4 - Bacterial Pathogenicity Flashcards
Define pathogenicity
ability of a microorganism to cause disease
Define virulence
degree or intensity of pathogenicity
Define pathogen
An organism that causes disease by impairing or interfering with a host’s normal physiological activities
What’s the difference between infection and disease
In an infection, the bacteria will persist in a host without always causing damage where as a disease causes damage to the host and prevent the host from carrying out normal physiological functions
What are opportunistic pathogens?
Pathogens that only cause serious disease when a host’s immune system is impaired
What is a reservoir?
A place where microorganisms survive, multiply, and await transfer to a susceptible host
What are primary pathogens?
Pathogens that can cause disease in healthy host I.e. those with out immune system defects
Give some examples of bacterial reservoirs
Humans, animals and certain environments
What are some examples of direct transmission of a pathogen?
Airborne (e.g via coughing and sneezing) and via body contact
What are some examples of in direct transmission of a pathogen?
Via a vector (a living organism) or a vehicles ( non living materials or objects)
What is colonisation?
The establishment of a stable population of bacteria within a host
What are the two stages in adherence of bacteria
Association and adhesion
What is the difference between association and adhesion?
Association involves non specific forces (such as charge) whereas adhesion involves specific bacterial adhesions and host receptors
Give some examples of adhesins that bacteria can use?
Fibriae and pili, capsules and slime layers, flagella (only certain species) and lipoteichoic acids in gram positive bacteria
Give some examples of host receptors used in bacterial adhesion
Blood group antigens and extra cellular proteins (such as collagen)
What are siderophores are what do they do?
They are small molecules with a high affinity for iron that bind with iron and bring it into bacterial cells
Give some examples of barriers to colonisation of pathogens in the body
Lyzozyme in eyes dissolves cell walls, the skin provides a physical barrier and produces antimicrobials, mucus in the lungs and flushing of the urinary tract prevents colonisation, stomach pH inhibits bacteria and our normal flora will compete with pathogens.
What is invasion of bacteria?
When bacteria penetrate into, through or between cells
How can bacteria resist phagocytosis?
They can produce structures that prevent contact with phagocytes such as capsules and specific surface proteins
How can bacteria avoid antibodies?
They use capsules, the can change the antigens on their surface and sometimes they can degrade antibodies
Give some examples of virulence factors
Toxins, extent of invasion
Give some ways in which tissue damage can occur by bacteria
Direct and indirect effects of bacterial damage and an induction of autoimmune responses
What is the difference between exotoxins and endotoxins
Exotoxins are proteins secreted from gram negative and positive bacteria and act on specific targets
Endotoxins are lipopolysaccharides on the membrane of gram negative bacteria that don’t have a specific target and can act on many host systems
