Micro Final

• Autoclave


  121°C, 15 psi, for 20 minutes
• Pasteurization


  72°C, 15 seconds
• 4°C does not sterilize and does not affect endospores
• Heating inoculating loop to kill microbes

  1. Heat

  2. Burn contaminated objects
• Lyophilization


  Does NOT kill microbes, just hampers growth by taking away water so the microbe cannot grow
• Irradiation


  • Dosage measured in units of "gray" (Gy)
  • Ultraviolet (UV) light
  • Gamma rays (cobalt-60)
  • Electron beams
  • X-rays
• Irradiation reduces microbial numbers for longer shelf life but does NOT sterilize, exception is herbs and spices
• Chemicals used to control microbial growth

  • Phenolics
  • Halogens (Cl, I, Fl, Br, etc.)
  • Alcohols
  • Aldehydes
• Cidal agents


  Lethal effects
• Static agents


  Slow or stop metabolism/reproduction; not necessarily lethal
• Antibiotics


  Chemicals that are naturally produced by microbes that kill other microbes

  
• Antibiotic types


  • Semisynthetics
  • Synthetics
• Narrow spectrum antibiotics


  Target specific groups of microbes

  
• Broad spectrum antibiotics


  Target a wide range of microbes

  
• Antibiotic mechanisms of action

  • Destroy cell wall
  • Destroy cytoplasmic membrane
  • Shut down metabolic pathways
  • Block DNA replication
  • Block DNA transcription
  • Block translation (protein synthesis)

  
• Antibiotic resistance mechanisms


  • Altered DNA gyrase
  • Beta-lactamase destroys penicillin
  • Enzyme modification inactivates aminoglycosides
  • Efflux pump flushes out tetracycline

  
• Vaccine types

  • Killed whole cell or inactivated viruses
  • Live, attenuated (weakened) bacteria or viruses
  • Antigen molecules purified from the pathogen
  • DNA vaccines
• Herd immunity


  Requires 3/4 or more of the population to be immunized to reduce disease
• Normal microbiota (flora)


  Microbes that live on/in many areas of the body and don't normally cause disease
• Types of symbiotic relationships

  • Mutualism
  • Commensalism
  • Parasitism
• Pathogens


  Microbes that normally cause disease
• Pathogenicity


  Disease-causing potential of a given microbe, dependent on host's genetics/physiology and microbe's virulence

  
• Virulence


  Level of harm caused by pathogen after infection
• Virulence factors


  • Promote attachment/colonization of host tissues
  • Facilitate pathogen spread from the initial infection site
  • Have toxic effects on host cells, tissues, or physiology
• ID50


  Infectious dose (of bacteria/virus) for 50% of the test population
• LD50


  Lethal dose (of bacteria/virus) for 50% of the test population
• Primary pathogens


  Likely to cause disease after infection in a healthy host, rapidly reproduce/increase in number, moderate to high virulence
• Opportunistic pathogens


  Less likely to cause disease in a healthy host, low virulence
• Examples of pathogens with different host ranges


  • Salmonella gallinarum (poultry)
  • Salmonella pullorum (poultry)
  • Salmonella choleraesuis (pigs)
  • Salmonella dublin (cattle)
  • Salmonella typhi (humans)
  • Salmonella typhimurium (humans, livestock, domestic fowl, rodents, birds)
• Infection


  Occurs when microbes enter your body and start to multiply
• Disease


  Occurs when microbes evade immune system and alter bodily function
• Infectious disease


  A disease caused by a microbe that can be transferred from one host to another
• Types of diseases

  • Acute
  • Chronic
  • Subacute
  • Latent
• Symptoms


  Subjective characteristics of a disease that are only felt by the patient
• Signs


  Objective manifestations of disease; observed/measured by others
• Stages of infectious diseases

  • Incubation
  • Prodromal
  • Acute
  • Convalescence
  • Carrier
• Syndrome


  Group of symptoms that consistently occur together and collectively characterize a condition
• Morbidity


  The rate of illness due to a disease
• Mortality


  The rate of death due to disease
• Direct contact transmission


  Disease transmission through close proximity (less than 1 meter)