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PCM1 Exam 3 > RHS11 - Respiratory Tract Infections 3 > Flashcards

RHS11 - Respiratory Tract Infections 3 Flashcards

1
Q

List the basic shape and arrangement nomenclature for bacteria we need to know.

A
  • Shape
    • -Coccus - round/oval
    • -Bacillus - rod
    • -vibrio, -spirillum, -spirochete - spiral
  • Arrangement
    • Strepto- - chain
    • Staphylo- - grape like cluster
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2
Q

Describe the two basic types of bacteria membranes and say which ones are gram positive and gram negative.

A
  • Gram Positive - a regular cell membrane surrounded by a thick peptidoglycan cell wall
  • Gram Negative - two regular cell membranes separated by a thinner peptidoglycan cell wall
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3
Q

Describe what bacterial hemolytic activiy classification is.

A

α hemolysis is partial hemolysis, causing the agar underneath to appear green

β hemolysis is complete hemolysis, causing the agar underneath to appear yellow

γ hemolysis is no hemolysis, causing the agar underneath to be unchanged

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4
Q

What is lancefield grouping?

A

A grouping system used to organize bacteria into 21 different serological groups (A-H and K-W) based upon the carbohydrate composition of bacterial antigens found on their cell walls.

Bacteria that didn’t fit it any of the groups were assigned Group O

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5
Q

What is M protein and why do we care?

A

M protein is virulence factor that is present in the cell wall of about 80 different serotypes of Streptococcus, most notably S. pyogenes. Bacteria with the M protein are in the Lancefield A group (group A streptococcus (GAS)).

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6
Q

Which is unique about the bacterial capsule of GAS species?

A

It contains hyaluronic acid and M protein

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7
Q

What is the Quellung reaction and what is it used for?

A

The Quellung reaction is a biochemical reaction used to identify bacterial species that do not fit into any of the Lancefield groups.

The reaction is between antibodies and the bacterial capsule, causing the capsule to appear swollen.

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8
Q

What bacteria species (that we need to know) elicit a positive Quellung reaction?

A
  • Streptococcus pneumoniae
  • Klebsiella pneumoniae
  • Haemophilus Influenzae
  • Neisseria meningitidis
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9
Q
A

C

  • Runny nose means common cold so probably viral
  • Not Rhino because it’s winter
  • RNA virus means Coronavirus
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10
Q

What are the species of Strep we need to know for respiratory path? What is their lancefield group and hemolysis type? What respiratory diseases do they commonly cause?

A
  • S. pyogenes - GAS - β hemolysis - pharyngitis
  • S. pneumoniae - GOS - α hemolysis - pneumonia
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11
Q

List the identifying lab information for S. Pyogenes?

A
  • Cocci in chains or pairs (diplococci)
  • Gram Positive
  • Catalase Negative
  • Aerotolerant (they possess SOD)
  • β hemolysis
  • Sensitive to the abx bacitracin
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12
Q

What is a sign that a pharyngitis is caused by S. pyogenes? Why?

A
  • The presence of tonsilar pus
    • S. Pyogenes produces leukocidins which kills leukocytes (pus is mostly dead neutrophils)
  • The presence of a heart murmur
    • S. Pyogenes infections can progress to rheumatic fever
    • If there is a pseudomembrane seen over the the pharynx as well, than it is more likely a Corynebacterium diphtheriae infection
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13
Q

S. pyogenes virulence factors to know and what they do.

A
  • The M proteins, F proteins, and Lipoteichoic acid within the bacterial capsule all aid in both avoiding phagocytosis by leukocytes and adhering to and invading host cells
  • Steptococcal pyrogenic exotoxins (SPEs) cause fever
  • Streptolysin S & O - breaks down RBCs, WBC, and platelets. This is what causes the petechiae on the tonsils and palate
  • Streptokinase - breakdown of fibrin to allow for faster dissemination
  • DNAse
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14
Q

List the sequelae we need to know of S. pyogenes infections. Include if and how these can be treated/prevented.

