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• pathogen 


  any microorganism that has the capacity to cause disease
• virulence 


  a measure of the 'pathogenicity' or likelihood that a microorganism will cause disease after infection
• principal pathogens 


  may cause disease in presence of intact immune system (highly virulent)
• opportunistic pathogens


  only cause disease in those with underling disease or compromised immune system
• classification important gram negative

  comma shaped - vibrio cholera, rods - e.coli, salmonella, pseudomonas
• vibrio cholera burden of disease

  7 pandemics, 3-5 million cases a year mostly in africa
• vibrio cholera clinical features

  severe watery diarrhoea leading to death due to dehydration or electrolyte imbalance
• infection triad 


  results in disease - combination of environment, host, infecting agent
• infection tried - infecting agent

  virulence factors, size of infecting dose
• infection tried - host

  genetic (blood groups), immune status, gastric acidity
• infection triad - environment


  climate, sanitation, water supply
• where cholera lives


  niche is saline coastal waters and estuaries, lives in association with zooplankton on exoskeleton
• cholera when nutrient deficient 


  forms viable, non culturable form in biofilms, when environment and nutrients better starts proliferating again
• who cholera into food chain

  humans ingest contaminated water (faeces in water)
• V.cholera colonisation 


  colonize the gut mucosa, doesn't invade, flagella moves bacteria towards epithelial surface (wall of intestine)
• how cholera strains acquire pillus and toxin


  1 - non pathogenic strain infected by a bacteriophage VPI0 2. VPI0 encodes TcpA (pilus) 3. TcpA acts as receptors for second bacteriophage CTX0 4. CTX0 has genes for cholera toxin CTX
• nosocomial infections


  healthcare associated, acquired as a direct or indirect result of healthcare
• common nosocomial infections


  UTI (can't get up and go), bloodstream (catheter portal of entry), pneumonia (tubes bypassing upper airways defences)
• common bacterial causes of nosocomial

  gram negative bacilli
• enterobacteriaceae family


  facultative anaerobes, simple nutritional requirements, intestinal tract of humans and animals
• 3 enterobacteriaceae examples 


  E.coli, Klebsiella, Salmonella
• salmonella infections


  acquired by eating contaminated food or via person to person spread, from commensals of animals, high infectious dose
• typhoidal serotypes of salmonella enterica

  infect humans only, may be asymptomatic carriers and cause typhoid fever a serious illness with bacteraemia
• 2 strains of salmonella enteric that cause enteric fever (typhoid)


  salmonella Typhi and salmonella Paratyphi types A,B,C
• non typhoidal serotypes of salmonella enterica

  commensals of animals species, acquire by infected foods, self limiting diarrhoea and disseminated disease in immunocompromised people
• one health 


  concept that human health is closely linked to environment around use (e.g drug resistance) want to achieve optimal health for human, environment and animals
• multi drug resist Salmonella infections

  public health treat, antimicrobial resistance spreads through humans, food chain and environment
• how antibiotic resistance spreads

  animals given antibiotics to prevent spread (high transmission) - select for pre existing mutants in gut - they grow, become high density antibiotic resistant - enter human food chain
• e.coli 


  common inhabitant of GI tract, commensal not normally pathogen, some strains acquired virulence factors
• E.coli strain that is in cattle

  O157:H7, EHEC causes blood diarrhoea
• feedlot cattle


  30% reservoirs for E.coli, fed high grain ratio to increase feed efficiency.
• how feedlot cattle promote E.coli growth

  cattle digestive system not adapted to metabolise lots of grain, goes to hindgut and is food source for E.coli which increase risk of food contamination
• pseudomonas aeruginosa


  in soil, water environments but only in habitats contaminated by human activity
• pseudomonas aeruginosa réservoirs 


  urban communities - hot tubs, pools hospitals - sinks, plumbing, water systems
• pseudomonas aeruginosa how infect humans

  animals (pets/food source) contaminate environment with stool, bacteria then like living in water and hard to eradicate
• P.aeruginosa infections healthy patients

  uncommon, puncture wound food, swimmers ear, hot tub folliculitis
• pseudomonas aeruginosa infection immunocompromised 


  forms biofilms that colonises the surface - CF, diabetes, burn wound infections