Paradigms of infectious disease and antimicrobials

Question 1

What are some virulence strategies?

Answer 1

exposure to pathogens / adherence / invasion through epithelium / colonisation and growth / toxicity / invasiveness and tissue damage or disease

Question 2

What is attenuation?

Answer 2

decrease or loss of virulence

Question 3

How can you measure virulence?

Answer 3

virulence can be estimated from experimental studies of the LD50 which is the amount of an agent that kills 50% of animals in a test group

Question 4

Describe the causative agent of diphtheria

Answer 4

corynebacterium diphtheriae, gram-positive , non-motile

Question 5

Describe the clinical presentation of diphtheria

Answer 5

affects throat, difficulty swallowing, systemic effects including heart complications, coma and death

Question 6

Describe the pathogenesis of diphtheria

Answer 6

inhalation of aerosols, colonisation of throat, produces A-B toxin (DT), pseudomembrane formation in throat, AB toxin inhibits EF2 in eukaryotic cells which inhibits protein synthesis

Question 7

Describe the causative agent of whooping cough

Answer 7

bordetella pertussis, gram negative, aerobic cocco-bacillus

Question 8

Describe the clinical presentation of whooping cough

Answer 8

paroxysms of cough, CNS effects and secondary pneumonia

Question 9

Describe the pathogenesis of whooping cough

Answer 9

attachment and replication on ciliated URT mucosa, produces toxins: pertussis exotoxin, tracheal toxin & invasive adenylate cyclase toxin

Question 10

Describe the causative agent of cholera

Answer 10

vibrio cholera, comma shaped, gram negative

Question 11

Describe the clinical presentation of Cholera

Answer 11

in severe cases rice water stools

Question 12

Describe the pathogenesis of Cholera

Answer 12

acute infection of GIT, production of cholera toxin, AC upregulation, fluid loss to GIT

Question 13

What are some examples of partially invasive pathogens?

Answer 13

shigella dysentriae, enteropathogenic E.coli, influenza

Question 14

What are the causative agents of Shigellosis?

Answer 14

shigella sonnei (mild), shigella flexneri (severe), shigella dysentriae (very severe) / gram negative rods / facultative anaerobes

Question 15

What is the clinical presentation of Shigellosis?

Answer 15

blood and pus in diarrhoea

Question 16

What is the pathogenesis of shigellosis?

Answer 16

attachment and invasion of distal ileum and colonic epithelia, shiga toxin

Question 17

What is the causative agent of enteric fever (typhoid)

Answer 17

salmonella enterica serovar typhi

Question 18

What is the clinical presentation of enteric fever (typhoid)?

Answer 18

systemic infection, constipation or diarrhoea, fever for 3 weeks

Question 19

Pathogenesis of enteric fever

Answer 19

primary infection via jejunum or distal ileum, m cells transport antigens from lumen to cells of immune system / Macrophage containing viable bacteria / systemic dissemination

Question 20

What is bacillus cereus and its two forms?

Answer 20

a foodborne pathogen that can produce toxins its two disease forms are emetic toxin and enterotoxins Nhe and HBL

Question 21

Describe staphylococcus aureus food poisoning?

Answer 21

food borne disease which produces toxin (SE) which is ingested and interacts with gastric mucosa

Question 22

What is another food borne disease we haven’t mentioned?

Answer 22

botulism caused by clostridium botulinum

Question 23

Describe the action of non-invasive pathogens

Answer 23

involves viable bacteria but no penetration, localised at point of entry and mediated by toxins

Question 24

Describe action of partially invasive pathogens

Answer 24

invasion of epithelial layer, no penetration into deeper tissue, no septicaemia

Question 25

Describe the action of primary invasive pathogens

Answer 25

produce minimal damage at site of infection, spread via lymph

Question 26

What is selective toxicity?

Answer 26

finding a drug that is toxic to invader and not host cell

Question 27

What is syphilis caused by?

Answer 27

spirochete bacterium Treponoma pallidum

Question 28

What is salvarsan and its mechanism of action?

Answer 28

a pro drug used to treat syphilis, its metabolised slowly to oxophenarsine which reacts with thiol groups in proteins causing denaturation

Question 29

TB, leprosy and Buruli ulcer are all caused by what?

Answer 29

Mycobacteria

Question 30

What is vancomycin used to treat?

Answer 30

multiply resistant Strep pneumonia and MRSA

Question 31

What are some bacterial targets for selective inhibition?

Answer 31

cell wall, cell membrane, DNA synthesis, transcription, protein synthesis in the cytoplasm & other metabolism

Question 32

What are prodrugs?

Answer 32

Drugs activated by metabolism

Question 33

What are structure-activity relationships?

Answer 33

the synthesis of chemical variants of an active compound to try to improve activity