Characterization of a beta-lactamase from Pasteurella multocida

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Enzymology

Background:

• Bovine Pasteurella multocida is a significant veterinary pathogen.
• Beta-lactamase production is a key mechanism of antibiotic resistance.
• Understanding resistance mechanisms in animal pathogens is crucial for effective treatment.

Purpose of the Study:

• To characterize the beta-lactamase produced by a bovine Pasteurella multocida strain.
• To determine the enzyme's substrate profile and resistance conferral.
• To investigate the enzyme's characteristics, including location and genetic relatedness.

Main Methods:

• Isolation and identification of Pasteurella multocida from bovine samples.
• Determination of minimal inhibitory concentrations (MICs) for beta-lactam antibiotics.
• Enzyme assays to characterize substrate specificity and inhibition patterns.
• Analysis of enzyme location (periplasmic) and production (constitutive).

Main Results:

• The bovine P. multocida strain exhibited high MICs for amoxicillin (128 mg/l) and ticarcillin (512 mg/l).
• A periplasmic beta-lactamase was constitutively produced, with no apparent permeability barrier.
• The enzyme displayed a TEM-substrate profile but was not inhibited by anti-TEM-1 or anti-TEM-2 antisera.
• The isoelectric point of the enzyme was estimated at 8.8.

Conclusions:

• The identified beta-lactamase contributes significantly to amoxicillin and ticarcillin resistance in this bovine P. multocida strain.
• The TEM-substrate profile suggests a potential link to known beta-lactamase families, despite lack of serological inhibition.
• Further investigation into the genetic basis of this beta-lactamase is warranted to understand its evolution and spread in veterinary settings.