期刊
FRONTIERS IN VETERINARY SCIENCE
卷 9, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fvets.2022.806674
关键词
virulence factor; persistent intramammary infection; transient intramammary infection; Streptococcus uberis; mastitis
资金
- Royal Golden Jubilee (RGJ)
- [5.VS.CM/61/D.1]
The objectives of this study were to compare the virulence patterns between transient and persistent intramammary infection (IMI) of Streptococcus uberis and determine the changes in virulence patterns after long-term transmission. The results showed that approximately 50% of field S. uberis IMI were spontaneously cured within 1 week, while 25% were not cured within 10 weeks. Regardless of transient or persistent IMI, a high similarity of the virulence pattern within a PFGE strain was found.
The objectives of this study were determined by two experiments including Experiment 1 (EXP1) using Streptococcus uberis obtained from a weekly longitudinal study to compare virulence patterns between transient and persistent intramammary infection (IMI), and Experiment 2 (EXP2) using a stored-known-appearance PFGE strain of a contagious S. uberis to determine a change of virulence patterns after long-term transmission. For EXP1, quarter milk samples from 31 milking cows were aseptically and longitudinally collected once a week for 10 weeks. A total of 14 S. uberis isolates from quarters with 1 and > 4 weeks of duration of IMI were categorized as transient and persistent IMI, respectively. For EXP2, 11 isolates of a stored-known-appearance PFGE strain of S. uberis from our previous study (1) were randomly selected, including 5 from transient IMI (1 month) and 6 from persistent IMI (> 1 month). The virulence profiles of all isolates were investigated, including sua, hasAB, hasC, gapC, pauA, and CAMP factor or cfu, using PCR. The Kaplan-Meier estimates were used to calculate the duration of IMI in EXP1. Approximately 50% of field S. uberis IMI was spontaneously cured within 1 week, while 25% was not cured within 10 weeks. From EXP1, 4 virulence patterns were found in 14 isolates. The majority of patterns for transient S. uberis did not include hasAB (63.6%), the gene relating to capsule formation. Regardless of transient or persistent IMI, a high similarity of the virulence pattern within a PFGE strain was found in EXP2. Few changes of virulence pattern within a PFGE strain were found or were related to its subsequently changing to transient IMI.
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