(VI)Gram Positive Cocci (4)*Streptococcus pneumoniae + Viridans Steptococcus Flashcards
Name 2 α-hemolytic organisms
(1) Strep. viridans
(2) Strep. pneumoniae
Name 3 virulence factors of Strep. pneumoniae
(1) Anti-Phagocytic Capsule
(2) IgA protease
(3) Pneumolysin
Describe the appearance of Strep. pneumoniae under the microscope
Gram Positive (Lancet-shaped) diplococci
Name 3 ways to differentiate Strep. pneumoniae from Strep. viridans
Describe the pneumonia caused by Strep. pneumoniae
(1) Lobar
(2) “rust-colored”
(Most common cause of community acquired pneumonia)
What type of infections are most commonly due to Strep. pneumoniae?
(1) Meningitis
(2) Otitis media
(3) Pneumonia
(4) Sinusitis
What population is particularly susceptible to Strep. pneumoniae infections?
Sickle cell disease
(Due to functional asplenia and inability to clear encapsulated organisms)
Treatment (2) : Strep. pneumonia
(1) Macrolide
(2) Ceftriaxone
What is the difference in immunological response to Strep. pneumoniae vaccine for children and adults?
(1) Children: Develop IgG
(2) Adults: Develop IgM
(Children are given 13 valent vaccine conjugated to a protein, whereas adults are given 23 valent polysaccharide vaccine)
What organism is most associated with dental caries?
Strep. viridans mutans
What organism is most associated with subacute endocarditis?
Strep. viridans sanguis
(Sangre ∝ Blood ∝ Heart)
Name 2 unique characteristics of Strep. viridans
(1) Adheres to platelets
(2) Produces dextrans
(Ability to adhere to platelets explains its relation to SUBacute endocarditis)
What valve is most commonly damaged by S. viridans?
Mitral
Both Viridans Streps and Staph. Aureus causes Endocarditis, but what is the difference??? (IMPT!)
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Both Viridans Streps and Staph. Aureus causes Endocarditis, but what is the difference??? (IMPT!)
Viridan Streps causes Subacute Bacterial Endocarditis (SBE) while Staph. Aureus causes Acute Bacterial Endocarditis
“Viridans Streptococcus is eating heart valves slowly, while Staphylococcus aureus is eating fast. Viridans Streptococcus, slowly eats away at the valve just as a plant slowly grows into soil. This is in sharp contrast to Staphylococcus aureus, who received his Olympic gold ( aureus) medals for his ability to rapidly bind to and destroy the heart valves.”
How to differentiate between Strep Pneumo and Viridans Strep if they are both alpha hemolytic?
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How to differentiate between Strep Pneumo and Viridans Strep if they are both alpha hemolytic?
Strep Pneumo is optochin sensitive
Strep pneumo knight’s chin is protected (cuz sensi)
Pneumococci are cultured on […] agar, resulting in […] colonies (raised rim + sunken in the middle)
Pneumococci are cultured on blood agar, resulting in draughtsman colonies (raised rim + sunken in the middle)
Catalase negative cuz sketchy microb picture no cats lol
Under the microscope, Pneumococci appear as? (IMPT!)
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Under the microscope, Pneumococci appear as? (IMPT!)
Gram positive diplococci in chains (LANCET SHAPED)
What are clinical presentations of Viridan Strep infections?
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What are clinical presentations of Viridan Strep infections?
- Dental carries (S. Mutans)
- Mucosa-associated infections
- Subacute Bacterial Endocarditis (SBE)(commonly mitral valve)(via extracellular dextran production)
“Interestingly, the streptococci work together as a team to establish SBE. Initially, Streptococcus pyogenes causes rheumatic fever, which damages the heart valves. Now, viridans Streptococcus or the group D streptococci can more easily adhere to the heart valves and cause SBE!!!”
What are the 3 virulence factors of Pneumococci? (IMPT!!!)
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What are the 3 virulence factors of Pneumococci? (IMPT!!!)
- Anti-phagocytic capsule
- IgA Protease
- Pneumolysin (membrane damaging toxin)
Anti-phagocytic capsule seen in both pneumococcus and meningococcus (and H.influenzae)
What are the clinical presentations of pneumococcal infection? (vvvvvvvvvvvv IMPT!!!)
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What are the clinical presentations of pneumococcal infection? (vvvvvvvvvvvv IMPT!!!)
- Pneumonia (commonly lobar, bronchopneumonia is possible)
- Meningitis (high mortality, common sequelae include deafness)(more severe than N.meningitidis and H. Influenzae)
- Sinusitis
- Septicaemia
- URTI: Otitis media (common in young children), sinusitis
- Spontaneous bacterial peritonitis
“The pneumococcus is a very important organism because it is a major cause of bacterial pneumonia and meningitis in adults, and otitis media in children.** P**neumococcus is to Parents what group **B **streptococcus is to Babies.”
What are the risk factors to Pneumococcal infections? Think Tim’s alcoholic baby beanbag party pic lol. (vvvvv IMPT!!!)
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What are the risk factors to Pneumococcal infections? Think Tim’s alcoholic baby beanbag party pic lol. (vvvvv IMPT!!!)
- Alcoholism
- Young & Old age
- Hypospenism/asplenia (celiac syndrome/sickle cell anaemia/splenectomy
- Crowding
- Immunosuppression
- Chronic lung/heart/liver/renal disease
- Malignancy
Who are pneumococcal vaccines given to? (vvvv IMPT!)
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What are the two types of pneumococcal vaccines? Which one elicits better immune system response?? (vvvv IMPT!)
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What are the limitations of pneumococcal vaccines?
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Who are pneumococcal vaccines given to? (vvvv IMPT!)
All adults >65yrs, and also 2-65yrs who are “at risk”
What are the two types of pneumococcal vaccines? Which one elicits better immune system response?? (vvvv IMPT!)
- The old polysaccharide vaccine PPSV23 (IgM response) does not work well on the very young
- The newer conjugate vaccines PCV7/10/13 (IgG response) elicits better immature immune system response because it is polysaccharide + carrier protein (hence “conjugate”)
What are the limitations of pneumococcal vaccines?
- Does not cover all serotypes. Strep pneumo has over 90 serotypes (antigen diversity)
- Old vaccine not very immunogenic, especially for certain serotypes
- Not life long protection
Note: The conjugate vaccines PCV10/13 in the National Childhood Immunization Schedule
https://www.moh.gov.sg/resources-statistics/nationally-recommended-vaccines
Old Polysaccharide PPSV23
New Conjugate PCV7/10/13
PPSV23 = Pneumococcal PolySaccharide Vaccine 23 valent
PCV7/10/13 = Pneumococcal Conjugate Vaccine 7/10/13 valent
7 + 3 = 10
10 + 3 = 13
10 + 13 = 23
OH!!!!! Omgosh actually proud of myself lol wtf…
