Phenotypic and Genotypic Characterisation of Gram-negative Enterobacterales Causing bloodstream infections in trauma patients: an observational study.

INTRODUCTION: Antimicrobial resistance due to bloodstream infections (BSIs) in low and middle-income countries remains unclear. Characterising the resistant patterns is crucial for limiting the spread of resistance and improving treatment strategies. This study aims to evaluate the antimicrobial resistance profile and co-existence of genes in organisms causing BSI. MATERIAL & METHODS: This is a 5-year retrospective cohort study conducted in an Indian tertiary care hospital. The blood samples collected from BSI patients were cultured in BacT/ALERT blood culture bottles. Pathogens were identified using MALDI-TOF, and antimicrobial susceptibility profiling was done using the automated VITEK-II system. The presence of antimicrobial-resistant genes was identified using PCR. The statistical analysis was done using SetupStata17. RESULTS: A total of 296 isolates were obtained from 281 patients having BSIs. Klebsiella pneumoniae (115/296, 38.8%), Acinetobacter baumannii (51/296, 17.2%), Escherichia coli (34/296, 11.4%) and Pseudomonas aeruginosa (14/296, 4.76%) were the most commonly isolated Gram-negative bacilli (GNB) (214/296, 72.29%). A higher frequency of MDR 149/214 (69.6%) was observed in overall GNBs. The highest percentage (>70%) of resistance was observed for K. pneumoniae and A. baumannii to most cephalosporins, carbapenems, and fluoroquinolones. The prevalence of ESBL producers was observed in 168/214 (78.5%) isolates, whereas the Carbapenemase gene was observed in 176/214 (82.2%) isolates, where bla-NDM (144/214, 67.2%) was the most predominant gene. A lower proportion of AmpC producers (117/214; 54.6%) was observed out of all three β-lactamases classes studied. The co-occurrence of ESBL genes was observed in 95.4% (168/176) carbapenemase producers. CONCLUSION: The high prevalence and co-occurrence of bla-NDM, ESBLs, and carbapenemase indicate an evolving resistance pattern across ICU and ward settings. Strengthening infection prevention, integrated surveillance, and antimicrobial stewardship is essential to limit the emergence and transmission of resistant GNBs and support timely, appropriate clinical management.