bio 251 chapter 15 second half

Explain the importance of adhesion molecules in the establishment of infectious disease and know examples

the importance of adhesionis that it allows for the pathogen to bind to its host receptors such as colonization and invasion.

adhesin for streptococcus pyrogenes

protein F m protein and lipoteichoic acid

adhesin for streptococcus mutans

adhesin P1

adhesin for neisseria gonorrhea

Type iv Pili

Adhesin for vibrio cholerae

N-methylphenylalanine pili

What does Hyaluronidase do?

Hyaluronidase degrades hyaluronic

acid, which holds cells together

examples of hyaluronidase

Staphylococcus, Streptococcus pyogenes, Clostridium perfringens

What does collagenase do?

is a protease produced by C. perfringens degrades the collagen between the endothelial cells, allowing the bacteria to enter the bloodstream

examples of collagenase

Clostridium perfringens

Clostridium perfringens

is a bacterium that produces collagenase, which helps it invade host tissues by breaking down collagen. perfringens produces toxins and phospholipase

C which lyse cells, leading to necrosis

• C. perfringens ferment the muscle carbohydrates,

producing gas

• Gas gangrene

Why is hyperbaric oxygen therapy used to treat patients with C. perfringens infection?

It is used to increase oxygen supply to tissues, inhibit the growth of anaerobic bacteria, and promote healing of infected areas.

streptococcus pyrogenes

Protein F is a fibronectin binding protein

• Adheres to respiratory epithelial cells

neiserria Gonorrhoeae

Gram-

negative diplococci

Cysteine Protease

hydrolyzes peptide bonds with cysteine

Necrotizing fasciitis

Skin infections caused by Streptococcus that spread elsewhere in the body

• S. pyogenes and other bacterial species

• Also referred to as flesh-eating disease

Explain the differences between endotoxin and exotoxins

endotoxins are Only Gram-negative bacteria and exotoxins are produced by both gram negative and positive bateria.

What are the properties of exotoxins?

Proteins, most are enzymes, soluble and diffusible

• High toxicity

• Damage host cells by inhibiting a specific metabolic function

Cytotoxins - Kill host cells or inhibit function(s)

• Enterotoxins - Affect epithelial cells of GI tract

• Neurotoxins - Interfere with nerve impulse transmission

the three classses of exotoxins are?

Intracellular targeting toxins

• Membrane disrupting toxins

• Superantigens

intracellular targeting toxin

In A-B toxins, the B component binds to the host cell through its interaction with specific cell surface receptors.

(b) The toxin is brought in to the cell through endocytosis.

Membrane disrupting toxins

bacterial phospholipases that

disrupt eukaryotic cytoplasmic membranes, lyse cells

examples of membrane disrupting toxin

Phospholipases hydrolyze phospholipids of membrane

Hemolysins – Pore-forming toxins insert into membranes,

form pores

Streptolysin O from Streptococcus pyogenes

superantigens

are a class of antigens that provoke excessive immune responses by activating a large number of T-cells, leading to a cytokine storm.

Explain how AB toxins work; which toxins work by this mechanism

In A-B toxins, the B component binds to the host cell through its interaction with specific cell

surface receptors.

(b) The toxin is brought in to the cell through endocytosis.

(c) Once inside the vacuole, the A component (active component) separates from the B

component and the A component gains access to the cytoplasm.

examples of A-B toxin

our unique examples of A-B toxins are the diphtheria, cholera, botulinum, and tetanus toxins

botulinum Toxin

is an A-B toxin produced by the bacterium Clostridium botulinum that inhibits neurotransmitter release, leading to muscle paralysis.

Botulinum toxin is a neurotoxin

• Acts by inhibiting acetylcholine release from the presynaptic nerve terminal

• Causes flaccid paralysis due to the inhibition of muscle contraction

• Death in botulism exposure is generally due to respiratory failure.

• Cosmetic use: Very low concentrations of the toxin are in Botox

Tetanus Toxin

Tetanus toxin binds to inhibitory interneurons

• Tetanus toxin inhibits the release of glycine and GABA from the

interneuron, resulting in permanent muscle contraction

• Violent muscle spasms in other parts of the body follow, typically

culminating with respiratory failure and death

What virulence factor does E. coli O157:H7 produce that allows it to cause HUS?

The virulence factor produced by E. coli O157:H7 that causes Hemolytic Uremic Syndrome (HUS) is the Shiga toxin (also called verotoxin). Life threatening pathogen

Why are biofilms considered to be a virulence factor?

Biofilms are considered a virulence factor because they enhance microbial survival by providing protection from the host's immune system and antibiotics, allowing bacteria to adhere to surfaces and resist removal.

listeria monocytogenes

Gram-positive, nonspore forming, rod-shaped (0.5 – 2.0 microns)

• Motile; peritrichous flagella; Facultative, catalase positive, non acid fast

• Psychrotrophic; optimum 30 – 37 degrees C; can grow in 1 – 45 degree temps

• Survives in up to 10 – 12% NaCl; grows well up to 6.5%

• known to survive under various conditions of refrigeration, freezing, heating, and

drying and is among the most heat-resistant of vegetative bacterial cells.

phospholipasephospholipase• found in soil, silage, decaying vegetation, animal feces, sewage water, and

other environmental sources and often in the intestines of healthy animals,

including humans

phospholipase

membrane disrupting toxin hydrolyze phospholipids of membrane

hemolysins

membrane disrupting toxin that is Pore-forming toxins insert into membranes,

form pores

What do superantigens do?

Superantigens cause excessive activation of T-cells by binding to the T-cell receptor and major histocompatibility complex (MHC) molecules, leading to a massive immune response and the release of cytokines. Causes cytokine storm or whatever

How do capsules help bacteria evade host defenses?

Slime layers and capsules can also make some bacteria adherent Capsule production

• Avoid phagocytosis