Lecture 7- Infection, Pathogenicity + Virulence- Bacterial Toxins

Question 1

Pathogenicity

Answer 1

The ability of an organism to cause disease

Question 2

Virulence

Answer 2

The relative ability of the pathogen to infect a host + cause disease
-degree of pathogenicity

Question 3

Virulence factors

Answer 3

-molecules
-cellular structures
-regulatory systems that enable microorganisms to cause disease

Question 4

Bacterial toxins

Answer 4

-virulence factor
-protein, peptide/ any other substance produced by bacteria which is highly poisonous for living cells in other organisms

Question 5

Why do bacterium’s harm its host?

Answer 5

Main goal of bacteria cell= multiply
Killing host= kills bacteria = no nutrients
Successful bacteria= obtain nutrients + spread with the least amount of energy and host damage

Host damage=
-facilitate invasion (weakened barriers/ immune responses)
-access/liberate nutrients
-reduce competition from other microbes

Question 6

Host response vs disease

Answer 6

Immune response too weak to be effective= no benefit to the host

Immune response excessive= damaging to the host

Question 7

Extracellular enzymes

Answer 7

Slides 9-10

Question 8

Bacterial toxins

Answer 8

Contribute significantly to bacterial disease
Primary causes of some diseases= anthrax + tetanus
-highly potent
-act away from where they are secreted

Question 9

Bacterial toxins

Answer 9

Endotoxins;
-produced when bacteria die/ phagocytosed
-gram negative bacteria only e.g. endotoxic septic shock

Exotoxins;
-secreted by bacteria
-can travel through the body + have an effect far from the site of infection e.g. botulism, tetanus etc

Question 10

Types of toxins

Answer 10

Endotoxin; a lipopolysaccharide component of the gram - bacteria cell = released during active cellular growth + cell lysis

Exotoxin; group of soluble proteins that are secreted by the bacterium; enter host cells + catalyse the modification of a host cell component

Enterotoxin; a protein exotoxin released by a microorganism that targets the intestines. Involved in diarrhoea + food poisoning

Question 11

Impacts of bacterial toxins

Answer 11

-changes to target cells
-facilitate bacterial spread through tissues
-damages cell membranes
-dampen the host immune system
-inhibit protein synthesis

Question 12

Bacterial cell envelope

Answer 12

2 major categories; gram + and gram -

Gram + = no LPS= no endotoxin
LPS release can cause host immune system to be hyper-activated

Question 13

Immune response to endotoxins

Answer 13

-they have pattern recognition receptors that recognise pathogen specific moieties
-known as pathogen-associated molecular patterns (PAMPs)

Examples;
-flagellin, LPS, DNA, chitin and peptidoglycan

Question 14

Endotoxins- host immune system hyperactivation

Answer 14

Inflammation= increases permeability of tissue to immune cells and promotes healing

Uncontrolled, systemic inflammation + septic shock

Inflammatory response can fail to localise + deal with the pathogen ;
-immune cells become overwhelmed
-bacteria spread to other areas of the body
-large amounts of LPS can enter blood circulation

Question 15

Endotoxins- host immune system hyperactivation

Answer 15

Antibiotics?
-antibiotic therapy can aggravate symptoms of massive gram-negative sepsis
-LPS is released simultaneously from all cells being destroyed