What is the capsule of Streptococcus pneumoniae?
The polysaccharide capsule of Streptococcus pneumoniae is the dominant surface structure of the organism and plays a critical role in virulence, principally by interfering with host opsonophagocytic clearance mechanisms.
Is penicillin effective against Streptococcus pneumoniae?
Penicillin- and cefotaxime-susceptible strains of S pneumoniae were estimated at 96% and 97.9%, respectively. In most cases, macrolides have activity against penicillin-susceptible strains of S pneumoniae.
Does Strep pneumoniae have a capsule?
The polysaccharide capsule surrounding S. pneumoniae has been well established as a major virulence factor in nonocular pneumococcal infections such as systemic infections, lung infections, and bacteremia. The function of the capsule in these infections is to allow the bacterium to evade phagocytosis.
Why is Streptococcus pneumoniae sensitive to penicillin?
pneumoniae involves genetic mutations which alter penicillin-binding protein structure, resulting in a decreased affinity for all beta-lactam antibiotics.
How does capsule prevent phagocytosis?
Capsules can resist unenhanced attachment by by preventing pathogen-associated molecular patterns or from binding to endocytic pattern-recognition receptors on the surface of the phagocytes. The capsules of some bacteria interfere with the body’s complement pathway defenses.
What is the function of capsule in the bacteria?
Function. The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages. A capsule-specific antibody may be required for phagocytosis to occur.
What antibiotics is Streptococcus pneumoniae susceptible to?
Over the years, the prevalence of susceptibility to cefuroxime was 98%–100% among S. pneumoniae. Resistance in S. pneumoniae to some older antibiotics between 2007 and 2009 was high (86.8% for trimethoprim/sulfamethoxazole and 57.2% for tetracycline).
What is the bacterial capsule made of?
The bacterial capsule is usually a hydrated polysaccharide structure that covers the outer layer of the cell wall, and in most bacteria it is composed of monosaccharides linked together via glycosidic bonds. However, amino acid (peptide) and protein–carbohydrate capsules have also been described.
How is Streptococcus penicillin-resistant?
Pneumococci and viridans streptococci are often resistant to penicillins owing to mutations in the target penicillin-binding proteins. These mutations have accumulated in strains of Str. mitis and Str. oralis, and the altered genes have subsequently been transferred by genetic transformation to Str.
How do capsules protect bacteria?
Capsules can protect a bacterial cell from ingestion and destruction by white blood cells (phagocytosis). While the exact mechanism for escaping phagocytosis is unclear, it may occur because capsules make bacterial surface components more slippery, helping the bacterium to escape engulfment by phagocytic cells.