Staphylococcus schleiferi, Staphylococcus lugdunensis, and Staphylococcus epidermidis produce a high incidence of abscesses in a mouse model with an implanted foreign body. We investigated the significance of the foreign body in this process. Fourteen strains of S. schleiferi, S. epidermidis, and S. lugdunensis were tested in our model. A preadhered foreign body was implanted into one mouse group, followed by injection of a test strain. Another group received injection without implant. Abscesses were assessed at 7 days; foreign bodies and infected tissues were cultured. The percent of samples that developed abscesses or were culture positive was compared for each strain. Nearly all mice infected with S. schleiferi developed abscesses and were culture positive. The foreign body made no difference in abscess formation for three of four S. schleiferi but increased the incidence of both organism recovery and abscess for three of five S. epidermidis. The foreign body enhanced abscess formation for four of five S. lugdunensis, with all five strains yielding significantly more culture recovery. Although the pathogenicity of nine strains was increased by the foreign body, five strains yielded high abscess and culture recovery rates that were not enhanced by its presence.

Staphylococcus lugdunensis and Staphylococcus schleiferi, two newly described species, have been isolated from numerous types of human infections. We compared the pathogenicity of 30 strains of S. lugdunensis, S. schleiferi, Staphylococcus epidermidis, Staphylococcus warneri, and Staphylococcus hominis, using a mouse model in which a foreign body preadhered with the test strain was implanted subcutaneously, followed by injection of the test strain. All five species of staphylococci produced abscesses. Staphylococcus epidermidis, S. schleiferi, and S. lugdunensis yielded species means of 76-91% abscess formation; 80-100% of the infected foreign bodies and tissues were culture positive. These three species were more virulent than S. warneri or S. hominis, which produced abscesses in 54 and 65% of mice, respectively; only 10-48% of the infected samples were culture positive. Transmission electron microscopy of pure cultures of selected strains showed that all species possessed glycocalyx. All species produced a variety of possible virulence factors, such as α and δ hemolysins, as well as the aggressins lipase and esterase. The production of exoenzymes did not always correlate with virulence as demonstrated by abscess formation in mice.