Shared Flashcard Set

Details

Gram Positive Bacteria
Aerobic and Anaerobic spore-forming bacilli
41
Microbiology
Graduate
03/27/2011

Additional Microbiology Flashcards

 


 

Cards

Term
single greatest biological warfare threat
Definition
bacillus anthracis
Term
bacillus anthracis characteristics and identifying features
Definition

gram+ rods

non-motile

nonfastidious

non-hemolytic

 

spore-forming (resistant to heat, UV, gamma-radiation, & disinfectants; may be dormant for decades; "medusa head" on agar surf)

Term
bacillus anthracis epidemiology
Definition

commonly infects grazing herbivores

more serious w/o animal vaccination

human-->human transmission: RARE

human infection (US): RARE

Term
bacillus anthracis virulence factors
Definition

2 large plasmids account for ALL virulence:

1. pXO1: toxin proteins (PA; LF; EF) combine to form binary exotoxins = lethal toxin/LeTx (PA+LF); edema toxin/EdTx (PA+EF)

*individually, toxin proteins harmless

2. pXO2: genes encode protein for capsule syn 

*unique capsule: polyglutamate (antiphag)

Term
entry/action of anthrax toxin: PA binds anthrax receptor --> processed by furin on cell surf
Definition

--> PA oligomerizes => EF/LF binding sites --> toxins endocytosed --> PA conform chg w/ pH chg --> toxins in cytosol

 

EF (adenylate cyclase): releases cAMP

LF (protease): degrades MAPKK

Term
[image]
Definition

cutaneous anthrax

common affected areas: head, neck, & extrem

description: nondescript 1* lesion (painless papule, no pus)

progression: w/in 2-3d vesicles --> central necrosis & drying => eschar (usually surrounded by eroded areas/edema- may be self-limiting)

left untx: bacteremic/fatal

Term
[image]
Definition

inhalational anthrax (woolsorter's disease)

initial symptoms: flu-like (fever, cough, myalgia, malaise)

characteristic: widened mediastinum (this is where the org is prolif & prod toxins)

progression: 1-3d fulminant course (dyspnea, strident cough, chills, usually fatal)

associated: gastrointestinal & leptomeningeal lesions <= hematogenous spread

Term
intestinal anthrax
Definition

cause: eating anthrax-infected meat

fatality: 25-60%

symptoms: severe GI difficulty, vomiting blood, diarrhea, acute inflamm

(Bacillus anthracis)

 

Term
anthrax hemorrhagic meningitis
Definition

fatality: 100%

symptoms: lots of edema, blood CSF (w/ gram+)

"Cardinal's cap" appearance (lots of hemorrhage of leptomeninges)

spreads: to CNS from any kind of anthrax infection

Term
identify cutaneous anthrax specimens
Definition

vesicular stage: vesicular fluid

eschar stage: eschar material

Term
identify gastrointestinal anthrax in these specimen:
Definition
blood, stool, rectal swab
Term
identify inhalational anthrax in these specimen:
Definition
blood & sputum
Term
[image]
Definition

id bacillus anthracis on sheep blood agar

non-motile

non-hemolytic

irregularly round

medusa head colony (comma shaped projection)

PLET for isolation

bicarbonate agar => capsule formation

Term
identifying features of Bacillus cereus
Definition

beta hemolytic on sheep blood agar

string of pearls test-

motile

glutamyl-polypeptide capsule-

Term
Bacillus cereus virulence factors (2 toxins)
Definition

heat-labile (diarrheal): stim adenylate cyclase (=> cAMP); SLOW onset

heat-stable (emetic): RAPID onset

Term
ALL gram+ anaerobic spore formers
Definition

Clostridium

part of normal colonic flora

most abundant: C. ranosum, then C. perfringes

most pathogenic: C. perfringes

Term
Clostridium perfringes epidemiology
Definition

most predominant (spores/vegetative bacteria): serotype A in human fecal flora & in soil (most virulent)

growth time: very fast (3xs faster than E. coli)

infections endo/exogenous

 

Term
pathogenesis of C. perfringes
Definition

growth requirements: ~14 AAs & 6 other factors (most body fluids are deficient of these materials EXCEPT necrotic tissues)

*produces ~12 toxins  (alpha toxin=gas gangrene)

Term
types of diseases caused by C. perfringes
Definition

1. soft tissue infections: cellulitis, suppurrative myositis, myonecrosis (gas gangrene)

2. gastroenteritis: food poisoning, necrotizing enteritis

Term
[image]
Definition

clostridial cellulitis

doesn't involve muscle/deeper tissue

anaerobic

less aggressive than gas gangrene

after surgery/trauma (dmg to arteries reduces 02 supply)

Term
suppurative myositis
Definition
suppuration in muscle planes w/o necrosis or systemic symptoms
Term

gas gangrene=clostridial myonecrosis

what does the "gas" come from?

