Phenotypic and molecular characterization of extended-spectrum β-lactamases and AmpC β-lactamases in Klebsiella pneumoniae.

The incidence of resistance to extended-spectrum cephalosporins (ESC) among Egyptian isolates of Klebsiella pneumoniae has already been increasing and previously reported. This work devotes to investigate the genetic basis of resistance to ESC in K. pneumoniae isolates. Disc diffusion test, minimum inhibitory concentrations (MIC) determination and phenotypic screening for extended spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases (PABLs) were carried out for 21 K. pneumoniae isolates, collected during 2011 at Sayed Galal Hospital, Cairo. Genes for ESBLs, PABLs and class 1 integrase were sought by PCR and DNA sequencing. Matting out assay was performed to determine the mobility of bla genes. Six (28.57%) of 21 clinical isolates K. pneumoniae were non-sensitive to ESC. ESBL and PABL phenotypes were identified in 5 and one K. pneumoniae isolates, respectively. PABL-producing isolate was found to carry blaCMY-2 and blaSHV-1. All five ESBL-producing isolates carried blaCTX-M-15. CTX-M-15 was associated with SHV-1 and SHV-12 in three isolates and two isolates respectively.TEM-1 was associated with CTX-M-15 and SHV in two isolates. Both CTX-M-15 and CMY-2 genes were located on conjugative plasmids and associated with class 1 integrase. Resistance to ESC was due to CTX-M-15, SHV-12 and CMY-2 in K. pneumoniae. This study represents the first report of CMY-2 and SHV-12 β-lactamase-producing K. pneumoniae isolates in Egypt.