Staphylococcus aureus microcapsule expression attenuates bacterial virulence in a rat model of experimental endocarditis.

Abstract

The virulence of the Staphylococcus aureus strains that differed only in capsule expression was compared in a rat model of catheter-induced experimental endocarditis. The ID50 of all the strains was low (less than 3 x 10(3) cfu of S. aureus), suggesting that this model may be more sensitive than other animal models to differences in bacterial virulence. Compared with the wild-type strains that expressed type 5 or type 8 capsular polysaccharides, mutant strains devoid of capsule had significantly lower ID50 values. In contrast, a mutant that produced scant amounts of the type 5 polysaccharide had an ID50 similar to that of the parental type 5 isolate. As the bacterial inoculum was increased, each of the S. aureus strains reached final concentrations of 10(10)-10(11) cfu/g of vegetation; however, the nonencapsulated mutants colonized the left-sided vegetations at lower inocula than did the wild-type strains. This study indicates that microcapsule expression attenuates bacterial virulence in a rat model of catheter-induced endocarditis.

• Authors: L M Baddour, C Lowrance, A Albus, J H Lowrance, S K Anderson, J C Lee
• Journal: The Journal of infectious diseases (J Infect Dis) Vol. 165 Issue 4 Pg. 749-53 (Apr 1992) ISSN: 0022-1899 [Print] United States
• PMID: 1552206 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Topics

• Animals
• Bacterial Capsules (biosynthesis, physiology)
• Disease Models, Animal
• Endocarditis, Bacterial (microbiology)
• Male
• Rats
• Rats, Inbred Strains
• Staphylococcal Infections (microbiology)
• Staphylococcus aureus (pathogenicity)
• Virulence