Genotypic and phenotypic assessment of AmpC beta-lactamase in Klebsiella pneumoniae isolates from educational hospitals in Qazvin

Introduction and Objectives: Advent of resistance to beta lactam antibiotics in Gram negative pathogens, especially Escherichia coli and Klebsiella pneumonia, frequently results from the production of β-lactamase enzymes. In the Enterobacteriaceae, AmpC enzymes are encoded by either chromosomal or plasmid-mediated genes. Majority of the plasmid-mediated AmpC β-lactamases can be found in klebsiella and E. coli. K. pneumonia is mostly plasmid mediated AmpC β-lactamase (PABls) producer. Since PABls represent a new threat of spread to other organisms within a hospital or geographic region, the aim of the study was to evaluate the occurrence of PMABLs in clinical isolates of K. pneumonia. Materials and Methods: A total of 183 Klebsiella pneumonia isolates were recovered from urine culture of patients admitted in four major educational hospitals of Qazvin city, between 2017-2019. Screening for AmpC β-lactamase production was done using cefoxitin disks. Confirmatory phenotypic identifications were done for the Cefoxitin-resistant isolates using Boronic Acid for combined and AmpC induction tests using azteronam, amoxicillin- clavulanic acid and ceftazidime disks. PCR was used as the genotypic confirmatory test using DHA, CIT, MOX, FOX, EBC and ACC primers. Results: The AmpC-producing isolates among all identified K. pneumonia were 18% (32/183) as detected by cefoxitin screening method. Among AmpC-producing isolates, 9% (3/33) were positive for AmpC by combined disc method (Cefoxitin and Boronic Acid) and induction test. Eighteen percent (6/33) and 12% (4/33) of AmpC-producing isolates were positive for presence CIT and DHA Plasmid-mediated AmpC genes, respectively. Other PABL genes including ACC, EBC, MOX and FOX were not found among AmpC-producing isolates. Conclusion: Accurate and fast identification of AmpC beta-lactamases using combined disc method (Cefoxitin and Boronic Acid) and induction test in the routine diagnostic microbiology laboratories can help reduce the burden of these pathogens.

Keywords:

AmpC beta-lactamases , Klebsiella pneumoniae , Qazvin