Distribution, epidemiology, and antimicrobial resistance pattern of gram-negative bacteria isolated from blood: a retrospective study in a tertiary care hospital, Dhaka, Bangladesh

The effective treatment of bloodstream infections caused by gram-negative bacteria (GNB) poses significant challenges as their distribution and resistance patterns vary across geographic locations and healthcare settings. The objective of this study was to identify the prevalence, distribution, and antimicrobial resistance patterns of commonly isolated GNB from the blood cultures of patients. This retrospective study was conducted between November 2023 to October 2024 in the Department of Microbiology, Dhaka Medical College, Bangladesh. Bacterial blood culture and susceptibility testing records of GNB from both inpatient department (IPD), intensive care units (ICU), and outpatient department (OPD) samples, irrespective of age and sex, were included and analyzed in this study. Total isolated gram-negative bacteria were 87.6%, with a slightly higher prevalence in male patients. Salmonella spp was the most prevalent isolate from the OPD, while Acinetobacter spp was predominant in IPD and ICU. Among the antimicrobial agents, the highest resistance was observed to ceftazidime in all isolated GNB, except Salmonella spp, which were highly resistant to fluoroquinolones. Acinetobacter spp was predominantly multidrug-resistant (MDR) (75.4%), and the lowest was Salmonella spp (40.7%). Among 15% extensively drug-resistant (XDR) isolates, the majority were Acinetobacter spp, followed by Pseudomonas spp and Klebsiella spp. The highest prevalence of both multidrug-resistant (MDR) and XDR organisms were observed in the ICU. The antibiotic resistance trends display restricted effectiveness of commonly used antibiotics, such as cephalosporins and fluoroquinolones, compelling dependence on last-resort antibiotics like colistin. Systematic local surveillance and epidemiological studies of antimicrobial resistance would assist in taking measures to slow down the spread of resistance.