Microbio Flashcards
Giemsa stain
Certain Bugs Really Try my Patience
Chlamydia, Borrealia, Rickettsiaae, Trypanosomes, Plasmodium
PAS
stains glycogen / mucopolysaccharides –> whipple disease
Ziehl-Neelsen (carbol fuchsin)
acid fast organisms (nocardia / mycobacterium)
India ink
cryptococcus neoformans (also mucicarmine for thick polysaccharide capsule)
Silver stain
Pneumocystic, Legionella, H. Pylori
Obligate Aerobes
O2 dependent system to generate ATP:
Nocardia, Pseudomonas, M. TB
obligate anaerobes
Clostridum, Bacteroides, Actinomyces (lack catalase / superoxide dismutase –> susceptible to oxidative damage).
1) contain short-chain fatty acids –> foul smelling
2) difficult to culture
3) produce gas in tissue (Co2 /H2)
Aminoglycosides are ineffective against anaerobes
capsule + protein conjugate
antigen in vaccines
effect of immune system on encapsulated bacteria
capsules = antiphagocytic virulence factor –> opsonized and cleared by spleen. increased risk for asplenics
catalase-positive organisms:
you need PLACESS for your cats
Pseudomonas Listeria Aspergillus Candida Ecoli S. aureus Serratia
catalse degrades H2O2 before it can be converted to a microbicidal by myeloperoxidase.
urease-positive bugs
Cryptococcus, H. pylori, Proteus Ureaplasma, Nocaria, Klebsiella, S. epidermis, S. saprophyticus
Protein A
binds to Fc region of IgG –> prevent opsonization / phagocytosis. found on Staph Aureus
IgA protease
cleaves IgA. secreted by S. pneumo, H. influenzze, Neisseria –> allows colonization of respiratory mucos
M protein
prevents phagocytosis (found on group A strep)
more specific test for TB
interferon gamma release assay (IGRA)
mechanism of TB virulence
1) cord factor inhibits macrophage maturation + induces release of TNF-alpha
2) sulfatides (glycolipids) inhibiting phagolysosomal fusion
2 forms of leprosy
1) lepromatous: lion-like faces –> communicable. low cell-mediated immunity +humoral Th2 response
2) tuberculoid: hypoesthetic hairless skin plaques; high cll-mediated immunity w/ a large Th1-type immune response
treatment of leprosy
1) tuberculoid: dapsone + rifampin for 6 months
2) lepromatous: dapsone, rifampin, clofazimine for 2-5 years
legionella staining
silver stain
growth of legionella
charcoal yeast extract w/ Fe / Cysteine
legionnaires disease presentation
severe pneumo, fever, GI / CNS symptoms
labs for legionella
hyponatremia
yersinia enterocolitica transmission
pet feces, contaminated milk, pork –> mesenteric adenitis –> mimics crohn’s disease / appendicitis
h. pylori
curved ram-neg rod –> catalase, oxidase, urease +
spirochetes
borrelia, leptospira, treponema.
treponema on microscopy
dark-field microscopy; no seen on gram stain
leptospira interrogans presentation
flu-like symptoms, jaundice, photphobia w/ conjunctival suffusion (erythema w/o exudate)
weil disease
icterohemorrhagic leptospirosis: severe leptospirosis w/ jaundice + azotemia from liver / kidney dysfunction (fever, hemorrhage, anemia)
stages of syphilis
1) painless chancre
2) dissseminated w/ maculopapular rash on palms / soles, condylomata lata
3) gummas (chronic granuloma), aortitis (vasa vasorum destruction), neurosyphilis, argyll-roberson pupil
signs: broad-based ataxia, +romberg, charcot joint, stroke w/o HTN
neurosyphilis test
test spinal fluid w/ VDRL / RPR
congenital syphilis
saber shins, saddle nose, CN 8 deafness, Hutchinson teeth, mulberry molars
what are the bacteria that share a toxin with the mechanism of inactivating EF-2?
pseudomonas
c. diphtheria -
what two bacteria have an exotoxin that inactivates the 60S ribosome by removing adenine from rNA?
