AmpC β-lactamases in Urinary Klebsiella pneumoniae Isolates: First Report of ACC Type AmpC β-lactamase Resistance in Iran

Background & Objective: The production of plasmid-mediated AmpC beta-lactamases (PMABLs) among urinary Klebsiella pneumoniae isolates causes a severe problem to the successful treatment of urinary tract infections (UTIs). This study was designed to evaluate antimicrobial resistance, the presence of AmpC beta-lactamase genes, and the genetic relatedness among K. pneumoniae strains separated from patients with UTI. Materials & Methods: In this cross-sectional descriptive study, a total of 100 K. pneumoniae isolates were collected from UTI cases in Milad Hospital, Tehran, Iran. The sensitivity of the isolates to 12 antibiotics was tested using the Kirby-Bauer disk diffusion method. AmpC production was determined using a boronic acid combined-disk test. Polymerase chain reaction (PCR) was carried out to screen all isolates with family-specific PMABL genes. The genetic relatedness of AmpC-producing isolates was determined by an enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR). Results: Over a period of 11 months, PMABLs were detected in 49 isolates (49%) of K. pneumoniae. Resistance to at least three classes of antimicrobials was detected in 30 (61.2%) PMABL producers. Among AmpC producers, 34 isolates harbored only one AmpC gene group, including MOX (n=11), EBC (n=8), ACC (n=7), CIT (n=4), FOX (n=2), and DHA (n=2). Multiple AmpC gene groups were detected in 15 isolates. The ERIC-PCR showed the polyclonal distribution of AmpC-producing isolates. Conclusion: In our study, a high frequency of AmpC-producing K. pneumoniae was observed. This is the first report of ACC type AmpC beta-lactamase in Iran. Strategies to minimize the spread of AmpC beta-lactamase-producing isolates should be implemented.