Characterization of inducible stx2-positive Escherichia coli O157:H7/H7- strains isolated from cattle in France.
OBJECTIVE
To quantify the variability of the Shiga toxin 2 (Stx2) production by a panel of stx2-positive Escherichia coli O157:H7/H7- isolates from healthy cattle before and after induction with enrofloxacin.


RESULTS
ProSpecT ELISA was used to quantify the Stx2 production by stx2-positive E. coli O157:H7/H7- isolates in native conditions (basal level) or after induction with enrofloxacin. Whereas only 15.2% of the E. coli O157:H7/H7- strains studied displayed significant amounts of detectable Stx2 without induction, most of them were shown to be inducible, and at various levels, in presence of subinhibitory concentrations of enrofloxacin.


CONCLUSIONS
We demonstrated the capability of a highly elevated proportion of stx2-positive, but constitutively Stx2-negative, E. coli O157:H7/H7- isolates from healthy cattle to produce significant levels of Shiga toxin Stx2 in presence of subtherapeutic concentrations of enrofloxacin, an antibiotic of the fluoroquinolones family only licensed for veterinary use.


CONCLUSIONS
This study documents the risk that bovine-associated Shiga toxin producing E. coli isolates may become more frequently pathogenic to humans as a side-effect of the increasing use of veterinary fluoroquinolones in the oral treatment of food animals like cattle or poultry.
Maurer
C
C
Agence Française de Sécurité Sanitaire des Aliments (AFSSA), Unité Bactériologie Bovine et Hygiène des Viandes, Lyon, France.
Lazizzera
C
C
Madec
J-Y
JY
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D016521:Electrophoresis, Gel, Pulsed-Field; D000077422:Enrofloxacin; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D024841:Fluoroquinolones / Q000627:therapeutic use*; D005516:Food Microbiology; D005602:France; D008826:Microbial Sensitivity Tests; D022641:Shiga Toxin 2 / Q000032:analysis / Q000096:biosynthesis; D013045:Species Specificity; D013053:Spectrophotometry
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D022641:Shiga Toxin 2; D000077422:Enrofloxacin