Colistin susceptibility pattern in gram negative bacilli isolated from patients of dhaka medical college hospital with distribution of antibiotic resistance genes among them

Colistin is one of the last resort of antibiotics used specifically in the treatment of multidrug resistant gram negative bacilli. Though an older class of antibiotic with no use in last four decades, resurgence of colistin use is also causing emergence of colistin resistant gram negative bacilli.The aim of this cross sectional study was to investigate the colistin susceptibility and resistant pattern along with colistin resistant genes in gram negative bacilli among different samples in Dhaka medical college hospital. Total 300 samples (wound swab, urine, endotracheal aspirate, blood and sputum) were collected from 2015 to 2016. 204 gram negative bacilli were isolated and tested for resistance to colistin by disc diffusion method. Then, the prevalence of colistin resistant genes (pmrA, pmrB, pmrC, mgrB, phoP, phoQ, lpxA, lpxC, lpxD, mcr-1) was detected by polymerase chain reaction method (PCR). Among 204 gram negative bacilli, 22 (10.78%) colistin resistance was identified. PCR analysis revealed that 50% of these isolates contained pmrA gene, followed by phoP gene (27.27%). The prevalence of pmrB, phoQ, mgrB, lpxC and lpxD were 22.72%, 13.63%, 13.63%, 13.63%, 13.63%, and 13.63% respectively among the isolates. Colistin resistance is widespread among gram negative bacilli isolated from human infections. Colistin resistance (10.78%) found in the study is quite alarming. A restricted and rational use of the colistin is the need of hour.