Staphylococcus lugdunesis 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 alpha and delta 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.
A surgical procedure allowed the placement of a silicone rubber catheter in the marrow cavity of the tibia of a rabbit and also allowed the introduction of a sclerosing agent (sodium morrhuate) and cells of Staphylococcus aureus. Osteomyelitis developed in 60% of the animals so treated, and the infecting microorganism was recovered from the infected tibias of the animals that developed this disease. All blood cultures taken 24 h after the infection were negative for S. aureus. Radiological findings consisted of osteolytic changes, the occurrence of sequestration and periosteal reactions, and sclerosis in the infected bones. Sections of bone prepared for histological examination confirmed the diagnosis of osteomyelitis. Transmission and scanning electron microscopy of samples of bone marrow, bone chips, and the catheters taken from the infected tibiae revealed gram-positive cocci embedded in a very extensive matrix of ruthenium red-staining glycocalyx adhering to the bone and the implanted catheter. It is proposed that this extensive glycocalyx served a protective function for the bacteria and was important in bacterial adherence and thus played an important role in bacterial persistence and the development of osteomyelitis in these rabbits.
Fluorescein isothiocyanate-labeled antibody reagents (conjugates) were prepared to one strain of each of the three subspecies of Bacteroides melaninogenicus: B. melaninogenicus subsp. melaninogenicus, B. melaninogenicus subsp. asaccharolyticus, and B. melaninogenicus subsp. intermedius. These three conjugates were specific; thus, they provided a new serological classification of B. melaninogenicus. The three serogroups were designated A, B, and C. Most test strains (98%) isolated from human clinical specimens were assigned to a specific serogroup by immunofluorescence, and the serogroup of these test strains corroborated the biochemical characterization of the three subspecies of B. melaninogenicus. The conjugates failed to cross-react with other anaerobes or aerobes tested. This fluorescent antibody technique provided a more rapid classification of the three subspecies of B. melaninogenicus than did conventional biochemical methods.
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