Characterization of fluoroquinolone-resistant Escherichia coli causing septicemic colibacillosis in calves in Italy: emergence of a multiresistant O78 clonal group.
An increased incidence of enrofloxacin-resistant Escherichia coli associated with septicemic colibacillosis in calves was observed recently in northern Italy. The aim of this study was to investigate this phenomenon. A total of 47 consecutive E. coli isolates exhibiting reduced susceptibility to enrofloxacin (intermediately resistant or resistant) causing septicemic colibacillosis in calves from 45 large-scale farms during 2006-2008, were studied. Phylogenetic group, antimicrobial agents susceptibility, and O serogroup were determined with randomly amplified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) typing, providing additional discrimination. All of the microorganisms carried resistance to two or more additional drugs, with the pattern fluoroquinolone-ampicillin-co-trimoxazole-tetracycline-gentamicin-thiamphenicol being the most represented (18/47; 38.3%). Plasmid-mediated extended-spectrum and AmpC β-lactamases and plasmid-mediated fluoroquinolone resistance genetic determinants were not detected. Third-generation cephalosporins emerged as the most active antimicrobial agents tested (97.9% of susceptible strains). Overall, 37 different RAPD profiles and 18 different O serogroups could be distinguished among the typeable strains, indicating a substantial heterogeneity and suggesting the occurrence of several independent selection events. However, approximately one-fourth (11/47) of the strains belonged to serogroup O78, and PFGE revealed that the great majority (7/11) of these were clonally related, indicating the selection of a O78 clonal group. This is the first report investigating the molecular epidemiology of fluoroquinolone-resistant E. coli in calves and describing the emergence of a fluoroquinolone-resistant E. coli clonal group in these animals.
Microbiology Section (DISC), University of Genoa, Genoa, Italy. anna.marchese@unige.it
Anna
A
Marchese
Erika
E
Coppo
Ramona
R
Barbieri
Simona
S
Zoppi
Carla
C
Pruzzo
Francesca
F
Rossi
Stefania
S
Bergagna
Alessandro
A
Dondo
Eugenio
E
Debbia
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D000077422:Enrofloxacin; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D024841:Fluoroquinolones / Q000494:pharmacology*; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D010802:Phylogeny; D019105:Random Amplified Polymorphic DNA Technique; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones; D000077422:Enrofloxacin; C048795:AmpC beta-lactamases; D001618:beta-Lactamases