Important pathogens

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  • Created by: JS007
  • Created on: 02-01-18 15:47

Mycobacterium tuberculosis

  • Bacterium which causes tuberculosis
  • 1/3 (2 billion) of the worlds population is infected, this figure includes carriers
  • Causes a cough initially, which deteriorates into more life-threatening symptoms
  • Diagnosis: Heaf or Mantoux skin test combined with chest x-rays
  • Treatment: Combination of 3 or 4 antibiotics for a period of 6 months
  • BCG vaccine is available
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Stapylococcus aureus

  • Bacterium responsible for skin infections such as spots and boils
  • Enters via breaks in the skin, where it is able to kill neutrophils, resulting in pus
  • MSRA is a particular strain which is resistant to multiple antibiotics
  • A strain which produces an endotoxin is associated with TSS
  • Treatment: antibiotics
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Influenza A

  • Virus causes flu
  • A is avain flu which has recently crossed over into humans
  • Viron comprised of an RNA genome which is in 8 sections
  • Genetic material is surrounded by a lipoprotein envelope (hemagglutinin & neuraminidase)
  • Symptoms: fever, headache, general feeling of malaise & is considered a serious illness
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Yersinia pestis

  • Bacterium which causes bubonic plague
  • Is zoonotic and is carried by rats and other vermin
  • Rare in Europe but still present in the USA and Asia 
  • The infection cycle is termed the sylvatic infectious cycle
  • Bubonic plague has a 50% mortality rate
  • May progress into pneumonic plague (into the lungs) which has a 100% mortality rate
  • Treatment: antibiotics 
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Rabies Virus

  • Virus which causea rabies
  • Transferred directly through bites and scratches
  • Enters the peripheral nervous system where it travels to the brain
  • Symptoms: Hydrophobia, excessive salivation, eventual death
  • Treatment: May be treated after infection with the rabies vaccine, this is because the virus has varying incubation times (a bite on the foot may take 9 months to reach the brain) 
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Rickettsia

  • Obligate intracellular bacteria
  • May result in either spotted fever or typhus (genus dependent)
  • Treatment: antibiotics, specifically tetracycline or doxycycline
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Neisseria gonorrhoeae

  • Bacterium which causes gonorrhoea
  • Attaches to epithelia and replicates at basement membranes
  • Diagnosis: microscopy
  • Symptoms: Causes painful discharge from the urethra/ rectum in men, causes discharge from the cervix but may not be painful and so could go unnoticed in women
  • Treatment: antibiotics. Doxycycline is a good choice as it also treats chlamydia, 50% of people infected with gonorrhoea also have chlamydia but symptoms may mask each other 
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Chlamydia trachomatis

  • Bacterium which causes chlamydia 
  • Symptoms: discharge from the urethra/rectum/cervix
  • Most common in 18-24 age group
  • May exist in 2 forms: elementary bodies or reticulate particles
  • Diagnosis: PCR, immunofluorescence 
  • Treatment: antibiotics, specifically doxycycline 
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Treponema pallidum

  • Bacterium which causes syphillis
  • Symtoms: a painless ulcer on the genitals
  • Diagnosis: microscopy
  • Treatment: antibiotics, usually penicillin
  • Infection is systemtic (spreads throughout the body)
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Haemophilus ducreyi

  • Bacterium which causes chancroid
  • Uncommon in Europe but common in the tropics
  • Symptoms: painful ulcer on the genitals
  • Diagnosis: Microscopy
  • Treatment: antibiotics
  • Has an association with HIV, increases the risk of infection and speeds up progression of the disease
  • Chancroid in HIV +ve patients is difficult to treat and the infection may become chronic 
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Salmonella

  • Food-borne bacterium
  • Associated with poultry
  • A toxin causes bloody diarrhoea 
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E.Coli 0157

  • Causes bacterial food poisoning
  • Associated with minced beef; occurs due to contamination with cattle faeces at the abattoir 
  • Toxin causes diarrhoea, may eventually lead to kidney failure 
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Campylobacter

  • Causes bacterial food poisoning
  • Associated with poultry
  • Toxin causes bloody diarrhoea 
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Listeriosis

  • Bacterium (almost anaerobic)
  • Associated with unwashed vegetables and soft cheese
  • Not usually pathogenic to adults
  • Causes serious disease in pregnant women, may lead to abortion or meningitis in the newborn 
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Bacillus cereus

  • Bacterial food poisoning 
  • Associated with rice and vegetables
  • Produces spores and heat-stable toxins
  • Causes vomiting
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Taenia

  • Tapeworm
  • A parasite
  • Associated with spoiled food
  • May grow the entire length of the intestine
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Vibrio cholerae

  • Causes cholera
  • Water-borne
  • Toxin affects ion channels to disrupt osmosis
  • Causes severe diarrhoea and dehydration
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Cryptosporidium parvum

  • Water-borne illness
  • Is immune to treatment with chlorine, but may be killed with heat
  • Causes diarrhoea
  • Infection may become chronic in immunosuppressed individuals
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Typhoid

  • Water-borne bacterium
  • Induces apoptosis to invade tissues
  • Causes fever, headache and rash 
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Legionnaires

  • Spread via water droplets (e.g. in air conditioning)
  • Survives inside cells of the immune system
  • Causes severe pneumonia
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Schistosoma

  • A parasite found in water snails
  • Burrows into the skin
  • Is excreted in urine for further propogation
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Leptospira interrogans

  • Zoonotic, spread by rats
  • Causes flu-like symptoms
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Norovirus

  • Water-borne illness
  • Associated with water contaminated with raw shellfish
  • Causes vomiting & diarrhoea 
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