Molecular Epidemiology of Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Strains Isolated from Children with Urinary Tract Infections

Uropathogenic Escherichia coli (UPEC) and Klebsiella pneumoniae (K. pneumoniae) are major pathogens which cause urinary tract infections (UTI) in pediatric patients. The presence of extended-spectrum β-lactamases (ESBLs) in these pathogens may further exacerbate infections and hamper successful treatment.
We undertook a study to investigate the prevalence of ESBL genetic indicators among K. pneumoniae strains isolated from pediatric patients in Tehran, Iran. Moreover, genotyping of blaCTX-M-15-positive isolates was determined through repetitive extragenic palindromic sequence polymerase chain reactions (REP-PCR).
A total of 76 non-duplicate K. pneumoniae isolates were collected from outpatients admitted with UTIs at the pediatric nephrology wards of two hospitals in Tehran, Iran. The antibacterial susceptibility of K. pneumoniae isolates was determined by the disk diffusion method. The isolates were examined phenotypically and genotypically for ESBL production using the combined-disk method and PCR, respectively. The blaCTX-M-positive isolates were subjected to minimal inhibitory concentration (MIC) testing for ceftazidime and cefotaxime. The clonal relationships of blaCTX-M-15-positive isolates were determined through REP-PCR.
The highest rates of antibiotic resistance were obtained for ampicillin (92.1%), followed by ceftazidime (40.8%), cefotaxime (40.8%), and aztreonam (39.5%). However, only one isolate (1.3%) was resistant to imipenem. Among the ESBL-positive isolates, blaCTX-M(64.5%) was the most prevalent gene, followed by blaSHV (54.8%) and blaTEM (41.9%). Of 20 blaCTX-M-carrying isolates, 14 isolates showed MICs of 256 μg/mL against cefotaxime. The other six isolates had MICs of 512 μg/mL. However, 16 out of 20 blaCTX-M-carrying isolates exhibited MICs of 128 μg/mL against ceftazidime. The other four K. pneumoniae isolates showed MICs of 256 μg/mL. Of 17 blaCTX-M-15-positive K. pneumoniae isolates, 16 distinct REP-PCR patterns (genotypes) were obtained..
The frequency of blaCTX-Mamong K. pneumoniae isolates was at an alarming rate, indicating that more efforts should be undertaken to track and monitor the spread of K. pneumoniae that produce CTX-M β-lactamases.