RT3 Flashcards
viral agents that cause infectious pharyngitis (strep throat)
Rhinovirus
Adenovirus
Coronavirus
bacterial agents that cause infectious pharyngitis (strep throat)
Strep pyogenes (usuallyGroupA β‐Strep) Corynebacterium diphtheriae
signs and symptoms of strep throat/infectious pharyngitis
- Throat pain
- Difficulty swallowing
- Red and swollen tonsils, sometimes with white patches or streaks of pus
- Tiny red spots on the soft or hard palate — the area at the back of the roof of the mouth
- Swollen, tender lymph glands (nodes) in the neck
- Fever
- Headache
- Rash
- Stomachache and sometimes vomiting, especially in younger children
- Fatigue
why must you test specifically for strep throat to diagnose it
one can have all the signs and symptoms and not have a true strep throat infection – more likely to get these symptoms from a viral infection or less likely from other illnesses
can you tell by looking into the mouth if the cause of an infectious pharyngitis is bacterial or viral
no you cannot tell by looking so one must do a point of care test to be sure
viral agents that cause bronchiolitis
Adenovirus
Influenza Virus
Respiratory Syncitial Virus
think AIR through the bronchioles
bacterial agents that cause bronchiolitis
Bordetella pertussis
Mycoplasma pneumonia
what are the assays used for the microbial agents of bronchiolitis
you do a swab to use the assay
for the viral AIR agents
Adenovirus: PCR, antigen detection
Influenza virus: virus isolation
Respiratory syncitial virus: antigen detection
for the bacterial agents
bordatella pertussis: culture, DFA, serology, PCR
mycoplasma pneumonia: acid fast, culture
respiratory bacteria by definition have what type of oxygen requirements
aerobes and facultative anaerobes
how do you culture media for respiratory bacteria
get a routine sputum specimen and you can use either a blood, chocolate, or macconkeys agar
significance of using chocolate and mcconkey agar
chocolate agar - blood agar that has been heated to break open RBCs and release their content
mcconkeys: for selection and differentiation
what pathogens required special growth media that is not standard and what agar do they use
bordatella pertussis: bordet- gengou
c. diphtheria: tinsdale agar
characteristic of streptococci
small, gram positive, cocci in shape, metabolized through fermentation with lactic acid production, facultative anaerobe (but actually have all the qualities of aerotolerant anaerobe - grow in presence of oxygen, metabolize via fermentation, have only superoxide dismutase)
clinical syndrome of streptococci pyogenes
pharyngitis (strep throat)
describe the name streptococci pyogenes
Group A streptococcus according to Lancefield classification
pyogenes = induce of pus formation due to leukocidin production (leukocidin destroys leukocytes which will make pus)
how are streptococci classified
based on 16s rRNA sequencing
streptococci are classified by groups based on
polysaccharides (major cell wall carbs)
there’s group A –> W though there is no I or J
example of streptococci that does not have a carb group
S. pnuemonia
lab identifications of streptococci
- Gram Positive Spheres in chains (Older cultures become Gram Variable)
- Lack catalase (facultative anaerobes)
- Growth enhanced by CO2
- Nutritionally fastidious (Normal culture medium = Blood agar (BA) Yeast extract + peptone +5% blood)
streptococcal have large amounts of virulence factors which is not all expressed by all strain. what determines this variability?
transduction mediated gene transfer or transformation
describe s. pyogenes on blood agar
- where there is production of streptolysin S, there is beta hemolysis (tot destruction of erythrocytes) making the plate transparent
- sensitive to bacitrain so no growth where this antibiotic is present
clinical syndrome of corynebacterium diphtheria
severe pharyngitis (diphtheria)
physical features of corynebacterium diphtheria
gram positive, club shaped, nonsporeforming rods that are pleomorphic with chinese letter arrangement
what does corynebacterium diphtheria looks like on a gram stain
purple
irregular in shape
rod shaped
one end is thicker than the other
why is corynebacterium diphtheria unusual in developed countries
because of DPT vaccine – the D component is diphtheria toxoid
where are endemics and outbreaks of diphtheria seen
endemics - subtropical and tropical areas
outbreak - places with breakdown in health infrastructure
pathogenesis of corynebacterium diphtheria
organism is non invasive and does not enter the bloodstream but the toxin that it releases enters the blood stream and invades tissues
organism grows in a biofilm on the surface of the pharynx while its necrotizing toxin kills the tissue that it gets to
main virulence factor of diphtheria
the diphtheria exotoxin
how are the genes for diphtheria toxin acquired
via lysogenic conversion
complication of diphtheria
pharyngitis can be so severe that it blocks the airway –> suffocation
bull neck, pseudomembranous
what three tests can be done to see if you grew diphtheria toxin on the blood agar aka testing for toxigenicity
Elek, EIA, PCR
Elek, EIA, PCR – which is more effective and which is more probable (cheaper to use)
more effective - PCR
Elek test is cheaper, quicker, simpler
explain what positive elek test would look like
beneath the filter paper that has the antitoxin, there will be lines of precipitin (at angles) indicating presence of diphtheria toxin
viral agents of infectious sinusitis and otitis media
Rhinovirus
Adenovirus
Coronavirus
if you see viral agent in an infectious sinusitis and otitis media, what type of infection is it mostly
it is mostly an exogenous infection
bacterial agent of infectious sinusitis and otitis media
Streptococcus pneumoniae Haemophilus influenzae (part of normal flora)
if you see bacterial agent in infectious sinusitis and otitis media, what type of infection is it mostly
it is mostly an endogenous infection
clinical syndromes of haemophilus influenzae
otitis media, pneumonia, epiglottis
what is haemophilus influenzae the most common cause of
swelling of epiglottis and supraglottic tissue
describe physical features of haemophilus influenzae
gram negative, pleomorphic, facultative anaerobe, normal component of normal flora, IgA proteases
does h. influenza cause influenza
no
pathogenesis of h. influenzae
it is gram neg bacteria so it has LPS which impairs ciliary function
it has a pili
also has a non-pilus adhesins –> P-2 outer membrane protein; attaches to sialic acid-containing mucin oligosaccharides
what is the h. influenzae antiphagocytic capsule composed of
Polyribose Ribitol Phosphate (PRP)
how do you culture and diagnose h. influenzae
catalase: positive
coagulase: negative
culture with chocolate agar with X and V growth factors
what do the X and V factor do
X = acts as hemin V = acts as NAD
what other haemophilus require both X and V factor
none just h. influenza
