8. Introduction to microbiology

Question 1

which terms are used to described micro-organisms that cause disease?

Answer 1

virulent or pathogenic

Question 2

what do Koch’e postulates state?

Answer 2

1. the causative organism must be isolated from every individual suffering from the disease
2. the causative organism must be cultivated artificially in pure culture
3. when the causative organism is inoculated from pure culture, the typical symptoms of the infection must result
4. the causative organism must be recoverable from individuals who are infected experimentally

Question 3

what are Koch’s postulates for genes?

Answer 3

1. introduction of the gene into a strain that previously did not cause the disease should transform the strain into one that does cause disease
2. gene must be expressed during infection
3. antibodies raised against the gene product or other immunity should protect experimental subjects against disease

Question 4

what constitutes a virus?

Answer 4

nucleic acid core and a protein coat. some viruses may also have an envelope, but some others are naked

Question 5

what is the genetic material in a virus?

Answer 5

either DNA or RNA, but not both

Question 6

what is the protein coat in viruses made of?

Answer 6

capsomeres

Question 7

which viruses attack bacteria?

Answer 7

bacteriophage

Question 8

what are viroids?

Answer 8

infectious naked RNA molecules that infect plants. they are not associated with any proteins

Question 9

what is a prion?

Answer 9

an infectious protein

Question 10

what is the cell wall in microfungi made of?

Answer 10

chitin

Question 11

what are hyphae and mycelia?

Answer 11

hyphae - tiny filaments formed by fungi

mycelia - mats of hyphae

Question 12

what infections do moulds cause?

Answer 12

common, superficial infections eg. ringworm, athlete’s foot

Question 13

what is the most common yeast infection, and which species is responsible?

Answer 13

thrush, candida albicans

Question 14

what are the 4 classes of protista?

Answer 14

1. apicomplxa
2. flagellate protista
3. ciliate protista
4. amoebae

Question 15

what is the shape of most bacteria?

Answer 15

round (cocci) or rod shaped (bacilli)

Question 16

what differentiates gram positive bacteria from gram negative bacteria?

Answer 16

gram positive - peptidoglycan in their cell wall

gram negative - very little or no peptidoglycan in their cell wall

Question 17

what allows gram negative substances to adhere to surfaces?

Answer 17

hair like structures called fimbriae

Question 18

which bacteria cannot be killed by phagocytosis?

Answer 18

those which are enclosed in a capsule

Question 19

what is the function of endospores/spores?

Answer 19

protect bacteria against heat, radiation and desication

Question 20

what are the ways in which infections can be spread?

Answer 20

1. airborne
2. faecal-oral route
3. sexually transmissible
4. direct inoculation
5. animal vectors
6. animal reservoirs
7. inanimate vectors (fomites)

Question 21

what does control of infection depend upon?

Answer 21

identifying the mode of spread

interrupting the cycle of infection, replication and spread

Question 22

what does the cycle of infection require to sustain itself?

Answer 22

1. encounter an adhere to a host
2. multiply within that host
3. be dispersed to encounter other hosts

Question 23

examples of intoxication illnesses

Answer 23

tetanus

botulism ergotism

Question 24

what is an intoxication illness?

Answer 24

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

Question 25

what is the mechanism by which bacteria cause diseases?

Answer 25

1. production of structures that enable the micro-organism to attach to the surface at which they cause disease
2. production of one or more toxins
3. production of aggressins
4. initiating undesirable consequences of the host defences

Question 26

what are the types of toxins?

Answer 26

endotoxins (found in cell wall)

exotoxins (produced by the bacteria)