Characteristics of staphylococci isolated from clinical and subclinical mastitis cows in Shahrekord, Iran

Staphylococci isolated from 98 mastitic cow’s milk samples were analyzed for the production of alpha,beta and delta-hemolysin on sheep, bovine and horse red blood cells and in vitro susceptibility to several antimicrobial agents. Out of a total of 18 isolated strains, 100% demonstrated hemolytic activity either alone or in combined forms. Among 8 isolates of S. aureus 3 isolates produced α/β and 5 produced α/β/δ hemolysins. From 10 isolates of coagulase-negative staphylococci (CNS), 2 α, 2 δ, 2 α/δ and 4 α/β/δ hemolysins producing isolates were confirmed. S. aureus isolates were resistant to cloxacillin (100%), penicillin (87%) and ampicillin (62.5%). CNSs showed resistance only to amoxicillin (60%). The results suggest that a cow’s infected mammary glands are an important reservoir of hemolytic staphylococci. A high degree of S. aureus antimicrobial resistances was detected.