Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

M2 | Microbiolgy > Bacterial Dysentery (Gram Positive) > Flashcards

Bacterial Dysentery (Gram Positive) Flashcards

1
Q

Important properties of Bacillus cereus

A
  • Gram-positive
  • facultative anaerobic
  • sporeforming, large rod
  • Motile & beta hemolytic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Mode of transmission in Bacillus cereus

A
  • Spores on grains such as rice survive steaming & rapid frying

• Spores germinate when rice is kept warm for many hours (e.g. reheated fried rice), then bacteria produce exotoxin, which are ingested steaming

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Pathogenesis of B.cereus

A
  • Produces 2 enterotoxins :
    1. Similar to cholera toxin ——> increased cyclic AMP
    2. Similar to staphylococcal enterotoxin —-> superantigen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Clinical findings in B.cereus

A
  1. Vomiting (emetic): short incubation period —-> 4 hours
    * nausea
    * vomiting
  2. Diarrheal: long incubation period ——> 18 hours
    * watery
    * nonbloody diarrhea
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Important properties of Clostridium botulinum

A
  • Anaerobic
  • gram positive
  • Spore forming rods
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Transmission of C.botulinum

A
  • Spores in soil, contaminate vegetables & meats
  • Canned foods or vacuum-packed without adequate sterilization ———-> spores survive & germinate in anaerobic environment.
  • Toxin is produced within canned food & ingested preformed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which food/s are the highest risk of C.botulinum infection?

A

(1) Alkaline vegetables (green beans, peppers & mushrooms)
(2) Smoked fish

• Toxin is heat-labile (inactivated by boiling for several minutes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Pathogenesis of C.botulinum

A

Botulinum toxin is absorbed from gut & carried via blood to

peripheral nerve synapses ——> blocks release of acetylcholine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the botulinum toxin ?

A
  • A protease that cleaves proteins involved in Ach release
  • Among the most toxic substances
  • 8 types : type A , B & E are most common
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Clinical findings of C.botulinum

A
  1. Descending weakness & paralysis
  2. Diplopia (double vision), blurred vision, slurred speech (difficulty talking), dysphagia & respiratory muscle failure
  3. No fever
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the 2 special forms that are clinically found in C.botulinum?

A
  1. Wound botulism: spores contaminate wound, germinate & produce toxin at site (drug abuse)
  2. Infant botulism: organisms grow in gut & produce toxin
    * Ingestion of honey containing organism
  • Infants (between 6 weeks & 6 months of age) develop muscular weakness or paralysis, loss of head control & need respiratory
    support (usually recover spontaneously)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Important properties of Clostridium perfringens

A
  • Large Gram postitive rods
  • Anaerobic
  • Spore forming
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Laboratory diagnosis of C.botulinum

A
  • Not cultured
    1. Mouse protection tests:
  • Botulinum toxin is found in uneaten food & patient’s serum
  • Mice are inoculated with clinical specimen & will die unless protected by antitoxin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

State the diseases that occur from C.perfringens

A
  1. Gas gangrene

2. Food poisoning

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which type of tissue does the C.perfringens grow in ?

A

traumatized tissue (especially muscle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which toxin is produced in gas gangrene by c.perfringens ?

A

Alpha toxin (lecithinase)

17
Q

What does the alpha toxin do ?

A

Alpha toxin (lecithinase) ——> damages cell membranes , including those of erythrocytes ——-> hemolysis

18
Q

How production of gas happen in gas gangrene ?

A

Degradative enzymes produce gas in tissues

19
Q

Clinical findings of C.perfringenes

A
  1. Pain,edema, cellulitis & gangrene (necrosis) in wound area
  2. Crepitation indicates presence of gas in tissues
  3. Hemolysis amd jaundice
  4. Shock & death can ensue
20
Q

Laboratory diagnosis of gas gangere due to c.perfringens

A
  1. Smears of tissue & exudate show large gram-positive rods
  2. Cultured anaerobically & colonies exhibit double zone of hemolysis on blood agar
  3. Organisms identified by sugar fermentation reactions &
    organic acid production
  4. Egg yolk agar :
    * demonstrate presence of lecithinase
21
Q

How food poisoning occur by c.perfringens ?

A
  1. Spores are located in soil & contaminate food
  2. Heat-resistant spores survive cooking & germinate
  3. Organisms grow in reheated foods, especially meat dishes
22
Q

Pathogenesis of c.perfringens

A
  • Member of normal flora in colon
  • Enterotoxin acts in small bowel diarrhea
  • Enterotoxin: similar to staphylococcal enterotoxin —-> superantigen
23
Q

Clinical findings of c.perfringens

A

Watery diarrhea with cramps & little vomiting (resolves in 24 hours)

24
Q

What is the incubation period in food poisoning?

A

8-16 hour

25
Q

Laboratory diagnosis of c.perfringens

A
  • Not usually done
  • No assay for toxin
  • Organisms isolated from uneaten food
26
Q

Important properties of Clostridium difficile

A
  • gram positive
  • anaerobic
  • spore froming rods
27
Q

How is c.difficile transmitted ?

A
  1. Fecal oral route

2. Ham]nds of hospital personnel

28
Q

Explain the transmission of c.difficile

A
  • Organism is carried in gastrointestinal tract in 3% of general population & 30% of hospitalized patients
  • Most people are not colonized most people who take antibiotics do not get pseudomembranous colitis
29
Q

Explain the pathogenesis of antibiotics in helping c.difficile

A

Antibiotics suppress members of normal flora, allowing C. difficile to multiply & produce exotoxin A (enterotoxin) & exotoxin B (cytotoxin)

30
Q

What are the antibiotics used ?

A
  1. Clindamycin :
    * 1st recognized to cause pesudomembranous colitis
  2. Third-generation cephalosporins:
    * most common used
  3. Ampicillin & fluoroquinolones (Gentamicin)
    * common
31
Q

Whixh chemotherapy is a direct cause if pseudomembranous colitis?

A

Cancer chemotherapy

32
Q

Explain the pathogenesis of Endotoxin A & B

A

They are glucosyltransferases (i.e., enzymes that glucosylate [add glucose to] G protein called Rho GTPase)

Exotoxin B ——> depolymerization of actin —-> loss of cytoskeletal integrity, apoptosis & death of enterocytes.

33
Q

C. difficile rarely invades______

A

intestinal mucosa

34
Q

Clinical finding of c.difficile

A
  1. Foul smelling diarrhea + pseudomembranes (yellow-white plaques ) on colonic mucosa
  2. Nonbloody diarrhea
  3. Neutrophils found in stool
  4. Fever and abdominal pain
35
Q

In 2005, new hypervirulent strain of C. difficile emerged & causes:?

A
  • severe disease
  • recurrences
  • less responds to metronidazole
  • resistance to quinolones
36
Q

Laboratory diagnosis of c.difficile

A
  1. Culture stool :
    * insufficient for presence of C. difficile
    * because people can be colonized by organism & not have disease
  2. Stool isolation:
    * evidenced by stool toxin test
  3. PCR : presence of toxin gene DNA
37
Q

What are the 2 types of tests done to detect c.diificile exotoxins ?

A
  1. ELISA :
    * using antibody to exotoxins (rapid but less sensitive)
  2. Cytotoxic test :
    * Human cells in culture are exposedto exotoxin in stool filtrate & death if cells is observed
  • It is more sensetive & specific but requires 24 to 48 hours

M2 | Microbiolgy (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions