Toxicity of Haemophilus pleuropneumoniae for porcine lung macrophages, peripheral blood monocytes, and testicular cells.

Strain CM5 of Haemophilus pleuropneumoniae was toxic for porcine lung macrophages in minimum doses of 10(6) colony-forming units per ml and for peripheral blood monocytes at 10(7) colony-forming units per ml. The organism was not toxic for porcine testicular cells in a concentration of 10(8) colony-forming units per ml. Filtered sterile culture supernatant diluted 10(0), 10(-1), and 10(-2) was toxic for porcine pulmonary lavage cells. In dilutions of 10(0) and 10(-1), culture supernatant was toxic for peripheral blood monocytes, and at 10(0) it was toxic for testicular cells. Toxicity associated with bacterial cells was sensitive to heating (60 degrees, 60 min), whereas that of the culture supernatant was heat stable (100 degrees C, 15 min). Swine convalescent serum neutralized supernatant toxicity in dilutions of greater than or equal to 1:320. The findings promote the understanding of the pathogenesis of pleuropneumonia in swine caused by H. pleuropneumoniae.