Prevalence of colistin resistance among gram-negative rod-shaped bacteria isolated from Mulago National Referral Hospital

Abstract

This study determined the prevalence of colistin resistance among Gram-negative rod- shaped bacteria isolated from various units of Mulago National Referral Hospital. It determined the susceptibility patterns of the organisms using colistin pre- diffusion method and plasmid mediated resistance of mcr gene using Ethylenediaminetetraacetic acid test method. The study informs on the clinical practices that will help mitigate colistin resistance. Knowing the prevalence of colistin resistance will inform infection control practices and need of novel antibiotics to avoid a problematic post antibiotic era. The study was conducted at the Clinical Microbiology Laboratory under the College of Health Sciences, Makerere University using a retrospective observational design of 114 samples, archived in 2021 comprising of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Most of the samples analyzed were from Intensive care unit, 48.2% with tracheal aspirates constituting 61.8%. The other units included pediatric, dialysis, surgical and medical wards unit. Additional units including Out-patient department and the private wing were also included. Surgical wards unit contributed most pus swabs, 50.0%. Escherichia coli, 42.0% and Pseudomonas Aeruginosa, 5% contributed the highest and the lowest number of isolates respectively. The overall resistance of the isolates to colistin observed in this study was 6.1%. There were no isolates with indeterminate patterns (not exactly known or defined). E coli had the highest percentage of resistance, 57.1%. There was no resistance observed in the Ethylenediaminetetraacetic acid samples suggesting that all isolate did not have mcr genes. From this study, it can be concluded that there is resistance to the last resort antibiotics such as colistin. This has to be managed both locally and on a global scale. This study recommends the development of antibiotics to avoid a problematic post antibiotic era.