Streptococcus pneumoniae Flashcards
What makes pneumococcus Gram positive?
Peptidoglycan in cells walls
Two components of peptidoglycan?
Alternating G,M,G,M
- glucosamine
- muramic acid
How is pneumococcus identified? (Structural features on a culture)
- gram positive
2. elongated cocci in pairs or chains
Significance of polysaccharide capsule?
- prevents neutrophil (PMN) from recognizing antibody that is attached to bacteria, unless antibody SPECIFICALLY recognies the capsule
- best defense you can have to pneumococcus is an antibody that recognizes the capsule (either naturally acquired or via vaccine_
- different polysaccharide capsules = way to differentiate between 93 types of pneumococcus
Dissection of streptococcus pneumoniae name
streptococcus = genus pneumoniae = species name
What predisposes you to pneumococcus infection?
- multifactorial (life extremeties, alcoholism, malnutrition)
- decreased pulmonary clearance (lung disease, smoking, pollution)
- DIMINISHED NEUTROPHIL FUNCTION (diabetes, cirrhosis, glucocorticosteroids)
- defective IgG production
- absence of spleen (doesn’t predispose you to infection but does increase risk of shock/sepsis)
Most common cause of pneumonia in adults?
pneumococcus is most commonly identified bacteria!
Clinical manifestations of pneumococcus (symptoms and signs)
- OFTEN preceded by viral illness that goes on for several days
- SOMETIMES sudden onset of shaking chill and fever
- Cough, fever, sputum production, and chest pain (but sometimes harder to find in older patients)
- general appearance (patients “looks sick” vs. viral harder to see symptoms)
- abnormal chest exam (dullness to percussion, wheezes, rales)
Proper way to diagnose pneumonia
CHEST X-RAY
Common laboratory findings in pneumococcus infection
- Higher WBC count = higher neutropihls
“left shift” - more band (immature) forms present
However, in OVERWHELMING infection, you will see a REDUCTION in WBC which has a bad prognosis
- CHEST X-RAY - segmental, lobar, multilobar (viral)
- low oxygen and pCO2 saturation
Besides chest x-ray, how do you diagnose pneumococcus infection?
- sputum
- blood culture (bacteremia)
- urine antigen test detects cell wall polysaccharide (specific)
What other diseases to pneumococcus cause?
- Acute otitis media
- actue sinusitis
- primary bacteremia - bacteria detected in blood with no apparent source called primary when no focus is recognized. Common cause of meningitis (esp when there’s no outbreak of meningococcal infection)
- Lots of ITIS (septic arhtritis, osteomyelitis, peritonitis, cellulitis, endocaditis, pericarditas
- acute cardiac event (23% of all patients)
When you don’t have the antibody that recognizes the capsule, how do you defend against pneumococcal infection?
- local (non-immunologic) - good patency of Eustachian tube and sinuses, ability to clear lower airways)
- good general health (live stress free!)
- innate immunity
- humoral but not capsule related (i.e. an antibody that recognizes pneumolysin or other surface protein antigens)
Significance of pneumolysin
stimulates inflammatory response and activated complement when recognized (IMPORTANT VIRULENCE FACTOR aka factor that produces disease). Produced by pneumococcus
What is the adult vaccine for pneumococcus?
Pneumovax (intuitive huhhh???)…works via T-cell independent immune reaction
Is Pneumovax preventative in children under 2? Why not?
No. Immature response to polysaccharide capsular material (but you can administer protein-conjugated vaccine to help with this)
How do protein conjugated vaccines work?
Chemical conjugation of polysaccharide (attaching) to a protein to ALTER MODE OF PRESENTATION. Also, stimulates antibody in nasopharynx which will prevent colonization, which will help eliminate these serotypes from the population
What kind of endotoxins does pneumococcus produce?
TRICK QUESTION BEEYATCH. NONE.
they do have peptidoglycan which is analagous to endotoxin though
How do we acquire the bacterium?
Pretty much confined to human beings, lives normally in healthy individuals, initially acquired via close contact
Remember, pneumococcus can colonize host without causing disease (like many other bacteria that can potentially cause infections)
During invasion, what constituent protrudes through capsule to interact with epithelial cell surface?
lipotichoic acid
How does one develop pneumonia? (pathogenesis)
- attachment in nasopharynx followed by proliferation
- then, carried by secretions to a place where clearance is poor (due to obstruction of damage to clearance function like cilia) or via local invasion via lymphatics or blood (unusual in pneumococcus)
Basic property of pneumococcal disease
organisms get where they don’t belong, clearance is damaged, they induce inflammation -> disease results. Much of the disease is inflammatory response
Difference between inhalation and aspiration
inhalation - breathing in aerosolized organisms
aspiration - mouth contents bypass trachea, occurs during sleep.
MOST PNEUMOCOCCUS INFECTION CAUSED BY ASPIRATION
