Characterization of CTX-M ESBLs in Enterobacter cloacae, Escherichia coli and Klebsiella pneumoniae clinical isolates from Cairo, Egypt

Background: A high rate of resistance to 3rd generation cephalosporins among Enterobacteriaceae isolates from Egypt has been previously reported. This study aims to characterize the resistance mechanism (s) to extended spectrum cephalosporins among resistant clinical isolates at a medical institute in Cairo, Egypt. Methods: Nonconsecutive Klebsiella pneumoniae (Kp), Enterobacter cloacae (ENT) and Escherichia coli (EC) isolates were obtained from the clinical laboratory at the medical institute. Antibiotic susceptibility was tested by CLSI disk diffusion and ESBL confirmatory tests. MICs were determined using broth microdilution. Isoelectric focusing (IEF) was used to determine the pI values, inhibitor profiles, and cefotaxime (CTX) hydrolysis by the β-lactamases. PCR and sequencing were performed using bla_CTX-M and ISEcp1-specific primers, with DNA obtained from the clinical isolates. Conjugation experiments were done to determine the mobility of bla_CTX-M. Results: All five clinical isolates were resistant to CTX, and were positive for ESBL screening. IEF revealed multiple β-lactamases produced by each isolate, including a β-lactamase with a pI of 8.0 in Kp and ENT and a β-lactamase with a pI of 9.0 in EC. Both β-lactamases were inhibited by clavulanic acid and hydrolyzed CTX. PCR and sequence analysis identified bla_CTX-M-14. in Kp and ENT and a bla_CTX-M-15 in EC. Both bla_CTX-M-14 and bla_CTX-M-15 were preceded by ISEcp1 elements as revealed by partial sequence analysis of the upstream region of the bla_CTX-M genes. bla_CTX-M-15 was transferable but not bla_CTX-M-14. Conclusion: This is the first report of CTX-M-14 in Kp and ENT isolates from Egypt, the Middle East and North Africa.