Ramalingam Sekar1, Seetharaman Srivani2, Narayanan Kalyanaraman3, Pandiyan Thenmozhi3, Murugesan Amudhan3, Sivathanu Lallitha3, Manoharan Mythreyee3. 1. Department of Microbiology, Faculty of Medicine, Government Theni Medical College, Tamil Nadu Dr M.G.R. Medical University, Theni 625512, India; Department of Microbiology, Faculty of Medicine, Dr A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai 600113, India. Electronic address: sekaralingam@gmail.com. 2. Department of Microbiology, Faculty of Medicine, Dr A.L.M. Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai 600113, India. 3. Department of Microbiology, Faculty of Medicine, Government Theni Medical College, Tamil Nadu Dr M.G.R. Medical University, Theni 625512, India.
Abstract
OBJECTIVES: The emergence and dissemination of carbapenem-resistant Enterobacteriaceae (CRE) is an important public health problem. This study aimed to understand the prevalence and mechanisms of carbapenem resistance in clinically important members of Enterobacteriaceae in rural South India. METHODS: Routine clinical isolates of Escherichia coli and Klebsiella spp. were tested for Ertapenem (ETP) non-susceptibility by the disk diffusion method over a 3-year period (2012-2014). The ETP non-susceptible isolates were preserved, and tested for the MIC of carbapenems and the carriage of major carbapenemase-encoding genes. Representative genes were sequenced and selective isolates were tested for the production of carbapenemase by carbapenem inactivation method. RESULTS: A total of 444 ETP non-susceptible isolates were identified in increasing incidence over the study period. Among them, MIC50 and MIC90 of carbapenems (excluding ETP) were 0.25-0.5μg/mL and 8-16μg/mL, respectively, and the prevalence of non-ETP carbapenem resistance was estimated as 3%. Among the 177 tested isolates, 65 (37%) had one or more carbapenemase-encoding genes with a predominance of New Delhi Metallo-β-lactamase (NDM; 32 of 65; 49.2%). CONCLUSIONS: This study documented the MIC range for carbapenems, prevalence and mechanisms of carbapenem resistance among Enterobacteriaceae in rural South India. It substantiated NDM as a leading mechanism of carbapenem resistance and highlighted the importance of MIC testing in patient management.
OBJECTIVES: The emergence and dissemination of carbapenem-resistant Enterobacteriaceae (CRE) is an important public health problem. This study aimed to understand the prevalence and mechanisms of carbapenem resistance in clinically important members of Enterobacteriaceae in rural South India. METHODS: Routine clinical isolates of Escherichia coli and Klebsiella spp. were tested for Ertapenem (ETP) non-susceptibility by the disk diffusion method over a 3-year period (2012-2014). The ETP non-susceptible isolates were preserved, and tested for the MIC of carbapenems and the carriage of major carbapenemase-encoding genes. Representative genes were sequenced and selective isolates were tested for the production of carbapenemase by carbapenem inactivation method. RESULTS: A total of 444 ETP non-susceptible isolates were identified in increasing incidence over the study period. Among them, MIC50 and MIC90 of carbapenems (excluding ETP) were 0.25-0.5μg/mL and 8-16μg/mL, respectively, and the prevalence of non-ETPcarbapenem resistance was estimated as 3%. Among the 177 tested isolates, 65 (37%) had one or more carbapenemase-encoding genes with a predominance of New Delhi Metallo-β-lactamase (NDM; 32 of 65; 49.2%). CONCLUSIONS: This study documented the MIC range for carbapenems, prevalence and mechanisms of carbapenem resistance among Enterobacteriaceae in rural South India. It substantiated NDM as a leading mechanism of carbapenem resistance and highlighted the importance of MIC testing in patient management.