title: Influence of the virulence plasmid and the Congo red reaction on the antimicrobial susceptibility of Yersinia species.
abstract: Seventeen strains of Yersinia enterocolitica and related species were examined for their susceptibility to a variety of antimicrobial agents. Twelve of the strains were clinical isolates which carried a virulence plasmid; five were food isolates which lacked plasmids. When grown on agar containing Congo red or haemin, each strain yielded pigmented (CR+) and non-pigmented (CR-) variants. CR+ bacteria of clinical origin were virulent, whereas CR+ food isolates and all CR- bacteria were avirulent. The susceptibility of CR+ and CR- bacteria to the following agents was compared: ampicillin, chloramphenicol, latamoxef, nalidixic acid, novobiocin, polymyxin B, rifampicin, streptomycin, tetracycline and tobramycin. The results showed that bacteria which bound Congo red were more susceptible to each drug examined than their CR- counterparts. This relationship held regardless of whether the CR+ bacteria possessed a virulence plasmid or not. The findings suggest that binding of antimicrobial agents by yersiniae may parallel binding of haemin and Congo red.
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D003224:Congo Red / Q000378:metabolism*; D006427:Hemin / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D014774:Virulence; D015007:Yersinia / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D015008:Yersinia enterocolitica / Q000187:drug effects / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D003224:Congo Red; D006427:Hemin