39 terms

Micro: Bacterial/Fungal Respiratory Infections

Streptococcus is catalase...? What medium grows them? Strep is ___-hemolytic
Negative. They're fastidious--blood agar! (Peptone, 5% blood, and yeast). Beta-hemolytic (clear area around bacteria where eat medium--alpha turns it green)
Strep pyogenes=Group ___ strep
What makes strep pyogenes pyogenic?
Leukocidin enzyme
What does the hyaluronic acid of strep pyogenes do? How does the human body counter this?
It forms the CAPSULE! But because it's something found in us, it's NOT antigenic--like an invisible cloak allowing it to move through us undetected. BUT, the M protein peeks through the cloak, and THAT is what the body recognizes and attacks.
Name four toxins associated with strep pyogenes.
Hyaluronidase, streptolysin, streptokinase, exotoxins
(streptolysin dissolves blood cells, streptokinase dissolves nucleic acids)
Name 3 clinical presentations of primary strep pneumo infection.
1. pneumonia
2. sinusitis
3. otitis media
**slide on hemophilus influenza says that strep pneumo can also cause epiglottitis and supraglottitis
How is strep pneumoniae different from strep pyogenes?
Strep pneumo is alpha-hemolytic; use optochin to diagnose
What's the most common cause of CAP?
Strep pneumo
Is strep pneumo transmitted endogenously or exogenously? Name the specific method. When is the infection most prevalent?
it's both endo and exo--can be found in nasopharyngeal flora in 5-20% of people....no animal reservoir; occurs in WINTER and EARLY SPRING
Name 3 things released by strep pneumo that lead to pneumococcal pneumonia
1. IgA protease
2. pneumolysin (inhibits cilia, causes inflammation, decreases PMN effectiveness, cytotoxic for alveoli)
3. autolysin
What shape is corynebacterium diphtheriae? GP or GN? Is it pleomorphic? Is it part of normal flora?
"Chinese letters"/club shaped, GP, non-sporulating ROD. Part of normal flora.
How does normal flora version of diphtheria become bad? Where are the normal flora found?
Normal flora found in pharynx, nasopharynx, and skin (so mostly upper RT) A bacteriophage comes along and infects the bacteria. Via lysogenic conversion, it causes it to start producing the diphtheria exotoxin, which is an A-B component toxin that attacks ADP-Ribosylation
Diphtheria should be cultured on .... agar. What color are the colonies?
Tellurite. Black urease positive colonies.
What method does prof recommend for diagnosing diphtheria?
Elek test (two diph strains, toxic and cultured, across which is laid a strip of paper impregnated with antitoxin...leave it overnight and if the cultured version is branched away from sheet like xmas tree you know it's toxic form)
What are the three clinical symptoms of Hemophilus influenzae?
1. otitis media
2. pneumonia
3. epiglottitis
What's the clinical symptoms of strep pyogenes AKA Group A Strep?
Pharyngitis (aka "Strep Throat"). Note that Strep pneumo does NOT cause strep throat!!
What's the Lancefield group of Strep pneumo? How are the cocci arranged?
It's NOT Lancefield groupable; the cocci are arranged in chained pairs (diplococci)
Give the gram stain, the shape, and the morphism of H. influenza.
gram negative, rod-shaped, pleomorphic
H. influenza...
1. Part of normal flora? Where?
2. Coagulase?
3. Catalase?
4. What is "type b"?
5. Capsule?
1. yes; UPPER RT
2. coagulase-negative
3. catalase-positive
4. type b=invasive form; carried by 2-4% of people
5. Yes
How do you culture H. influenza?
Chocolate agar with X (hemin) and V (NAD) factors; X and V released from blood component with gentle heating
*only hemophilus species that requires both X and V
How do H. influenza adhere to the glottis?
via pili and non-pilus adhesins like the P2 outer membrane protein; attaches to sialic acid-containing mucin oligosaccharides
How does LPS of H. influenza affect the RT?
impairs ciliary function
Where is strep pneumo normal flora found?
nasopharynx (note that almost all bacterial RT's that are found in normal flora are found in the upper RT; and their virulent versions are found lower down)
What age group most common in H. influenza?
Older children
What clinical syndrome(s) produced by Bordetella pertussis?
Only 1: Whooping Cough (chronic bronchitis)
Describe the structure of Bordetella pertussis.
Gram negative coccobacillus with a biofilm
How is the pertussis toxin produced?
a biofilm forms that leads to its growth and release.
Which stage of pertussis (whooping cough) makes it unique?
Paroxysmal stage, in which the cough is so bad that vomiting can occur (during weeks 2-4)
1. How do you culture pertussis?
2. How do you collect a sample? WHERE do you collect a sample from?
1. Cultured on charcoal blood agar with cephalosporin (fatty acids are nasty to it so need charcoal to absorb them)...aka Bordet-Gengou. Don't forget it's gram negative.
2. Don't use cotton swab--use dacron, because again cotton has fatty acids that will mess up your sample...get a nasopharyngeal sample--no SPUTUM; it's NOT an LRT infection.
What are 2 clinical syndromes caused by Klebsiella pneumoniae?
1. bronchopneumonia
2. lung abscesses
*chronic alcoholics especially susceptible
Describe klebsiella pneumo regarding gram stain, shape, capsule (y/n; how large), endotoxin fx.
Gram negative bacillus-shape with a LARGE capsule. The endotoxin can cause lung necrosis, which can lead to abscesses or debris-filled cavities
Describe the features of necrotizing pneumonia and list the species potentially involved.
- >1 area of lung parenchyma replaced by cavities of debris
-putrid breath and sputum
-often polymicrobial (S. aureus, anaerobes, microaerophiles from normal mouth flora
-linked with aspiration (aka aspiration pneumonia!)
A patient is coughing up sputum that looks like red currant jelly. You take one look and dx him with what?
Klebsiella pneumonia--red currant jelly sputum is pathognomic for this disease; coughing up chunks of lung that's been necrotized.
What's unusual about where you can find klebsiella bacteria?
It's a member of Enterobacteriaceae; usually found in the GIT of people who develop klebsi pneumonia (usually 2/2 aspiration).
Describe Legionella pneumophila's gram stain, shape, motile/non motile, sporulating/non-sporulating.
WEAKLY gram negative...motile...non-spore forming...facultatively INTRACELLULAR
What causes most of the symptoms of Legionnaire's? How does one get exposed?
Inflammatory response of the human body...person to person transmission is rare, exposure usually comes from inhalation of contaminated aerosols. (wet a/c units)
What clinical syndromes are caused by Pseudomonas spp? Where is it usually found?
Necrotizing Bronchial pneumoniaa (opportunistic pathogen; loves CF, burn victims, AIDS)...and Swimmer's Ear (otitis externa)...usually found near stagnant saltwater or freshwater.
Describe how pseudomonas species appear under microscopy and any unusual features (how appear on culture, foul smell, etc)
GN rods; STRICTLY AEROBIC; motile; non-hemolytic; secrete pyocyanin --> green colored culture and fluorescin --> glowing culture...smells like GRAPES!
What is it about CF patients that makes them so susceptible to Pseudomonas?
Their mucus, because it tends to pool and become quite thick, is pretty much a ready-made biofilm...the pseudomonas inflammation then makes things worse by causing necrosis that leads to accumulation of WBCs...plus it's got multiple methods of resistance