FOUND-viruses and bacteria

Question 1

what are the different modes of transmission and examples of diseases transmitted this way?

Answer 1

• Respiratory-TB/ COVID
• oral/faecal- polio
• Contact-(skin-skin/mucous/mucous)
• blood-borne-HIV
• Vector-mosquitos-malaria
• vehicle-non-living thing
• nosocomial-contracted in hospital
• zoonotic-viruses

Question 2

what is the approx size of bacteria?

Answer 2

-1000 x2-3000nm

Question 3

what is the function of flagella?

Answer 3

movement and adhesion

Question 4

what is the function of pili?

Answer 4

adhesion, conjugation (transfers genetic material to another through direct contact) and movement found in many gram negatives

Question 5

what is the capsule of bacterias function?

Answer 5

adhesion
protection

contribute to disease

Question 6

what is the role of chromosomes in bacteria?

Answer 6

contain genetic code

Question 7

what is the role of plasmids?

Answer 7

contain some genes-can confer advantage-antibiotics

Question 8

what is the difference between gram-positive and gram-negative?

Answer 8

gram-positive

• thick peptidoglycan layer
• no LPS

gram-negtaive

• lipopolysaccharide and proteins
• thin peptidoglycan layer

Question 9

what does LPS act as when released?

Answer 9

an endotoxin

Question 10

what are examples of endospore-forming bacteria?

Answer 10

Bacillus

• B. anthracris -anthrax
• B. cereus -food poisoning

Clostridium (strict anaerobes)

• C. botulinum- botulism
• C. difficile-diarrhoea
• C. perfringens- gas gangrene
• C. tetani- tetanus

Question 11

what is virulence?

Answer 11

the relative ability of a pathogen to cause disease in the host

Question 12

what is an opportunistic pathogen?

Answer 12

normally harmless but can cause disease due to lowered host immunity

Question 13

what is the incubation period?

Answer 13

between time of infection and appearance of symptoms

Question 14

what are the two types of toxins produced by bacteria?

Answer 14

exotoxins
endotoxins (LPS)

Question 15

Explain the steps in bacteria pathogenicity

Answer 15

-exposure to pathogens
-adherence to skin or mucosa
-invasion through epithelium
-colonisation and growth
(production of virulence )
-toxin effects local or systemic
-or invasiveness-further growth at original site and distant site
-tissue damage/ inflammation/ disease

Question 16

what are the 2 types of infection response?

Answer 16

extracellular

intracellular

Question 17

describe extracellular infection response

Answer 17

• main response is antibody response

- also innate immunity-phagocytosis by neutrophils, monocytes and tissue macrophages

Question 18

describe intracellular infection response

Answer 18

specific cell-mediated responses

-eg macrophage activation

Question 19

are streptococcal species of bacteria gram positive or gram negative?

Answer 19

spherical gram + bacteria

Question 20

what can streptococcus species can be classified into?

Answer 20

either alpha-haemolytic or beta-haemolytic depending on ability to haemolyse RBCs

Question 21

what can beta-haemolytic streptococci be further divided into?

Answer 21

groups A-T based on polysaccharide capsular structure- Lancefield serotyping

Question 22

what are the 3 main clinically important species of streptococci?

Answer 22

-S. pyogenes- group A
(strep throat, scarlett fever, toxic shock, necrotising fasciitis)
-S. agalactiae- group B
(neonatal sepsis and meningitis)

-S.pneumoniae
(lobar pneumonia)

Question 23

describe the features of streptococcus pneumoniae

Answer 23

• gram positive alpha-haemolytic non-motile coccus

- over 90 capsular serotypes

Question 24

how is DNA organised in bacteria?

Answer 24

singular circular chromosomes and plasmids

not contained within nucelus

Question 25

what are the features of gram positive bacteria?

Answer 25

- phospholipid bilayer - thick peptidoglycan layer - no extra phospholipid bilayer with lipopolyscaccharide

Question 26

what are some examples of gram-positive bacteria?

Answer 26

- staphlococcus aureus (cocci) - stretococcus pyogenes (cocci) - clostridium sporogenes (rod)

Question 27

what colour does gram positive bacteria stain?

Answer 27

blue/ purple

Question 28

what are the features of gram negative bacteria?

