Serology of staphylococci isolated from the udders of dairy cattle in relation to the epizootiology of bovine mastitis | The serology of staphylococci isolated from the udders of dairy cattle in relation to the epizootiology of bovine mastitis

Two serological typing methods devised for use with staphylococci from human sources were used to examine strains of bovine origin. One was unsatisfactory, but with the other 91% of the coagulase positive bovine strains were typable. All the coagulase negative strains failed to react with the typing sera. The antigenic patterns revealed by this method of typing appeared to be reasonably stable. Milk samples were collected at intervals from the individual quarters of all the cows in four dairy herds. These were examined for bacteria and cells so that the type of infection could be related to the amount of inflammation present in each quarter. Milk samples from clinical cases of mastitis were also examined. It was found that infection with 'haemolytic' staphylococci -was associated with both clinical and subclinical mastitis. However, this association was more marked i n some farms than in others. There were differences in the dairy husbandry on these farms which might account for this variation in the apparent pathogenicity of the staphylococci. Representative strains of the 'haemolytic' staphylococci isolated from the quarter milk samples from the four herds and staphylococci from clinical cases of mastitis in these and other herds were typed serologically and examined for production of coagulase, haemolysins and opacity in egg yolk broth, growth and acid production in mannite salt agar and penicillin sensitivity. Since the source of each strain was known it was possible, in many cases, to ascertain the degree of udder inflammation with which each had been associated. When the results were compared it was found that there was no association between either clinical or subclinical mastitis and any serological group or any pattern of haemolysins in coagulase positive staphylococci. Neither the mannite salt agar nor egg yolk test could be used as a substitute for the coagulase test and neither indicated whether a staphylococcus came from a quarter with acute mastitis or not. No association was evident , between specific haemolysins and serological groups . Penicillin resistance was more commonly found in strains of serological groups 1 and 3 than strains of groups 2 and 4. A variety of serotypes were encountered among the bovine staphylococci but three were particularly widely represented. The main serotypes were not the same as those observed in a survey of strains from human sources.