Streptococcus pneumoniae
- epidemiology
- classification and characteristics
- virulence factors
- transmission and infection
- clinical manifestations
- diagnosis
- treatment
Epidemiology
- colonizes the nasopharynx in 5-10% of adults and 20-40% of children
- most common bacterial cause of RTIs
- incidence increases during winter months
- predisposition in pts with defective antibody formation or neutropenia, or with chronic respiratory disease
- more common in infants or elderly
- more common in patients with diabetes, alcoholism, or liver disease
- more common in asplenic patients
Classification and Characteristics
- small gram positive diplococci
- alpha hemolytic, bile soluble, optochin S
- most are encapsulated
Virulence Factors
- capsule
- most important virulence factor
- aids in escape from phagocytic cells
- helps bacteria adhere and colonize
- pneumolysin (hemolysin)
- destroys ciliated epithelial cells
- activates classical complement pathway
- supresses oxidative burst from phagocytic cells
- secretory IgA protease
Transmission and Infection
spread via
increased transmission in day cares, military, and prisons
Clinical Manifesations
- serious problem for infants
- most common bacterial cause of community-acquired pneumonia
- acute sinusitis
- otitis media
- bacterial meningitis
Diagnosis
Treatment
Antibiotic used depends on site of infection, co-morbidities, degree of illness, and ambulatory vs inpatient. Choices include penacillins, cephalosporins, macrolides, and fluoroquinolones.
Penicillin resistance has increased in recent years, and there are also high levels of resistance to TMP/SMX.