Evidence of lateral gene transfer among strains of Streptococcus zooepidemicus in weanling horses with respiratory disease

Streptococcus zooepidemicus in dogs: Exploring a canine pathogen through multilocus sequence typing

Streptococcus equi. subsp. zooepidemicus (S. zooepidemicus) associated diseases in dogs have emerged as a significant concern over recent decades. S. zooepidemicus occurs sporadically in dog populations globally, with increased prevalence in shelters/kennels. This study used multilocus sequence typing (MLST) of 149 independent canine S. zooepidemicus isolates to assess associations between sequence type and breed, country of origin, disease severity, sampling type, year, and behaviour within an outbreak. No clear associations for breed, country, sampling type and year were determined in this study. ST-10 and 123 strains were present within all disease categories, from no clinical signs to severe disease. Assessment of S. zooepidemicus infection in 3 UK outbreaks at the same location found ST-10, 18, 123 strains, and a ST-173 strain in a US outbreak, were associated with haemorrhagic pneumonia and persisted in kennelled populations over time. The ST-173 clonal complex has been noted to have severe virulence capabilities in dogs and other species. S. zooepidemicus seems to thrive in environments with a high risk of transmissibility, overcrowding, stress and naïve populations, particularly for those in shelters/kennels. MLST alone cannot determine the virulence phenotype of S. zooepidemicus in dogs. However, a level of conservancy and diversity within ST allelic loci aids the opportunity to cause severe disease in dogs. Thus, further research into whole genome sequencing and characterising the virulence factors of S. zooepidemicus is warranted in dogs.

Identification of Key Genes during Ca2+-Induced Genetic Transformation in Escherichia coli by Combining Multi-Omics and Gene Knockout Techniques

The molecular mechanism of the Ca²⁺-mediated formation of competent cells in Escherichia coli remains unclear. In this study, transcriptome and proteomics techniques were used to screen genes in response to Ca²⁺ treatment. A total of 333 differentially expressed genes (317 upregulated and 16 downregulated) and 145 differentially expressed proteins (54 upregulated and 91 downregulated) were obtained. These genes and proteins are mainly enriched in cell membrane components, transmembrane transport, and stress response-related functional terms. Fifteen genes with these functions, including yiaW, ygiZ, and osmB, are speculated to play a key role in the cellular response to Ca²⁺. Three single-gene deletion strains were constructed with the Red homologous recombination method to verify its function in genetic transformation. The transformation efficiencies of yiaW, ygiZ, and osmB deletion strains for different-size plasmids were significantly increased. None of the three gene deletion strains changed in size, which is one of the main elements of microscopic morphology, but they exhibited different membrane permeabilities and transformation efficiencies. This study demonstrates that Ca²⁺-mediated competence formation in E. coli is not a simple physicochemical process and may involve the regulation of genes in response to Ca²⁺. This study lays the foundation for further in-depth analyses of the molecular mechanism of Ca²⁺-mediated transformation. IMPORTANCE Using transcriptome and proteome techniques and association analysis, we identified several key genes involved in the formation of Ca²⁺-mediated E. coli DH5α competent cells. We used Red homologous recombination technology to construct three single-gene deletion strains and found that the transformation efficiencies of yiaW, ygiZ, and osmB deletion strains for different-size plasmids were significantly increased. These results proved that the genetic transformation process is not only a physicochemical process but also a reaction process involving multiple genes. These results suggest ways to improve the horizontal gene transfer mechanism of foodborne microorganisms and provide new ideas for ensuring the safety of food preservation and processing.

Reducing exposure to pathogens in the horse: a preliminary study into the survival of bacteria on a range of equine bedding types

AIMS

To compare the rate of growth of four microbial strains that cause disease in the horse, on four commonly used types of bedding. The moisture-holding capacity of each bedding type was also tested.

