[Pasteurelloses]

According to the genetic relationships among Gram-negative bacilli the genus Pasteurella is included with the genus Haemophilus and the genus Acinobacillus within the family Pasteurellacae. Pasteurella multocida, the type species, is responsible for the majority of human Pasteurella infections. P. multocida is a member of the normal flora in the upper respiratory tract of many mammals or birds. It causes sporadic or epidemic diseases among different animal species, particularly pneumonia and atrophic rhinitis in swine in intensive breeding stations. The most common human infection with P. multocida is a local cellulitis following dog or cat bites and scratches. Serious local complications are sometimes responsible for prolonged disability. The respiratory tract is the second human source of P. multocida isolates. The frequency of recovery of P. multocida from oropharynx of apparently healthy pig breeders suggests that respiratory pasteurellosis could be an occupational disease. The mechanisms of virulence of P. multocida are unclear. Several factors are involved: capsules preventing phagocytosis, a dermonecrotic toxin causing experimental atrophic rhinitis, hyaluronidase, neuraminidase and proteases. Penicillin is considered to be the drug of choice for Pasteurella infection. Tetracyclin is efficient for bites but has no bactericidal effect. Oxacillin, first-generation cephalosporins, macrolides and aminoglycosides have poor activities. In the case of beta-lactamase producing strains a bactericidal effect could be achieved with fluoroquinolones or third generation cephalosporins.