A
  • Suppurative diseases (only sequelae of pharyngitis)
    • Scarlet Fever - diffuse erythematous rash beginning on chest and spreading to extremities, strawberry tongue.
  • Non-Suppurative Diseases
  • Rheumatic Fever - inflammatory lesions of the heart (carditis), joints (polyarthritis), subcutaneous tissue, and CNS (chorea). Only a sequelae of pharyngitis. Preventable with penicillin prohphylaxis
  • Acute Glomerulonephritis - presents with edema, HTN, hematuria and proteinuria. Can be a sequelae of a S. pyogenes skin (impetigo) or throat (pharyngitis) infection.
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15
Q

List the identifying lab information for Corynebacterium diphtheriae.

A
  • Gram-Positive rods that appear in a “Chinese Letter” arrangement (V or L shape) on a Gram stain
  • When grown on Loeffler Coagulated Serum medium they develop these granules (volutin) that stain metachromatically (pinkish) with methylene blue
  • They grow on a Tellurite plate into black colonies with a clear halo and have a positive Elek test (a test for toxigenicity)
  • Aerobic
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16
Q

List the C. diphtheria virulence factors we need to know and what they do.

A

The diphtheria exotoxin is a toxin that inhibits EF-2 of the ribosome by ADP-ribosylation. This leads to cell death.

The genetic information for this exotoxin actually originally comes from prophage DNA (lysogenic DNA from a previous bacteriophage infection). This bacteriophage, if it gets produced, has the ability to infect and convert the nontoxigenic corynebacteria species (part of normal pharyngeal, nasopharyngeal, and skin flora) into toxigenic variants.

17
Q

What are the clinical signs that a pharyngitis is caused by C. diphtheriae

A
  • Pharyngitis has normal Sx for the first few days but eventually a thick pseudomembrane develops over the pharynx which can potentially cause respiratory obstruction
  • Once the patient becomes severely ill they can develop carditis (heart murmurs) and larngeal nerve palsy (hoarseness)
  • Recent travel to troplical or subtropical countries
  • Lack of DTaP vaccine
18
Q

What causes stridor? Why is this important for micro?

A

Stridor is caused by partial obstructions of the large airways (trachea and primary bronchi)

Corynebacterium diphtheriae and other infections that cause obstruction of the airways either through airway swelling, pseudomembrane formation (diphtheriae), or epiglottitis (H. influenzae) will present with stridor

19
Q
A

C

20
Q

What are the most common sequelae of infectious rhinitis? What pathogens most commonly cause these conditions?

A
  • Sinusitis and Acute Otitis Media (AOM)
  • Viral Causes (same as rhinitis)
    • Rhinovirus
    • Adenovirus
    • Coronavirus
  • Bacterial Causes
    • Streptococcus pneumoniae
    • Haemophilus influenzae
    • Moraxella catarrhalis
21
Q

What are the most common Sx of sinusitis and AOM?

A
  • Sinusitis - halitosis, loss of smell, cough that is usually worse at night (post nasal drip), pressure-like pain, pain behind eyes, toothach, and/or facial tenderness
  • AOM - ear pain, which often presents as ear tugging in children, hearing loss, and/or inflammation/perforation/bulging of tympanic membrane
22
Q

What are the major clinical features of Hemophilus influenzae infections?

A
  • Otitis media
  • Pneumonia
  • Epiglottitis
  • Meningitis
  • DOES NOT CAUSE INFLUENZA!
23
Q

How is H. influenzae serotyped? Which types are important to know about and why?

A
  • Serotyped according to capsule content (“a” thru “f”) or are said to be non-typeable
  • The non-typeable strain is carried by most people as part of the normal flora
  • Type B is the strain associated with invasive disease, there is a vaccine against this type
24
Q

List the identifying lab information for H. influenzae.

A
  • Pleomorphic but typically coccobacillus
  • Gram Negative
  • Only grows on chocolate agar (blood agar where the RBCs have been lysed) with growth factors X (hemin) and V (NAD). Grows as round opaque grey colonies
25
Q

List the H. influenzae virulence factors we need to know.

A
  • Pili for cell adhesion
  • Non-pilus adhesions
    • P2 outer membrane protein
  • Antiphagocytic capsule composed of polyribose ribitol phosphage (PRP).
26
Q

What are the clinical features of epiglottitis?

A
  • Fever and Sore throat
  • Stridor
  • Drooling
  • Hoarseness
  • Muffled Voice (called hot potato voice)
  • Tripod positioning (leaning forward on elbows with neck hyperextended and chin thrust forward)(
  • Tumb sign (enlarged epiglottis) on Xray (refer to image)

PCM1 Exam 3 (31 decks)

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