Micro - Clinical Bacteriology (Gram + Rods)

Question 1

What disease does Corynebacterium diphtheriae cause, and how?

Answer 1

Causes diptheria via exotoxin endoded by Beta-prophage; Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2

Question 2

What are the symptoms of Diphtheria?

Answer 2

(1) Pseudomembranous pharyngitis (grayish-white membrane) with LAD (2) Myocarditis (3) Arrhythmias

Question 3

How is a lab diagnosis of Diphtheria made?

Answer 3

(1) Gram-positive rods with metachromatic (blue and red) granules (2) Elek’s test for toxin

Question 4

What prevents diphtheria?

Answer 4

Toxoid vaccine

Question 5

What special agar is used to isolate Corynebacterium diphtheriae, and how does it appear on this agar?

Answer 5

Cystine-tellurite agar; Black colonies

Question 6

What does Coryne mean?

Answer 6

Club shaped

Question 7

What is a useful mnemonic to relate to Corynebacterium diphtheria?

Answer 7

ABCDEFG = (1) ADP-ribosylation (2) Beta-prophage (3) Corynebacterium (4) Diphtheria (5) Elongation Factor 2 (5) Granules (metachromic)

Question 8

When do spore-forming bacteria produce spores, and why?

Answer 8

End of stationary phase, when nutrients are limited

Question 9

What advantages do spores have?

Answer 9

Highly resistant to heat and chemicals

Question 10

What is found in the core of spores?

Answer 10

Dipicolinic acid

Question 11

What is important to remember about the metabolism of spores?

Answer 11

No metabolic activity

Question 12

How are spores killed?

Answer 12

Must autoclave (as is done to surgical equipment) by steaming at 121 C for 15 minutes

Question 13

What are 3 examples of spore-forming gram-positive bacteria that are found in soil? What are 3 examples spore formers not found in soil?

Answer 13

SOIL - (1) Bacillus anthracis (2) Clostridium perfringens (3) C. tetani; OTHER - (1) B. cereus (2) C. botulinum (3) Coxiella burnetii

Question 14

What kind of bacteria are Clostridia?

Answer 14

Gram-positive, spore-forming, obligate anaerobic bacilli

Question 15

What are the Clostridia with exotoxins?

Answer 15

(1) C. tetani (2) C. botulinum (3) C. perfringens (4) C. difficile

Question 16

What kind of exotoxin does C. tetani produce? What is the general mechanism of this exotoxin? What other toxin has the same general mechanism?

Answer 16

TETANOSPASMIN (exotoxin causing tetanus); Tetanus toxin is a protease that cleaves releasing proteins for neutrotransmitters; Botulinum toxin

Question 17

In general, what is tetanus? More specifically, what is the mechanism by which it occurs?

Answer 17

Tetanic paralysis; Tetanospasmin blocks glycin and GABA release [inhibitory neurotransmitters] from Renshaw cells in spinal cord

Question 18

What symptoms does tetanus cause?

Answer 18

(1) Spastic paralysis (2) Trismus (lock jaw) (3) Risus sardonicus

Question 19

What kind of exotoxin does C. botulinum produce? What is the general mechanism of this exotoxin? What other toxin has the same general mechanism?

Answer 19

BOTULINUM TOXIN; Protease that cleaves releasing proteins for neurotransmitters; Tetanospasmin (i.e., Tetanus toxin)

Question 20

What is botulinum toxin? What is the specific mechanism by which it works?

Answer 20

Preformed, heat-labile exotoxin; Inhibits ACh release at neuromuscular junction, causing botulism

Question 21

What kind of paralysis does botulism cause? What is this disease called in babies?

Answer 21

Flaccid paralysis; Floppy baby syndrome

Question 22

What is the cause of botulism in adults versus babies?

Answer 22

ADULTS - ingestion of preformed toxin; BABIES - ingestion of spores in honey –> floppy baby syndrome

Question 23

What exotoxin does C. perfringens produce? What kind of activity does it have?

Answer 23

Alpha toxin (lecinthinase); phospholipase (activity)

Question 24

What does C. perfringens’ alpha toxin (i.e., lecinthinase) cause?

