Purpose: Enterobacteriaceae encoding plasmid-mediated AmpC (pAmpC) β-lactamases confer resistance to the third generation cephalosporins. pAmpC association with extended spectrum β-lactamases (ESBLs), plasmid-mediated quinolone resistance (PMQR) and aminoglycoside modifying enzymes (AMEs) is well documented. There are limited data regarding the epidemiology and clinical significance of pAmpC in Saudi Arabia. This study aimed to determine the prevalence of pAmpC and its coexistence with ESBLs, PMQR and AMEs in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis isolates in Saudi hospitals from January to December 2015.
Methodology: The VITEK 2 system was used for organism identification and susceptibility testing. PCR and sequencing were used to detect pAmpC, ESBL, AME and PMQR genes.
Results: Out of 3625 isolates of E. coli, K. pneumoniae and P. mirabilis, 200 cefoxitin-resistant isolates were identified, making the prevalence of cefoxitin resistance 5.5 % (200/3625). CMY-2 and DHA were detected in 24 and 12 isolates, respectively. The prevalence of pAmpC was 1 % (36/3625). In several isolates, pAmpC β-lactamases were associated with PMQR genes including aac(6')-Ib-cr and qnrB and/or with AMEs including aacA4, aacC2, aadA1, aphA6, armA and rmtB genes. No ESBLs were detected in pAmpC β-lactamase-harbouring isolates.
Conclusions: To our knowledge, this is the first study determining the prevalence of pAmpC β-lactamases and their association with PMQR and/or AME genes in Saudi Arabia and the Gulf States. CMY-2 is the most prevalent pAmpC β-lactamase in this study. These data emphasize the importance of surveillance studies and implementation of antimicrobial stewardship programmes to reduce infections caused by such resistant organisms.