Bacteria Flashcards
Bacillus Anthracis
Distinctive features:
G(+), Rod, spore-forming
Poly-D-glutamic acid capsule
Facultative anaerobe (usually aerobe)
PA (pore forming), EF (edema), LF (lethal)
"binary toxin"
Soil
Modes of transmission:
Inoculation/Cutaneous
black necrotic lesion, depressed eschar, no lymphadenopathy, small, painless, pruritic papule
Ingestion
Most common in livestock
upper GI ulcers –> lymphadeno –> sepsis
lower GI ulcers –> malaise –> systemic disease
Inhalation (most virulent) Infects lung APCs --> lymphatics Sepsis and rapid death Enlargement of medistinal lymph nodes ~50% meningeal involvement, 85-97% mortality if untreated NO PNEUMONIA
Tx:
Amox, Cipro, Doxy, Human Ig
Vacc for high risk
Bacillus Cereus
Distinctive features:
G(+), rod, spore-forming
Food borne intoxication: Short-incubation or emetic-toxin form toxin already made, upper GI, N&V, abdominal cramps Rice, milk, pasta S. aureus
Long-incubation
Spore internalized farther down, deeper = diarrhea
Clostridum perfringens
stimulates cAMP in intestinal epithelium
Bacillus Thuringiensis
Similar to cereus
EYE infection & implicated toxins:
Necrotic toxin: heat-labile entero
Cereolysin: hemolysin
Phospholipase C: lecithinase that attacks phospholipids in retinal tissue
Clostridium Botulinum
Anaerobic bacteria
Enviro: neutral/basic (not acidic), Low O2, high water content
Soil
Characteristic Sx:
Flaccid baby (hypotonia, decreased sucking, gurgling) & constipation
Respiratory problems
Types A-G; A > 60% cases
LChain: Zinc endopeptidase
HChain: cholinergic specificity and binding of toxin to presynaptic receptors; promotes LC translocation across endosomal membrane; goes to the peripheral nerves (ACh)
Similar to tetanus toxin
Mechanism: Bind ACh receptors, cleave ACh releasing peptides and –> flaccid paralysis
–> life-threatening for intercostal muscles/diaphragm
Modes: Infant: intestine (spore matures here) Wound infxn/IV drug users Contaminated food Inhalation (terrorist) Iatrogenic: accidental botox overdose
Infant Botulism
1st sign: constipation
Other: lethargy, poor feeding, gag reflex/swallowing
Link to honey
Abx not recommended (may lyse and release more toxin
Tx: Antitoxin
Food Botulism
Home-canned foods
Spore germination
6h - 2 weeks
Sx: blurriness/double, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, muscle weakness (shoulders–> other extremities)
Sx: many “D’s”
Clostridium Tetani
G(+), rod, spore-forming
Distinctive features: resistant to heat sensitive to O2 --> sporulatoin relatively inactive metabolically Incubation 3-21 days (~8 avg) Soil
Toxins:
Tetanolysin: O2-labile hemolysin
Tetanospasmins: heat-labile neurotoxin, plasmid encoded (A-B toxin)
**Tetanospasmin:
HC: binds R on neuronal membrane
LC: zine endopeptidase, retrograde axonal transport –> gangliosides at preganglionic inhibitory motor nerve endings –> inhibit GABA and glycine –> muscle spasms
(nerve impulses not checked by normal inhibitory mechanisms)
Sx: Trismus (lockjaw) Risus sardonicus (sardonic smile) Stiff neck, diff swallow, rigid ab muscles low grade fever, elevated BP, rapid HR
Tx:
Metronidazole (DOC)
Human tetanus immune globulin/equine antitoxin
*natural infxn ≠ immunity (too low doses of toxin)
Localized Tetanus
persistent muscle contractions, especially at site of injury
uncommon, rarely fatal
Cephalic Tetanus
Cranial Nerves involved (facial area)
Otitis media
uncommon – poor outcomes
Clostridium Perfringens
G(+), rod, spore-forming Distinctive features: Anaerobic, nonmotile (but rapid spread), resistant endospores Metabolically active Types A-E
Intestine/Fecal contaminated water
Toxins (12):
ALPHA:Lecithinase (phospholipase c): lyses host cells & increase vascular perm. and tissue destruction
BETA: necrotic lesions in enteritis
EPSILON: protoxin celaved to form permease (increase VP)
weird l (not lambda): necrotic activity, increase VP
Enterotoxin: heat-labile, released in alkaline intestine, alters membrane permeability
Food-poisoning: more commonly reported food-borne illnesses (8-24hr incubation)
Sx:
food-poison: abdominal cramps, diarrhea, necrotic enteritis
-rare, mortality 50% (necrotic intestines)
cellulitis (skin/CT already dead gets infected)
crepitance between muscles
deep –> gas gangrene = crepitance too
-clostridial myonecrosis
-impairs blood supply (ALPA TOXIN)
-fever and intense pain
-purple mottling, edema, foul-smelling exudate, gas bubbles
==> shock, renal failure, death withi 48 hr
Diag: culture (quick), increased Creatinine kinase and neutrophilia
Tx: debridement, high dose penicillin, hyperbaric oxygen (controversial), anti-toxin has been discont. proper wound care is a must
Clostridium Difficile
G(+), rod, spore-forming
Distinctive features:
Largely nosocomial
Relatively abx resistant
Toxin:
A-Enterotoxin
B-Cytotoxin
-actin depolymerization, cytoskel. destruction, inflamm cks released, recruitment of neutrophils
Sx:
watery, stools w/o blood – for days
slight tem, high pulse, elevated RR
cramps, pain, vomitting
pseudomembranous colitis: leuko infiltration into lamina propria, elaboration of fibrin, mucus, and leuko, patches on mucosa (pseudomembrane)
Diag: immature polymorphonuclear cells, endoscopy, MUST HAVE positive test:
- anaerobic culture that displays cytox
- PCR of stool positive for toxin gene
- ELISA for tox
- stool positive for glutamate dehydrogenase
- colonospic findings
*C diff in stool is NOT enough
Risk: older age, hospitals
Tx: amp, amox, cephalo, clinda, fluoro
METRONIDAZOLE and vanco
monoclonal ab
