Bacillus

Question 1

General characteristics of Bacillius

Answer 1

rod-shaped
gram positive
catalase positive
endospore forming

Question 2

key characteristics of B. anthracis

Answer 2

• white, non-hemolytic rough-edge colonies on blood agar can be drawn upward
• capsule surrounding chains of vegetative cells in infected spleen tissue

Question 3

distinguishing B. cereus from B. anthracis

Answer 3

B. cereus are motile and flagellated (96%)
B. anthracis are non-motile (100%)

B. cereus are beta hemolytic; B. anthracis are not.

B. cereus vegetative cells are longer.

Question 4

disease caused by b. cereus

Answer 4

food poisoning

Question 5

disease caused by b. antracis

Answer 5

anthrax

Question 6

virulence factors of bacillus

Answer 6

toxins, capsule production, germination control, regulators

Question 7

anthrax transmission

Answer 7

spores –> germinate in host –> vegetative cells kill host –> sporulation –> spores dispersed back into environment

Question 8

virulence factors of anthrax

Answer 8

germination factors; toxins; capsule production; virulence regulators; siderophores

Question 9

cutaneous anthrax

Answer 9

B. anthracis spores enter abrasion, cut, or insect bite in skin; paupule forms; vesicles around papule that ulcerates into coal black eschar; edema occurs at site of infection, but eschar is “painless;” left untreated can go to sepsis in ~20% of cases; sepsis if often fatal

Question 10

gastrointestinal anthrax

Answer 10

ingestion of spore-contaminated meat; abdominal symptoms; oro-esophageal symptoms

Question 11

inhalation anthrax

Answer 11

inhalation of B. anthracis spores; symptoms 2-5 days post-exposure; non-specific-symptom stage; acute disease; extremely fatal

Question 12

anthrax virulence factors

Answer 12

anthrax toxin: Protective antigen (PA); lethal factor (LF); edema factor (EF). Individually PA, LF and EF are nontoxic; anthrax toxin is a binary toxin, such that PA must be combined with LF or EF to make a toxin. Two possible toxins: Lethal Toxin = PA +LF. Lethal toxin causes shock-like death. Edema toxin (EdTx) is Pa + EF and causes edema/swelling. Translocation of LF/EF across host cell membranes is required for LeTx or EdTx action. Translocon machinery is found in the PA oligomer complex. Protein unfolding must occur to allow LF and EF to transverse the PA pore. Cytosolic LF and EF harm host cells by their catalytic activities: LF –> proteolytic cleavage of host signaling factors; EF–> production of cyclic AMP second messenger.

poly-gama-glutamic acid (gamaPGA) capsule - capsule is anti-phagocytic.

Question 13

B. cereus food poisoning

Answer 13

“fried rice syndrome;” endospores are heat-stable

slow-onset enterotoin diarrhea or rapid-onset emetic vomiting

Question 14

B. cereus toxins

Answer 14

emetic toxin, cereulide

enterotoxins: cereolysin O and phospholipase C

Question 15

cereulide

Answer 15

cyclic-peptide ionophore, like valinomycin
emetic toxin: potent cytotoxin causing vomiting and diarrhea
ionophore: inserts in membrane, creates leaks to weaken ion gradients across membranes
destroys mitochondria
extremely heat resistant

Question 16

cereolysin O (CLO)

Answer 16

large cytolytic protein toxin
Cholesterol-dependent cytolysin (CDC) common to gram+ pathogens
hemolytic pores assemble in membranes
membrane permeability can have profound effects even at low toxin levels
heat labile and destroyed by autoclaving, cooking and baking

Question 17

anthrax-like B. cereus pneumonia in US

Answer 17

severe and fatal pneumonia mimicking anthrax; nonspecific anthrax-like initial symptoms; motile and hemolytic B. cereus isolate, yet anthrax-like
toxins
capsule