Characterisation of Staphylococcus aureus strains isolated from mastitis bovine milk in Argentina

USONGO V.; ARCHAMBAULT M.; SREDNIK M. E.; JANVIER X.; LÉPINE S.; GENTILINI E. R.

Journal of Dairy Research

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2017 vol. 85 p. 57 - 63

0022-0299

The study reported in this Research Communication was conducted to characteriseStaphylococcus aureus isolates recovered from mastitic bovine milk from dairy herds inArgentina. A total of 829 mastitic milk samples, both clinical and subclinical, were collectedfrom 21 farms by veterinarians and submitted to the laboratory for testing from which 229 S.aureus isolates were recovered, an isolation rate of 28·1%. These isolates were tested for susceptibilityto the antibiotics penicillin, erythromycin and clindamycin. Of the 229 isolates, 53 (23·1%)were resistant to penicillin, 31 (13·5%) to erythromycin and 28 (12·2%) to clindamycin. All isolateswere negative for the mecA, mecC and pvl genes by PCR. Southernblot hybridisationrevealed that the ermC gene was located on plasmid bands. Eighty isolates were randomly selectedfrom the 229 for further characterisation. Restriction analysis of chromosomal DNA with Cf9I followedby PFGE of the 80 isolates revealed 23 distinct pulsotypes at 80% similarity. Seven majortypes (A, B, N, P, S, T, U and V) accounted for 68·7% of these isolates and 12 pulsotypes (A, B,F, G, J, K, M, N, P, S, T and U) occurred on more than one farm indicating genetic diversitywithin the farms. MLST of a representative isolate from dominant types identified the STs 97705, 746, 2102 and 2187 with ST97 being the most predominant. Antibiotic susceptibilitytesting showed that 53·7% of the 80 randomly selected isolates were resistant to at least one ofthe three antibiotics tested. To our knowledge, this study represents the first large scale molecularstudies on S. aureus isolates from dairy farms in Argentina.