Fluoroquinolones (FQs) are the drugs of choice for prophylaxis of bacterial infections in immunocompromised cancer patients. This study aimed to investigate FQ resistance and the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in 239 Gram-negative isolates collected at a tertiary care cancer hospital in Cairo, Egypt. Disc diffusion and broth microdilution tests showed that 70.7% of the isolates were nonsusceptible to ciprofloxacin (MIC50 = 64 μg/ml). Polymerase chain reaction (PCR) revealed that 53.6% of the isolates carried at least one PMQR determinant, of which 23.4% were susceptible to ciprofloxacin. The most prevalent gene, aac(6')-Ib-cr, was identified in 36.8% of the isolates, while qnr genes were harbored by 31.0% (qnrS, 24.3%; qnrB, 7.1%, and qnrA, 0.4%). The oqxAB genes were only detected in Klebsiella sp. isolates (92.5%). PMQR determinants were more likely detectable among isolates recovered from pediatric patients than adults (59.3% vs. 43.8%) and were significantly associated with ceftriaxone and gentamicin resistance. A combined genetic analysis using random amplified polymorphic DNA-PCR and enterobacterial repetitive intergenic consensus-PCR showed that most of the qnr-positive isolates were not clonal. Findings of the current study raised concerns about the efficacy of prophylactic use of FQs in cancer patients in our region. It also demonstrates the possible role of PMQR-positive ciprofloxacin-susceptible isolates in the dissemination of resistance to other antimicrobial agents and the urgent need to reconsider the existing FQ breakpoints defined by the Clinical and Laboratory Standards Institute.
Keywords: Egypt; Gram negative; PMQR; cancer patients; fluoroquinolones.