Prevalence of carbapenem resistance among enterobacteriaceae isolated from patients in Mulago Hospital and complex from 2011 to 2014

Abstract

Background: Carbapenemases have increasingly been reported in Enterobacteriaceae worldwide.Chromosomal and plasmid mediated resistance in Enterobateriaceae, renders them the most variable of all bacteria in susceptibility to antimicrobial agents. Most of carbapenemases are plasmid encoded hence this allows them to easily spread from onebateria to another. Carbapenem-resistant Enterobacteriaceae cause a high mortality as they kill up to 50% of patients who acquire bloodstream infections from them and yet their prevalence in Uganda is not known. This study determined the prevalence of carbapenemases and carbapenemase encoding genes among clinical isolates.

Methods: This was a cross-sectional study with a total of 196 clinical isolatesobtained from department of medical microbiology clinical laboratory, Makerere University. The isolates included;41.8%E.coli, 39.8% K. pneumoniae, 5.6% Enterobacterspp, 4.1% Citrobacterfreundii, 3.1% Proteus mirabilis, 2.0% Klebsiellaoxytoca, 1.5% Proteus vulgaris, 1.0% Serratiamarcescens, Pantoeaagglomerans and Salmonella spp 0.5%each.These organisms were isolated frompus swabs, urine, blood, sputum, tracheal aspirates, cervical swabs, endomentrial aspirates, rectal swabs, Vaginal swabs, ear swabs, products of conception, wound biopsy and amniotic fluid. AllIsolates were subjected to phenotypic carbapenemasescreening using Boronic acid-based inhibition, Modified Hodgeand EDTA double disk test. In addition, all the isolates were subjected to PCR assay to confirm presence of carbapenemase encoding genes.

Results; This study found carbapenemase prevalence of 22.4% of the 196 clinical isolates using phenotypic tests. The genotypic prevalence was slightly higher at 28.6% of which 7.5% carried NDM-1, 31.3% VIM-2, 17.9% IMP-2, 14.9% KPC and 28.4% OXA-48. Among 56 isolates positive for carbapenemase encoding genes, Klebsiellapneumoniaewas the specieswith the highest number of these genes 52.2% and the least wasProteus vulgaris and Salmonella spp at 0.0% each. Most of these resistance genes were in bacteria isolated from pus swabs and no such bacteria were found in wound biopsies.

Conclusion All the five genes studied, that is, NDM-1, VIM, IMP, KPC and OXA-48 were detected in the study isolates. Isolates resistant to two third generation cephalosporins should always be subjected to carbapenemase activity test as there is a high chance of resistance to carbapenems.