Molecular epidemiology of recurrent clinical mastitis due to Streptococcus uberis: Evidence of both an environmental source and recurring infection with the same strain

• Published in: Journal of dairy science 2014-01, Vol.97 (1), p.285-290
• Main Authors: Abureema, Salem, Smooker, Peter, Malmo, Jakob, Deighton, Margaret
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Electrophoresis, Gel, Pulsed-Field; Environment; Female; Mastitis, Bovine - blood; Mastitis, Bovine - microbiology; Molecular Epidemiology - methods; pulsed-field gel electrophoresis; Recurrence; recurrent clinical mastitis; Streptococcal Infections - blood; Streptococcal Infections - veterinary; Streptococcus - classification; Streptococcus - isolation & purification; Streptococcus uberis
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2013-7074

This study was undertaken because clinicians and farmers have observed that a considerable number of cows diagnosed with Streptococcus uberis mastitis have recurrences of mastitis in the same or a different quarter. The study was an attempt to answer whether these recurring cases were due to treatment failure (in which case a search would have begun for a better treatment for Strep. uberis mastitis) or due to reinfection with a different strain of Strep. uberis. Using pulsed-field gel electrophoresis (PFGE), we determined that the majority of recurrences (20 of 27) were caused by a new strain of Strep. uberis, indicating that treatment of the initial infection had been successful. A small number of recurrences (5 of 27) were caused by the initial strain, indicating persistence. The remaining 2 recurrences occurred in a new quarter but with the initial strain of Strep. uberis, indicating either spread between quarters or reactivation of a previous subclinical infection. Analysis of the PFGE profiles failed to reveal any strain-specific propensity to persist, because strains causing recurrences occurred in most of the major clusters.