Streptococcus Pneumonia Flashcards
List the general characteristics of streptococci
Non motile
Non sporing
Catalase negative
Facultative anerobe
Gram positive cocci
They grow in pairs and chains
Some species are capsulated
The streptococci are divided on which basis?
Classic appearance on horse blood agar
The streptococci are divided into??
Alpha
Beta
Non hemolytic (gamma)
What feature on blood agar is characteristic of alpha hemolytic streptococci?
Incomplete haemolysis, resulting in greenish tinge.
Examples of alpha hemolytic streptococci are?
S. Pneumonia and S. Viridans
The feature on blood agar that is characteristic of beta hemolytic streptococci is?
Complete haemolysis, having a clear zone on blood agar.
Beta hemolytic streptococci are grouped on the basis of??
On the basis of their lancefield carbohydrate antigen (a, b, c, f, g)
Non hemolytic streptococci include?
Viridans
Anaerobic
Nutritionally variant streptococci
List the viridans streptococci
S. Mitis
S. Mutants
S. Salivarius
S. Anginosus
S. Sanguinus
The clinical features of s. Pneumonia include??
Bacterial pneumonia
Otitis media
Bacteriemia
Meningitis
The species under alpha hemolytic strep include?
S. Pneumonia
Viridans streptococci
The A lancefield group is made up of which spp??
S. Pyogens
The invasive clinical syndromes for s. Pyogens are??
Necrotizing fascitis
Bacteriemia
GAS TSS
The spp under lancefield group B include??
S. Agalactiae
The clinical syndromes for s. Agalactiae are?
Neonatal meningitis
Bacteriemia
The spp under lancefield group c are?
S. Dysgalactia
S. Equi
The spp under lancefield group D include??
S. Bovis and others.
What is the site of infection of s. Pneumonia?
Nasopharynx. It affects 5-10% of adult and 20-40% healthy children.
What is the mode of transmission?
Inhalation of contaminated droplet nuclei.
Invasive pneumococci is commonest in <2 and >65.
T/F
True.
What are the risk factors for pneumococcal infection??
Antibody deficiencies
Complement deficiencies
Neutropenia
Asplenia
Malnutrition
Alcoholism
Chronic diseases
Overcrowding
Pathogenesis of s. Pneumonia
Capsular Polysaccharide.
Cell wall Polysaccharide.
PspA
PspC
Pneumolysin
Autolysin
PsaA
Neuraminidase
What is the fxn of neuramidase in s. Pneumonia?
Mediates adherence.
What is the fxn of PsaA in s. Pneumonia?
Adherence
What is the fxn of PspC in s. Pneumonia?
Inhibits phagocytosis by binding to complement H.
What is the fxn of Autolysin?
Causes release of bacterial components and activates complement system.
What properties give s. Pneumonia the ability to resist antibiotics?
Penicillin resistance - mutations in the pbp2x (high level resistance) and Pbp2A (low level resistance).
Macrolide resistance - ermB (methylase enzyme) and MefA (efflox genes) confer resistance to macrolide antibiotics.
What are the clinical features of s. Pneumonia?
- Lobar pneumonia.
- Pyogenic meningitis-expect in neonates.
- Non invasive diseases like otitis media and Sinusitis.
- Invasive diseases like osteomyelitis, septic arthritis, peritonitis, endocarditis, pericarditis etc.
Diagnosis of s. Pneumonia??
- BC bottles may flag positive but no result on gram stain because of autolysis of pneumococci. Pneumococcal antigen test on blood maybe positive.
- Grows on routine media and causes alpha haemolysis on blood agar. May see central autolysis of colonies (draughtsmen).
- Gram positive lancelot Diplococci often with visible capsule.
- Catalase negative, optochin sensitive, soluble in 10% bile salt.
- Penicillin MIC should be used for invasive isoletes
Treatment for s. Pneumonia??
Penicillin MIC <0.1% use penicillin or ampicilin
Penicillin mic 0.1-1.0% use ceftriaxone or ceftoxamide for meningitis.. High doses of penicillin for other infections
Penicillin MIC >1.0 use vancomycine with/ wo refampicin for meningitis, ceftriaxone or high doses of penicillin, carbapenem or floroquinolones.
What are the vacancies for s. Pneumonia??
13 valent pneumococcal conjugate vaccine given in three doses at 2, 4 and 12mnths respectively.
23 valent unconjugated vaccine given to pts >65 and also risk pts.
Children with special risk should have pcv 13 followed by ppv23 after their second birthday.
For prophylaxis, po penicillin but not for pts with csf leaks.
