Gram-Positive Bacilli

Question 1

Gram-positive bacilli are subdivided in which ways?

Answer 1

Spore and non-spore forming and based on need for anaerobic conditions for growth

Question 2

Describe spore forming gram positive bacilli

Answer 2

Includes:
Aerobic bacillus
Anaerobic clostridium

Not many spore-forming organisms are of clinical significance

Question 3

Describe non-spore forming gram positive bacilli

Answer 3

Many more of these are clinically significant

Corynebacterium
Propionibacterium
Listeria
Lactobacilli
Nocardia
Actinomyces

Question 4

What are the two types of toxins associated with bacteria, and why is this important when discussing gram positive bacilli?

Answer 4

Endotoxins: released upon cell death; highly present in
gram positive bacilli which can result in endotoxic shock

Exotoxins: released by living bacteria.
Clostridia species release exotoxins. They are responsible for illnesses like botulism, tetanus and food poisoning.

Question 5

How do exotoxins move around the body?

Answer 5

released from a small infection, travel in the bloodstream to the gut

Question 6

Are antitoxins effective on bound or unbound toxins?

Answer 6

Unbound (travelling around the body); toxins already bound to tissues cannot be treated by antitoxin.

An antitoxin can prevent further damage from toxin but not reverse damage already occured

Question 7

What is an example of a modified exotoxin?

Answer 7

Toxoids, used in immunization.

Question 8

Where can bacillus species be found?

Answer 8

Environmental
Skin flora
Often found in non-sterile environmental cultures
Often in the air

Question 9

What are the two most relevant bacillus spp?

Answer 9

B. anthracis

B. cereus

Question 10

Anthrax is caused by which organism?

Answer 10

B. anthracis; primarily in animals
very rare in N. america
Potential bioterrorism agent

Question 11

Bacillus cereus is associated with which types of infections?

Answer 11

Blood stream

Food poisoning

Question 12

What are the most significant clostridium species?

Answer 12

Clostridium botulinum
Clostridium tetani
Clostridium perfringens
Clostridioides difficile

Question 13

Which organism is responsible for botulism?

Answer 13

Clostridium botulinum
anaerobic, gram-positive, spore-forming bacteria
Routine precautions (not person-to-person)

Question 14

What is Botulism?

Answer 14

neuroparalytic disorder mediated by toxin production. Source is usually contaminated food

Question 15

What is Tetanus?

Answer 15

Toxin mediated neurologic disease acquired mainly from contaminated wounds

Question 16

Which organism is responsible for tetanus?

Answer 16

Clostridium tetani
Gram-positive bacilli, spore-forming, anaerobic
Routine precautions (not person-to-person)

Question 17

What two syndromes can clostridium perfringens cause?

Answer 17

Food poisoning
Gas gangrene (clostridial myonecrosis)

Question 18

Summary of C. diff

Answer 18

anaerobic gram positive spore forming bacillus
Spores can survive long time in environment
Clinical disease mainly mediate by enterotoxins
Toxins A & B are most common toxins
No single test can be reliably used for Cdiff
Can be detected in asymptomatic pts
high rate of c diff colonization in children

Question 19

Which bacteria is responsible for diphtheria

Answer 19

corynebacterium diphtheriae

Gram-positive bacilli, non-spore forming, aerobic

Question 20

How does c. diphtheria appear on agar?

Answer 20

Using tellurite agar
Grows as a black colony
Sometimes diphtheroids and some staphylococci will appear black, but grow poorly

Question 21

Differentiate between respiratory and cutaneous diphtheria

Answer 21

Respiratory: faucial (narrow pass from mouth to pharyx), nasal, laryngeal
Cutaneous: non-specific ulcers; usually no complication but myocarditis and neuritis possible

Question 22

What are the possible outcomes of respiratory diphtheria?

Answer 22

1) full recovery
2) complications:
- airway obstruction (week 1)
- myocarditis (week 2)
- neuritis - cranial or peripheral (up to months later)

Question 23

Who are typically affected by Listeria?

Answer 23

immunocompromised and newborns

Question 24

Describe the listeria bacteria

Answer 24

non-spore forming
gram- negative
bacilli

Question 25

What is the impact of listeria monocytogenes?

Answer 25

Food poisoning
meningitis
bacteremia
outbreak-causing

Question 26

Where is lactobacillus normally found?

Answer 26

normal adult vaginal flora

bowel flora of breatfed infant