Answer 28

- phospholipid bilayer - thin peptidoglycan layer - extra phospholipid bilayer-integration of lipopolysaccharide

Question 29

what are some examples of gram negative bacteria?

Answer 29

- neisseria gonorrhoeae (cocci) - pseudomonas aeruginosa (rod) - haemophilus influenzae (rod)

Question 30

what colour does gram negative bacteria stain?

Answer 30

red/pink

Question 31

what is a virus?

Answer 31

a small, infectious, obligate intracellular parasite

Question 32

what is a parasite?

Answer 32

an organism that benefits at the expense of the host

Question 33

what do viruses need to do to function?

Answer 33

can only function after they are replicated in a cell as they are obligate molecular parasites

Question 34

how do viruses cause disease?

Answer 34

viruses make mRNA that can be translated by host ribosomes-they then hijack host protein synthesis machinery

Question 35

what is a virion and what is their function?

Answer 35

virus paticle that protects the genome as it is transmitted from one host to another

Question 36

why is it important to be able to classify viruses?

Answer 36

classification makes possible predictions about the properties of a virus -particularly important when a new virus is identified

Question 37

what properties are used for classification of viruses?

Answer 37

- size of virion and capsid - presence or absence of an envelope (membrane) - symmetry of protein shell (capsid) - nature and sequence of nucleic acid (virus genome) - symptoms - routes of transmission

Question 38

what are the steps in virus infection and replication?

Answer 38

- infecting virus attaches to host cell - capsid penetrates host cell - capsid uncoats- is shed - repication-synthesis of mRNA (direct or via host machinery) synthesis of viral protein for new capsid, synthesis of viral nucleic acid - assembly-capsids from around nucleic acid - viral nuclic acid is released by cytolysis

Question 39

how is bacteria replicated?

Answer 39

binary fission

Question 40

are virus genomes DNA or RNA?

Answer 40

can be either

Question 41

are virus genomes single or double stranded?

Answer 41

can be either

Question 42

if the viral genome is single-stranded is it +ive or -ive sense?

Answer 42

can be either

Question 43

is viral genome linear or circular?

Answer 43

can be either

Question 44

is viral genome single or segment?

Answer 44

can be either or more than 1

Question 45

why do viral genomes have to be abLe to make mRNA?

Answer 45

- to be translated by ribosomes to make viral proteins | - to make new virus particles-virions

Question 46

what is Baltimore classification?

Answer 46

- based on mRNA as the common theme | - viruses (genomes) classified depending on how they make mRNA (+sense)

Question 47

what are the different methods of viral transmission?

Answer 47

- respiratory - oral/faecal - blood borne viruses - other bodily fluids - arboviruses (vector)

Question 48

define the infectious period

Answer 48

the period when you are releasing virus which can infect others

Question 49

define the incubation period

Answer 49

period in between when you are first infected with the virus, the virus is replicating

Question 50

what's the difference between droplet and airborne transmission?

Answer 50

droplet infection-coughs and sneezes can spread droplets of saliva and mucus (more than 5 microns) airborne transmission-tiny particles, possibly produced by talking, are suspended in the air for longer and travel further (less than 5 microns)

Question 51

what is the basic reproductive number?

Answer 51

R0 | A means of expressing how many uninfected people can be infected by one infectious person

Question 52

what does R0<1 mean?

Answer 52

the infection will generally dies out in the the population

Question 53

what does R0>1 mean about an infection?

Answer 53

the infection will be maintained and spread in the population

Question 54

what does a high R0 mean?

Answer 54

the virus will spread quickly

Question 55

what is viral pathogenesis?

Answer 55

mode of production or development of disease

Question 56

do all viruses cause noticeable disease?

Answer 56

no some may be asymptomatic

Question 57

what are systemic infections?

Answer 57

- spread of virus throughout the body multiple organs are infected - virus gains access into blood stream (lymph system) - extreme rapid virus dissemination throughout the body

Question 58

what is the definition of viraemia?

Answer 58

the existence of viruses/ virus particles in the blood stream

Question 59

what is lytic infection?

Answer 59

infection as a result of active replication of the viral genome, characterised by making of new viral particles

Question 60

what is latent infection?

Answer 60

when virus is in a state of non replication-quiescent state