A Pasteurella multocida strain affecting nulliparous heifers and calves in different ways

Area of Science:

• Veterinary Microbiology
• Bovine Diseases
• Bacterial Pathogenesis

Background:

• Pasteurella multocida is a significant pathogen in cattle, causing respiratory and mammary infections.
• Distinguishing between strains of P. multocida is crucial for understanding disease transmission and implementing control measures in dairy herds.

Purpose of the Study:

• To investigate whether isolates of Pasteurella multocida from calf pneumonia and heifer mastitis on a Spanish dairy farm represent the same or different strains.
• To characterize the genetic relatedness of P. multocida isolates from distinct clinical presentations in cattle.

Main Methods:

• Species-specific polymerase chain reaction (PCR) for P. multocida identification.
• Serotyping using the Heddleston scheme.
• Molecular genotyping including multi-locus sequence typing (MLST) and repetitive extragenic palindromic PCR (REP-PCR).

Main Results:

• All 11 isolates were confirmed as P. multocida but were not serotypable by the Heddleston scheme.
• All isolates belonged to lipopolysaccharide (LPS) type L3, associated with Heddleston serovars 3 and 4.
• MLST analysis revealed all isolates belonged to sequence type (ST) 79 within clonal complex ST13.
• Minor genetic variation was observed in only one isolate by REP-PCR.

Conclusions:

• A single P. multocida strain was responsible for both pneumonia in calves and mastitis in heifers on the studied farm.
• The findings suggest a common source or efficient transmission of this specific P. multocida strain within the dairy herd.
• Molecular techniques like MLST are valuable for strain differentiation and epidemiological investigations of bovine P. multocida infections.