Study on some characteristics of Staphylococci isolated from sheep sub clinical mastitis milk in Shahrekord, Iran

Introduction: Staphylococci release a large number of enzymes. Some of these, such as coagulase, beta lactamase, hemolysins and biofilms are considered indices of pathogenicity. The aim of the current study was based on the isolation and identification of Staphylococcus aureus and coagulase negative Staphylococci (CNS) strains from sheep sub clinical mastitis and examining their biofilm, beta lactamase, hemolysins production and antibiotic resistance pattern. Materials and methods: 55 Staphylococci strains were isolated from seventy cases of sheep subclinical mastitis. Thirty three were determined as Staphylococcus aureus (60%) and 22 (40%) as CNS. The hemolytic activity was evaluated by plating Staphylococci strains on 5% bovine blood agar. The biofilm assay was performed by using micro titer plates. Beta Lactamase production was detected by test tube iodometric technique and susceptibility to antimicrobial agents was determined for isolated strains by the disk diffusion method. Results: Twenty six (78.8%) S. aureus strains were biofilm producers. For CNS (59.9%) strains were positive in biofilm production. Two isolates (6.06%), of S. aureus were α, the same number β and 6 (18.2%) isolates were ∂ hemolysin producers. Six isolates of CNS (27.27%) were α and ten (45.45%) ∂ hemolysin producers. Sixteen S. aureus (48.5%) and five CNS (22.72%) isolates were positive in beta lactamase production. The isolated Staphylococci show a low sensitivity pattern to methicillin and streptomycin. Discussion and conclusion: A high percentage of strains make α toxin that play a role in S. aureus biofilm formation. Twenty one out of 33 (63.63%) isolated Staphylococci were biofilm producers that can have deleterious effects because biofilm formation is thought to play an important role in the survival of virulent strains of Staphylococci. Sixteen out of 33 (48.5%) isolated S. aureus were positive in beta lactamase test, Excluding resistant to methicillin, all of these isolates show a marked sensitivities to other examined beta lactam drugs. High percentage of hemolysins, biofilm and beta lactamase production by isolated Staphylococci, suggest an important role of these virulence factors in the pathogenesis of isolated Staphylococci from mastitis sheep milk samples.