Infectious agents

Question 1

What are the classifications of microbes

Answer 1

-Viruses
-Bacteria
-Fungi
-Parasites(Protozoa, helminths and ectoparasites)

Question 2

What is the size range for viruses?

Answer 2

-Most are 20nm to 300nm

Question 3

What is the structure of viruses?

Answer 3

DNA or RNA(not both) core within protein capsid bade up of individual capsomeres with a helical, cubic or more complex arrangement

Question 4

Do viruses have cytoplasm?

Answer 4

No Cytoplasm

Question 5

What may the envelopes from viruses be derived from?

Answer 5

-May have envelope derived from host cell

Question 6

What components are membrane bound in viruses?

Answer 6

Proteins are membrane bound

Question 7

What is a rotavirus?

Answer 7

A cause of infantile diarrhoea

Question 8

What can adenoviruses cause?

Answer 8

-May cause diarrhoea, respiratory tract infections, keratitis, hepatitis

Question 9

What arrangement can adenoviruses have?

Answer 9

-May have an icosahedral arrangement

Question 10

What is the size range of bacteria?

Answer 10

-0.5μm to 3μm

Question 11

What is the structure of bacteria

Answer 11

-Prokaryotic
-Haploid DNA
-No nucleus
-Usually have a rigid cell wall outside cytoplasmic membrane
-No mitochondria
-some may have flagella

Question 12

Structure of Gram positive bacteria cell wall

Answer 12

-Gram positive bacteria have a thick layer of peptidoglycan and no outer lipid membrane

Question 13

Structure of Gram negative bacteria

Answer 13

-Gram negative bacteria have a thin peptidoglycan later and have an outer lipid membrane

Question 14

What bacteria causes urinary tract infection?

Answer 14

Proteus mirabilis is the cause of a urinary tract infection

Question 15

What does bacterial growth require?

Answer 15

-Carbon
-Water
-Nitrogen
-Nutrients
-Minerals
-Correct pH, osmotic pressure, temperature, atmosphere

Question 16

By what process does bacterial growth occur?

Answer 16

-Growth occurs by binary fusion

Question 17

What is the approx doubling time for bateria?

Answer 17

-Doubling time approx 20-30 mins

Question 18

How many hours does it take for mycobacterium tuberculosis to double?

Answer 18

-Mycobacterium tuberculosis approx takes 18 hours to double

Question 19

What oxygen environment do strict aerobes grow in?

Answer 19

Free oxygen

Question 20

What oxygen environment do facultative aerobes grow in?

Answer 20

Free oxygen and absence of oxygen

Question 21

What oxygen environment do strict anaerobes grow in?

Answer 21

Absence of oxygen

Question 22

What oxygen environment do microaerophil anaerobes grow in?

Answer 22

Absence of oxygen

Question 23

What is the size of fungi?

Answer 23

Size is over 2μm

Question 24

What is the structure of fungi?

Answer 24

-Eukaryotic
-Haploid or diploid DNA
-Single or multiple nuclei
-Rigid chitinous cell wall outside cytoplasm.
-May be multicellular
-May be dimorphic

Question 25

What are parasites?

Answer 25

Single or multicellular eukaryotic organisms

Question 26

What type of cell is protozoa?

Answer 26

Single cell

Question 27

Size range of protozoa

Answer 27

5 to 300μm

Question 28

What is the nuclei like in protozoa

Answer 28

Single or multiple nuclei

Question 29

What are the 3 main groups of eukaryotic parasites?

Answer 29

-Cestodes -Trematodes -nematodes

Question 30

What is an example of cestodes and how do they get into humans?

Answer 30

-an example would be beef tapeworm 1. Egg shed in faeces i) Ingested by cows 2. This develops into cysts in beef which is eaten by humans 3. This then develops into adult tapeworm from GI tract

Question 31

What is an example of trematode and how does it get into humans?

Answer 31

-an example would be flukes flatworms 1. Egg shed in urine by human i) Hatches into miracidium that infects a freshwater snail, where it develops further. 2. It is then release as cercaria in water ii) It penetrates skin of human and enters circulation to migrate to venules of bladder or bowel before maturing into an adult fluke in humans

Question 32

What is an example of nematodes and how do they get into humans?

Answer 32

-an example is roundworms 1. Egg shed in faeces i) If ingested by humans, it will develop into larvae and enter circulation to migrate to lungs. Coughed up and then swallowed to re-enter the gut. 2. This then develops into an adult worm

Question 33

What are ectoparasites and what are examples of it?

Answer 33

-Parasites that live on the skin -Example -Human body louse -Human flea -Ticks -Mites

Question 34

How can bacteria, fungi, protozoa and helminths be seen?

Answer 34

-Bacteria, fungi, protozoa and helminths can be seen using light microscopy x400-x1000

Question 35

What can viruses be seen by?

Answer 35

-Viruses can be seen by electron microscopy x40,000

Question 36

What does gram staining do?

Answer 36

-Separates between gram positive and gram negative bacteria

Question 37

What colour is gram positive bacteria stained as?

Answer 37

-Gram positive bacteria is blue/purple

Question 38

What colour is gram negative bacteria stained as?

Answer 38

-Gram negative bacteria is red

Question 39

What are the 2 main morphologies of bacteria?

Answer 39

-Cocci -Rods or bacilli

Question 40

How do cocci appear under microscope?

Answer 40

Spherical