Microbiology Flashcards
corynebacterium diphtheriae
nonspore forming, non capsulated, gram positive bacteria
medium that c. diphtheriae is grown on
Loeffler’s medium (coagulated serum). potassium tellurite (grayish black colonies)
in the US, c. diphtheriae is a disease of
elderly, urban poor and immigrants from developing countries
Diptheriae is caused by
the local and systemic effects of diphtheria toxin
c. diptheriae toxin
A fragment inhibits protein synthesis, B fragment binds specifically to a cell surface receptor. systemic effects are seen mostly in the heart and peripheral nerves
bull neck
grey-brown psuedomembrane from the pharynx to the larynx that causes severe respiratory distress. do not try to remove
neuropathy can progress to
respiratory failure
strep
gram positive, non spore forming, catalase negative, grows in pairs or chains of varying length
strep are primarily
microaerophilic or facultative anaerobes
β hemolysis
complete lysis, s. pyogenes
α hemolysis
green, incomplete lysis, s. pneumoniae, viridians
γ hemolysis
enterococcus
GABHS
Group A β hemolytic strep, sensitive to bacitracin
methods of transmission of GABHS
- air (air not fomites); 2. food (open lesion); 3. hands
hyaluronate capsule
virulence factor - binds to CD44 on host tissue
extracellular matrix binding protein
surface proteins that bind fibronectin, fibrinogen, and collagen
avoidance of immune response
m protein, hyaluronate capsule, Ig binding proteins, C5a peptidase
C5a peptidase
cleaves the complement c5a chemotaxin to prevent recruitment of neutrophils to the site of infection
invasion and spread to other tissues
spe B protease: secreted protease degrades host tissues, streptolysins: hemolysis, DNAses, streptokinase: degrades clots by activating host plasminogen, hyaluronidase
superantigens
activates t cells in absence of MHC releasing large amounts of inflammatory cytokines
primary method for clearance of GABHS
opsonophagocytosis by neutrophils or PMNs
GABHS
aerobic sensitivity, rapid diagnostic test for strep throat, anti streptolysin O serology
GABHS disease
asymptomatic carriage; purulent, self limiting infections of the oropharynx or skin,
nonsupparative sequelae of GABHS
acute rheumatic fever, acute post streptococcal glomerulonephritis
rapid onset strep throat
sore throat with malaise, feverishness, and headache
acute otitis media
opaque, red/yellow/cloudy, bulging or full position, reduced mobility with pneumatic otoscopy, effusion present
otitis media with effusion
neutral or retracted, reduced mobility, effusion present
diagnosis of AOM requires
- history of acute symptom onset; 2. MEE; 3. signs/symptoms of middle ear inflammation
MEE
- TM bulge, 2. limited TM mobility, 3. air fluid level behind TM; 4. otorrhea
ME inflammation
TM erythema, distinct otalgia (discomfort referable to the ear that interferes with normal activity/sleep)
bacterial pathogens from middle ear fluid (top 3)
s. pneumoniae, h. influenzae, m. catarrhalis
h. influenzae
gram negative coccobacilli to filarmentous bacterium, type A encapsulated
m. catarrhalis
gram negative diplococcus
most important diagnosis for AOM
bulging, red TM
why observe AOM?
often mild, self limited disease, with low incidence of complications, could reduce antibiotic use substantially
spontaneous AOM resolution
a result of immune responses, eustachian tube drainage, bacteria dependent, age dependent
h. influenzae cannot be treated with amoxicillin
has caluvanic acid (a β-lactamase inhibitor)
