Emergence and maintenance of multidrug-resistant Escherichia coli of canine origin harbouring a blaCMY-2-IncI1/ST65 plasmid and topoisomerase mutations.
OBJECTIVE
To characterize the mechanisms implicated in fluoroquinolone (FQ) and expanded-spectrum cephalosporin (ESC) resistance in three clinical and seven faecal multidrug-resistant (MDR; resistant to at least three antimicrobial classes) Escherichia coli isolates from a dog with atopic dermatitis, also suffering from recurrent otitis, that had already been exposed to prolonged antimicrobial treatment and colonized for a long period.


METHODS
MICs of FQs, ESCs and other antimicrobials were determined by the broth microdilution method. Phenotypic tests (efflux pump inhibition and combination disc tests) and isoelectric focusing were combined with genotypic analyses [PCRs, sequencing, conjugation, S1 nuclease PFGE, PCR-based replicon typing, plasmid multilocus sequence typing (pMLST) and PCR mapping] to characterize the molecular basis of FQ and ESC resistance. Isolates were further characterized by MLST and PFGE.


RESULTS
Three otitis and five faecal isolates with enrofloxacin MICs of 32 to >128 mg/L displayed the GyrA:S83L+D87N/ParC:E62K/ParE:G545D pattern harbouring novel ParC and ParE substitutions, whereas the two remaining faecal isolates were susceptible or borderline resistant single-step mutants (GyrA:S83L pattern) and carried qnrS1. Efflux pump overexpression also contributed to FQ resistance and the MDR phenotype. The three otitis and five faecal isolates also exhibited cefoxitin/ceftazidime MICs of 32-64 mg/L and harboured blaCMY-2, adjusted to ISEcp1, on an IncI1/ST65 conjugative plasmid, previously described in Salmonella Heidelberg from poultry. Interestingly, all isolates shared an identical MLST type (ST212), with the otitis isolates showing indistinguishable patterns with the high-level resistant faecal E. coli isolates.


CONCLUSIONS
The long-term maintenance of FQ- and ESC-resistant clones harbouring topoisomerase mutations and a blaCMY-2-IncI1/ST65 plasmid in canine commensal flora after prolonged antimicrobial use may contribute to the dissemination of multidrug resistance.
Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
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Vingopoulou
Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece vickysi@vet.auth.gr.
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Siarkou
Laboratory of Veterinary Pharmacology, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
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Batzias
Companion Animal Clinic, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54627, Greece.
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Kaltsogianni
Department of Clinical Microbiology, Hippokration General University Hospital, Thessaloniki GR-54642, Greece.
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Sianou
Laboratory of Microbiology and Infectious Diseases, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
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Tzavaras
Companion Animal Clinic, School of Veterinary Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki GR-54627, Greece.
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Koutinas
Clinic of Medicine, School of Veterinary Science, Faculty of Health Sciences, University of Thessaly, GR-43100 Karditsa, Greece.
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Saridomichelakis
Department of Clinical Microbiology, Hippokration General University Hospital, Thessaloniki GR-54642, Greece.
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Sofianou
Laboratory of Bacteriology, Hellenic Pasteur Institute, Athens GR-11521, Greece.
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Tzelepi
Laboratory of Bacteriology, Hellenic Pasteur Institute, Athens GR-11521, Greece.
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Miriagou
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D015373:Bacterial Typing Techniques; D002440:Cefoxitin / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D003876:Dermatitis, Atopic / Q000382:microbiology; D004285:Dogs; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy; D005243:Feces / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010031:Otitis / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D024841:Fluoroquinolones; D000077422:Enrofloxacin; D002440:Cefoxitin; D002442:Ceftazidime; C103022:beta-lactamase CMY-2; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase
AmpC; DNA gyrase and topoisomerase IV mutations; IncI1 plasmids; dogs; otitis