METHODS AND RESULTS

Microbial strains included Streptococcus equi, Streptococcus zooepidemicus, Fusobacterium necrophorum, Dichelobacter nodosus and Dermatophilus congolensis. The bedding types tested were Pinus sylvestris (Scots pine shavings), Pinus nigra (Corsican pine shavings), Picea sitchensis (Sitka spruce shavings), Cannabis sativa (hemp) and chopped wheat straw. A suspension of each microbial strain was spread in triplicate on agar media and incubated in its optimal growth conditions. The viable count (colony-forming unit per ml) was determined for each bacterial strain for the five different bedding types. Pinus sylvestris bedding resulted in significantly less (P = 0·001) bacterial growth of all strains tested.

CONCLUSIONS

Factors resulting in the inhibition of bacterial growth include the antibacterial effects reported in the Pinacea family and the physical properties of the bedding substrate. Research is currently focussed on the diagnosis and management of disease. Prevention of disease is also important for matters of biosecurity. Strategies should include the provision of a hygienic environment and the use of specific types of bedding.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bedding choice has implications for global equine health and disease prevention as well as potential benefits in other animal species.

Rapid and accurate identification of Streptococcus equi subspecies by MALDI-TOF MS

Streptococcus equi includes very important animal and human pathogens. S. equi subsp. equi (SEE) is a highly pathogenic equine specific subspecies, while S. equi subsp. zooepidemicus (SEZ) and S. equi subsp. ruminatorum are opportunistic pathogens of various animal species and humans. Due to great phenotypic and sequence similarity between three subspecies their discrimination remains difficult. In this study, we aimed to design and validate a novel, Superspectra based, MALDI-TOF MS approach for reliable, rapid and cost-effective identification of SEE and SEZ, the most frequent S. equi subspecies in horses. Superspectra created in this study enabled correct identification of 86 strains belonging to different subspecies of S. equi, isolated from various hosts, infection sites and years. In general, higher average identification accuracy was achieved for SEE (99.0±3.0%) than for SEZ (93.3±7.5%). This result may be attributed to the highly clonal population structure of SEE, as opposed to the diversity of SEZ seen in horses. Importantly strains with atypical colony appearance both within SEE and SEZ did not affect correct identification of the strains by MALDI-TOF MS. Atypical colony variants are often associated with a higher persistence or virulence of S. equi, thus their correct identification using the current method strengthens its potential use in routine clinical diagnostics. In conclusion, reliable identification of S. equi subspecies was achieved by combining a MALDI-TOF MS method with spectra analyses using the SARAMIS database. Additionally, first results on subtyping of SEZ indicated that a more refined discrimination, for example for epidemiological surveys, may be possible.

Clones of Streptococcus zooepidemicus from outbreaks of hemorrhagic canine pneumonia and associated immune responses

Acute hemorrhagic pneumonia caused by Streptococcus zooepidemicus has emerged as a major disease of shelter dogs and greyhounds. S. zooepidemicus strains differing in multilocus sequence typing (MLST), protective protein (SzP), and M-like protein (SzM) sequences were identified from 9 outbreaks in Texas, Kansas, Florida, Nevada, New Mexico, and Pennsylvania. Clonality based on 2 or more isolates was evident for 7 of these outbreaks. The Pennsylvania and Nevada outbreaks also involved cats. Goat antisera against acutely infected lung tissue as well as convalescent-phase sera reacted with a mucinase (Sz115), hyaluronidase (HylC), InlA domain-containing cell surface-anchored protein (INLA), membrane-anchored protein (MAP), SzP, SzM, and extracellular oligopeptide-binding protein (OppA). The amino acid sequences of SzP and SzM of the isolates varied greatly. The szp and szm alleles of the closely related Kansas clone (sequence type 129 [ST-129]) and United Kingdom isolate BHS5 (ST-123) were different, indicating that MLST was unreliable as a predictor of virulence phenotype. Combinations of conserved HylC and serine protease (ScpC) and variable SzM and SzP proteins of S. zooepidemicus strain NC78 were protectively immunogenic for mice challenged with a virulent canine strain. Thus, although canine pneumonia outbreaks are caused by different strains of S. zooepidemicus, protective immune responses were elicited in mice by combinations of conserved or variable S. zooepidemicus proteins from a single strain.