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42 Cards in this Set

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Streptococcus pneumoniae (pneumococcus) is the major bacterial cause of what 4 disease processes?
pneumonia, otitis media, acute sinusitis and, absent an outbreak of meningococcal disease, meningitis in all age groups except newborn
(MOPS)
What is the major virulence (disease-causing) factor in streptococcus pneumoniae?
The capsule is a major virulence (disease-causing) factor because it enables the bacterium to escape ingestion and killing by polymorphonuclear leukocytes (PMN) or alveolar macrophages; organisms then replicate and cause disease. Cell wall contains substantial peptidoglycan and organisms produce pneumolysin both of which stimulate an inflammatory response.
Pneumococci colonize _______.
nasopharynx (children>>adults)
day care centers are BAD. kids bring home organisms to adults
The incidence of pneumococcal pneumonia greater in YOUNG/ELDERLY.
elderly
What does viral infection generally do?
Viral infection increases bacterial adherence and damages clearance. Bacteria proliferate, and disease results.
Describe the morphology of pneumococcal pneumonia by microscope exam.
1. pairs/chains of elongated cocci
2. gram positive
Name the toxin produced by all pneumococci that breaks hemoglobin to a greenish pigment.
alpha hemolysin
Pneumococci are catalase POSITIVE/NEGATIVE, while staphylococci are catalase POSITIVE/NEGATIVE.
pneumococci-NEGATIVE!!!!

staphylococci-positive ("a cat has joined the staff")
Define optochin susceptibility as it relates to pneumococci.
nearly all pneumococci are susceptible to inhibition by optochin and do not grow around disk that contains this substance (optochin diffuses into the agar). Where the optochin is most concentrated, pneumococci don’t grow.
A culture of pneumococci does not grow around: (2)
1. optochin
2. bile salts
Name the 3 big-picture layers from outside going in of pneumococci
capsule, cell wall, cell membrane
Why can't organisms, absent Ab's to specific capsular polysaccharide, not be readily ingested by PMNs?
capsule is not recognized by receptors on PMN

All humans have IgG to cell wall of pneumococcus. Ig and complement can diffuse through capsule and attach. But capsule prevents PMN receptors from interacting with IgG and Fc.
Best bacterial defense against host is ______; our best defense against infection is ______.
capsule; Ab to capsule
What is teichoic acid? What is the importance of it?
it protrudes into the capsule all the way from cell membrane and mediates ATTACHMENT (TLR 2>>4) to cells of innate system and this binding/activation causes inflammation
- contains unique, choline-rich C-polysaccharide of S. pneumoniae
- C reactive protein produced by liver in inflammatory diseases/infections will react with this substance
- there are other important proteins that make pneumococcus virulent that attach to this choline
Define virulent
disease-causing
Importance of choline-binding proteins.
choline-binding proteins (ie. PspA, PspC) are important virulence factors that may have anti-phagocytic function. Abs to them may provide some immunity, enabling phagocytosis.
What does Choline binding protein D do?
lyses pneumococci: cell division and cell wall remodeling
Name principal constituent of cell wall.
peptidoglycan (alternating glucosamine and muramic acid in long chains)
Basic function of peptidoglycan within cell wall of pneumococci.
-activate complement (by alternative pathway)
-stimulate inflammatory response. it is analogous to endotoxin (principal cell wall constituent in gram neg bacteria): activate release of TNF, IL 1/6, etc.
Name 3 things in pneumococci that produce virulence.
teichoic acid, peptidoglycan, pneumolysin
What is pneumolysin?
major virulence factor w/i pneumococci
- substance (toxin) released that activates complement, stimulating inflammation
- reproduces changes of pneumonia
Define autolysin.
cell wall hydrolase that lyses pneumococci (normally, for cell cycle and to help it form new organism)
- releases substances like pneumolysin that cause inflammation and damages tissue
How is pneumococci spread?
intimate facial contact, hand to hand contact or aerosol (sneezing, coughing)
Mechanism of pneumococcal entry and pathogenesis.
-Attaches by adhering to epithelial cells (through lipoteichoic acid, protruding through capsule to surface of bacterium, interacting with epithelial cell surface of nasopharynx)
- next, 1 or 2 things could happen: 1) pneumococci carried by secretions to space where clearance is poor (bc of damage to clearance mechanisms) or obstruction - bacteria get where they don't belong -like alveoli
2)local invasion through respiratory epithelial cell layers with organisms going directly to blood stream or lymphatics (ie. direct to CNS - meningitis; spread bodywide in blood) ==> less common
- evade phagocytosis (due to capsule), replicate, spread from one alveolus to another
- cause activation of inflammatory response (virulent)

