4.1. Strains

Two hundred Staphylococcus spp. strains, 50 S. aureus isolates and 150 CoNS isolates, were studied. The CoNS strains included 50 S. epidermidis, 20 S. haemolyticus, 20 S. warneri, 20 S. hominis, and 3 S. lugdunensis strains isolated from blood cultures and 20 S. saprophyticus isolated from the urine of patients with urinary tract infection seen at the University Hospital of FMB, Unesp, São Paulo, Brazil. The present study was approved by Committee for Ethics in Research (“Comitê de Ética em Pesquisa” from “Faculdade de Medicina de Botucatu”, Botucatu, São Paulo State, Brazil—Protocol 3783–2011). In view of the difficulty of isolating S. lugdunensis from human clinical samples, 13 S. lugdunensis strains isolated from milk samples of goats with mastitis were included. The following international reference strains were used: S. epidermidis ATCC 12228 and S. aureus ATCC 33591 (negative control), and S. epidermidis ATCC 35983 and S. aureus ATCC 29213 (positive control).