Encapsulated Organisms to Know Flashcards
What is the mnemonic to remember the most important encapsulated bacteria?
‘Some Nasty Killers Have Serious Capsule Protection’ (Strep pneumoniae, Neisseria meningitidis, Klebsiella pneumoniae, Haemophilus influenzae type B, Salmonella typhi, Cryptococcus neoformans, Pseudomonas aeruginosa)
Why are bacterial capsules important for virulence?
Capsules prevent phagocytosis by inhibiting opsonization and complement activation.
What immune cells are primarily responsible for clearing encapsulated bacteria?
Splenic macrophages (spleen is essential for clearance).
Why are asplenic patients (e.g., sickle cell disease, splenectomy) at high risk for infections by encapsulated bacteria?
They lack splenic macrophages to clear opsonized bacteria, making them highly susceptible.
Which encapsulated bacteria is a fungus and causes meningitis in immunocompromised patients?
Cryptococcus neoformans.
What test is used to visualize bacterial capsules under the microscope?
Quellung reaction (capsules swell when exposed to specific antibodies).
What major encapsulated bacteria cause meningitis?
Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type B, Cryptococcus neoformans (fungal meningitis).
What major encapsulated bacteria cause pneumonia?
Streptococcus pneumoniae, Klebsiella pneumoniae, Haemophilus influenzae type B.
What major encapsulated bacteria cause sepsis in asplenic patients?
Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type B.
What major encapsulated bacteria cause UTIs and pneumonia in hospitalized patients?
Klebsiella pneumoniae, Pseudomonas aeruginosa.
What encapsulated bacteria is associated with a thick, mucoid capsule and causes currant jelly sputum in pneumonia?
Klebsiella pneumoniae.
What encapsulated bacteria is a common cause of otitis media and epiglottitis?
Haemophilus influenzae type B.
What encapsulated bacteria can be detected with India ink staining and causes meningitis in AIDS patients?
Cryptococcus neoformans.
What encapsulated bacteria has a vaccine containing polysaccharide conjugated to a protein carrier for better immunogenicity?
Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type B.
What are the three vaccines for encapsulated bacteria and their target organisms?
Pneumococcal vaccine (S. pneumoniae), Meningococcal vaccine (N. meningitidis), Hib vaccine (H. influenzae type B).
How do patients with sickle cell disease have increased susceptibility to encapsulated bacteria?
Autosplenectomy leads to decreased clearance of encapsulated bacteria.
What complement deficiency leads to increased risk of Neisseria meningitidis infections?
Terminal complement deficiencies (C5-C9).
What laboratory test is used to confirm encapsulated bacteria in CSF or blood?
Latex particle agglutination test.
Why are conjugate vaccines more effective than polysaccharide-only vaccines?
Conjugate vaccines induce a T-cell-dependent response, leading to stronger and longer-lasting immunity.
What is the main virulence factor of encapsulated bacteria?
The polysaccharide capsule, which prevents phagocytosis and complement activation.
