Characterization of Trueperella pyogenes strains from uterus of cow and an analysis of their phylogenic association with strains from other anatomic locations and hosts

Trueperella pyogenes is an important pathogen of ruminants and occasionally other animals. In the current study, we isolated bacteria from uterus of Danish healthy dairy cows (n = 56) and cows judged by veterinarians to suffer from post partum uterine disease (n = 25). T. pyogenes was more frequently isolated from cows judged to be sick than from healthy cows (odds ratio 37.09), and the average quantity of T. pyogenes was significantly higher in these cows (p = 0.0002). Eleven Danish isolates from uterus of cows and 26 strains from bronchial lavage samples of calves with or without clinical signs of bovine respiratory syndrome were de novo sequenced, and the sequences were compared to each other and to all available genomes of sufficient quality in NCBI database (n = 126). The genome size of T. pyogenes varied between 2.19 and 2.46 megabases with GC content within 59.3 % and 59.9 %. Core-genome SNP analyses showed that Danish strains did not form a cluster of their own, and that strains from healty and sick animals clustered together. In analyses of all available genomes, two main clusters were found where strains from pigs and strains from cattle with a few exceptions clustered in separate branches, however, without indications of clustering depending on geographical location or anatomical site of the strain. This lack of host, geographic, and anatomic location-specific clustering was also evident by analyses of gene presence/absence matrixes and sequence alignments of the proteins encoded by the major virulence associated genes plo, fimA, fimE, fimC and cbpA. Danish strains of T. pyogenes from uterus and bronchial lavage had MIC₅₀ and MIC₉₀ values at or below the lowest dilutions tested for 11 out of 18 antimicrobials tested, indicating a high susceptibility. Indications of widespread low susceptibility was observed for tetracyclines (MIC₅₀ >8 µg/ml) and sulfonamides (MIC₅₀ >256 µg/ml). High MIC values to tetracyclines were assocatied to the presence of acquired resistance genes, most commonly the tet(W) gene, and high values to sulphonamides to the presence of the gene sul1.