Identification and Characterization of Conjugative Plasmids That Encode Ciprofloxacin Resistance in Salmonella.

This study aimed to characterize novel conjugative plasmids that encode transferable ciprofloxacin resistance in In this study, 157 nonduplicated isolates were recovered from food products, of which 55 were found to be resistant to ciprofloxacin. Interestingly, 37 of the 55 Cip isolates (67%) did not harbor any mutations in the quinolone resistance-determining regions (QRDR). Six isolates were shown to carry two novel types of conjugative plasmids that could transfer the ciprofloxacin resistance phenotype to J53 (azithromycin resistant [Azi]). The first type of conjugative plasmid belonged to the ∼110-kb IncFIB-type conjugative plasmids carrying -bearing and -bearing mobile elements. Transfer of the plasmid between and could confer a ciprofloxacin MIC of 1 to 2 μg/ml. The second type of conjugative plasmid belonged to ∼240-kb IncH1/IncF plasmids carrying a single PMQR gene, Importantly, this type of conjugative ciprofloxacin resistance plasmid could be detected in clinical isolates. The dissemination of these conjugative plasmids that confer ciprofloxacin resistance poses serious challenges to public health and infection control.