Damage and Pathophysiology of microbial disease Flashcards

Question

(Virulence factors) Explain Super Antigen toxins

Answer 1

-Produced by some bacteria and viruses For example: •S. aureus – Toxic shock syndrome toxin and enterotoxin B -‘Short circuit’ the immune system Allow non-specific activation of immunity Switches on cells that produce chemical messengers -For example: Cytokines – chemicals that activate or repress immune responses Can activate >30% of total T cells to produce cytokines Leads to damage of blood vessels, shock and multi-organ failure

Answer 2

Invasins promote spread

Answer 3

Degredative enzymes used often used in nutrition •Increase the severity of disease by allowing penetration to deeper tissues –Kill cells directly, destroy the structure of the tissue, destroy clotts For example: Group A Streptococcus pyogenes – Necrotising fasciitis Extensive destruction of subcutaneous fat and muscle Production of Hyaluronidase Streptokinase produced that prevents blood clotting The net effect is massive and rapid destruction of whole soft tissue areas.

Answer 4

Intrinsic factor found only in G – ve bacteria •Forms a large component of the outer membrane For example: –Lipopolysaccahride - LPS •Contains Lipid A which anchors the LPS into the outer menbrane–Lipid A is the toxic moiety •Plays a major role in G –ve bacterial disease –Endotoxic shock –Endotoxaemia –1 ng introduced intravenously = temp > 1 deg C

Answer 5

–Interfer with cellular processes •Increase cAMP, stop protein synthesis –Cause lysis •Form pores or disrupt membranes –Hyper activation of processes •Super antigens, cAMP levels causing fluid imbalances –Effect neurones at synapses •Tetanus and botulinum toxin

Answer 6

–Causative agent – Clostridium perfringens •G +ve anaerobic rod •Infects deep wounds – post operative infections –Very common before antibiotics ``` •Produces a variety of secreted factors –α – toxin – phospholipase C - hydrolyses phospholipids »Detergent like –β – toxin – haemolysin –Collagenase ``` •Colonises areas of no blood flow –Very difficult to treat – defences, drug delivery –smells bad – production of volatile amines

Answer 7

The enzyme binds to membrane phospholipids and then cleaves the heads away from the tails causing membrane integrity to be compromised and the cell to lyse. This enzyme basically works a bit like a detergent. This toxin also can control the movement of immune cells

Answer 8

Systemic intoxication caused by Clostridium tetani •Gram + ve anaerobic rod •Contaminates deep wounds where O2 concentration is very low •Produces Tetanospasmin –Secreted during growth –Diffuses into neuromuscular synapses –Blocks release of inhibitory neurotransmitters – glycine –Induces continuous stimulation and contraction of muscules –Causes a RIDGID PARALYSIS –Contraction of the respiratory system leads to death

Answer 9

The toxin prevents the release of inhibitory chemicals causing over stimulation

Answer 10

Systemic intoxication caused by Clostridium botulinum •Gram +ve anaerobic rod •Germination of spores and growth in foods liberates botulinum toxin –Damaged canned goods, honey, hazelnut yoghurt? •On ingestion diffuses to neuromuscular synapses –Blocks release of stimulatory neurotransmitter - acetylcholine –Induces a FLACCID PARALYSIS –Death occurs through respiratory/cardiac failure –May be used medically or in cosmetic surgery

Answer 11

The toxin blocks the release of stimulatory neurotransmitters leading to a lack of contraction

Answer 12

Toxigenic disease caused by enterotoxin produced by Vibrio cholera Gram –ve Comma shaped organism found in faecally contaminated water –Non-invasive colonisation of the intestinal mucosa –Cholera toxin secreted and enters cells (A-B toxin) –Effects c-AMP to cause massive efflux of fluid and electrolytes –Leads to fatal dehydration –Fluids and electrolytes need replacing for recovery

Answer 13

The toxin interacts with G-coupled proteins to induce the adenylate cyclase enzyme to make huge amounts of cAMP. This leads to an imbalance of electrolytes which induces massive water loss