Detection of biofilm formation and its associated genes in coagulase negative staphylococci isolated from milk of cows affected with subclinical mastitis

الملخص EN

Staphylococcus pathogenicity is attributed to the presence of extracellular elements and invasive mechanisms including biofilms formation.

The present study was designed to estimate the frequency of coagulase negative staphylococci (CNS) in cow’s milk affected with subclinical mastitis, determine its ability to form biofilms on polyesterne surface, and for detection of biofilms associated genes (bap, icaA and icaD) using PCR.

Accordingly, a total of 160 milk samples from cows affected with subclinical mastitis based on the results of California Mastitis Test (CMT) were collected from individual quarters of lactating cows.

All collected milk samples were subjected to bacterial isolation procedures following the standard procedures.

The overall prevalence of CNS was 69 (43.12%), S.

chromogenes was the predominate CNS isolates followed by S.

epidermidis.

The phenotypic biofilms formation was tested using microtitre plate technique, 56( 81.15%) strains were tested positive for biofilm formation of them, 53.57% (30/56) were strong, 32.14% (18/ 56) were moderate and 14.28% (8/56) were week biofilms producers.

Among the CNS species, S.

chromogenes was the predominated biofilm producing stains.

Regarding the existence of biofilm associated genes, icaA was detected in 25(36.23%) isolates, icaD was harbored by 33(47.82%) CNS strains and bap gene couldn’t be identified in all of the tested CNS isolates.

icaD was correlated with biofilm formation on polysterne surface of microtitre plate.

In conclusion, this study provides information about the frequency of CNS in bovine subclinical mastitis and its pathogenicity which is necessary to enterprise efficient approaches to control bovine mastitis.