Helcococcus ovis in a patient with an artificial eye: a case report and literature review

Sequencing and characterization of Helcococcus ovis: a comprehensive comparative genomic analysis of virulence

BACKGROUND

Helcococcus ovis (H. ovis) is an emerging bacterial pathogen that commonly causes opportunistic respiratory, mammary, and uterine infections across mammalian hosts. This study applied long- and short-read whole genome sequencing technologies to identify virulence factors in five H. ovis isolates with low, medium, and high virulence phenotypes.

RESULTS

The resulting assemblies contained one circular chromosome ranging from 1,744,566 to 1,850,083 bp in length and had a mean GC content of 27.6%. Phylogenetic and nucleotide identity analyses found low virulence strain KG38 to be part of a clade that forms an outgroup apart from the rest of the H. ovis taxon. Assembling the first complete genomes of the species revealed major genomic rearrangements in KG38. One to six prophage regions were identified in each genome. A novel pathogenicity island was found exclusively in the two high virulence strains (KG37 and KG104), along with two hypothetical transmembrane proteins designated as putative VFs. Finally, three zinc ABC transporters and three Type-II/IV secretion systems were identified as possible virulence determinants in this species. The low virulence strain KG38 has fewer intact paralogs of these operons in its genome compared to the higher virulence isolates, which strongly suggests a role in virulence. This strain is also missing four putative virulence factors (VFs) found in other isolates associated with adherence (collagen adhesin precursor), immune evasion (choline-binding protein A and a PspA-like hypothetical protein) and cell wall synthesis (glycerol-3-phosphate cytidylyltransferase).

CONCLUSIONS

In this study, we assembled reference-quality complete genomes for five H. ovis strains to identify putative virulence factors. Phylogenetic analyses of H. ovis isolates revealed the presence of a clade representing a potentially novel species within the genus Helcococcus. A novel pathogenicity island and two hypothetical transmembrane proteins were found exclusively in high-virulence strains. The identification of Zinc ABC transporters and Type-II/IV secretion systems as possible virulence determinants, along with the differences in operon content between the low and high virulence isolates, strongly suggests they also play a role in the bacterium's pathogenicity. Taken together, these findings are a valuable first step toward deciphering the pathogenesis of H. ovis infections.

Biological Characteristics and Pathogenicity of Helcococcus ovis Isolated From Clinical Bovine Mastitis in a Chinese Dairy Herd

Helcococcus ovis (H. ovis) was first reported in ovine subclinical mastitis milk and post-mortem examination organs in Spain and the United Kingdom in 1999; subsequently, it appeared in cattle, horse, goat, and human. However, isolation and characterization of the pathogen from clinical bovine mastitis is unknown. The objective of this study was to identify the pathogen in clinical bovine mastitis. A total of four strains were isolated from bovine mastitis milk samples from a Chinese dairy farm, and they were identified as H. ovis by microscopic examination and 16S rRNA gene sequencing. Phylogenetic tree was constructed using 16S rRNA gene, and the isolates were closely related to other China strains and strains from Japan. The growth speed of the H. ovis isolated was relatively slower than Streptococcus agalactiae, and the phenotypic characteristics were similar to H. ovis CCUG37441 and CCUG39041 except to lactose. The isolates were sensitive to most of the common used antimicrobials. The H. ovis isolates could lead to mild murine mastitis alone and induce severe mastitis when co-infected with Trueperella pyogenes in the murine mammary infection model constructed.

Helcococcus kunzii, a skin-colonising microorganism with pathogenic capacity: a case of polymicrobial intracranial empyema

Helcococcus kunzii is a Gram-positive anaerobic facultative coccus that colonises the skin. Human infection is rare, with very few cases being described in the literature. The authors present the case of a 17-year-old man, with a history of cholesteatoma, diagnosed with mastoiditis complicated by intracranial empyema. After urgent surgical drainage, Gram staining revealed a Gram-negative bacillus and a Gram-positive coccus. The latter exhibited fastidious growth, presented as small grey colonies in blood agar, and was afterwards identified as H. kunzii The patient was started on intravenous antibiotics, switched to oral route after 8 weeks and fully recovered. To the best of our knowledge, this is the third case of an intracranial infection in which H. kunzii is involved, two of them occurring in patients with cholesteatoma.

Helcococcus ovis associated with septic arthritis and bursitis in calves - a case report

BACKGROUND

Septic arthritis often occurs in young calves when the passive transfer of maternal immunoglobulins has failed, which results in hypogammaglobulinaemia in the calf. Another important cause is suboptimal herd health management which often leads to general health impairment and, subsequently, to septic arthritis.

CASE PRESENTATION

A dairy farmer consulted the Herd Health Service of the University Clinic reporting general herd health impairment, a high incidence of respiratory diseases, unsatisfactory weight gain and arthritis in calves, as well as mastitis and high milk cell counts. Clinical examinations were performed, and diagnostic measures were taken. A transtracheal lavage (TTL) was performed, and synovial swab samples were taken from the carpal joint and the subcutaneous tarsal bursae of two calves. Microbiological examinations of synovial swabs revealed co-infections of Trueperella pyogenes and Helcococcus ovis in one calf and Helcococcus ovis in pure culture in the other. The TTLs confirmed the presence of Mycoplasma spp. associated with respiratory diseases.

CONCLUSIONS

Helcococcus ovis is currently regarded as a co-infective bacterial agent. However, it seems to play a significant role as the primary pathogen in this case.