Streptococcus Pneumoniae Flashcards
List the microbial features of streptococcus
Facultative anaerobic
Gram positive cocci
Non sporing.
Non acid fast
Non motile.
Catalase negative.
Hemolytic on horse blood agar (Alpha,beta, gamma).
Encapsulated or noncapsulated
Enterococcus is in what Lancefield classification
Group D
What is the feature of alpha hemolytic streps
no complete hemolysis.
They form greenish tinge due H2O2 that converts hemoglobin to methemoglobin.
When was strep pneumonia first identified or isolated?
pneumoniae was first isolated in 1881 by sternberg in the USA and Louis Pasteur in France.
List disease caused by s.pnemonia.
MOSS PEe
meningitis,
sinusitis,
otitis media,
endocarditis,
septic arthritis,
peritonitis,
Source of infection of S.pnemo
Nasopharynx colonization.
20-40% in healthy children
10% in healthy adultd.
Mode of transmission of S.pneumonia
Inhalation of contaminated respiratory droplets
The rate of invasive pneumococcal disease in persons per year is
15/100000
Incidence of pneumococcal is up to 10 folds higher in population race
African-Americans
At what age is invasive pneumococcal commoner
<2yrs or>65yrs
List the risk factors of Strep Pneumonia.
Tip: it’s associated with things that impairs immune system.
Antibody deficiency.
Complement deficiency.
Neutropenia or impaired neutrophil fxn.
Asplenia
Corticosteroids.
Malnutrition.
Alcoholism.
Chronic conditions (liver, renal, asthma, diabetes,COPD)
Overcrowding.
VIRULENCE FACTORS
Function of capsular polysaccharide
Activates complement,
Inhibts phagocytosis.
Function of Cell wall polysaccharide;
Activate complement and cytokines
Function of Pneumococcal surface protein A
Blocks complement deposition,
Hence inhibiting phagocytosis
Fxn of PsaA(pneumococcal surface adhesin A)
Adherence
Fxns of pspC
Inhibts phagocytosis by binding to complement factor H
What is the fxn of pneumolysine
Direct fxn: binding to cholesterol,form cell membrane pores, depreciating cell integrity,leads to cell death.
Indirect; Mediate inflammatory response by activating Chemokines and cytokines.
Fxn of autolysin
Releases bacteria components resulting in trigger of cytokine cascade.
Fxn of Neuraminidase
Mediates adherence by digesting sialic acid on cells exposing binding receptor sites
ANTIMICROBIAL RESISTANCE
Penicillin resistance is seen as a mutation in which of the penicillin binding proteins;
pbp2B(low resistance)
Pbp2X(high resistance)
pbp2B resistance can be overcome using high dose of Antibiotics T/F.
Why?
True..
This because It confers low resistance
List the two genes involved in macrolide resistance
ErmB: erythromycin ribosomal methylase B
MefA: macrolide efflux A
Clinical manifestation
Let’s go😂
List the clinical features of streptococcus pneumoniae
Most common; Lobar pneumonia and pyogenic Meningitis.
Non invasive; Otitis media, sinusitis
Invasive: Endocarditis
pericarditis,
septic arthritis
Osteomyelitis.
Primary peritonitis (less common)
Abscess.
Empyema,
Parapneumonic effusions.
DIAGNOSIS!!!
Let’s go!
What are Biochemical diagnosis of Strep Pneumonia
Catalase negative.
Optochin sensitive,
10% soluble in bile solutions.
Inulin positive (a fermenter)
List the microscopy features of streptococcus pneumoniae
Gram positive cocci in pairs.
Lanceolate or flame shaped.
List the culture features of streptococcus pneumoniae
Culture medium; Routine media.
Features;
Alpha hemolysis; present with greenish tinch.
Central autolysis of colonies(Draughtsman colony or Carom coin)
Colony is occasionally mucoid
Uniform turbidity of culture.
What is used in serotyping?
Quellung’s reaction to identify capsulated organisms which strep pneumonia tests positive for.
Treatment!!!
What are the treatments
PMIC<0.1mg/l : use penicillin and amplicilin.
PMIC: 0.1-1.0mg/l :
Meningitis: Ceftriaxone and cefotaxime.
Non menigeal: high dose penicillin.
PIMC: >2.0mg/l :
Vancomycin+_ Rifampicin
Use Ceftriaxone for non menigeal cases
High dose of ampicillin, carbapenems, fluroquinolones.
Pneumococcal Meningitis will benefit from adjunct corticosteroids T/F
Reasons?
True,
It confers antiinflammatory roles to Meningitis
VACCINATION!!
PCV 13; for children..<2yrs
PPV23 for adults>65
How many times is PCV 23 administered and at what ages
3 times
2 months, 4 months, 12months
List the risk groups that require PPV23
Sickle cell anaemia
Asplenia
Chronic kidney disease/ nephrotic syndrome.
Coeliac disease.
HIV,
Drugs; can led to immunosuppression.
Chronic diseases like(cardiac, respiratory, fever, cardiac,)
Diabetes.
PTS with cochlear implants.
C.S.F leak
