Prevalence of fosfomycin resistance genes and antimicrobial susceptibility of clinical urinary extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates

ISSN The antimicrobial susceptibility testing of 284 Enterobacteriaceae isolates responsible for urinary tract infections to ampicillin, ceftazidime, ciprofloxacin, nitrofurantoin, trimethoprin-sulfamethaxole, and fosfomycin was performed by disk diffusion method. Additionally, in fosfomycin-resistant and intermediate susceptible isolates using disk diffusion method, the minimum inhibitory concentration (MIC) of fosfomycin was determined by agar dilution. The presence of fosA and fosA3 genes and ESBL genes was investigated in fosfomycin-resistant isolates and ESBL-producing isolates, respectively. Klebsiella pneumoniae [72.34% (34/47)], and Escherichia coli [58.23% (138/237)] were identified as ESBL-producers by phenotype. These isolates were positive for the presence of blaTEM, blaSHV, blaCTX-M genes in 56.97% (n1⁄498), 55.23% (n1⁄495), and 78.48% (n1⁄4135), respectively. Resistance to fosfomycin was detected in 9.4% (13/138) and 5.9% (2/34) of the ESBL-E. coli and ESBL-K. pneumoniae isolates. In fosfomycin-resistant isolates, the presence of the fosA gene was detected in two ESBL-E. coli isolates; the fosA3 gene in one non-ESBL E. coli isolate; and the fosA3 gene co-harboured with blaCTX-M in six ESBL-E. coli (n1⁄45) and one K. pneumoniae isolates. A high prevalence of ESBL-producing Enterobacteriaceae (72.6%) was detected in urine samples. Fosfomycin showed the highest susceptibility rate ( 87%) of antimicrobials tested in ESBL-producing E. coli and K. pneumoniae isolates. Copyright 2019 Wolters Kluwer Health, Inc. All rights reserved.