Ciprofloxacin-resistant and CTX-M-15-producing Escherichia coli from extra-intestinal infections in Italy

Abstract number: P1196

Cerquetti M., Giufrè M., Garcìa-Fernández A., Accogli M., Fortini D., Luzzi I., Carattoli A.

Objectives: The increasing resistance to fluoroquinolone in Escherichia coli is a major problem worldwide and the association with extended spectrum b-lactamase (ESBL) is of particular concern. This study investigated the molecular basis of resistance and phylogenetic relationship among ciprofloxacin-resistant E. coli strains isolated from human extra-intestinal infections occurring in hospital and community in Rome, Italy.

Methods: 64 ciprofloxacin-resistant strains isolated from urinary or bloodstream infections were examined for several gene markers including plasmid-mediated quinolone resistance genes (qnrA, qnrB, qnrS, and aac(6')-Ib) and b-lactamase-encoding genes (blaCTX-M, blaSHV, blaTEM and blaOXA) by PCR and sequencing. Eighteen strains were positive for at least one of these markers and they were further investigated by analysis of the mutations in the quinolone resistance-determining region (QRDR) of gyrA, gyrB and parC genes, plasmid transferability, PCR-based replicon typing, Southern blot analysis, phylogenetic grouping, PFGE and MLST.

Results: 15/64 ciprofloxacin-resistant strains (23%) were found to be ESBL producers, and all except one were positive to the blaCTX-M15 gene, the remaining isolate harboured blaSHV-12. Most of the CTX-M15-producers also carried the blaOXA (85%), the aac(6')-Ib-cr (78.6%) and belong to the ST131 type (71%). The blaCTX-M15 gene was located on plasmids of the IncF group, but notably, in one isolate it was integrated within the chromosome. ST131 appeared strictly associated with the following amino acid substitutions in the topoisomerase genes: Ser83Leu and Asp87Asn in gyrA; Ser80Ile and Glu84Val in parC. The remaining blaCTX-M15-positive strains all carried IncF plasmids but they belonged to the ST12, ST167, ST410 and ST405, demonstrating later transfer of this gene among different E. coli types. One ST131 isolate was positive for the blaSHV-12 gene. Two of 64 strains (3.1%), ESBL-negative, possessed both qnrB1 and aac(6')-Ib-cr genes located on an IncHI2 plasmid and belonged to ST648.

Conclusion: The epidemic E. coli clone ST131 carrying the IncF-plasmid mediated blaCTX-M15 gene is prevalent among our isolates collected from urinary and bloodstream infections occurring in both hospitals and community. This clone combines high ciprofloxacin-resistance (MICgeqslant R: gt-or-equal, slanted32 mcg/ml) and ESBL production and is of particular concern for the treatment of human extra-intestinal infections.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
Back to top