Pasteurella
multocida is a Gram-negative
bacterium with a broad host range. This opportunistic pathogen is a common
inhabitant of the upper respiratory tract of various mammal and avian species.
In the presence of predisposing factors, it causes several diseases, which lead
to major welfare problems and remarkable economic losses. The association of P. multocida
and bovine respiratory disease complex (BRDC) has been well known since the
early 1950s. Despite the using of efficient vaccines against other respiratory
pathogens, the increased number of cases suggests that P. multocida have
a definite role in the etiology of BRDC. The aim of our study was to
characterize 39 P. multocida strains of bovine origin isolated from
different herds in Hungary. The studied strains represented only three
serotypes: A:3, A:3,4, and A:4. The most frequent biovars, determined by their sugar
fermentation abilities and enzyme activities, were biovar 2 (33%) and 3 (44%). Their
subspecies were defined with biochemical tests and molecular methods (M13 PCR,
16S rDNA PCR-RFLP). These methods delineated two dominant groups (I and II). Group
I consisted of strains belonging to biovar 2, they showed α-glucosidase
activity and presented type „B” M13 profile. Whereas group II contained strains
with biovar 3, and type „A” M13 profile without α-glucosidase activity. The
existence and separation of these groups were confirmed by ERIC-PCR. Looking at
the diagnostic background, all strains in group I were associated with
pneumonia while the strains in group II originated from various clinical cases.
The filamentous hemagglutinin (pfhA) that plays an important role in the
early colonization of the respiratory tract could only be detected in group I.
It may explain why these strains were isolated from cases of bovine pneumonia.