Infection, Pathogenicity, and Virulence – Bacterial Toxins

What is pathogenicity?

The ability of an organism to cause disease by harming the host.

Define virulence.

The degree of pathogenicity, indicating how severe the disease caused by a pathogen can be.

What are virulence factors?

Molecules, structures, or systems that enable microorganisms to cause disease.

What are bacterial toxins?

Substances produced by bacteria that are harmful to host cells.

How do bacteria use motility mechanisms?

To reach entry sites like wounds.

What is the purpose of host damage during bacterial pathogenesis?

Facilitates invasion, accesses nutrients, reduces competition, aids dissemination, and can be accidental.

What characterizes highly virulent pathogens?

They consistently cause disease.

What characterizes less virulent pathogens?

They cause disease in weakened hosts or when present in large numbers.

What do hyaluronidase and collagenase do?

Break down connective tissues, aiding bacterial spread and increasing infection severity.

What is the function of coagulase?

Induces clot formation, shielding bacteria.

What is the role of kinase?

Dissolves clots, allowing dissemination of bacteria.

What are endotoxins?

Found in Gram-negative bacteria; released upon bacterial death and trigger strong immune responses.

What are exotoxins?

Secreted by both Gram-positive and Gram-negative bacteria; highly potent and specific toxins.

What are cytotoxins?

Toxins that target and destroy host cells.

What are superantigens?

Bypass normal antigen presentation, activating a large proportion of T-cells and causing toxic shock syndrome.

What are AB toxins composed of?

Two parts: A (active) and B (binding) subunits.

Describe cholera toxin.

Produced by Vibrio cholerae; binds to GM1 ganglioside receptors, leading to severe diarrhoea.

Describe botulinum toxin.

Produced by Clostridium botulinum; blocks acetylcholine release, causing flaccid paralysis.

How is botulinum toxin used medically?

To treat muscle spasms and cosmetically to reduce wrinkles.

Describe tetanus toxin.

Produced by Clostridium tetani; inhibits release of inhibitory neurotransmitters, causing spastic paralysis.

What is the prevention method for tetanus?

Vaccination with tetanus toxoid.

What are toxoids?

Inactivated toxins that retain their antigenicity.

How are toxoids used?

Employed in vaccines to elicit immune responses without causing disease.

What is one example of a disease targeted by toxoids?

Diphtheria.

What is another example of a disease targeted by toxoids?

Tetanus.

What is the mechanism of cholera toxin?

Increases cAMP levels, leading to chloride and water efflux.

What does Staphylococcus aureus α-toxin do?

Forms pores in cell membranes, leading to cell lysis.

What is the impact of superantigens on T-cells?

Cause massive cytokine release.

What kind of bacteria produce exotoxins?

Both Gram-positive and Gram-negative bacteria.

What triggers strong immune responses from endotoxins?

Lipopolysaccharides (LPS) found in Gram-negative bacteria.

What is the effect of tetanus toxin on muscle function?

Causes continuous muscle contraction.

What mechanism does botulinum toxin use to affect neurotransmission?

Blocks acetylcholine release at neuromuscular junctions.