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Short communication: Diversity of species and transmission of antimicrobial resistance among Staphylococcus spp. isolated from goat milk

Coimbra-e-Souza, Viviane, Rossi, Ciro C., Jesus-de Freitas, Luana J., Brito, Maria Aparecida V.P., Laport, Marinella S., Giambiagi-deMarval, Marcia
Journal of dairy science 2019 v.102 no.6 pp. 5518-5524
Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus lugdunensis, ampicillin, antibiotic resistance, antibiotic resistance genes, bacteria, biofilm, drugs, essential genes, goat milk, goats, herds, interspersed repetitive sequences, matrix-assisted laser desorption-ionization mass spectrometry, monitoring, plasmids, pulsed-field gel electrophoresis, species diversity, zoonoses
The increasing production of goat milk and its derivatives is affected by the occurrence of intramammary infections, which are highly associated with the presence of Staphylococcus species, including some with zoonotic potential. Staphylococci in general can exchange mobile genetic elements, a process that may be facilitated by the isolate's capacity of forming biofilms. In this study we identified, to the species level, Staphylococcus isolated from goat milk samples by MALDI-TOF and confirmed the identification by sequencing housekeeping genes (rrs and tuf). Eight species were identified, more than half being either Staphylococcus epidermidis or Staphylococcus lugdunensis. The isolates were shown by pulsed-field gel electrophoresis to be genetically diverse between the studied herds. Resistance to ampicillin and penicillin was widespread, and 2 Staph. epidermidis isolates contained the methicillin-resistance gene mecA. Most of the isolates that were resistant to at least 1 of the 13 antimicrobials tested harbored plasmids, one of which was demonstrated to be conjugative, being transferred from a Staph. epidermidis to a Staphylococcus aureus strain. Biofilm formation was observed in almost every isolate, which may contribute to their capacity of exchanging antimicrobial resistance genes in addition to acting as a physical barrier to the access of drugs. Our results showed that antimicrobial resistance among goat staphylococci may be emerging in a process facilitated by the exchange of mobile genetic elements between the bacteria and the establishment of biofilms, which calls for careful monitoring and more effective control therapies.