Streptococcus dysgalactiae—Contagious or Environmental?

Nicole Wente,Volker Krömker

doi:10.3390/ani10112185

Abstract

Simple SummaryThe usual routes of transmission of Streptococcus dysgalactiae in the development of bovine mastitis are unclear. For the control of mastitis in dairy practice, improved knowledge about the transmission of this pathogen would be very helpful. The variety of strain within a herd can be used to describe its transmission behavior. Isolates of Strep. dysgalactiae were collected from clinical mastitis samples on different farms, and the strains were typed using a molecular method. Overall, we performed strain typing on isolates from 16 farms in Germany and found signs of the contagious transmission of Strep. dysgalactiae on all the farms. We observed a variety of outcomes, from a single strain in all six Strep. dysgalactiae cases recorded on one farm, to five strains in six cases recorded on another farm.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.

Highlights

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
Clinical mastitis (CM) in dairy cows is a common disease that significantly hampers the sustainability of milk production, as it is associated with a high consumption of antibiotics and significant economic losses [1]
All 93 isolates were analyzed by the PFGE method (Table 1)

Summary

Introduction

Clinical mastitis (CM) in dairy cows is a common disease that significantly hampers the sustainability of milk production, as it is associated with a high consumption of antibiotics and significant economic losses [1]. In Germany, Streptococcus (Strep.) dysgalactiae (2.8–5.5% of all clinical mastitis cases) is the second most frequently encountered Streptococcus in mastitis, behind Strep. Uberis (29–30.5% of all clinical mastitis cases) [2,3]. To identify the appropriate measures in case of a high-case frequency at a farm, it is important to understand whether this pathogen is transmitted between cows or from the environment to the cow. Some previous studies have described this species as being cow-associated [4,5], while some others have described it as being environment-associated [6,7]. In a recent Swedish study comparing isolates of Strep. In a recent Swedish study comparing isolates of Strep. dysgalactiae from

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