Emergence of blaCTX-M-15 Gene and Its Transferability in Enterobacter spp. Isolated From the Hospitals of Tehran, Iran

Enterobacter spp. is increasingly recognized as an important nosocomial pathogen and implicated in many episodes of hospital acquired infections. The current study aimed to describe distribution and transferability of blaCTX-M-15 gene, and the antibiotic susceptibility pattern in the clinical isolates of Enterobacter spp. A total of 110 Enterobacter isolates were collected from five hospitals in Tehran, Iran from May 2012 to April 2013. Enterobacter species were identified by API 20E system. Antibacterial susceptibility was determined by disk diffusion method, and extended spectrum beta lactamase (ESBL) production was confirmed by combined disk method. The blaCTX-M-15 gene was identified by PCR with specific primers. The transferability of the blaCTX-M-15was tested by conjugation with broth matting method. The prevalence of Enterobacter species was E. cloacae (78.2 %), E. aerogenes (6.13 %) and E. sakazakii (8.2%). They were from different clinical sources. Maximal resistance in Enterobacter isolates was noticed against Augmentin®, trimethoprim - sulfamethoxazole and cefoxitin 75.5%, 64.5%, and 59.1%, respectively. Fourteen isolates, showed ESBL phenotype. The blaCTX-M-15 gene frequency in Enterobacter isolates was 11.8%. Three conjugative plasmids containing blaCTX-M-15 were found in one Enterobacter isolate. It was the first report on the blaCTX-M-15 gene emergence in clinical Enterobacter spp. in Iran. The current study demonstrated the predominant presence of the gene encoding CTX-M-15 among ESBL producing Enterobacter spp. commonly with a large plasmid, in the setting