title: Microbiological results from milk samples obtained premilking and postmilking for the diagnosis of bovine intramammary infections.
abstract: Bacteriological culture results were compared between 336 pairs of quarter milk samples collected premilking and postmilking. Using a positive result on either premilking or postmilking samples as the definitive diagnosis, premilking sampling sensitivity was 91% for Staphylococcus aureus, 91% for coagulase-negative staphylococci, and 97% for Streptococcus other than agalactiae. Postmilking sampling sensitivities were 81, 45, and 58%, respectively, for the same pathogens. Requiring both premilking and postmilking samples for the definitive diagnosis, specificities were 92, 86, and 95% for premilking sampling alone and 96, 98, and 99% for postmilking sampling alone. Such differences in specificity would result in major differences in predictive value of a positive culture for herds with a low prevalence. Multiple isolates were significantly more common from premilking samples.
authors.affiliation: Quality Milk Promotion Services, Cornell University, Ithaca, NY 14850.
authors.forename: P M
authors.initials: PM
authors.lastname: Sears
authors.forename: D J
authors.initials: DJ
authors.lastname: Wilson
authors.forename: R N
authors.initials: RN
authors.lastname: Gonzalez
authors.forename: D D
authors.initials: DD
authors.lastname: Hancock
mesh_terms: D000818:Animals; D002417:Cattle; D005260:Female; D008414:Mastitis, Bovine / Q000175:diagnosis*; D008892:Milk / Q000382:microbiology*; D011237:Predictive Value of Tests; D013203:Staphylococcal Infections / Q000175:diagnosis / Q000662:veterinary*; D013211:Staphylococcus aureus / Q000302:isolation & purification*; D013290:Streptococcal Infections / Q000175:diagnosis / Q000662:veterinary; D013291:Streptococcus / Q000302:isolation & purification