Flagella are an important virulence factor in the subclinical persistence ofin bovine mammary gland.

Abstract

We compared the virulence profile and REP-PCR genotypes ofstrains isolated from subclinical and clinical mastitis cases and dairy farm environments in Minas Gerais State, Brazil, to determine virulence factors and genotypes potentially associated with subclinical persistence in the udder. The virulence profile was obtained by the search for three virulence genes:A (long polar fimbriae),C (flagella), andN (type III secretion system). Subclinical isolates exhibited mainly thegene (33.33%) and+genes (30.30%). Clinical isolates exhibited mainly+genes (50%) and environmental isolates the+genes (58.04%). Strains isolated from subclinical mastitis showed 6.75 times more positivity toC than environmental isolates. Thirty-four genotypes were observed in the REP-PCR analysis, and clinical mastitis isolates indicated more genetic proximity to dairy farm environment isolates than subclinical mastitis isolates. In conclusion, the results suggested that flagella may be an important virulence factor for mammary persistentinfection in cattle, however, none of theREP-PCR genotypes were associated with subclinical infection.