Molecular Epidemiology of Streptococcus uberis Clinical Mastitis in Dairy Herds: Strain Heterogeneity and Transmission.
Multilocus sequence typing was successfully completed on 494 isolates of Streptococcus uberis from clinical mastitis cases in a study of 52 commercial dairy herds over a 12-month period. In total, 195 sequence types (STs) were identified. S. uberis mastitis cases that occurred in different cows within the same herd and were attributed to a common ST were classified as potential transmission events (PTEs). Clinical cases attributed to 35 of the 195 STs identified in this study were classified PTE. PTEs were identified in 63% of the herds. PTE-associated cases, which include the first recorded occurrence of that ST in that herd (index case) and all persistent infections with that PTE ST, represented 40% of all the clinical mastitis cases and occurred in 63% of the herds. PTE-associated cases accounted for >50% of all S. uberis clinical mastitis cases in 33% of the herds. Nine STs (ST-5, -6, -20, -22, -24, -35, -233, -361, and -512), eight of which were grouped within a clonal complex (sharing at least four alleles), were statistically overrepresented (OVR STs). The findings indicate that 38% of all clinical mastitis cases and 63% of the PTEs attributed to S. uberis in dairy herds may be caused by the nine most prevalent strains. The findings suggest that a small subset of STs is disproportionally important in the epidemiology of S. uberis mastitis in the United Kingdom, with cow-to-cow transmission of S. uberis potentially occurring in the majority of herds in the United Kingdom, and may be the most important route of infection in many herds.
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom peers.davies@nottingham.ac.uk.
P L
PL
Davies
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom.
J A
JA
Leigh
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom QMMS Limited, Cedar Barn, Easton Hill, Easton, Wells, Somerset, United Kingdom.
A J
AJ
Bradley
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom.
S C
SC
Archer
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom.
R D
RD
Emes
University of Nottingham School of Veterinary Medicine and Science, Sutton Bonington Campus, Leicestershire, United Kingdom.
M J
MJ
Green
D000818:Animals; D002417:Cattle; D018562:Disease Transmission, Infectious; D014644:Genetic Variation; D008414:Mastitis, Bovine / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D013291:Streptococcus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D006113:United Kingdom / Q000453:epidemiology