Phenotypic determination of carbapenemase producing enterobacteriaceae isolates from clinical specimens at a tertiary hospital in Lagos, Nigeria

Niger Postgrad Med J. Oct-Dec 2015;22(4):223-7. doi: 10.4103/1117-1936.173973.


Aims and objectives: Carbapenemase production among clinical isolates of Enterobacteriaceae has been widely reported with prevalence rates ranging from between 2.8% and 53.6%. The aim of this study was to assess the prevalence of carbapenemase production among clinical isolates of Enterobacteriaceae from a Tertiary Hospital in Lagos, Nigeria, and to characterize the type of carbapenemase produced.

Materials and methods: Carbapenemase production was detected phenotypically using a commercially available combination disc test (Rosco Diagnostica carbapenemase detection Neo-Sensitab) containing inhibitors to the various carbapenemase classes. The Neo-Sensitabs were used for Enterobacteriaceae isolates that were resistant after the initial antibiotic susceptibility testing with meropenem (10 μg).

Results: A total of 177 Enterobacteriaceae isolates were investigated and 27 (15.2%) were carbapenem-resistant. From the 27 carbapenem non-susceptible isolates, 22 (12.4%) were carbapenemase producers while 5 (2.8%) exhibited carbapenem resistance due to extended spectrum beta-lactamase production. Of the 22 isolates that were positive for carbapenemase production, 15 (8.5%) were metallo beta-lactamase (MBL) producers, 6 (3.4%) produced oxacillinase-48 while 1 (0.5%) produced both MBL and Klebsiella pneumoniae carbapenemase. Hence, the overall prevalence of carbapenemase-producing Enterobacteriaceae in this study was 12.4%.

Conclusion: Carbapenemase-producing Enterobacteriaceae was indeed prevalent in our institution. The combination disc test was a cost effective and suitable method for the initial detection of carbapenemase-producing Enterobacteriaceae within the clinical setting especially when molecular detection methods are not available.