Microbial Pathogenicity Flashcards
What are the important microbial pathogens?
Viruses, fungi, prions, protozoa, helminths and bacteria
What can viruses cause?
H1N1 influenza virus (single stranded RNA, enveloped)
How is H1N1 influenza virus described?
Easily spreads and is rarely fatal
What can fungi cause?
Tricophyton spp. (ringworm)
What is trichophyton spp.?
A colony of fungi growing on the skin which produces legions
What can prions cause?
Kuru
What is kuru?
A degenerative brain disease caused by a misfiled protein (prion)
How do prions reproduce?
When pathogenic prions interact with a normal prion, it mutates the normal one. chain reaction
What can protozoa cause?
Plasmodium spp. (malaria parasites)
What can helminths cause?
Ancylostoma duodenale (hook worm)
What can bacteria cause?
Bacillus Anthracis
What is bacillus anthracis?
A gram positive, endospore forming rod shaped bacterium
What is the forms of bacillus anthracis?
Cutaneous anthrax and inhalation anthrax
What is cutaneous anthrax?
Infects the skin (papule>ulcer>eschar)
What is inhalation anthrax?
If spores enter lungs (mediastinal lymphadenopathy)
What do gram positive bacteria have?
Thick cell walls that consist primarily of peptidoglycan
What does gram positive bacteria do in the stain?
Traps and retains crystal violet stain
What do gram negative bacteria have?
Cell walls with two layers (a thin peptidoglycan layer and a thick outer membrane that contains polysaccharides bonded to lipids)
What do gram negative bacteria do in the stain?
Do not retain the stain, crystal violet is easily rinsed away
What is koch’s postulates?
Guidelines used to demonstrate that a specific pathogen causes specific disease symptoms
Where must the pathogen be present (koch’s postulates)?
In every individual with the disease
What can a sample of the microorganism taken from the diseased host do (Koch’s postulates)?
be grown in pure culture
What can a sample of the pure culture do (koch’s postulates)?
Cause the same disease when injected into a health host
What can the microorganism do (koch’s postulates)?
Be recovered from the experimentally infected host
What are the exceptions to koch’s postulates?
Microbes that can’t be cultured (treponema pallidum) and pathogens that can also be found in healthy subjects and don’t produce the same symptoms (vibrio cholera)
What happens before the key stages of microbial pathogenesis?
Exposure to the pathogen
What is the first stage of microbial pathogenesis?
Adherence to host cells (skin or mucous)
What happens after adherence to host cells?
Invasion of host tissues (through epithelium)
What happens after invasion of host tissues?
Replication within the host tissue (fast so immune system can’t act on it)
What happens after replication within the host tissue?
Disease causing damage to host tissues (pathology)
What can disease causing damage to host tissues be caused by?
Toxicity and invasiveness
How can toxicity cause damage to host tissues?
Toxin effects are local or systematic
How can invasiveness cause damage to host tissues?
Further growth at original sites and distant sites
What are the bacterial virulence factors for adherence to host cells?
Adhesions such as fimbria (bind to cells) e.g. neisseria gonorrhoeae
What are the bacterial virulence factors for invasion of host tissues?
Motility (move through mucus) (flagella) and internal-related proteins (InIB)
What are the bacterial virulence factors for replication within host tissues?
Siderophores (bind iron) the siderophore yersinia actin solubilises metal bound to host proteins and transports it back to the bacteria.
Capsules (resist phagocytosis)
What are the bacterial virulence factors for disease causing damage to host tissue?
Endotoxins which cause inflammation and exotoxins which an be fatal
What are endotoxins and exotoxins?
Toxic virulence factors
What are endotoxins?
Lipopolysaccharide (LPS) components found in the outer membrane of gram negative bacteria (released after bacteria is destroyed/dies) and elicit a strong immune response. e.g. neisseria gonorrhoeae (causes inflammation)
What are the possible effects of endotoxin Lipid A?
Fever, blood clotting, inflammation and shock
What are exotoxins?
Produced within the living bacteria and then released into the surrounding medium
What are the three types of exotoxins?
Cytotoxins (destroy red blood cells), neurotoxins (effect the nervous system) and enterotoxins (effect the gut)
