The aim of this study was to analyse florfenicol-resistant Mannheimia haemolytica isolated from a calf, to determine the genetic basis of its florfenicol-resistance. The antimicrobial susceptibility and plasmid content of the isolate were determined. A florfenicol resistant plasmid carrying the floR gene was identified by PCR and transformed into Escherichia coli strains JM109 and HB101. The plasmid was then mapped and sequenced completely.
The isolate was resistant to chloramphenicol, florfenicol, oxytetracycline, kanamycin, dihydrostreptomycin, nalidixic acid, ampicillin, and amoxicillin; it carried a floR plasmid of 7.7 kb, designated pMH1405.
The mobilisation and replication genes of pMH1405 showed extensive similarity to the 10.8-kb pCCK381 plasmid from Pasteurella multocida. A plasmid-mediated floR gene was responsible for florfenicol resistance in the bovine respiratory tract pathogen M. haemolytica. The pMH1405 plasmid is the smallest floR-carrying plasmid reported to date. To the best of our knowledge, this is the first report of a florfenicol-resistant gene in M. haemolytica.
(Tohoku Research Station,Viral Disease and Epidemiology Research Division)
References:
Katsuda K. et al. (2012) Vet. Microbiol. 155:444-447
