Cerytain plasmid-mediated characters of staphylococci isolated from bovine mastits

Abstract

Twenty – six staphylococci were isolated from 70 cases of clinical / sub – clinical bovine mastitis. They were characterized by various biochemical tests and biotyped using coagulase production, haemolysin production, pigment production, Tween – 80 hydrolysis and casein hydrolysis. These 26 isolates comprised 19 biotypes of which, most preponderating one was biotype – B comprising of 5 isolates. The reliability of biotyping in distinguishing the isolates was found to be 73.08 per cent. The antibiogram study revealed that chloramphenicol and vancomycin were cent per cent effective. Cloxacillin, nitrofurantoin, pefloxacin and polymixin – B were also effective. Ampicillin and nalidixic acid were found to be least effective. The reliability of this method was found to be 96.15 per cent. Resistogram study revealed that maximum degree of resistance was noticed against barium chloride and potassium permanganate. All the isolates were found to be sensitive to antimony trichloride, cetrimide, copper sulphate, ferrous sulphate, iodine and potassium tellurite. The reliabiling of resistogram study was found to be 76.92 per cent. Production of haemolysin and resistance to antibiotics were found to be plasmid – mediated. Correlation between resistances to certain antibiotics and metal salts/chemical agents was also found. The plasmid profiling revealed only 16 isolates carrying plasmids. No plasmid was found common to in all the isolates. The maximum number of plasmids in an isolate was five, and this isolate carried both the largest and smallest plasmids. The reliability of plasmid profiling was 61.54 per cent. Conjugation studies revealed transfer of ampicillin, penicillin, streptomycin, erythromycin and gentamicin resistances and beta- haemolysin production to the recipient. But alpha – haemolysin was not transferred. Protoplast fusion studies revealed the expression of only ampicillin, pencillin and streptomycin resistance and alpha – haemolysin production, by the biparental strains. Determination of Numerical Index of Discrimination indicated that antibiogram typing and all its combinations were having the maximum ‘D’ value of one. Plasmid profiling was having the least value, i.e. 0.862. So it is suggested that antibiogram typing and its combinations can be used in differentiating and identifying the staphylococci causing bovine mastitis, more accurately.