Molecular epidemiology of recurrent clinical mastitis due to Streptococcus uberis: evidence of both an environmental source and recurring infection with the same strain.
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.
School of Applied Sciences, Royal Melbourne Institute of Technology (RMIT) University, Bundoora, Victoria 3083, Australia.
Salem
S
Abureema
School of Applied Sciences, Royal Melbourne Institute of Technology (RMIT) University, Bundoora, Victoria 3083, Australia.
Peter
P
Smooker
Maffra Veterinary Centre, Maffra, Victoria 3860, Australia.
Jakob
J
Malmo
School of Applied Sciences, Royal Melbourne Institute of Technology (RMIT) University, Bundoora, Victoria 3083, Australia. Electronic address: margaret.deighton@rmit.edu.au.
Margaret
M
Deighton
D000818:Animals; D002417:Cattle; D016521:Electrophoresis, Gel, Pulsed-Field; D004777:Environment; D005260:Female; D008414:Mastitis, Bovine / Q000097:blood / Q000382:microbiology*; D017720:Molecular Epidemiology / Q000379:methods*; D012008:Recurrence; D013290:Streptococcal Infections / Q000097:blood / Q000662:veterinary*; D013291:Streptococcus / Q000145:classification / Q000302:isolation & purification*
Streptococcus uberis; pulsed-field gel electrophoresis; recurrent clinical mastitis