Basic property of pneumococcal disease: organisms get where they do not belong; clearance is damaged; they induce inflammation, disease results. Much of the disease is the inflammatory response
T or F. Most common infectious diseases are caused by organisms that normally colonize humans.
T. they make disease by getting where they don't belong in absence of protective immunity
Pneumonia results from what 2 things of adherent bacteria?
aspiration (back flow from mouth into trachea during sleep-- more important way esp in elderly) or inhalation
What could cause apirated or inhaled material to not be expelled like normally - leading to bacteria being able to reach distal bronchioles or alveoli?
1. Alcohol, codeine, morphine suppress cough
2. Smoking increases mucus production and causes inflammation, diminishing clearance
3. Inflammation, e.g. due to smoking or viral infection, or direct effect of viral infection damages ciliary clearance (viruses predisposes to pneumonia)
Pneumoccocus activates inflammatory response. Name three ways it does this.
1. alternative complement pathway - mostly by peptidoglycan and also pneumolysin (generating C5a)
2. classical pathway - form Ab's to cell wall
3. Taken up by dendritic cells and macrophages, activating TLRs
What do these 5 things have in common: alcohol/opiates, smoking, viral respiratory infection, pollution and asthma.
they all contribute to a decreased pulmonary clearance
What do these 5 things have in common: diabetes mellitus, glucocorticosteroids, renal insufficiency, cirrhosis, alcohol ingestion.
all lead to diminished neutrophil function
-poor migration of PMN to an infected area; and once they get there, they don’t ingest bacteria as well; once they ingest them, they don’t kill them so well (will make you much more susceptible to pneumonia and bacterial infections)
List some ways to get defective IgG production (3)
-congenital
-acquired: myeloma, lymphoma, CVID
- HIV infection (AIDS pts 50-100x more likely to get pneumococcal infection)
What is the most common cause of adult pneumonia either outpatient or leading to hospitalization?
pneumococcus
Name 5 clinical manifestations of pneumococcal infection.
1. often preceded by viral illness
2. sometimes sudden onset shaking cill and fever (this is actually uncommon)
3. cough, fever, sputum production, chest pain (some patients, esp elderly, may be asymptomatic)
4. patient "looks sick"
5. abnormal chest exam - dull percussion, wheezing, rales (BUT NOT ENOUGH TO DIAGNOSE)
What is the only proper way to diagnose pneumonia?
CHEST X-RAY!!!
Name some lab findings consistent with pneumonia.
- PMN count usually elevated with band forms present. 2/3 chance of dying if it is reduced below 6,000 (indicates overwhelming infection)
- chest x-ray: fluid accumulation in costo-phrenic angle)
Name urine test to detect cell wall pneumococcal polysaccharide.
Binax test - detects c-polysaccharide of pneumococcus (can't use this test on kids bc of high rate of false pos)
Parapneumonic effusion vs. empyema
Parapneumonic effusion - collection of fluid in pleural space that's uninfected and spontaneously resolves (in 30-40% of patients)

Empyema - collection of fluid in pleural space that's infected with bacteria; most common complication of pneumonia and requires surgery (in 5% of patients)
What does pneumococcus do by proliferation in respiratory tract?
otitis media (not seen much in adults), sinusitis, acute exacerbation of chronic bronchitis, pneumonia
T or F. Antibiotic will need to be given to patients with acute bronchitis.
F. Pneumococcus doesn't cause acute bronchitis - it is viral and therefore antibiotics don't do anything. Pneumoccocus only exacerbates chronic bronchitis (most commonly caused by cigarette smoking)
Who is least likely to have pneumococcal disease? young adult with cough, fever chest pain; 3 year old child with fever, earache; 3 yr old with no symptoms but high fever and pos blood culture; school teacher with sudden onset severe sore throat fever
school teacher with sudden onset of sore throat; acute onset of sore throat w/o any other symptoms is not streptococcal!!
Name current vaccine for pneumococcus and how it works.
Pneumovax. Capsular polysaccharide of 23 serotypes. Level of protection best in healthier, younger adults, worse in diseased and elderly who need it most. Antibody probably lost in 5-10 years
- Polysaccharides largely stimulate T cell independent immune reaction.
What type of vaccine do kids under 2 need to get for pneumococcus?
Prevnar. protein-conjugated vaccine, which alters mode of presentation, enhancing antigenicity, perhaps by invoking different sets of T helper cells