- Extracellular enzyme; secreted by the cell and functions outside the cell. - Invade host cells within deeper tissues. - Specific to particular tissues. - Enables invasion, supports own growth and defends against immune system.

Virulence Factors Flashcards by Emily H

Pathogen examples

Bacteria
Virus
Fungi
Protozoa

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What is a pathogen

Any microorganism that is able to cause disease in a host organism.

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Primary pathogen

Environmental microbe that is able to cause disease in an otherwise healthy individual.

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Opportunistic pathogens

Member of the normal microbiota and only causes disease to an immunocompromised host.

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Pathogenicity

The ability of the pathogen to cause disease.

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What pathogenic diseases do bacteria form

Ear infections
Pneumonia
Food poisoning
Dental caries
Gingivitis/peridontitis

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What pathogenic diseases do viruses form

Common cold
Influenza
AIDS

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What pathogenic diseases do protists form

Malaria

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What pathogenic diseases do funghi form

Athletes foot
Ringworm

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Virulence

Degree or intensity of pathogenicity

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Virulence factors

Mechanisms that determine the degree to which the pathogen causes damage, invasion and infectivity.

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What is the chain of infection

Agent
Virulence
Dose
Exposure
Susceptibility

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What do virulence factors allow a pathogen to do

Outcompete host cells and resist their defences.

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What do microorganisms require to survive;

A suitable environment
Source of nutrients
Protection from harmful elements (establish within the body)

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Virulence factor mechanisms

Adhesion
Evasion of phagocytosis
Immunoevasion
Immunosuppression
Toxigenicity (exotoxins, endotoxins)
Enzymatic (exoenzymes)

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How does adhesion happen?

Contains surface proteins/glycoproteins called adhesins.
Bins to targeted receptor molecules on host cell surfaces.
Bacteria adhere, resist physical removal and allow colonisation.
Can use one or more adhesin to colonise host cell.

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What type of pathogen causes dental caries and what is its adhesin?

Streptococcus mutants.
Adhesin P1.

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Examples of adhesion

Pili
Fimbriae
Capsules
Bacterial cell walls

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How do capsules aid in adhesion

Some bacteria produce capsules to prevent adhesion of antibodies causing them to breakdown and deterring phagocytosis.

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What is the function of Fimbriae?

Contains mycolic acid that alters surface of bacterium to prevent phagocytosis.

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What is mycolic acid

Produced in its cell wall and acts as protective coat which deters killing mechanisms when phagocytosed.

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What is an exoenzyme

Extracellular enzyme; secreted by the cell and functions outside the cell.
Invade host cells within deeper tissues.
Specific to particular tissues.
Enables invasion, supports own growth and defends against immune system.

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How are exoenzymes virulence factors?

Break down of cells structure allowing pathogen to invade.

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Examples of exoenzymes

Proteases - degrades collagen in connective tissue to promote spread
Nucleases
Phospholipases

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What are toxins and what do they do

Biological poisons produced by some pathogens. Invade and damage tissue cells.

Toxigenicity

Ability of a pathogen to produce toxins to cause damage to host cells. (More toxic, more damage)

2 types of toxins

Endotoxins Exotoxins

What bacteria are endotoxins derived from

Gram negative bacteria

What do endotoxins stimulate

General systemic inflammatory response

What happens if endotoxin concentration is low?

Hosts inflammatory response against infection is effective.

What happens if endotoxin concentration is high?

Causes severe drop in blood pressure, multi organ failure and possibly death.

What is an exotoxins

Potent protein molecule

What types of bacteria are exotoxins?

Mainly gram positive bacteria but some gram negative.

What do exotoxins target and what do they do?

Target specific receptors on specific cells. Damage cells through individual molecular mechanisms.

3 categories of exotoxins

Intracellular targeting Membrane disrupting Superantigens

Presence of bacteria in the blood

Bacteraemia

Pus forming bacteria in the blood

Pyaemia

Presence of toxins in the blood

Toxaemia

Multiplying bacteria in the blood

Septicaemia

Antigenic variations

Surface proteins alter to avoid recognition by hosts immune response

What does the product of exoenzyme coagulase do?

Triggers fibrinogen-to-fibrin cascade that enables bacteria to be coated by fibrin clots which prevents phagocytosis

Phagocytosis

Phagocytes engulf or ingest other living cells or particles.

The destruction of what is a virulence factor against immune system?

Destruction of phagocytes with production of leukocidins. Destruction of T lymphocytes.

Antigenic drift

Results of point mutations causing minor changes in the spike proteins.

Antigenic shift

Gene re assortment results in major changes in spike proteins.

Main virulence factors for porphyromonas gingivalis (periodontitis)

Fimbriae- modify and stimulate immune responses such as cytokine secretion and inhibition in the periodontium (tissue breakdown). Gingipains- exoenzyme produced by p.gingivalis which breaks down structural proteins of periodontium.

Cariogenicity

Ability of a substance or organism to cause tooth decay

Acidogenicity

Producing acid or causing acidity

Main virulence factors of associated with cariogenicity and what do they do and cause

Adhesion Acidogenicity Acid tolerance Work together to chance ecology of dental plaque. Cause susceptibility to enamel demineralisation.

Cariogenic bacteria

Live in biofilm and convert sugar and starch into acid that dissolve calcium from enamel. An increase causes a quick drop in pH levels.

Where does herpes simples virus hide from immune system and how do they emerge

In neurons and non neuronal cells. Emerge as pathogenic form when immune resistance is low.

Name for cold sore

Herpes labialis

Most common etiological factor of opportunistic human fungal infections

Candida albicans - pathogenic yeast-like fungus

Main virulence factors of Candida albicans

Exoenzymes; secretes aspartyl proteases which breakdown proteins. Adhesions. Pleomorphism; responds and adapts to changing environmental conditions.

Which type of antigenic variation results in a major change in spike proteins due to gene reassortment?

Antigenic shift

In order to survive, pathogens require a source of nutrients, protection from harmful elements and:

Colonization of a niche in the host

Which pathogen type is always a member of the normal microbiota and only causes disease in an immunocompromised host?

Opportunistic pathogen

Which type of pathogen is an environmental microbe that is able to cause disease in an otherwise healthy individual?

Primary pathogen

Virulence factors can be described as:

Mechanisms that determine the degree to which the pathogen causes damage to a host. A factor that helps an organism to invade a host. Factors which enable a pathogen to infect a host

What kind of virulence factors are proteases, nucleases, phospholipases and glycohydrolases?

Exoenzymes

Which of these virulence factors act as adhesins?

Proteins F and A Pili Fimbraie

Which of these virulence factors assist in promoting colonization of the host?

Adhesins

Which of these virulence factors enable damage to be caused to the host?

Toxins and exoenzymes

Which virulence factor does Porphyromonas Gingivalis use which leads to disregulated immunity in the gingival tissues and breakdown of the structures around the teeth?

Fimbraie and exoenzyme Gingipains