Phenotypic Detection of Carbapenem Resistance in Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter Species at a Tertiary Care Hospital.

Background Carbapenem resistance in Gram-negative Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species (ESKAPE) pathogens has emerged as a significant concern in hospital settings, particularly in developing regions, due to its association with multidrug resistance and limited therapeutic options. The present study was designed to assess the prevalence, specimen-wise distribution, and phenotypic detection of carbapenemase production among these pathogens in a tertiary care setting using Clinical and Laboratory Standards Institute (CLSI) M100, 33rd edition, 2023, recommended methods, including the modified carbapenem inactivation method (mCIM) and the EDTA-modified carbapenem inactivation method (eCIM). Methodology This is a prospective observational study conducted at a tertiary care hospital in southwest Maharashtra from January to December 2024. A total of 312 non-duplicate Gram-negative ESKAPE pathogens isolated from various clinical samples were included. Identification and antimicrobial susceptibility testing were performed according to the CLSI M100, 33rd edition, 2023 edition. Carbapenem-resistant isolates were further analyzed for the detection of carbapenemase production by the phenotypic method, mCIM, and eCIM. Results Among the 312 Gram-negative ESKAPE isolates studied, 94 (30.13%) were identified as carbapenem-resistant. K. pneumoniae accounted for the largest proportion of carbapenem-resistant isolates, 41/94 (43.62%), whereas the highest species-specific carbapenem resistance rate was observed in A. baumannii, with 23/57 (40.35%) isolates carbapenem-resistant. Urine was the most frequent source of specimens (54.24%). Carbapenemase production was detected in 62/94 (65.96%) carbapenem-resistant isolates by mCIM, and among these, 39/62 (62.90%) were identified as metallo-β-lactamase (MBL) producers by eCIM. High resistance rates were observed against cephalosporins, fluoroquinolones, and aminoglycosides. In the study setting, colistin resistance was 8/94 (8.51%), with higher resistance in P. aeruginosa, 4/23 (17.39%). Conclusions A considerable burden of carbapenem-resistant Gram-negative ESKAPE pathogens was observed, with the majority producing carbapenemases and a significant proportion producing MBLs. The presence of multidrug resistance and emerging resistance to last-line agents is concerning. Strengthening routine carbapenemase detection, infection control practices, and antimicrobial stewardship programs is essential.