Bacterial Toxins

Question 1

Exotoxin

Answer 1

Produced by gram neg and positive bacteria
Proteins, released by the bacteria
Heat labile
AB toxins or cytolytic toxins

Question 2

Endotoxin

Answer 2

Cell wall components of gram neg bacteria
LPS of outer membrane
Heat stable

Question 3

AB toxins

Answer 3

A and B subunits
B = binding, A = action
AB and AB5
Targets are specific

Question 4

Superantigens

Answer 4

Bind TCR and MHC 2 of APC
Ex: TSST1 for S. aureus
Non specific, so they can activate a huge number of T cells and cause a polyclonal response

Question 5

LPS effects at low concentrations

Answer 5

Fever
Vasodilation
Inflammatory response

Question 6

LPS effects at high concentration

Answer 6

Fever
Vasodilation
Disseminated intravascular coagulation
Hypotension
Shock and death

Question 7

Clostridium spp

Answer 7

Gram positive
Spore forming
Anaerobic rods
Ubiquitous: soil, sewage, normal flora in GI of animals and humans

Question 8

4 Clostridium spp and what they cause

Answer 8

tetani: tetanus
botulinum: botulism
perfringens: gangrene, food poisoning
difficle: C diff associated diarrhea

Question 9

Tetanus

Answer 9

Spastic contraction of muscles
Often associated with puncture wound
Infection remains localized then the toxin is absorbed systematically

Question 10

2 tetanus toxins

Answer 10

1. Tetanolysin: oxygen-labile hemolysin

2. Tetanospasmin: plasmid encoded, heat-labile, AB toxin

Question 11

Tetanospasmin

Answer 11

Binds to specific sialic acid receptors and glyoproteins of motor neurons
Internalized in endosome
Attache to peripheral nerve endings and travels along to CNS and blocks inhibitory impulse to motor neurons
Inactivates proteins that regulate release of inhibitory transmitters glycine and GABA
Toxin binding is irreversible

Question 12

Botulinum toxin

Answer 12

AB toxin
Human disease caused by types A, B, E, F
Binds specific sialic acid receptors and glycoproteins on motor neurons (different ones than tetanospasmin)
Stays at the NMJ
Blocks release of Ach
Leads to acute flaccid paralysis

Question 13

What does clostridium perfringiens cause?

Answer 13

Gas gangrene
Food poisoning
Enteritis necroticans

Question 14

Gas gangrene

Answer 14

Significant injury (crush, open fractures)
Contamination with soil containing spores
Leads to tissue necrosis
Infection rapidly progressive

Question 15

2 Gas gangrene toxins

Answer 15

Alpha: lethal lecithinase that has both phospholipase C and sphingomyelinase activities
Theta (perfringolysin): cholesterol-dependent cytolysins, forming a pore and resulting in cell lysis upon contact with cholesterol in the host’s cell membranes

Question 16

2 C diff toxins

Answer 16

Toxin A (TcdA) enterotoxin
Toxin B (TcdB) cytotoxin
Only strains producing B (or A and B) cause disease

Question 17

E. coli

Answer 17

Gram negative rods
Motile, facultative anaerobe
Normal inhabitant of human and animal digestive tracts
Certain strains cause intestinal/diarrheal disease
Others cause UTIs, neonatal meningitis, septicemia

Question 18

Enterotoxigenic (ETEC) E. coli

Answer 18

Acquired from contaminated food/water
Watery diarrhea in young children in developing countries
Travellers diarrhea to tropical region
Pathogenesis from intestinal attachement (fimbriae) and elaborate toxins (2 types)

Question 19

2 ETEC toxins

Answer 19

LT: heat labile, AB5 toxin, similar to cholera toxin, stimulates adenylate cyclase, increases cAMP leading to electrolytes and water excretion in intestinal lumen (watery diarrhea)
ST: heat stabile, STa and STb, activates guanylate cyclase, increases cyclic guanosine monophasphate, increases fluid and electrolyte excretion (watery diarrhea)

Question 20

Enterohemorrhagic (EHEC) E. coli

Answer 20

Causes hemorrhagic colitis (bloody diarrhea) and may lead to HUS
Acquired from contaminated food: undercooked ground beef, raw milk, unpasteurized apple juice, vegetables
Many serotypes, O157:H7 most common
AB5 toxin
Similar to Shiga toxin
Bind glycolipid receptors (gb3), found in varying degrees in membranes of eukaryotic cells

Question 21

Shigella spp

Answer 21

Gram negative rod, non motile
Causes diarrheal disease, could be severe
4 species: dysenteriae, boydii, fleneri, sonnei
Human pathogen, no animal reservoir
Spread by fecal oral route, less by contaminated food and water
Bloody diarrhea
Infectious dose 10-100

Question 22

Vibrio spp

Answer 22

Curved gram negative rods
Highly motle
Facultative anaerobes
Typically found in salt water
Environmental organism and human intestinal pathogen
Infection acquired from contaminated water or food
Severe watery diarrhea, can lead to dehydration and death in untreated patients

Question 23

3 species of Vibrio

Answer 23

cholerae: cholera
parahaemolyticus: gastroenteritis
vulnificus: cellulitis, septicemia

Question 24

Cholera toxin

Answer 24

AB5 toxin
Bind ganglioside GM1 receptor on intestinal cells
Increase cAMP, leading to electrolytes and water secretions

Question 25

Staph aureus

Answer 25

Non-motile, gram positive cocci
Colonizes anterior nares
Causes toxin mediated diseases, skin and soft tissue infections, systemic infections

Question 26

Staph aureus exfoliative toxins

Answer 26

SSSS: staphlococcal scalded skin syndrome
ETA & ETB: In 5% of strains, either can cause disease
ETA: heat stable, chromosomal
ETB: heat labile, on plasmid
Serine proteases
Disrupt cell-adhesion structures

Question 27

Toxic shock syndrome toxin-1

Answer 27

Causes TSS
Super antigen
Fever, hypotension, rash, and multi-organ failure
Have to treat with penicillin to get rid of the bacteria, as well as clindamycin and Igs to get rid of the toxin

Question 28

Staph aureus enterotoxin

Answer 28

Multiple enterotoxins identified
Enterotoxin A most commonly associated with food poisoning
Heat stable
Resistant to gastric enzymes
Produced by 30-50% of s. aureus