Evaluation of Chromogenic Medium chromID OXA-48 for Detection of OXA-48 Producing Enterobacteriaceae

Abstract

Background: In the last years there has been an increased incidence of carbapenemase-producing Enterobacteriaceae which has become a major public health concern. One of the major concerns for controlling the spread of OXA-48- producers is the absence of reliable phenotypical tests that might contribute to their easy recognition. Objectives: This study aimed to determine the presence of OXA-48 carbapenemases among a group of carbapenem resistant Enterobacteriaceae (CRE) isolates and to assess the performance of chromID OXA-48 medium for rapid detection of OXA-48 producing Enterobacteriaceae in comparison with blaOXA-48 gene amplification by PCR. Methodology: Different clinical samples were obtained from 100 patients. They were outpatient clinic attendants and inpatients admitted to the Intensive Care Unit and different wards of Bolak EL-Dakror Hospital over the period from July 2015 to July 2016. Samples were cultured and Enterobacteriaceae isolates were identified. The antimicrobial susceptibility patterns were determined by disc diffusion test and Minimum Inhibitory Concentration of carbapenem resistant isolates was confirmed by E test. Carbapenem-resistant isolates were selected, cultured on chromID OXA-48 (bioMerieux) and subjected to real time PCR for detection of blaOXA-48 gene. Results: Ninety five Enterobacteriaceae isolates were cultured from the different samples. Screening for carbapenem resistance by disc diffusion and E test revealed 28 of the isolates (29.5%) were CRE. All CRE isolates were Klebsiella pneumoniae. Among CRE, 8 isolates (28.6%) were positive for blaOXA-48 gene. On chrom ID OXA-48 medium, 7 isolates gave visible growth of blue colonies. The sensitivity and specificity of chromID OXA-48 medium was 75%, and 95% respectively. C onclusion: OXA-48 carbapenemases pose a rising threat in our country. Early detection of OXA-48-producing Enterobacteriaceae isolates is important to start early administration of appropriate antimicrobial therapy as well as the enforcement of infection control measures. The chromID OXA-48 medium can be used for presumptive identification of OXA-48 carbapenemase producers. The medium is easy to interpret, inexpensive, and has acceptable specificity.