colistin as a last resort antibiotic reintroduced in the treatment pipeline to combat the drug resistant Enterobacter infection has led to emergence of colistin resistance. The study was designed to determine the prevalence of antibiotic resistance among isolated Enterobacter and to assess the occurrence of colistin resistance both phenotypically and genotypically in a tertiary care hospital, Bangladesh. This cross-sectional study was conducted during the period July2018 to June 2019. A total 350 different samples were processed. Enterobacter were identified phenotypically and were processed for antimicrobial susceptibility test (AST) by using modified disk diffusion method. Colistin resistance was determined by minimum inhibitory concentration (MIC) using agar dilution method. Colistin resistant strains were further processed for colistin resistance genes using polymerase chain rection (PCR). Among the total samples processed, 65.14% (228/350) yielded culture positive growth of which 12.28% (28/228) were Enterobacter species. Among isolated Enterobacter 22 (9.64%) were E. cloacae and 6 (2.63%) were E. aerogenes. In AST, 89.29%, 57.14% and 42.86% were resistant to ciprofloxacin, amikacin and imipenem respectively. Tigecycline and colistin were most effective antibiotics. Among colistin resistant Enterobacter isolates, 85.71%, 71.42%, 42.85% and 57.14% were positive for PmrC, PmrA, PhoP and PmrB respectively detected by PCR. Our study reports identification and distribution of drug resistant Enterobacter strains in a major tertiary care hospital. High prevalence of drug resistance and emergence of colistin resistance is indicative of deteriorating situation. Therefore, further extensive surveillance is mandatory.