Streptococcus Pneumoniae Flashcards
Bacterias which cause pneumonia
S. pneumonia
S. aureus
Group A streptococcus
Klebsiella pneumonia
H. influenza
Streptococci species and their typical hemolysis
S.pyogens (β)
S.agalactiae (β)
E.faecalis (α or β or none)
S.bovis (α or none)
S.pneumoniae (α)
Viridans (α)
Streptococci are catalase +ve or -ve
Catalase -ve
S.pneumoniae morphology
Lancet shaped
Gram +ve
Occur in pairs
Capsulated pairs
Nonmotile and nonsporing
Transmission occurs through
Respiratory droplets
Risk factors for pneumonia
Respiratory viral infections
Pulmonary congestion
Malnutrition
Immunodeficiency
Stress
Alcoholism
Antigenic structure includes
1) capsule polysaccharide: type specific antigen. Diffuses into infective tissue & culture medium so called as specific soluble substance (SSS)
2) C carbohydrate antigen: species specific antigen.
Virulence factors
Polysaccharide capsule (antiphagocytic)
Pneumolysin: membrane damaging toxin
Autolysin: helps to release bacterial toxins
Types of infections
Non-invasive
-otitis
-sinusitis
-recurrent bronchitis
Invasive
-pneumonia
-sepsis
-meningitis
Clinical findings
Abrupt onset of fever
Chills
Productive cough
Pleuritic chest pain
Dyspnea, tachypnea, hypoxia
Rusty colored sputum
Specimen to be collected for lab
Sputum
CSF
Blood
Synovial fluid
Laryngeal swab (children)
Lab tests for pneumococcus
Quellung reaction
Optochin sensitivity
Quellung reaction?
When pneumococci on slide mixed with antiserum and methylene blue, the capsule will swell. Used for rapid identification
Optochin sensitivity?
A disc impregnated with optochin is placed on the agar dish. The growth of s.pneumoniae will be inhibited.
Beta hemolytic streptococci?
Completely lyse the RBCs, leaving a clear zone of hemolysis around the colony
Alpha hemolytic streptococci?
Partially lyse the RBCs, leaving a greenish discolouration of the culture surrounding the colony
Gamma hemolytic streptococci?
Unable to lyse the RBCs. (Non-hemolytic)
Hemolysis of s.pneumoniae on blood agar
After incubation for 18h, the colonies are small dome shaped and glistening
Further 24-48h, the colonies become flat with raised edges called as Draughtsman or carrom coin appearance.
Treatment
Severe infections- penicillin G
Mild infections- oral penicillin V
Penicillin allergic patients- erythromycin or azithromycin
Vaccine for s.pneumoniae
Prevnar 13 (13-valent pneumococcal conjugate vaccine)
Pneumovax 23 (23-valent pneumococcal unconjugated vaccine) given to healthy individuals 50y or older
Fungi causing chronic pneumonia
Histoplasma capsulatum
Blastomyces dermatitidis
Coccidioidomycosis
Fungi causing pneumonia in immunocompromised patients
Pneumocystis jiroveci
Candida species
Aspergillus species
Phycomycetes
Cryptococcus neoformans
Lancefield group of S.pyogens
A
Lancefield group of S.agalactiae
B
Lancefield group of E.faecalis
D
Lancefield group of S.bovis
D
S.pneumoniae causes
Pneumonia in adults
Otitis media in children
Bacterial meningitis in adults
Tracheobronchitis
Major virulence factor of pneumococcus
Polysaccharide capsule
