Microbial Pathogenicity Flashcards
What are pathogen examples of important microbial pathogens
Viruses, Fungi, Protozoa, Helminths, Bacteria
What is Koch’s Postulates
Koch’s postulates are guidelines used to demonstrate that a specific pathogen causes specific disease symptoms
What are the 4 steps to Koch’s postulates
-The pathogen must be present in every single individual with disease.
-A sample of the microorganism taken from the disease host can be grown in a pure culture.
-A sample of the pure culture causes the same disease when injected into a healthy host.
-The microorganism can be recovered from the experimentally infected host
What are some exceptions to Koch’s postulates
Microbes that cant be cultured (e.g. treponema pallidum associated with syphilis)
Pathogens that also can be found in healthy subjects (e.g. Vibrio cholera)
What is pathogenesis
The process by which a disease or disorder develops
What are the key stages of microbial pathogenesis
Adherence to host cells
Invasion of host tissues
Replication within host tissues
(Builds to certain threshold)
Disease causing damage to host tissues (pathology)
Outline the Toxicity pathway leading to tissue damage and disease
Toxicity: Toxins are released causing local or systemic damage
Outline the invasiveness pathway leading to tissue damage and disease
Further growth at original site and distant sites leads to tissue damage and disease
What virulence factors are related to Adherence to host cells
Adhesions such as fimbriae for binding to host cells (also used in horizontal gene transfer).
E.g. Neisseria gonorrhoea
What virulence factors are involved in invasion of host tissues
Motility via flagella (mechanical movement through mucus). eg helicobacter pylori
Internalin related proteins (enables burrowing into cells. Eg listeria monocytogens
What virulence factors are involved with replication within host tissues
Siderphores that solubilise metal bound to host proteins and transport them back to back Terra (reaping metals from surroundings). Eg yersiniabactin
Capsules (resist phagocytosis). Streptoccoccus pneumoniae
What virulence factors are involved with disease causing damage to host tissues
Endotoxins - cause inflammation
Exotoxins - Can be fatal
What are endotoxins
Lipopolysaccharide components found in the outer membrane of gram negative bacteria, and elicit strong immune responses.
Are structural components, not bacterial products.
Immune aggravating, especially at bacteria death.
Usually released at bacteria death.
very potent, causing immune system overload.
What is an example of an endotoxin, and the potential effects it may have
Endotoxin lipid A
Fever, Blood clotting, Inflammation, Shock
What are exotoxins
Exotoxins are produced within living bacteria, and then released into the surrounding medium. There are 3 types: Cytotoxins, Neurotoxins, Enterotoxins
