Pulmonary isolation of Actinobacillus porcitonsillarum in pigs in Europe

Glaesserella australis sp. nov., isolated from the lungs of pigs

Twenty-nine isolates of an unknown haemophilic organism were isolated from the lungs of pigs from 14 farms in Australia. Phylogenetic analyses based on the 16S rRNA gene, recN and rpoA showed a monophyletic group that was most closely related to Glaesserella parasuis and [Actinobacillus] indolicus. Whole genome sequence analysis indicated that the Glaesserella parasuis and this group, using the type strain HS4635^T for comparison, showed a similarity of 30.9 % DNA-DNA renaturation. The isolates were Gram-stain-negative, NAD-dependent, CAMP-negative and were oxidase-positive, catalase-negative and produced indole but not urease. The isolates could be separated from all currently recognized haemophilic and non-haemophilic members of the family Pastuerellaceae. Key phenotypic properties were the production of indole, the lack of urease activity, production of β-galactosidase but not α-fucosidase, acid formation from (-)-d-arabinose, (+)-d-galactose, maltose and trehalose and a failure to produce acid from (-)-d-mannitol. Taken together, these data indicate that the isolates belong to a novel species for which the name Glaesserella australis sp. nov. is proposed. The type strain is HS4635^T (=CCUG 71931^T and LMG 30645^T).

Prevalence of granulomatous pleuropneumonia associated with Actinobacillus pleuropneumoniae serotype 2 in slaughter pigs

A total of 14,818 slaughtered pigs were examined macroscopically. Of these, 25 pigs with porcine pleuropneumonia were collected and the relations among Actinobacillus spp. and granulomatous lesions in organs (lungs and tonsils) were evaluated. In the lungs, only Actinobacillus pleuropneumoniae serotype 2 was isolated from 20 of the pigs. Histologically, granulomatous pneumonia with A. pleuropneumoniae antigen was detected in 8 of the pigs. The antigen was visible in the centers of the lesions along with asteroid bodies, epithelioid cells and multinucleated giant cells. In the tonsils, granulomatous lesions were not detected, although A. pleuropneumoniae serotype 2 (5 pigs), serotype 7 (1 pig), Actinobacillus porcitonsillarum (1 pig) and Actinobacillus minor (1 pig) were isolated. The present survey suggests that multifocal granulomatous pneumonia in slaughter pigs could be highly associated with A. pleuropneumoniae serotype 2 infection.

Production of haemolysins by strains of the Actinobacillus minor/"porcitonsillarum" complex

Actinobacillus minor and "Actinobacillus porcitonsillarum" are distinguished by their haemolytic activities, the latter organism being haemolytic and the former, non-haemolytic. Analysis of a whole genome shotgun sequence, however, revealed that A. minor strain 202, like "A. porcitonsillarum", possesses a haemolysin-encoding apxII operon. The purpose of this study was therefore to investigate haemolysin production by this organism and also by three additional members of the A. minor/"porcitonsillarum" complex, strains 33PN and 7ATS and A. minor strain NM305(T). Primers based on sequences within the apxII genes of strain 202 allowed the amplification of appropriately sized fragments from DNA from strain 33PN suggesting that this organism also possesses an apxII operon. Analysis of a whole genome shotgun sequence failed to reveal any trace of an apxII operon in strain NM305(T) and attempts to amplify apxII genes from DNA from strain 7ATS also failed. Strains 202 and 33PN, and surprisingly, the type strain of A. minor and strain 7ATS, were all found to be haemolysin-positive as growth media from cultures of these organisms could promote the lysis of erythrocytes in suspension. The erythrocyte specificities of the haemolysins produced by strains 202 and 33PN indicated that the haemolytic activities exhibited by these organisms were due to ApxII. In keeping with the apparent lack of apxII genes in strains NM305(T) and 7ATS, the haemolysins produced by these organisms were not erythrocyte-specific and with both organisms, haemolytic activity appeared to be due to a combination of heat-stable and heat-labile components. The identities of these components, however, remain unknown.