Antimicrobial Susceptibility and Clonal Relationship of Tetracycline Resistance Genes in -Positive .

NetF-producing type A , a pathotype of , causes necrotizing enteritis in neonatal foals and necrotizing and hemorrhagic enteritis in dogs. Recent core genome multilocus sequence typing study revealed that strains belong to two distinct clonal populations (clonal complexes I and II). There are no reports on susceptibility to antimicrobial drugs of isolates from this pathotype. The susceptibility to 13 different antimicrobial drugs of 49 strains recovered from foals or dogs with necrotizing enteritis in Canada, the United States, and Switzerland was assessed using a commercial microdilution panel designed for anaerobic human pathogens. All isolates were highly susceptible to 12 antimicrobial agents, including all beta-lactams tested, such as penicillin G and ampicillin, as well as clindamycin, chloramphenicol, and metronidazole. The isolates consistently presented a reduced susceptibility or resistance to tetracycline, which was associated with previously described tetracycline resistance genes. Clonal complex I isolates ( = 41) possessed the (P) gene, whereas clonal complex II isolates ( = 8) possessed the (P)-(P) genes and were more likely to be fully resistant.