6- bacteria as pathogens

Question 1

bacteria can be

Answer 1

Bacteria can be agents of infection, invading and destroying host tissues and producing toxins

Question 2

exotoxins

Answer 2

• Soluble protein toxins are produced and released outside the bacterial cell.
• These toxins can spread around the body in the blood or body fluids, affecting host cells far from the initial infection site.
• Exotoxins can rupture cell
membranes, cause internal bleeding, poison cells directly, or inhibit neurotransmitters in the nervous system.

Question 3

staphylococcus

Answer 3

Overstimulates the nonspecific immune system leading to a massive inflammatory response (toxic shock, often fatal).

Question 4

endotoxins

Answer 4

• Toxin molecules are produced in the lipopolysaccharide layer of gram-negative bacteria.
• These toxins may be released from the bacterium if it breaks down.
• Endotoxins cause localised effects to the area of infection (e.g. fever, vomiting).

Question 5

salmonella

Answer 5

Infections usually occur in the intestine where the endotoxin is released, leading to inflammation of the gut lining and diarrhoea.

Question 6

tissue invasion

Answer 6

Bacteria enter host cells and tissues to cause harm and destruction.

Question 7

TB (tuberculosis)

Answer 7

• Caused by Mycobacterium tuberculosis infecting phagocytes in the lungs.
• Effects include breathing problems, coughing, weight loss, and fever.
• If untreated, it can slowly destroy lung tissue and can be fatal.

Question 8

TB infection process

Answer 8

1. The first infection is symptomless.
   Infected phagocytes are sealed in tubercles as a result of an
   inflammatory response in the lungs.
2. The bacteria can lie dormant within tubercles for years. They are not destroyed by the immune system and the tubercles are covered with a thick waxy coat.
3. When the immune system becomes weakened, the bacteria become active and cause wider infection, slowly destroying the lung tissue.