8. Introduction to microbiology Flashcards
which terms are used to described micro-organisms that cause disease?
virulent or pathogenic
what do Koch’e postulates state?
- the causative organism must be isolated from every individual suffering from the disease
- the causative organism must be cultivated artificially in pure culture
- when the causative organism is inoculated from pure culture, the typical symptoms of the infection must result
- the causative organism must be recoverable from individuals who are infected experimentally
what are Koch’s postulates for genes?
- introduction of the gene into a strain that previously did not cause the disease should transform the strain into one that does cause disease
- gene must be expressed during infection
- antibodies raised against the gene product or other immunity should protect experimental subjects against disease
what constitutes a virus?
nucleic acid core and a protein coat. some viruses may also have an envelope, but some others are naked
what is the genetic material in a virus?
either DNA or RNA, but not both
what is the protein coat in viruses made of?
capsomeres
which viruses attack bacteria?
bacteriophage
what are viroids?
infectious naked RNA molecules that infect plants. they are not associated with any proteins
what is a prion?
an infectious protein
what is the cell wall in microfungi made of?
chitin
what are hyphae and mycelia?
hyphae - tiny filaments formed by fungi
mycelia - mats of hyphae
what infections do moulds cause?
common, superficial infections eg. ringworm, athlete’s foot
what is the most common yeast infection, and which species is responsible?
thrush, candida albicans
what are the 4 classes of protista?
- apicomplxa
- flagellate protista
- ciliate protista
- amoebae
what is the shape of most bacteria?
round (cocci) or rod shaped (bacilli)
what differentiates gram positive bacteria from gram negative bacteria?
gram positive - peptidoglycan in their cell wall
gram negative - very little or no peptidoglycan in their cell wall
what allows gram negative substances to adhere to surfaces?
hair like structures called fimbriae
which bacteria cannot be killed by phagocytosis?
those which are enclosed in a capsule
what is the function of endospores/spores?
protect bacteria against heat, radiation and desication
what are the ways in which infections can be spread?
- airborne
- faecal-oral route
- sexually transmissible
- direct inoculation
- animal vectors
- animal reservoirs
- inanimate vectors (fomites)
what does control of infection depend upon?
identifying the mode of spread
interrupting the cycle of infection, replication and spread
what does the cycle of infection require to sustain itself?
- encounter an adhere to a host
- multiply within that host
- be dispersed to encounter other hosts
examples of intoxication illnesses
tetanus
botulism ergotism
what is an intoxication illness?
illness in which the victim does not need to encounter live micro-organisms because disease results from exposure to a toxin rather than a living micro-organism
what is the mechanism by which bacteria cause diseases?
- production of structures that enable the micro-organism to attach to the surface at which they cause disease
- production of one or more toxins
- production of aggressins
- initiating undesirable consequences of the host defences
what are the types of toxins?
endotoxins (found in cell wall)
exotoxins (produced by the bacteria)
