Plasmid-borne florfenicol resistance in Pasteurella multocida

Area of Science:

• Veterinary Microbiology
• Molecular Genetics
• Antimicrobial Resistance

Background:

• Emergence of antimicrobial resistance in bacterial pathogens poses a significant threat to animal and public health.
• Pasteurella multocida is a key bovine respiratory tract pathogen, and resistance to crucial antimicrobials like florfenicol is a growing concern.
• Understanding the genetic mechanisms of resistance is vital for developing effective treatment and control strategies.

Purpose of the Study:

• To investigate the genetic basis and plasmid location of florfenicol resistance in a P. multocida isolate from a calf.
• To characterize the resistance plasmid and identify the specific gene responsible for florfenicol resistance.

Main Methods:

• In vitro antimicrobial susceptibility testing of the P. multocida isolate.
• Plasmid isolation, transformation into Escherichia coli, and characterization of the resistance plasmid (pCCK381).
• Restriction endonuclease mapping, cloning, and complete sequencing of the plasmid pCCK381.

Main Results:

• The P. multocida isolate exhibited resistance to florfenicol and chloramphenicol.
• Plasmid pCCK381 (10.8 kb) conferred resistance to both florfenicol and chloramphenicol upon transformation.
• Sequencing revealed the presence of the floR gene on pCCK381, showing high homology to known florfenicol resistance genes.

Conclusions:

• A plasmid-borne floR gene is responsible for florfenicol and chloramphenicol resistance in this P. multocida isolate.
• This study reports the first instance of a florfenicol resistance gene identified in P. multocida.
• The findings highlight the role of plasmids in the dissemination of antimicrobial resistance in important animal pathogens.