Streptococcus dysgalactiae—Contagious or Environmental?

Abstract

Streptococcus dysgalactiae is among the most important pathogens causing bovine mastitis. Unfortunately, there is presently a lack of clear knowledge about the mode of transmission—contagious or environmental—of this pathogen. To obtain more information on this, knowledge of the genetic diversity of the isolated microorganisms at the farm level can be useful. To observe the strain variety in different herds of cattle, isolates of Strep. dysgalactiae were collected from clinical mastitis samples at different farms, and the strains were typed using the pulsed-field gel electrophoresis (PFGE) method. Overall, we performed strain typing on 93 isolates from 16 farms in Germany and used an index to describe the degree of contagiosity of Strep. dysgalactiae at each farm. This index (CI) represents the number of isolates divided by the number of strains found in mastitis milk of clinical cases within a period of 14 months. The results differed between the farms. In one farm, all six Strep. dysgalactiae cases that occurred during the study period were caused by a single strain (CI = 6), while in another farm the six cases that occurred were caused by five different strains (CI = 1.2). All other farms fell between these two extremes. This indicates that Strep. dysgalactiae infections can occur via several routes of transmission. At the farm level, strain comparisons are necessary to determine the routes of transmission. Two strains were able to survive on the farm for a minimum of 14 months.

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

“…It also showed that the same SDSD strain caused IMI in multiple cows in the same herd. Similar findings have been described by others (Lundberg et al, 2016;Wente and Krömker, 2020) and can be taken as evidence of direct or indirect transmission between animals. Further studies are needed to determine whether some strains of SDSD have greater potential for contagious spread than others.…”

“…Using various strain-typing schemes, previous studies have suggested that the strain diversity, and hence also the epidemiology of SDSD, may differ between farms. For example, several different SDSD genotypes can be found in individual dairy farms, as might be expected for opportunistic bacteria (Gillespie et al, 1998;Wang et al, 1999;Lundberg et al, 2016;Wente and Krömker, 2020). However, the same studies also showed that in some herds one strain dominated and could be found in milk from multiple cows.…”

“…The genetic diversity of SDSD from Norwegian dairy herds is unknown, and we do not know whether certain bacterial genotypes are more often associated with mastitis than others. Previous studies investigating between-herd diversity of SDSD have used gel-based genotyping methods (Baseggio et al, 1997;Wang et al, 1999;Lundberg et al, 2014;Wente and Krömker, 2020) or biotyping (Aarestrup and Jensen, 1996). New studies using whole-genome sequencing (WGS), which has higher resolution, to investigate within-herd and between-herd diversity of SDSD are warranted.…”

The Role of Streptococcus spp. in Bovine Mastitis

“…For S. dysgalactiae , the classification in environmental or contagious is not clear. Due to its ability to survive within the host and in the environment, it is described as an intermediate pathogen [ 16 ]. The majority of S. dysgalactiae strains are non-hemolytic, although alpha-hemolytic exceptions exist.…”

Mini Review: Lactoferrin-binding protein of Streptococcus in Bovine Mastitis

“…Streptococcus dysgalactiae is able to endure within the host and in the environment, this uncertainty makes this bacteria counted as an intermediate pathogen [28]. Furthermore, S. dysgalactiae generally concurrent with the infectious problem in bovine and other ruminants.…”