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Phenotypic variation of Staphylococcus epidermidis slime production in vitro and in vivo
G D Christensen1, L M Baddour, W A Simpson
1Veterans Administration Medical Center, Memphis, Tennessee 38104.
Abstract:
Clinical studies performed by us and others have found an association between slime production and strains of coagulase-negative staphylococci that infect indwelling medical devices. By serial low-speed centrifugation of broth cultures we have isolated a stable, weakly adherent strain (RP62A-NA) from a strongly adherent, slime-producing, pathogenic strain of Staphylococcus epidermidis sensu stricto (RP62A, ATCC 35984). We obtained a second strain from RP62A-NA (RP62A-NAR) by serial subculture of glass-adherent cells of RP62A-NA. All three strains had the same pattern of biochemical reactions, antimicrobial susceptibilities, and plasmid analysis. Transmission electron micrograph sections stained with the mucopolysaccharide-specific stain alcian blue demonstrated that the adherent strains RP62A and RP62A-NAR were covered with an extracellular coat of polysaccharide-rich material. In contrast, the nonadherent RP62A-NA strain lacked this external coat. All three strains were used in a mouse model of foreign body infection and a rat model of catheter-induced infective endocarditis. The adherence characteristics of isolates of RP62A and RP62A-NA recovered from experimental animals were relatively stable, although we noted a slight but a significant increase in the adherence of RP62A-NA isolates recovered from the foreign body model. The adherence characteristics of RP62A-NAR isolates recovered from infected animals were variable; in general these isolates were less adherent than the laboratory strain of RP62A-NAR. In both models the 50% infective dose (calculated by the Reed and Muench method) was three times greater for the RP62A-NA strain than for the RP62A strain. The phenotypic expression of slime production is subject to both in vitro and in vivo variation and could play a role in the pathogenesis of foreign body infection.
Insights
Slime production in Staphylococcus epidermidis is linked to medical device infections. A non-adherent strain showed reduced infectivity, suggesting slime
Area of Science:
- Microbiology
- Infectious Diseases
- Biotechnology
Background:
- Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, are significant pathogens associated with indwelling medical device infections.
- Slime production, an extracellular polysaccharide matrix, is a key virulence factor in these staphylococcal infections.
- Understanding the role of slime and bacterial adherence is crucial for developing strategies to prevent and treat device-related infections.
Purpose of the Study:
- To investigate the role of slime production and bacterial adherence in the pathogenesis of Staphylococcus epidermidis infections.
- To compare the infectivity of slime-producing and non-slime-producing strains in animal models of foreign body infection and infective endocarditis.
Main Methods:
- Isolation of distinct Staphylococcus epidermidis strains with varying adherence and slime production capabilities (RP62A, RP62A-NA, RP62A-NAR) through serial centrifugation and subculture.
- Characterization of strains using biochemical tests, antimicrobial susceptibility, plasmid analysis, and transmission electron microscopy with Alcian blue staining.
- Evaluation of infectivity in a mouse foreign body infection model and a rat catheter-induced infective endocarditis model.
Main Results:
- Adherent, slime-producing strains (RP62A, RP62A-NAR) exhibited an extracellular coat of polysaccharide material, while the non-adherent strain (RP62A-NA) lacked this coat.
- In both animal models, the non-adherent, non-slime-producing strain (RP62A-NA) demonstrated significantly lower infectivity (threefold greater 50% infective dose) compared to the slime-producing strain (RP62A).
- Bacterial adherence characteristics showed some variation in vivo, but the general trend of reduced infectivity for the non-adherent strain was consistent.
Conclusions:
- The phenotypic expression of slime production in Staphylococcus epidermidis is variable both in vitro and in vivo.
- Reduced bacterial adherence and lack of slime production significantly decrease the infectivity of Staphylococcus epidermidis in foreign body infection and infective endocarditis models.
- Slime production is a critical factor in the pathogenesis of staphylococcal infections associated with indwelling medical devices.