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The aim of the present study was to investigate the mechanism of quinolone and beta-lactam resistance in an isolate of Citrobacter freundii PC2/08 collected from sewage effluent from l'Aquila, Italy. QnrB-9 and bla(TEM-116 )were co-expressed in a large plasmid identified in C. freundi PC2/08 strain. Compared to TEM-1, TEM-116 showed two single mutations: V84I and A184V. The plPC2/08 plasmid conferred resistance to several beta-lactams and fluoroquinolones. Tazobactam could be considered a good inhibitor whereas clavulanic acid was unable to restore susceptibility to amoxicillin. The QnrB-9 element seems to confer the same level of resistance to levofloxacin and ciprofloxacin with minimum inhibitory concentration (MIC) values of 4 mg/l for either. In this study, we confirm the common association of plasmid-mediated quinolone resistance with extended-spectrum beta-lactamase (ESbetaL) production. This is the first finding in Italy of qnrB9 and TEM-116 in a non-clinical or animal strain.

The aim of this study was to assess the possible circulation of genetic resistance determinants and chromosomal point mutations in quinolone-resistant Escherichia coli isolated from livestock from central Italy. Forty-nine E. coli isolates were recovered from animals during the surveillance activities of the Istituto Zooprofilattico Abruzzo e Molise (IZSA&M), Italy, over 2 years. The plasmid resistance determinants and point mutations in DNA gyrase and topoisomerase IV were characterized by PCR and DNA sequencing. Of the 49 E. coli isolates, 34 were resistant to nalidixic acid, 4 to ciprofloxacin and 11 to nalidixic acid, ciprofloxacin and enrofloxacin. Chromosomal point mutations were found in gyrA gene (Ser83Leu and Asp87Asn) and gyrB (Gln434His, Lys444Arg and Gly435Val). We also report the simultaneous presence of qnrS1 quinolone resistance determinant, dfrA1-aadA22 gene cassettes and amino acid substitution Ser83Leu in the gyrA gene in an E. coli strain resistant only to nalidixic acid.

In this work, we report the spread of CTX-M-producing uropathogenic ciprofloxacin-resistant Enterobacteriaceae. This is the first identification in Italy of the simultaneous presence of aac(6')-Ib-cr, qnrB1, and bla(CTX-M-15) resistance determinants in an Escherichia coli strain isolated from urine of a nonhospitalized patient.