Extended-Spectrum Beta-Lactamases in Cystic Fibrosis Isolates of Klebsiella pneumoniae

The emergence and spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae are recognized as a major clinical problem and a public health challenge. Enterobacteria are transient colonizers of lungs affected by cystic fibrosis (CF). Klebsiella pneumoniae has been shown to cause chronic obstructive pulmonary infections.
We aimed to determine the antibiotic resistance profile and ESBL production in K. pneumoniae isolates from Iranian patients with CF.
Sixteen K. pneumoniae strains were isolated from the sputum samples of 98 pediatric CF patients at Mofid children’s hospital in Tehran, Iran. Antibiotic susceptibility was determined via disc diffusion, and ESBL phenotype was detected by double disc synergy test (DDST). β-lactamase genes, including TEM, SHV, CTX-M, and OXA genes, were detected using polymerase chain reaction (PCR) and confirmed by sequencing the PCR products. Finally, genetic fingerprints of the isolates were determined via random amplified polymorphic DNA (RAPD)-PCR method.
Ten isolates had ESBL phenotypes, all of which contained non-ESBL blaTEM-1 genes. Seven isolates harbored blaCTX-M-15 genes (ESBL genes), five of which also showed non-ESBL blaSHV-11, blaTEM-1, and blaOXA-1 genes (1 isolate with blaTEM-1 and 1 isolate with blaTEM-1 plus blaOXA-1 gene). However, PER-1 and VEB-1 β-lactamase genes were not detected. Genetic fingerprinting profiles showed heterogeneity among K. pneumoniae isolates.
This study highlights not only the presence of multiple β-lactamases, but also the carriage of ESBL blaCTX-M-15 gene among K. pneumoniae isolates from CF patients.