Detection of plasmid-mediated AmpC β-lactamases in Klebsiella pneumoniae clinical isolates from Bushehr province, Iran

Khatereh Faghihi; Saeed Tajbakhsh; Moradali Fouladvand; Behrouz Latifi; Forough Yousefi

doi:10.18502/ijm.v15i3.12897

Khatereh Faghihi Department of Microbiology and Parasitology, School of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
Saeed Tajbakhsh Department of Microbiology and Parasitology, School of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
Moradali Fouladvand Department of Microbiology and Parasitology, School of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
Behrouz Latifi Department of Microbiology and Parasitology, School of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran
Forough Yousefi Department of Microbiology and Parasitology, School of Medicine, Bushehr University of Medical Sciences, Bushehr, Iran

DOI: https://doi.org/10.18502/ijm.v15i3.12897

Keywords: AmpC; Beta-lactamase; Modified three dimensional test; Klebsiella pneumoniae

Abstract

Background and Objectives: Plasmid-mediated AmpC producers are considered an increasing concern. The aim of this study was to investigate the prevalence of plasmid-mediated AmpC β-lactamases (pAmpCs) in Klebsiella pneumoniae iso- lates.

Materials and Methods: A total of 228 clinical isolates of K. pneumoniae were collected in Bushehr province, Iran, from December 2017 to February 2019. Cefoxitin disks were applied for screening AmpC-producing isolates. Furthermore, 3 phe- notypic confirmatory tests including combine disk test (CDT), double disk synergy test (DDST) and modified three dimen- sional test (M3DT) were used. Finally, the presence of pAmpC genes was tested by multiplex PCR.

Results: We identified 18 pAmpC-KP isolates among the 228 isolates (7.9%): 12 DHA (66.6%) and 6 CMY (33.3%). In the present study only 47% of cefoxitin-resistant isolates were pAmpC producers. The sensitivity of CDT, DDST, and M3DT was 89%, 67% and 100% and the specificity was 90%, 90% and 85%, respectively. In addition, M3DT displayed a higher rate of efficiency (92%) than CDT (89%) and DDST (79%) in detecting plasmid-meditated AmpC producers.

Conclusion: DHA was the most prevalent pAmpC beta-lactamase in this study. DDST and CDT tests proved inefficient to detect two and six pAmpC producers, respectively, while M3DT represented the best overall performance.