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.
Highlights
Infections due to carbapenem-resistant Enterobacteriaceae (CRE) are a growing concern both locally and internationally and pose a major threat to currently available antibiotics.[1,2] In addition, these infections have been associated with increased patient morbidity and mortality.[2,3]Prevention and control of these infections require proper antibiotic stewardship practices, timeous identification and implementation of effective infection prevention and control (IPC) interventions.[4]
Low-level resistance is defined as carbapenem MIC results that were in the susceptible range with a positive carbapenemase-producing Enterobacteriaceae (CPE) phenotypic screening test (i.e. Modified Hodge test (MHT) ± imipenem and imipenem + EDTA combined disk tests (CDT)) or carbapenem MIC results in the ‘susceptible to intermediate’ categories, with at least one carbapenem agent in the ‘intermediate’ category and without any carbapenem agent in the ‘resistant’ category according to the Clinical and Laboratory Standards Institute (CLSI) guidelines document,[10] regardless of the CPE phenotypic screening test results
In 2016, low-level resistance in the New Delhi metallo-βlactamase (NDM) isolates increased by 28% in comparison with 2015: low-level resistance was 40% (10/25) and high-level resistance decreased to 60% (15/ 25); in isolates with OXA-48 and variants, low-level resistance increased by 20% to 66% (47/71) and high-level resistance decreased to 33% (24/71)
Summary
Infections due to carbapenem-resistant Enterobacteriaceae (CRE) are a growing concern both locally and internationally and pose a major threat to currently available antibiotics.[1,2] In addition, these infections have been associated with increased patient morbidity and mortality.[2,3]Prevention and control of these infections require proper antibiotic stewardship practices, timeous identification and implementation of effective infection prevention and control (IPC) interventions.[4]. 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. 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. 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
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