Koch's postulate of Arcanobacterium pyogenes and its immunogenicity in local and imported Saanen goats

The aim of this survey was to study Koch's postulate of Arcanobacterium pyogenes recovered from the necrotic lung of a kid and to compare the immunogenicity of this isolate in local and imported Saanen goats. The disease was successfully reproduced in intrathoracically challenged hamsters which showed lung congestion and liver abscesses, while hamsters that were intraperitoneally challenged showed only the formation of intestinal abscesses. The percentage of histopathologic legions in 12 observed microscopic fields per lung of three groups of hamsters (unchallenged controls, challenged intrathoracically and challenged intraperitoneally) showed a significant increase in lung necrosis of the intrathoracically challenged group, followed by intraperitoneally challenged hamsters, in comparison to unchallenged controls (p<0.05). In addition, the frequency of mucus accumulation in alveolar ducts followed the same respective pattern (p>0.05), while there was no significant difference in the frequency of neutrophil infiltration (p>0.05). The isolate was successfully recovered from the lungs and livers of hamsters challenged by both routes. Saanen does showed significant seroconversion using the indirect haemagglutination (HA) test and slide agglutination test (SAT) and at three weeks following priming and boosting with A. pyogenes antigens (p<0.05); however, only SAT showed significant seroconversion in local does at three weeks post booster (p<0.05). The possible causes and impact of the greater immunogenicity to A. pyogenes antigens in Saanen goats compared to local does are discussed.