Answer 24

Cause myonecrosis (gas gangrene) & hemolysis; Think: “PERFringens PERForates a gangrenous leg”

Question 25

What kind of exotoxin(s) does C. difficile produce? What is/are the mechanism(s) of this/these exotoxin(s)?

Answer 25

(1) Toxin A (enterotoxin) - binds to brush border of the gut (2) Toxin B (cytotoxin) - destroys the cytoskeletal structure of enterocytes (causing pseudomembranous colitis)

Question 26

To what does C. difficile (and its two exotoxins) often occur secondary? Give specific examples.

Answer 26

Antibiotic use, especially clindamycin or ampicillin

Question 27

How is C. difficile diagnosed?

Answer 27

Detection of one or both toxins (A and B) in stool

Question 28

What does C. difficile cause?

Answer 28

DIfficile causes DIarrhea

Question 29

How is C. difficile treated?

Answer 29

Metronidazole or Oral Vancomycin

Question 30

Name and describe the bacteria that causes Anthrax. In this description, include gram stain, morphology, what it produces, & what makes it unique.

Answer 30

Bacillus anthracis - gram-positive, spore-forming rod that produces anthrax toxin; Only bacterium with a polypetide capsule (contains D-glutamate)

Question 31

How is cutaneous anthrax transmitted? How does it present?

Answer 31

Contact; Boil like lesion => Ulcer with black eschar/crust (painless, necrotic) => uncommonly progresses to bacteremia and death

Question 32

How is pulmonary anthrax transmitted? How does it present?

Answer 32

Inhalation of spores; Flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, & shock

Question 33

In general, what is Woolsorters’ disease? With which bacteria and condition should you associate it?

Answer 33

Inhalation of spores from contaminated wool; Bacillus anthracis - Pulmonary anthrax

Question 34

What does bacillus cereus cause? What is it sometimes called in this case, and why?

Answer 34

Food poisoning; Reheated rice syndrome - Spores survive cooking rice & Keeping rice warm results in germination of spores & enterotoxin formation

Question 35

Again, what kind of disease in general does Bacillus cereus cause? What are the types of this disease? What are their symptoms and time course?

Answer 35

Food poisoning; (1) EMETIC TYPE - nausea and vomiting within 1-5 hours (2) DIARRHEAL TYPE - watery, nonbloody diarrhea and GI pain in 8-18 hours

Question 36

With what kinds of food is the emetic type of food poisoning caused by B. cereus seen?

Answer 36

Rice and pasta

Question 37

What is the preformed toxin of B. cereus to remember? What kind of food poisoning does it cause?

Answer 37

Cereulide; Emetic type

Question 38

What kind of microbe is Listeria monocytogenes?

Answer 38

Facultative intracellular microbe; (also gram + rod)

Question 39

How is L. monocytogenes acquired?

Answer 39

By ingestion of unpasteurized milk/cheese and deli meats, via transplacental transmission, by vaginal transmission during birth

Question 40

How does L. monocytogenes move from one cell to another, and what advantage does this have? What is a defining characteristic of its movement?

Answer 40

Form “rocket tails” (via actin polymerization) that allow them to move through cytoplasm and into cell membrane, thereby avoiding antibody; Characteristic tumbling motility

Question 41

What disease(s) does L. monocytogenes cause in pregnant women?

Answer 41

(1) Amnionitis (2) Septicemia (3) Spontaneous abortion

Question 42

What disease(s) does L. monocytogenes cause in immunocompromised patients?

Answer 42

Meningitis

Question 43

What disease(s) does L. monocytogenes cause in neonates?

Answer 43

(1) Granulomatosis infantiseptica (2) Neonatal meningitis

Question 44

What disease(s) does L. monocytogenes cause in healthy individuals?

Answer 44

Mild gastroenteritis

Question 45

How is L. monocytogenes treated? Be specific to condition and affected population.

Answer 45

Gastroenteritis usually self-limited (in healthy individuals); Ampicillin in infants, immunocompromised patients, & elderly in empirical treatment of meningitis

Question 46

What is unique about L. monocytogenes among other gram positive organisms?

Answer 46

Only gram-positive organism to produce LPS