Paradigms of infectious disease and antimicrobials Flashcards
What are some virulence strategies?
exposure to pathogens / adherence / invasion through epithelium / colonisation and growth / toxicity / invasiveness and tissue damage or disease
What is attenuation?
decrease or loss of virulence
How can you measure virulence?
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
Describe the causative agent of diphtheria
corynebacterium diphtheriae, gram-positive , non-motile
Describe the clinical presentation of diphtheria
affects throat, difficulty swallowing, systemic effects including heart complications, coma and death
Describe the pathogenesis of diphtheria
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
Describe the causative agent of whooping cough
bordetella pertussis, gram negative, aerobic cocco-bacillus
Describe the clinical presentation of whooping cough
paroxysms of cough, CNS effects and secondary pneumonia
Describe the pathogenesis of whooping cough
attachment and replication on ciliated URT mucosa, produces toxins: pertussis exotoxin, tracheal toxin & invasive adenylate cyclase toxin
Describe the causative agent of cholera
vibrio cholera, comma shaped, gram negative
Describe the clinical presentation of Cholera
in severe cases rice water stools
Describe the pathogenesis of Cholera
acute infection of GIT, production of cholera toxin, AC upregulation, fluid loss to GIT
What are some examples of partially invasive pathogens?
shigella dysentriae, enteropathogenic E.coli, influenza
What are the causative agents of Shigellosis?
shigella sonnei (mild), shigella flexneri (severe), shigella dysentriae (very severe) / gram negative rods / facultative anaerobes
What is the clinical presentation of Shigellosis?
blood and pus in diarrhoea
What is the pathogenesis of shigellosis?
attachment and invasion of distal ileum and colonic epithelia, shiga toxin
What is the causative agent of enteric fever (typhoid)
salmonella enterica serovar typhi
What is the clinical presentation of enteric fever (typhoid)?
systemic infection, constipation or diarrhoea, fever for 3 weeks
Pathogenesis of enteric fever
primary infection via jejunum or distal ileum, m cells transport antigens from lumen to cells of immune system / Macrophage containing viable bacteria / systemic dissemination
What is bacillus cereus and its two forms?
a foodborne pathogen that can produce toxins its two disease forms are emetic toxin and enterotoxins Nhe and HBL
Describe staphylococcus aureus food poisoning?
food borne disease which produces toxin (SE) which is ingested and interacts with gastric mucosa
What is another food borne disease we haven’t mentioned?
botulism caused by clostridium botulinum
Describe the action of non-invasive pathogens
involves viable bacteria but no penetration, localised at point of entry and mediated by toxins
Describe action of partially invasive pathogens
invasion of epithelial layer, no penetration into deeper tissue, no septicaemia
