Colistin resistance among gram negative rods carried in the intestinal tract of patients admitted in the ICU of Mulago National Referral Hospital

Abstract

Background: The limited options for treatment of infections caused by MDR or XDR bacteria prompted the reintroduction of colistin, which coupled with extensive use in food-producing animals is driving increasing resistance to the drug. Recently described plasmid mediated (MCR) resistance has created a new threat due to possibility of horizontal transfer. Screening for colistin resistance and presence of such plasmid mediated resistance mechanism (MCR phenotype) may provide a clue to explore the extent of colistin resistance in Uganda which is largely unknown. Objectives: To determine the intestinal carriage rate, plasmid mediated mechanism and risk factors associated with colistin resistance in Mulago hospital, Kampala. Methodology: In this cross sectional study, we screened over 103 rectal swab specimens obtained from the same number of patients admitted in Mulago hospital ICUs. Bacterial identification, susceptibility to major drug classes, ESBL phenotype detection, Carbapenemase phenotype detection, broth microdilution for MIC colistin, and colistin pre-diffusion and differential inhibition of MCR enzyme by EDTA was done following standard microbiological methods. Data on demographic status and patient risk factors obtained from eligible patients after obtaining informed consent were analyzed. Results: A colistin resistance carriage rate of 16/103(16%) among ICU patients, and 16/78(21%) among recovered Gram negative bacilli, including 8/78(10.5%) Klebsiella pnumoniae and 8/78(10.5%) Escherichia coli were detected. An MDR (ESBL) carriage rate of 49/103(48%) among ICU patients, and 49/78(63%) among recovered isolates, including 9/49(18%) of ESBL producing colistin resistant isolates was detected. The CRE carriage rate of 1/103(1%), and 1/78(1.2%) didn‘t include any colistin resistant isolates. A Carbapenemase carriage rate of 12/103(12%) among ICU patients, 12/78(15%) among recovered isolates, 3/16(18.3%) among colistin resistant isolates was detected. At a P value of <0.05 at 95% CI, all the risk factors were found to be not significantly associated with carriage of colistin resistant isolates on multiple linear regression analysis. Conclusion: Intestinal carriage of colistin resistant K. pneumoniae and E. coli was low at the Mulago hospital ICU, representing an emerging threat, with completely no evidence of plasmid-mediated colistin resistance among the isolates. Hence, currently, MCR mediated resistance poses no threat to patients in Mulago ICU. Regular surveillance on the occurrence of colistin resistance and associated MCR phenotype at ward, unit, and department level within the hospital is essential to anticipate future trends in the prevalence and dissemination of the same.