Comparative study on genotypic properties of Staphylococcus aureus isolated from clinical and subclinical mastitis in Mexico.

Abstract

MASTITIS IS ONE OF THE MAJOR PROBLEMS CHALLENGING THE DAIRY INDUSTRY WORLDWIDE. AMONG THE VARIOUS ORGANISMS CAUSING MASTITIS, STAPHYLOCOCCUS AUREUS IS CONSIDERED TO BE ONE OF THE MAIN PATHOGENS CAUSING THIS DISEASE. IN THE PRESENT STUDY 40 S. AUREUS ISOLATED FROM MILK SAMPLES OF CLINICAL AND SUBCLINICAL MASTITIC COWS FROM DIFFERENT FARMS IN ONE AREA IN MEXICO, WERE GENOTYPICALLY COMPARED. USING 62 DIFFERENT OLIGONUCLEOTIDE PRIMERS AND PCR REACTIONS WERE CARRIED OUT TO DETECT GENES FOR A NUMBER OF STAPHYLOCOCCAL EXOPROTEINS, CELL SURFACE PROTEINS, AND TWO CLASSES OF THE ACCESSORY REGULATOR GENE AGR. THE INVESTIGATED S. AUREUS WERE UNIFORMLY POSITIVE FOR THE GENE SEGMENT ENCODING A S. AUREUS-SPECIFIC PART OF THE 23S RRNA, THE GENES ENCODING THERMOSTABLE NUCLEASE (NUC), CLUMPING FACTOR (CLFA), COAGULASE (COA) AND THE GENE SEGMENTS ENCODING THE XR REPETITIVE REGION AND THE IGG BINDING REGION OF PROTEIN A (SPA). ALL TESTED STRAINS WERE ADDITIONALLY POSITIVE FOR THE HLA, FNBA, EBPS AND SET1 GENES AND NEGATIVE FOR THE SBI, SEA, SEB, SEC, SED, SEE, SEG, SEH, SEJ, TST, ETA AND ETB GENES. THE REMAINING GENES, INCLUDING HLB, FNBB, CNA (DOMAIN A AND B), CAP5, CAP8, AGR CLASS I, AGR CLASS II AND SEI WERE DETECTED IN A VARIABLE NUMBER OF ISOLATES. SIGNIFICANT DIFFERENCES BETWEEN THE S. AUREUS STRAINS ISOLATED FROM CLINICAL AND SUBCLINICAL CASES COULD BE OBSERVED IN THE SIZE OF GENE CLFA, IN THE DISTRIBUTION OF AMPLICON SIZES OF GENE COA AND THE XR-ENCODING GENE SEGMENT OF GENE SPA AND IN THE OCCURRENCE OF THE GENES HLB, FNBB, AGR CLASS I AND AGR CLASS II, RESPECTIVELY.