IDENTIFICATION OF NUC GENE IN STAPHYLOCOCCAL SUB-CLINICAL MASTITIS IN CATTLE

Mastitis, caused by multifactorial etiopathological factors, is one of the costliest disease of dairy animals across the globe. For the epidemiological study 550 lactating cows were screened by modified California mastitis test (MCMT). Clinical examination of animals and their udder/milk, phenotypic and genotypic characterization of Staphylococcus spp. was carried out. A total of 212 MCMT positive quarter milk samples were processed for bacteriological examination and molecular identification of S. aureus by nuc gene amplification. Synthetic oligonucleotide primers of 21 and 24 bases, respectively, were used in the polymerase chain reaction (PCR) to amplify a sequence of the nuc gene, which encodes the thermostable nuclease of Staphylococcus aureus. A DNA fragment of approximately 270 bp was amplified from isolated DNA. The PCR product was detected by agarose gel electrophoresis. Amplification was not recorded when other staphylococcal species were tested. Some of the non-S. aureus staphylococci produced thermostable nucleases but were PCR negative. The overall occurrence of Staphylococcal SCM was reported to be 16.36% (90/550) animal wise and 6.07% (127/2092) quarter wise as identified on the basis of colony morphology, characteristic colour changes on Mannitol salt agar, positive catalase test, haemolysis pattern on blood agar and DNase activity on DNase agar. The occurrence recorded using PCR for identification of nuc was 14.62%.