Antimicrobial Susceptibility and Clonal Relationship of Tetracycline Resistance Genes in netF-Positive Clostridium perfringens

NetF-producing type A Clostridium perfringens , a pathotype of C. perfringens , causes necrotizing enteritis in neonatal foals and necrotizing and hemorrhagic enteritis in dogs. Recent core genome multilocus sequence typing study revealed that netF + C. perfringens 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 netF + 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 ( n = 41) possessed the tetA408 (P) gene, whereas clonal complex II isolates ( n = 8) possessed the tetA (P)- tetB (P) genes and were more likely to be fully resistant.