Definition

organism replication (there will be crepitus present)

extensive hemolysis

bacteria present

inflammatory cells absent

symptoms: shock, renal failure, death w/in 2d

Term
tx of clostridial myonecrosis
Definition
surgical debridement & frequently amputation
Term
2nd or 3rd most common cause of food poisoning in the US
Definition

Clostridium perfringes, usually type A

induces Ca++ dependent alteration in permeability

symptoms: epigastric pain, nausea, cramps, watery diarrhea

Term
other gastroenteritis caused by C. perfringes (other than food poisoning)
Definition

necrotizing enteritis (enteritis necroticans, pig-bel)

cause: strains prod beta toxin

occurs w/: high protein/trypsin inhibitor (sweet potato)

incr risk: decr intestinal proteases

symptoms: peritonitis, abdom px, vomiting, bloody diarrhea, shock

fatality: 50%

Term
septicemia from Clostridium perfringes
Definition
bacteremia: in pts w/ myonecrosis & necrotizing enteritis
Term
[image]
Definition

Clostridium perfringes

non-motile, box-car shaped gram+ rod

*rod presence w/o leukocytes in specimen

nagler rxn+ (anti-alpha-toxin added to egg yolk agar cultures (on upper half)- prevents visible opacity <= lecithinase action of alpha toxin)

Term
Clostridium tetani characteristics & epidemiology
Definition

motile, spore forming, gram+ rod, anaerobe

common in soil

most cases (developing countries): newborns

Term
2 potent toxins of C. tetani
Definition

1. chromosomally encoded 02 labile hemolysin (tetanolysin): unclear role 

2. plasmid encoded 02 labile neurotoxin (tetanospasmin-tetanus toxin): stationary phase, blocks release of inhibitory neurotrans

Term
C. tetani virulence factors
Definition

common entry to body: implanting spores in wounds

under anaerobic conditions: spores germinate --> produce toxins --> retrograde mvmt w/in CNS

char sympt: convulsive muscle contraction (lockjaw, back muscles)

cause of death: cardiac/respiratory complic

Term
generalized tetanus
Definition

C. tetani

most common

masseter muscles (trismus, lockjaw); risus sardonicans

early signs: drooling, irritability, back spasm (opisthotonus)

Term
localized tetanus
Definition

clostridium tetani

confined to musculature of 1* site of infection

Term
cephalic tetanus
Definition

Clostridium tetani

head is the 1* site of infection

poor prognosis

Term
neonatal tetanus
Definition

tetanus neonatorum

clostridium tetani

common 1* infection site: umbilical stump (dirty tools to sever cord)

symptoms: excessive crying, trismus, tetanic spasms, opisthotonus

fatality: >90% (survivors have developmental defects)

Term
name the 4 types of C. botulinum diseases (all paralytic diseases)
Definition

1. foodborne botulism 

2. infant botulism

3. wound botulism

4. inhalational botulism

Term
foodborne botulism
Definition

C. botulinum

characteristic: symmetric descending paralysis

*flaccid paralysis

initially: blurred vision, constipation, abd px, no fever

Term
bioterrorism concern
Definition
inhalational botulism caused by Clostridium botulinum <= toxin can be aerosolized 
Term
Clostridium difficile epidemiology
Definition

spores high conc in hospitals & LTCF (high antibiotic use)

risk of infection correl. to length of stay

 

Term
virulence of C. difficile
Definition

spores survive gastric acidity (germinate in LGT)

2 toxins: enterotoxin A & cytotoxin B (disrupt epithel cell barrier)

*pseudomembranes seen on colon endoscopy

Term
steps to C. difficile colitis:
Definition

1. exposure to antibiotics

2. exposure to C. difficile capable of producing toxins

3. inadequate immune response (antibodies to toxin A-protective)

Term
2 most likely causes of colitis:
Definition

1. Clostridium difficile

2. Staphylococcus aureus

Supporting users have an ad free experience!