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Category: Bacterial Pathogenesis
Staphylococcal Capsule, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap37-1.gif /docserver/preview/fulltext/10.1128/9781555816513/9781555813437_Chap37-2.gifAbstract:
This chapter focuses on major advances in staphylococcal capsule research. The cap5 and cap8 genes required for the synthesis of CP5 and CP8, respectively, have been cloned and characterized. The cap5(8) locus was replaced by IS257 in a small subset of bovine isolates of S. aureus from Argentina. Several findings reveal that lack of capsule expression in nontypeable (NT) Staphylococcus aureus can be explained by multiple mechanisms, and these data argue against the existence of capsule serotypes other than 1, 2, 5, and 8. The arl system has been shown to be a key regulator of autolysis and the synthesis of several S. aureus extracellular virulence factors. SigB is an S. aureus alternative stress sigma factor that regulates many staphylococcal genes, including some involved in bacterial virulence. A cap5O mutation created in S. aureus Reynolds rendered the bacterium negative for CP5; capsule expression was restored when cap5O was provided to the mutant in trans. Staphylococcal adherence to the damaged heart valve is critical to initiate infection in the endocarditis model of infection. The conjugate vaccines were highly immunogenic in mice and humans and induced antibodies that opsonized encapsulated S. aureus for phagocytosis.
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Structures of staphylococcal capsules. Abbreviations: GalNAcA, N-acetyl-galactosaminuronic acid; GlcNAcA, N-acetyl-glucosaminuronic acid; O Ac, O-acetyl.
Structures of staphylococcal capsules. Abbreviations: GalNAcA, N-acetyl-galactosaminuronic acid; GlcNAcA, N-acetyl-glucosaminuronic acid; O Ac, O-acetyl.
Transmission electron micrographs of S. aureus producing CP5 (A), CP8 (B), or no capsule (C). Prior to dehydration and embedding, the bacteria were incubated with capsular antibodies to stabilize and visualize the capsule.
Transmission electron micrographs of S. aureus producing CP5 (A), CP8 (B), or no capsule (C). Prior to dehydration and embedding, the bacteria were incubated with capsular antibodies to stabilize and visualize the capsule.
Comparison of cap5 and cap8 gene clusters. Gene designations are shown in boxes. Percent identity indicates the amino acid identity of the deduced proteins between the two clusters. The genes are transcribed from left to right.
Comparison of cap5 and cap8 gene clusters. Gene designations are shown in boxes. Percent identity indicates the amino acid identity of the deduced proteins between the two clusters. The genes are transcribed from left to right.
Proposed pathway for the biosynthesis of S. aureus CP5. The gene products for which functions have been experimentally confirmed are shown in boxes.
Proposed pathway for the biosynthesis of S. aureus CP5. The gene products for which functions have been experimentally confirmed are shown in boxes.