Detection of Carbapenemase Production by Modified Carbapenem Inactivation Method among Carbapenem Resistant Gram- negative Bacilli at a Tertiary Care Centre in Coimbatore, Tamil Nadu, India

Abstract

Introduction: In the era of increasing antimicrobial resistance, knowing the mechanism of carbapenem resistance can aid in choosing an apt drug for treatment of patients. There are only few studies estimating the burden of carbapenem resistance and determining the mechanism of resistance among the isolates in our locale. Aim: To determine the prevalence of carbapenemase production by modified Carbapenem Inactivation Method (mCIM) among the Carbapenem Resistant Gram-Negative Bacteria (CRGNB)- Enterobacteriaceae and Pseudomonas aeruginosa isolated in our hospital. Materials and Methods: This was a prospective observational study conducted in Department of Microbiology, KMCH, Coimbatore, Tamil Nadu, India during the period of June 2021 to August 2021. A total of 165 isolates of Enterobacteriaceae family and P. aeruginosa which were resistant to one of the carbapenems (imipenem, meropenem or ertapenem) by Vitek MIC testing were included in the study. All were subjected to mCIM and EDTA-modified CIM (eCIM) test and interpreted as per the CLSI M100 S31 guidelines. Results: Among the 165 isolates, 130 (78.8%) were K. pneumoniae, 27 (16.4%) were other Enterobacteriaceae and eight (4.8%) were P. aeruginosa. Prevalence of mCIM positivity was 51.5% (85 isolates). Approximately, 98% of the mCIM positives (Carbapenemase Producing Gram-Negative Bacteria [CPGNB]) were eCIM positive indicating Metallo-Beta- Lactamase (MBL) production. Conclusion: Performing mCIM in CRGNB is important in routine practice to identify CPGNBs. Due to very high prevalence of MBL among carbapenemase producers, it is advisable to choose ceftazidime avibactam plus aztreonam as the treatment option for CPGNB in our locale.