Slime production is considered to be a significant virulence factor for some strains of staphylococci (Christensen et al. 1982, Davenport et al. 1986, Kleeman et al. 1993, Ammendolia et al. 1999, Mack et al. 2000. In coagulase-negative staphylococci (CNS), a loosely bound exopolysaccharides layer (slime) has been found in addition to capsule, and it has been associated with sepsis, including intravenous-catheter-related bacteremia and other prosthetic device infections (Ishak et al. 1985, Diaz-Mitoma et al. 1987, Etienne et al. 1988, Rupp & Archer 1994.Similarly, Staphylococcus aureus strains have bacterial capsules, which are closely associated with the bacterial cell wall. These strains may also have an extracapsular and labile extrapolysaccharidic structure (Caputy & Costerton 1982). Formerly slime production of S. aureus has never been considered as a virulence factor. Recently, some investigators reported that slimeproducing S. aureus strains had a higher colonization capacity than its non-slime-producing variants did. Therefore, S. aureus slime may play a role in the establishment of infection (Baselga et al. 1993, Ammendolia et al. 1999.The importance of the role played by slime is further increased by its frequent association to reduced antibiotic susceptibility (Kloos & Bannerman 1994). The difficulty in eradicating a chronic infection associated with slime formation has been reported, and slime-producing bacteria has been shown to resist higher antibiotic concentrations than non-slime-producing bacteria (Gristina et al. 1987). Moreover, detection of resistance to oxacillin in staphylococci is important to guide the therapy and prevent the patient from being unnecessarily treated with vancomycin, which is an antimicrobial agent that presents therapeutic complications, high costs, and may lead to the selection of resistant mutants (Marshall et al. 1999).In this study, we wanted to evaluate the occurrence of slime production among clinical isolates of both CNS and S. aureus by comparing different methods. To assess the relationship between slime and pathogenicity, we investigated the susceptibility to certain antimicrobial agents, particularly oxacillin.
MATERIALS AND METHODSBacterial isolates -One hundred eighty seven staphylococcal isolates, provided by hospital laboratory, were obtained from culture of several specimens; 117 isolated from throat and nasal swabs, 32 from wounds, 21 from urine, 9 from blood, and 8 from catheters. Table I shows distribution of species and clinical samples in the 187 staphylococcal strains. These staphylococcal strains, specifically 115 S. aureus strains, 34 S. epidermidis strains, eight S. chromogenes strains, eight S. hominis strains, three S. saprophyticus strains, one S. lugdunensis strain, one S. capitis strain, one S. haemolyticus strain, one S. warneri strain, one S. cohnii subsp. cohnii strain, isolated from diverse clinical sources were studied. Isolates were characterized at the species level by the API Staph system (Biomerieux, France) according to the instruc...
