Trueperella pyogenesmultispecies infections in domestic animals: a retrospective study of 144 cases (2002 to 2012)

Arcanobacterium pyogenes is a commensal and an opportunistic pathogen of economically important livestock, causing diseases as diverse as mastitis, liver abscessation and pneumonia. This organism possesses a number of virulence factors that contribute to its pathogenic potential. A. pyogenes expresses a cholesterol-dependent cytolysin, pyolysin, which is a haemolysin and is cytolytic for immune cells, including macrophages. Expression of pyolysin is required for virulence and this molecule is the most promising vaccine candidate identified to date. A. pyogenes also possesses a number of adherence mechanisms, including two neuraminidases, the action of which are required for full adhesion to epithelial cells, and several extracellular matrix-binding proteins, including a collagen-binding protein, which may be required for adhesion to collagen-rich tissue. A. pyogenes also expresses fimbriae, which are similar to the type 2 fimbriae of Actinomyces naeslundii, and forms biofilms. However, the role of these factors in the pathogenesis of A. pyogenes infections remains to be elucidated. A. pyogenes also invades and survives within epithelial cells and can survive within J774A.1 macrophages for up to 72 h, suggesting an important role for A. pyogenes interaction with host cells during pathogenesis. The two component regulatory system, PloSR, up-regulates pyolysin expression and biofilm formation but down-regulates expression of proteases, suggesting that it may act as a global regulator of A. pyogenes virulence. A. pyogenes is a versatile pathogen, with an arsenal of virulence determinants. However, most aspects of the pathogenesis of infection caused by this important opportunistic pathogen remain poorly characterized.

The objective of this study was to evaluate the relationship between bacterial species-specific virulence factors (VFs) present in the uterus at 3 different stages of lactation (1-3, 8-10, and 34-36 days in milk (DIM)) and the incidence of metritis and clinical endometritis in dairy cows. The following VF genes were investigated: plo (pyolysin), cbpA (collagen-binding protein), and fimA (fimbriae expression) which are Arcanobacterium pyogenes specific; fimH (a type 1 pilus component), Escherichia coli specific; and lktA (leukotoxin), Fusobacterium necrophorum specific. Uterine swabs were collected from 111 postpartum dairy cows. PCR was used to detect the presence of plo, cbpA, fimA, fimH, and lktA genes. A. pyogenes cbpA was detected in only 5 samples and therefore was not subjected to further analysis. E. coli (fimH) was significantly associated with metritis and endometritis when detected at 1-3 DIM; F. necrophorum (lktA) was significantly associated with metritis when detected at 1-3 and 8-12 DIM and with endometritis when detected at 34-36 DIM; and A. pyogenes (fimA and plo) was associated with metritis (fimA) when detected at 1-3 DIM and endometritis (fimA and plo) when detected at 8-10 and 34-36 DIM. Copyright © 2011 Elsevier B.V. All rights reserved.

The results of a study comparing the chemotaxonomic characteristics and phylogenetic positions of members of the genus Arcanobacterium indicated that the genus was not monophyletic and, therefore, was in need of taxonomic revision. Phylogenetically, the genus Arcanobacterium consisted of two distinct lines; a group comprising the species Arcanobacterium haemolyticum (the type species of the genus), A. hippocoleae, A. phocae and A. pluranimalium and a robust group consisting of the species A. abortisuis, A. bernardiae, A. bialowiezense, A. bonasi and A. pyogenes. On the basis of 16S rRNA signature nucleotide comparisons and menaquinone and phospholipid compositions, it is proposed that of these nine species only four, A. haemolyticum, A. hippocoleae, A. phocae and A. pluranimalium, should be affiliated with the genus Arcanobacterium and the species A. abortisuis, A. bernardiae, A. bialowiezense, A. bonasi and A. pyogenes should be reclassified as members of a new genus, Trueperella, as Trueperella abortisuis comb. nov., Trueperella bernardiae comb. nov., Trueperella bialowiezensis comb. nov., Trueperella bonasi comb. nov. and Trueperella pyogenes comb. nov. Positive results in Christie-Atkins-Munch-Petersen (CAMP) tests on A. haemolyticum, A. hippocoleae, A. phocae and A. pluranimalium also supported the rearrangement of the nine species in to separate genera. As such, an emended description of the genus Arcanobacterium is provided.