South African vet lab investigates mastitis-causing bacteria

Compared to other countries, there is very little data available on the diversity, epidemiology and virulence potential of mastitis-causing bacteria in South African dairy herds. That will soon change, though, as Allerton Provincial Veterinary Laboratory has initiated a number of research activities. In collaboration with the University of Pretoria, the laboratory began research in 2013.

Allerton Provincial Laboratory is located in Pietermaritzburg, the capital city of the province of KwaZulu-Natal.
Allerton Provincial Laboratory is located in Pietermaritzburg, the capital city of the province of KwaZulu-Natal.

Allerton Provincial Veterinary Laboratory aims to conduct research in three main areas, including:

  • Investigating the diversity of Staphylococcus species in dairy herds in the province of KwaZulu-Natal
  • Evaluating the susceptibility of isolates to a panel of clinically relevant antimicrobials
  • Screening isolates for specific virulence markers, and genotypic characterization of S. aureus isolates using PFGE, spa typing and MLST

The initial study involved the sampling of cows from nine commercial dairy herds, two agriculture college herds and two communal animal herds within the province. During the course of the study, a total of 3,387 milk samples from 1,374 cows were evaluated. During the course of the evaluation, a collection of 146 S. aureus and 102 coagulase-negative staphylococcus (CNS) isolates were selected for further characterization.

In order to provide a better idea of the diversity of the different species within the herds sampled, the CNS were identified to the species level. Of those identified, Staphylococcus chromogenes was the predominant species; the species was recovered from all sampled herds. According to the researchers, only 1% of the isolates were identified as S. epidermidis.

More than half of the samples cultured (54.7%) in 2014 were bacteriologically negative.
More than half of the samples cultured (54.7%) in 2014 were bacteriologically negative.

The researchers also examined the herds for antimicrobial resistance. Overall, low levels of antimicrobial resistance were observed among the S. aureus and CNS isolates. The most common resistance observed was to penicillin, followed by tetracycline and streptomycin.

The researchers hope that the project and its results will inspire further studies within both the province and the country, creating positive outcomes for dairy producers and the industry as a whole.

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