A case-control study on clinical outcome and risk factors associated with carbapenem resistant isolates from critical care unit at a tertiary care hospital in Gujarat

Background: The increasing prevalence of carbapenemase-producing organisms (CPO) is concerning because of the rapid dissemination of carbapenemase genes. Main objectives of the work were to study the prevalence of CPO and their genes using the Xpert® Carba-R assay in bacterial isolates from critical care settings, as well as to study patient-specific risk factors and comorbidities associated with carbapenem-susceptible organisms (CSO) and carbapenem-resistant organisms (CRO). Methods: A prospective, observational, case-control study was conducted from January 2023 to March 2024. Bacterial identification & susceptibility testing was done using VITEK® 2 Compact and Kirby-Bauer disc diffusion method. Study consisted of 100 patients (50 carbapenem-resistant cases and 50 carbapenem-susceptible controls). CRO were further studied for carbapenemase production using the Xpert® Carba-R assay test to detect the blaKPC (KPC), blaNDM (NDM), blaVIM (VIM), blaOXA-48 (OXA-48), and blaIMP (IMP) genes. Results: Carbapenem Resistant Acinetobacter baumanii (CRAB) [40.35%] was the most common isolate, followed by Carbapenem Resistant Pseudomonas aeruginosa (CRPA) [23.95%], Carbapenem Resistant Klebsiella penumoniae (CRKP) [21.52%], and Carbapenem Resistant Escherichia coli (CREC) [15.27%]. CRKP showed the highest carbapenemase production (42%). NDM carbapenemases were most common (54%), followed by NDM + OXA-48 co-production (30%). No genes were detected in 12% of isolates. IMP, VIM, and KPC genes were not detected. Carbapenem resistance was significantly associated with male sex, lengthy hospital stays, in-situ Foley’s catheter, and multiple co-morbidities. Mortality was 14% in cases and 4% in controls (OR, 3.9; 95% CI, 0.76 to 19.83). Conclusions: In conclusion, CRO infections were associated with multiple risk factors, longer hospital stays and higher mortality compared to CSO infections.