Streptococcus dysgalactiae ssp. dysgalactiae in Norwegian bovine dairy herds: Risk factors, sources, and genomic diversity

Abstract

Despite the importance of Streptococcus dysgalactiae ssp. dysgalactiae (SDSD) as an udder pathogen, the reservoir and epidemiological characteristics of this bacterium are largely unexplored. The aims of this study were to investigate risk factors for SDSD intramammary infections (SDSD-IMI) in Norwegian bovine dairy herds, identify sources of SDSD on animals and in the environment, and elucidate the genetic diversity of SDSD isolates. Data from herd recordings and a questionnaire were used to investigate herdlevel risk factors for SDSD-IMI in 359 freestall dairy herds. Seven herds with a suspected high prevalence of SDSD-IMI were visited to sample extramammary sources (e.g., skin, wounds, mucous membranes, and freestall environment). Bacterial isolates were wholegenome sequenced to investigate the distribution of SDSD genotypes within herds and to assess the phylogenetic relationship between SDSD isolates from 27 herds across Norway. Risk factors for high incidence of SDSD-IMI in freestall dairy herds were related to housing, including closed flooring in alleys and rubber mats in cubicle bases. Parlor milking was also a risk factor compared with automatic milking systems. From herd visits, a considerable proportion of extramammary samples were SDSD positive, particularly from wounds and skin of the animals and the cubicle bases. Samples from mucous surfaces (nostrils, rectum, and vagina) and water troughs were least frequently positive. Eight multilocus sequence types (ST) were identified among the sequenced isolates from 27 herds, and phylogenetic analyses revealed 8 clades corresponding to ST. No significant association was identified between sampling site (milk, body sites, and environment) and ST. In 4 of 6 herds from which 5 or more isolates were available, one ST dominated and was found in milk and extramammary samples. One ST (ST453) was found in 15 of 27 herds, which implies that this is a widely distributed and possibly a bovine-adapted strain. Findings in this study suggest that SDSD is a cow-adapted opportunist with potential for contagious transmission, and that the freestall environment is likely to play a role in transmission between cows.

Reservoirs of Corynebacterium spp. in the Environment of Dairy Cows

“…Therefore, we cannot rule out that it was outgrown by the competitive flora in the samples and therefore not detected. In future research, an approach with a prescreening using PCR and consecutive cultivation under favorable conditions, as recently conducted for Streptococcus dysgalactiae [ 24 ], could increase the chances of isolating C. bovis from environmental samples.…”

Reservoirs of Staphylococcus spp. and Streptococcus spp. Associated with Intramammary Infections of Dairy Cows

“…One reason could be that we did not sample the skin of teats and udder, or skin wounds that were found in a study (published after the completion of the present study) to be major sources of Strep. dysgalactiae [ 21 ]. In that study, Strep.…”

“…uberis and Strep. dysgalactiae have been isolated from different niches in the cows’ environment, including bedding material, drinking troughs, and walking alleys in the barn or pasture [ 20 , 21 ].…”

ALPPACA - A tooL for Prokaryotic Phylogeny And Clustering Analysis

“…The ability to run different datasets through different tracks within the same framework makes ALPPACA unique compared to other phylogeny pipelines such as Bactmap (https://nfco.re/bactmap) and SNVPhyl (https://github.com/DHQP/SNVPhyl_Nextflow), where only mapping-based phylogeny is possible. Several research projects have provided the developmental platform of ALPPACA, and peer-reviewed papers have been published using this framework for phylogenetic analysis (Franklin-Alming et al, 2021;Kaspersen et al, 2020;Kravik et al, 2022;Smistad et al, 2022).…”