Protective Effect of Staphylococcus chromogenes Infection Against Staphylococcus aureus Infection in the Lactating Bovine Mammary Gland 1 K. R. MATTHEWS,1 R. J. HARMON, and B. A. SMITH Department of Animal ScIences University of Kentucky
lexington 40546-0215 ABSTRACT
tective mechanisms induced by S. chromogenes against superinfection by S. aureus are discussed. (Key words: Staphylococcus aureus, mastitis, bovine)
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. chromogenesinfected, 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-infeeted 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 pro-
INTRODUCTION
Received 1une 12, 1989. Accepted 1uly 18, 1990. l 1bis manuscript (89-5-22) is published with the approval of the director of die K.entucky Agricultural Experiment Station. 2Present address: Deputmcnt of Animal Science. University of Tennessee. Knoxville 37901. 1990 1 Dairy Sci 73:3457-3462
The study of colonization of the mammary gland by minor pathogens, especially coagulase-negative staphylococci that produce diffusible antagonistic substances effective against various pathogenic bacteria, may be valuable in developing alternative methods of ma~titis co~ trol. Coagulase-negative staphylOCOCCi are minor pathogens (9) rarely associated with clinical symptoms. The effects of coagulase-negative staphylococci on milk yield, composition, SCC, and secretory tissue have been reported (2, 3, 10, 12, 31). Edwards and Jones (6) reported that 23% of 434 coagulase-negative staphylococci strains isolated from 16 cows produced an antibiotic substance inhibitory to the growth of coagulase-positive staphylococci. Results indica!ed that infection with coagulase-negative staphylococci may interfere with the colonization of the udder by more pathogenic bacteria. Studies of protective effects show that natural or induced coagulase-negative staphylococci infections exert considerable protection against subsequent challenge using Staphylococcus aureus (16, 19, 22). However, conflicting results have been reported (28). The observation that a coagulase-negative staphylococci-infected quarter exhibits reduced susceptibility to challenge may simply be related to the increased migration of polymorphonuclear leukocytes into the milk. The dose of the challenge inoculum and the route of challenge (i.e., infusion through streak canal directly into teat cistern or immersion of the teat end in broth culture) may influence colonization of the quarter.
3457
3458
MATIHEWS BT AL.
The majority of research on bacterial antagonism has concentrated on quarters with preexisting Staphylococcus epidermidis (15, 22), or else coagulase-negative staphylococci were utilized but not identified by species (6, 28). In this study only quarters harboring Staphylococcus chromogenes were used due to its prevalence in the teat canal (2) and milk samples (9, 17). The purpose of this study was to measure the protective effect of preexisting S. chromogenes infection on subsequent challenge by S. aureus. MATERIALS AND METHODS
Ten Holstein and Jersey cows in the University of Kentucky dairy herd were used. All cows were in the 2nd to 11th mo of lactation and were housed in a three-sided free stall barn bedded with hardwood sawdust. Cows were pastured daily after the a.m. milking for approximately 5 h. Udders and teats were washed and thoroughly dried with single use paper towels before milking. An individual quarter milker (Alfa Laval Inc., Kansas City, MO) was used to record milk yield. Postmilking teat dipping was carried out routinely using a 1% iodophor or 1.94% linear dodecyl benzene sulfonic acid teat
lexington 40546-0215 ABSTRACT
tective mechanisms induced by S. chromogenes against superinfection by S. aureus are discussed. (Key words: Staphylococcus aureus, mastitis, bovine)
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. chromogenesinfected, 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-infeeted 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 pro-
INTRODUCTION
Received 1une 12, 1989. Accepted 1uly 18, 1990. l 1bis manuscript (89-5-22) is published with the approval of the director of die K.entucky Agricultural Experiment Station. 2Present address: Deputmcnt of Animal Science. University of Tennessee. Knoxville 37901. 1990 1 Dairy Sci 73:3457-3462
The study of colonization of the mammary gland by minor pathogens, especially coagulase-negative staphylococci that produce diffusible antagonistic substances effective against various pathogenic bacteria, may be valuable in developing alternative methods of ma~titis co~ trol. Coagulase-negative staphylOCOCCi are minor pathogens (9) rarely associated with clinical symptoms. The effects of coagulase-negative staphylococci on milk yield, composition, SCC, and secretory tissue have been reported (2, 3, 10, 12, 31). Edwards and Jones (6) reported that 23% of 434 coagulase-negative staphylococci strains isolated from 16 cows produced an antibiotic substance inhibitory to the growth of coagulase-positive staphylococci. Results indica!ed that infection with coagulase-negative staphylococci may interfere with the colonization of the udder by more pathogenic bacteria. Studies of protective effects show that natural or induced coagulase-negative staphylococci infections exert considerable protection against subsequent challenge using Staphylococcus aureus (16, 19, 22). However, conflicting results have been reported (28). The observation that a coagulase-negative staphylococci-infected quarter exhibits reduced susceptibility to challenge may simply be related to the increased migration of polymorphonuclear leukocytes into the milk. The dose of the challenge inoculum and the route of challenge (i.e., infusion through streak canal directly into teat cistern or immersion of the teat end in broth culture) may influence colonization of the quarter.
3457
3458
MATIHEWS BT AL.
The majority of research on bacterial antagonism has concentrated on quarters with preexisting Staphylococcus epidermidis (15, 22), or else coagulase-negative staphylococci were utilized but not identified by species (6, 28). In this study only quarters harboring Staphylococcus chromogenes were used due to its prevalence in the teat canal (2) and milk samples (9, 17). The purpose of this study was to measure the protective effect of preexisting S. chromogenes infection on subsequent challenge by S. aureus. MATERIALS AND METHODS
Ten Holstein and Jersey cows in the University of Kentucky dairy herd were used. All cows were in the 2nd to 11th mo of lactation and were housed in a three-sided free stall barn bedded with hardwood sawdust. Cows were pastured daily after the a.m. milking for approximately 5 h. Udders and teats were washed and thoroughly dried with single use paper towels before milking. An individual quarter milker (Alfa Laval Inc., Kansas City, MO) was used to record milk yield. Postmilking teat dipping was carried out routinely using a 1% iodophor or 1.94% linear dodecyl benzene sulfonic acid teat
