Phenotypic and genotypic characterization of extended-spectrum β-lactamases producing Escherichia coli and Klebsiella pneumoniae in a tertiary care hospital in Riyadh, Saudi Arabia

Abstract

BACKGROUND AND OBJECTIVES: Extended-spectrum beta-lactamase (ESBL)-producing pathogens remain a public health concern, with limited data on the molecular characterization of isolates. We aimed to determine the molecular characterization of ESBL-producers circulating in our setting and correlate the molecular types with the minimal inhibitory concentration (MIC) to third-generation cephalosporins. DESIGN AND SETTING: Retrospective study conducted during the period from January to June 2013 at King Khalid University hospital, a tertiary-care hospital in Riyadh, Saudi Arabia. MATERIALS AND METHODS: All Escherichia coli and Klebsiella pneumoniae confirmed to be ESBL producers were included. The MICs of ceftriaxone and ceftazidime were determined by the E-test. Molecular characterization of ESBL-genes was performed using the Check-MDR-CT102 DNA microarray. RESULT: Of 77 isolates comprising 50 (65%) E coli and 27 (35%) K pneumoniae, the majority (n=63; 81%) were from urine. Most isolates were blaCTX-M gene positive (n=72/77; 93.5%) comprising blaCTX-M1 (n=62), blaCTX-M9 (n=9) and blaCTX-M25 (n=1). Two or more ESBL genes were present in 45% of isolates with blaSHV predominating in K pneumoniae and blaTEM in E coli. Two isolates were positive for blaOXA-48 carried in combination with blaCTX-M9 and blaTEM in E coli and blaCTX-M1/CTX-M9 in K pneumoniae. Ceftriaxone MIC50 and MIC90 of ≥256 μg/mL were seen in E coli and K pneumoniae harboring blaCTX-M alone or in combination with blaSHV or blaTEM. For ceftazidime the highest MIC50 and MIC90 was seen in K pneumoniae harboring blaCTX-M+blaSHV and E coli with blaCTX-M+blaTEM combinations. CONCLUSION: A preponderance of blaCTX-M suggests dissemination of the gene in our setting. The MIC for ceftriaxone and ceftazidime correlate well with molecular characterization of ESBL-producing Enterobacteriaceae.