Plasmid-borne florfenicol resistance in Pasteurella multocida.
OBJECTIVE
A florfenicol-resistant Pasteurella multocida isolate from a calf was investigated for the genetic basis of florfenicol resistance and the location of the resistance gene.


METHODS
The P. multocida isolate 381 was investigated for its in vitro susceptibility to antimicrobial agents and its plasmid content. A 10.8 kb florfenicol-chloramphenicol resistance plasmid, designated pCCK381, was identified by transformation into Escherichia coli. The plasmid was mapped with restriction endonucleases, cloned and sequenced completely.


RESULTS
Of the antimicrobials tested, plasmid pCCK381 conferred resistance only to chloramphenicol and florfenicol. It showed extended similarity to the 5.1 kb plasmid pDN1 from Dichelobacter nodosus in the part carrying the mobilization and replication genes. An adjacent 3.2 kb segment was highly homologous to the florfenicol resistance gene region of plasmid pMBSF1 from E. coli. In pCCK381, combined resistance to chloramphenicol and florfenicol was based on the presence of a floR gene that showed 97.2-99.7% identity to so far known floR genes.


CONCLUSIONS
The results of this study showed that a plasmid-borne floR gene was responsible for chloramphenicol and florfenicol resistance in the bovine respiratory tract pathogen P. multocida. This is, to the best of our knowledge, the first report of a florfenicol resistance gene in a target bacterium.
Kehrenberg
Corinna
C
Institut für Tierzucht, Bundesforschungsanstalt für Landwirtschaft (FAL), Höltystr. 10, 31535 Neustadt-Mariensee, Germany.
Schwarz
Stefan
S
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology; D002701:Chloramphenicol / Q000494:pharmacology; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010326:Pasteurella Infections / Q000382:microbiology; D016979:Pasteurella multocida / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D010957:Plasmids / Q000235:genetics*; D012137:Respiratory System / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013839:Thiamphenicol / Q000031:analogs & derivatives* / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002701:Chloramphenicol; C035534:florfenicol; D013839:Thiamphenicol