Gram positive bacilli, packet #3

Question 1

Name your four gram + bacilli?

Answer 1

Bacillus and Clostridium are spore forming

Listeria and Corynebacterium are NON spore forming

Question 2

Which bacterium of your gram + rods is an obligate anaerobe?explain what this means

Answer 2

Clostridium- can only grow in a anerobic culture (will not grow in an oxygen rich environment)

Question 3

Name the gram + aerobic spore forming rods and its associated disease

Answer 3

**Bacillus anthracis- **

1. Cutaneous anthrax (most common): active rods release exotoxin that cause skin ulcers like malignant pustules with a black escher
2. Pulmonary anthrax: aka woolsorters disease cause life-threatening pneumonia
3. GI anthrax

Bacillus cereus - gastroenteritis

Question 4

What is so unique about bacillus anthracis?

Answer 4

only non motile bacilli AND it is the only bacterium with a capsule composed of protein (poly - D- glutamic acid) [it has a polypeptide instead of a polysaccharide]

• Capsule prevents phagocytosis

Question 5

Where does Bacillis anthrax live? and how is it transmitted?

Answer 5

Lives on animals, soil and skin (hair) for long periods resistant to drying, heat, and UV bc it forms a spore.

Transmitted by contact on skin, can be inhaled or ingested to cause GI problems.

Question 6

Which exotoxins are released by B. anthracis?

Answer 6

Protective antigen- promotes entry of toxin into phagocytic cells

Adenylate cyclase- increases the cAMP cascade that results in massive edema (edema factor)

Lethal factor- inactives protein kinase

Question 7

Pt. is a military personnel with high risk exposure to B. anthracis, can bacterium induced disease be prevented? how?

Answer 7

All high risk occupations (military, farmers or workers with goats/cows where diseas is prevalent) should be given a vaccine that contains the protective antigen (PA) to induces adaptive humeral immunity and make antibodies.

Question 8

Pt presents with painless black vesicles. If this is a result of B. anthracis how would you confirm? And what is the tx?

Answer 8

Do a gram stain smear (purple)

Aerobic culture on blood agar

Conduct a serology: look for increasing indirect hemagglutinating antibody titer in the plasma serum

TX: ciprofloxin (Cipro) PO/IV [Quinolones}

or doxycycline (doryx) PO [tetracycline]

Question 9

Pt presents with n/v/d. Which bacteria could have caused this?

Answer 9

Bacillus cereus spores found on rice (fried rice) held warm or reheated (not refridgerated)

or by Staph aureus

Question 10

Which toxins are released by B. Cereus?

Answer 10

Heat labile toxin: produces watery diarrhea similar to the LT from E. Coli lasting 12-24 hours

Emetic toxin (heat stable toxin): has a short incubation period with n/v and limited diarrhea similar to S. aureus lasting 1-6 hours.

Question 11

What are the unique factors of Listeria

Answer 11

Non spore forming rods: Have a tumbling motion, can grow both intracellularly and extracellularly, and prefers an immunocompromised host

Question 12

Why does Listeria have intracelular growth?

Answer 12

It can escape phagocytosis of macrophages by rapid egress thanks to it’s listeriolysin O virulance factor