The effect of pre-enrichment on recovery of Streptococcus agalactiae, Staphylococcus aureus and mycoplasma from bovine milk

Mark Thurmond, J. W. Tyler, D. M. Luiz, C. A. Holmberg, J. P. Picanso

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The study was conducted to determine whether pre-enrichment would increase sensitivity of detecting Streptococcus (Str.) aqalactiae, Staphylococcus (S.) aureus, and mycoplasma in bovine milk. Two procedures were followed, one involving direct inoculation of milk on bovine blood agar, and the other involving preenrichment in broth followed by inoculation on agar. Logistic regression was used to predict the probability of isolation as a function of culture procedure and two additional covariates. the California Mastitis Test (CMT) score of the milk and the type of sample (indicating sample storage temperature and herd mastitis status). A total of 13778 milk samples was cultured for each of the three bacteria. By using results of both direct inoculation and pre-enrichment, the probability of isolation compared to use of direct inoculation only and adjusted for effects of other variables was increased 3·6-fold for Str. agalactiae, 1·6-fold for S. aureus and 1·7- fold for mycoplasma. The probability of isolation for all three bacteria increased as the CMT score increased. For Str. agalactiae, there was a statistical interaction predicting that enrichment improved the odds of isolation more from milk with high CMT scores than from milk with low scores. Results indicate that preenrichment can substantially increase the sensitivity of bacteriological screening of dairy cows for mastitis caused by Str. agalactiae, S. aureus, and mycoplasma.

Original languageEnglish (US)
Pages (from-to)465-474
Number of pages10
JournalEpidemiology and Infection
Volume103
Issue number3
DOIs
StatePublished - Jan 1 1989

ASJC Scopus subject areas

  • Epidemiology
  • Infectious Diseases

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