Mycoplasma hyopneumoniae: interaction with other agents in pigs, and evaluation of immunogens

Mycoplasmal pneumonia of swine causes considerable economic losses in porciculture. Diverse agents, such as environmental stress and infectious microorganisms, increase the possibility of infection, an the damage to pulmonary tissue when the infection is established. It is known that Mycoplasma hyopneumoniae has an important role in this desease, in addition to secondary microbial agents, susch as Pasteurella mutocida and Actinobacillus pleuropneumoniae. However, the characteristics of this disease in farms are well known. In this work we review the interactions among the different microorganisms involved and the immunological strategies utilized to control this disease. The interaction between Mycoplasma hyopneumoniae and P. multocida in experimental pneumonia was reported by us in conventional pig. M. hyopneumoniae causes mild pneumonia, whereas P. multocida aggravates the pneumonia initiated by M. hyopneumoniae. The disease has been reproduced to test the efficacy of two immunogens, and can also be used to evaluate some antibiotics. A M. hyopneumoniae bacterine administered intraperiotoneally conferred more protection than when it was used with adjuvant, although protection was not complete and colonization by M. hyopneumoniae was not prevented, as is claimed to have been the case with other vaccines

Actinobacillus pleuropneumoniae: virulence and gene cloning

Actinobacillus pleuropneumoniae is the causal agent of porcine contagious pleuropneumonia(PCP). The infection produces important economic losses in porciculture due to its high morbidity and mortality. Survivors are asymptomatic carriers infectious to other pig and have low alimentary conversion. The causative agent possesses several virulence factor: adhesion fimbriae, lipopolysaccharide of the outer membrane, capsule, and cytolysins. In addition, our group has reported secretion proteases of a wide pH range of activity. These proteases degrade different substrates such as porcine gelatin, hemoglobin and IgA, and bovine or human hemoglobin. To control PCP dissemination, farmers require serodiagnostic tests which detect carriers and discriminate between vaccinated and infected animal. Bacterines used as immunogens are serotype specific and do not prevent the infection. Genes have been cloned that codify a cohemolysin, cytolysins, and an iron-binding protein. We have cloned A. pleuropneumoniae genes using the expression plasmids pUC19 and Bluescript, in Escherichia coli Q358 and DH5alpha; the screening for antigen production was made in four gropus of pigs (vaccinated, experimentally infected, naturally infected, and from alaughterhouses); two E. coli clones expressed polypeptides recognized by sera from all the groups