EMS Microbiology Flashcards
What are Koch’s Postulates?
Causative organism must be isolated from every sufferer
Organism must be cultivated in pure culture
Typical symptoms must result in an individual inoculated
Organism must be recoverable from individuals infected
What are koch’s postulates for genes?
The gene encoding the trait of interest should be present and transcribed/translated in a virulent strain
The gene encoding the trait should not be present or should be silent in a strain that does not cause disease
Disruption of the gene should result in the formation of a strain that is incapable of causing disease
Introduction of the gene into a strain that did not cause disease should make it cause disease
Gene must be expressed in infection
What are some problems with Koch’s postulates?
Difficulty to isolate organisms
Ethical obligations
Animal models may be sufficient
What are some characteristics of viruses?
Intracellular parasites
Nucleic acid core wrapped in a protein coat made of capsomeres
Some have an envelope
Retroviruses are unusual
What are some characteristics of microfungi?
Eukaryotic Cell wall made up of chitin Hairy growths are moulds Moulds have tiny filaments known as hyphae that form mycelia Mycelia subdivided by septa
What are the 4 classes of protozoa?
Apicomplexa
Flagellate Protista
Ciliate protista
Amoeba
Name some infections caused by protozoa?
Toxoplasmosis
Amoebic Meningitis
Malaria
Amoebic dysentery
What is mutualism?
Both organisms, in a symbiotic relationship, benefit
What is neutralism?
Neither organism, in a symbiotic relationship, derives benefit or harm
What is commensalism?
In a symbiotic relationship, one organism benefits and the other derives neither benefit nor harm
What is parasitism?
One organism, in a symbiotic relationship, benefits at the expense of the host
What is the difference between sterile and non sterile sites?
Sterile sites have no normal flora
How is sterility maintained?
Surface cleaning
Barriers that allow unidirectional flow
Physical separation from non sterile sites
What are some examples of sterile sites?
Lower RT Upper GT Spinal cord Meninges Middle Ear Urinary Tract
Coagulase Negative Staphylococci
Staphylococcus aureus
Propionibacterium acnes
Corynebacterium spp
Are examples of what?
Normal skin flora
Why is the skin difficult to colonise?
Variable temp
Dry
Aerobic environment
Nutrient Poor
Viridians
Oral strep
Anaerobes gram -ve and +ve
Candida spp
Are examples of what?
Normal mouth flora
Why are cavities in the mouth easy to colonise?
Constant temp
Moist
Rich nutrient source
Few physical challenges
What organisms make up the normal nasopharyngeal flora?
Same as skin flora
What organisms make up the normal flora of the pharynx?
S. pyogenes H. influenza S. pneumonia N. meningitides S. aureus M. catarhallis
When does the flora of the vagina change?
Puberty
Addition of Lactobacillus spp to the normal skin flora
What does lactobacillus spp do?
Ferment glycogen and maintain a pH of around 3
What is the make up of flora in the stomach?
Low pH inhibits bacterial growth
Acid tolerant lactobacilli
H. pylori
What happens to the amount of organisms as you descend through the GI?
They increase in number
