Epidemiology of carbapenem-resistant Enterobacteriaceae (CRE) and comparison of the phenotypic versus genotypic screening tests for the detection of carbapenemases at a tertiary level, academic hospital in Johannesburg, South Africa

Abstract

Background: Carbapenem-resistant Enterobacteriaceae (CRE) cause significant infections and pose a threat to the viability of available antibiotics. Understanding the epidemiology of these infections will assist in guiding appropriate treatment and infection prevention and control (IPC) practices in an institution. In addition, the phenotypic carbapenemase-producing Enterobacteriaceae (CPE) screening tests are widely used in South Africa. However, there is no published literature on their performance against PCR in that setting. Therefore, CRE epidemiology and performance of the Modified Hodge with Imipenem and Imipenem + EDTA combined disk tests (CDT) was evaluated at a tertiary academic hospital in Johannesburg.
Method: A retrospective collection of data was performed. Data from January 2015 to December 2016 of all clinical isolates that were CRE OR carbapenem-susceptible Enterobacteriaceae with at least one positive CPE screening test were collected. Information collected included the ward areas from which samples were sent, specimen type that cultured CRE, CRE identification and carbapenem MIC results, phenotypic and genotypic CPE results.
Results: Certain ward areas recurred as predominant areas with CRE infection in the two-year period. The prominent sample types that cultured CRE, the predominant Enterobacteriaceae species and carbapenemases identified corresponded with national surveillance data. The predominant carbapenemase type and level of carbapenem resistance conferred changed within one year. The Hodge test performed poorly for carbapenemase detection. The CDT detected metallo-β-lactamases adequately.
Conclusion: In this study, the use of the MHT to screen for CPEs performed poorly. Continued surveillance will (i) lead to an understanding of the patient population (including infection type) affected, (ii) detect changes in the carbapenemase profiles, and (iii) inform infection prevention and control and appropriate clinical management.