detection of plasmid-mediated ampc β-lactamases in klebsiella pneumoniae clinical isolates from bushehr province, iran

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.