Pathogénicité potentielle et résistance antimicrobienne des Escherichia coli isolés des poulets au Sénégal, au Canada (Québec) et au Vietnam

Escherichia coli is a normal inhabitant of the intestinal microbiota of chickens, a small proportion of which may be avian pathogenic E. coli (APEC) or potential extraintestinal pathogenic E. coli (ExPEC), capable of causing disease in humans. These E. coli may also be resistant to antimicrobials of critical importance for human or veterinary health. The dissemination of antimicrobial resistance (AMR) can be mediated by clones or plasmids. However, in Québec, Senegal and Vietnam, the role of clones and plasmids in the resistance and virulence of avian E. coli is still to be elucidated. In Senegal, 68.2% and 86.2% of E. coli isolated from healthy chickens (indicator isolates) and clinical isolates, respectively, were multidrug-resistant (MDR); this prevalence for indicator isolates was 62.6% in Québec and 99.0% in Vietnam. In clinical isolates from Senegal, non-susceptibility to 3rd generation cephalosporins (3GC) was exclusively due to blaCTX-M genes [5 isolates (8.6%)]. For isolates from healthy chickens, non-susceptibility to 3GC was due to both blaCTX-M genes [14 isolates (5.6%, 95%CI = 1.4 - 9.8) for Senegal and 37 (19.8%,. 95%CI = 4.3-35.3) for Vietnam] and blaCMY-2 gene [28 (11.2%, 95%CI = 2.7 - 19.6) in Senegal and 27 (14, 4%, 95%CI = 0.0 - 30.5) in Vietnam] whereas in Québec, this resistance is mainly due to blaCMY-2 [88 (50.3%, 95%CI = 34.9 - 65.7%)]; only three isolates (1.7%, 95%CI = 0.0 - 4.8) were positive for blaCTX-M. The prevalence of quinolone-resistance was very high in indicator isolates in Vietnam (83.7% for nalidixic acid and 59.6% for ciprofloxacin); medium in Senegal (44.0% for nalidixic acid and 22.9% for ciprofloxacin) and very low in Quebec (4.0% for nalidixic acid and 1.0% for ciprofloxacin). Ciprofloxacin resistance had chromosomal determinism, as the double serine mutation (gyrA Ser83Leu and parC Ser80Ile) was observed in 88.2% (95%CI = 81.8 - 94.5) of tested isolates in Senegal and 82.0% (95%CI = 69.9 - 94.1) in Vietnam. Both plasmids and clones appear to be involved in the spread of 3GC resistance. In fact, the blaCTX-M/blaCMY-2 genes were, whatever the country, carried mainly by the plasmid I1 and incidentally by other plasmids such as K/B, FIB, A/C, B/O, etc. and some isolates from different farms in Senegal and Vietnam were closely related. With respect to resistance to colistin, no isolates were resistant to this antimicrobial in Quebec. On the other hand, 11 (8.7%, 95%CI = 0.0-34.4) blaCTX-M/blaCMY-2-producer-isolates from Vietnam, all positive for the mcr-1 gene, and 2 (2.2%, 95%CI = 0.0 - 5.4) faecal blaCTX-M–producer isolates from Senegal were resistant to colistin. These two isolates from Senegal did not carry the mcr-1 gene, but rather mutations in the two-component system pmrA/pmrB. Finally, certain clinical isolates from Senegal and from healthy chickens in Senegal, Quebec and Vietnam were, on the basis of their virulence profile, defined as potentially capable of infecting humans. These results suggest that chickens are a reservoir of E. coli resistant to antimicrobials and are potentially pathogenic to humans.

Keyphrases: Virulence, Clones, Avian Escherichia coli, Antimicrobial resistance, Plasmids