[Mechanisms of pathogenicity and adhesion in Pasteurella haemolytica]. / Mecanismos de patogenicidad y adherencia de Pasteurella haemolytica.

Pasteurella haemolytica is one of the bacteria most commonly isolated from pneumonic cases in ruminants. Some of the mechanisms and factors involved in the pathogenesis of the disease are partially documented; and the early stages of bacterial colonization have not been totally clarified. Therefore a review is presented in this paper, particularly related with the mechanisms of bacterial pathogenicity responsible of pulmonary damage to ruminants, as well as a detailed analysis of the adherence process.

[Pathogenesis of lung damage caused by Pasteurella haemolytica]. / Patogénesis del daño pulmonar provocado por Pasteurella haemolytica.

Pneumonic pasteurellosis is the major economic problem of the cattle industry in North America. This disease is characterized by an acute, severe, fibrinonecrotic pleuropneumonia. Pasteurella haemolytica A1 is commonly isolated from these pneumonic lesions. It has been demonstrated that stress or viral infection compromises defense mechanisms of the upper respiratory tract and lung, predisposing to an initial multiplication of bacteria in the nasopharynx and, subsequently, lungs are deluged with large numbers of bacteria. Once multiplication in the alveoli has begun, virulence factors exert their influence to induce an excessive host inflammatory response that results in severe tissue damage. Despite a large number of studies conducted to explore the complex interaction between P. haemolytica and the host response, there still remains a lack of detailed understanding. This review discusses evidence of the role of the main virulence factors of P. haemolytica on the pathogenesis of pulmonary damage.

Serotypes of Pasteurella multocida and Pasteurella haemolytica isolated from pneumonic lesions in cattle and sheep from México.

A total of 13,000 pairs of lungs were examined at Mexico's City abbatoir, where 8,000 corresponded to sheep and 5,000 to cattle. From those, 224 pneumonic lesions were observed, obtaining 97 positive isolates, which yielded 112 strains of Pasteurella sp. Forty isolates were identified as P. haemolytica and 72 as P. multocida. One-hundred percent of P. haemolytica belonged to biotype A. Serotypes were determined by indirect haemagglutination. P. multocida isolates were classified according to the acriflavine and hyaluronidase techniques, 61% belonged to type A, 25% to type D and 14% were untypified. Somatic serotypes were determined by gel immunodiffusion; serotype 3 was more frequent, in sheep 72% and in cattle 77%.