title: Protective effect of Staphylococcus chromogenes infection against Staphylococcus aureus infection in the lactating bovine mammary gland.
abstract: The susceptibility of uninfected or Staphylococcus chromogenes-infected quarters to challenge with Staphylococcus aureus was measured. Seventeen S. chromogenes-infected quarters were challenged by infusion of S. aureus into the teat sinus; 47% (8 of 17) became infected and all 18 uninfected quarters challenged similarly with S. aureus became infected. No differences in daily milk yield were seen between uninfected quarters and S. chromogenes-infected quarters prior to S. aureus infusion. Postinfusion, milk yield for S. aureus-infected, S. chromogenes-infected, and S. chromogenes- and S. aureus-infected quarters differed. Somatic cell counts were elevated in S. chromogenes-infected quarters compared with uninfected quarters prior to S. aureus infusion. Somatic cell counts were not different between S. aureus- and S. chromogenes- and S. aureus-infected quarters postinfusion, but were different for S. chromogenes-infected quarters. Chloride concentrations in S. chromogenes- and S. aureus-infected quarters were different from either S. aureus-infected or S. chromogenes-infected quarters. Staphylococcus aureus colony forming units in quarters with preexisting S. chromogenes infections were lower than S. aureus colony-forming units in previously uninfected quarters. Possible protective mechanisms induced by S. chromogenes against superinfection by S. aureus are discussed.
authors.affiliation: Department of Animal Sciences, University of Kentucky, Lexington 40546-0215.
authors.forename: K R
authors.initials: KR
authors.lastname: Matthews
authors.forename: R J
authors.initials: RJ
authors.lastname: Harmon
authors.forename: B A
authors.initials: BA
authors.lastname: Smith
mesh_terms: D000818:Animals; D002417:Cattle; D002452:Cell Count / Q000662:veterinary; D002712:Chlorides / Q000032:analysis; D005260:Female; D007774:Lactation; D008414:Mastitis, Bovine / Q000276:immunology*; D008892:Milk / Q000737:chemistry / Q000166:cytology / Q000378:metabolism / Q000382:microbiology; D013203:Staphylococcal Infections / Q000276:immunology / Q000662:veterinary*; D013210:Staphylococcus / Q000254:growth & development / Q000276:immunology*; D013211:Staphylococcus aureus / Q000254:growth & development / Q000276:immunology*
chemical_list: D002712:Chlorides