1) shiga toxin - Shigella
2) Shiga-like toxin - EHEC (including O157:H7)
not that unlike shigella, EHEC does NOT invade host cell
what are the bacteria that increase fluid secretion (3)
1) ETEC
2) B. anthracis
3) v. cholerae
where are endotoxins found and what happens when they are released?
1) LPS found in gram-negative bacteria
2) macrophages, complement, tissue factor activated
describe what happens when macrophages are activated by endotoxin?
1) IL-1 –> fever
2) TNF –> hypotension + fever
3) nitric oxide –> hypotension
describe what happens when there is complement activation by endotoxin
1) C3a –> hypotension / edema
2) C5a –> neutrophil chemotaxis
describe what happens there is tissue factor activation by endotoxin
coagulation cascade activated –> DIC
describe the 2 toxins of ETEC:
1) heat-lable = overactivated adenylated –> incr. cAMP –> Cl- secretion in gut + H2O secretion
2) heat-stable toxin: overactivated gunylate cyclase: incr. cGMP –> dec. reabsorption of NaCl / H2O gut
what does the edema factor toxin of b. anthracis do?
mimics adenylate cyclase enzyme –> incr. cAMP
vibrio cholerae cholera toxin
overactivates adenylate cyclase –> icr. cAMP and activates Gs –> incr. Cl- secretion in gut + H2O efflux
compare and contrast Clostridium tetain vs. botulinum
both = proteases cleaving SNARE proteins that intefere with endocytosis necessary for NT release.
C. tetatin = inhibit GABA release –> spasticity & over-activity at Renshaw cells in the spinal cord
Botulinum = inhibit Ach release at NMJ –> flaccid paralysis
mechanism of pertussis
toxin overactivates adenylate cyclase –> incr. cAMP, disables Gi –> impaired phagocytosis
what organisms release superantigens that can cause shock?
1) staph aureus (TSST1):
2) group A strep = strep pyogenes (exotoxin A)
both bring MHC II + TCR in proximity to antigen binding site –> release IFN-y + IL-2 –> shock.
what exotoxins lyse cells?
1) c. perfringens: alpha toxin –> lecithinase degrades tissue / cell membranes
2) strep pyogenes: degrades cell membrane
what bacteria are capable of natural transformation
- can take up naked DNA from environment
- S. pneumo, Hinfluenze, Neisseria
- competence inhibited by deoxyribonuclease
which genes are encoded by a lysogenic phage? (5) ABCDE
1) shigA-like toxin
2) Botulinum toxin
3) Cholera
4) Diphtheria
5) Erythrogenic of s. pyogenes
which are alpha-hemolytic organisms?
- green ring on colonies on blood agar
1) strep pneumo
2) viridans streptococci
which are beta-hemolytic organisms?
- clear hemolysis on blood agar
1) staph aureus (catalase + coagulase)
2) strepto pyogenes: group A strep
3) strep. agalactiae: group B strep
4) listeria monocytogenes
for which neisseria is there a vaccine?
menigococci, though none for type B
gonococci has no vaccine b/c of rapid antigenic variation of pilus proteins
what are the different virulence factors for e. coli?
fibraie: cystitis / pyelonephritis
K capsule: pneumo / neonatal menigitis
LPS endotoxin: septic shock
which can spread hematogenously, shigella or salmonella?
salmonella
which produces hydrogen sulfide: salmonella or shigella?
salmonella
what’s the difference in administration of antibiotics for shigella vs. salmonella?
- shigella may shorten the duration of the organism’s fecal excretion
- antibiotics may prolong fecal excretion of salmonella
what disease mimics crohn’s / appendicitis?
yersenia
what is the treatment for all rickettsial diseases / vector-borne illnesses?
doxycycline
histoplasmosis
histo hides w/in macrophages. associated w/ bat / bird droppings
blastomycosis
granulomtaous nodules.
broad-based budding
coccidioddomycosis
spherule filled w/ endospoers
-causes pneumo / menigitis –> disseminated to bone / skin
