FINAL EXAM

• Contribution of each

  • Fleming: discovered penicillin
  • Lind: first experimental epidemiologists, scurvy (vitamin d disease) by using control and experimental group
  • Snow: first investigative epidemiologists
  • Landsteiner: first to connect viruses with human diseases (polio)
  • Hippocrates: father of medicine, discovered body humors
  • Galen: miasma theory, presence of bad air can affect the body
  • Leeuwenhoek: invented single lens, first to observe living organisms
  • Hooke: built first compound microscope (two magnifications)
• Modes of transmission


  • Direct: direct contact between skin or mucous membranes of infected person and non-infected
  • Indirect: indirect contact, infection agent passes from infected host -> intermediate -> another host
  • Fomite: inanimate object with microbes shared
  • Aerosol/droplet: from coughing & sneezing < than 1 m in distance
  • Airborne: aerosols suspended in air must be at least 1 m in distance
  • Mechanical vector: transmits disease without being infected (external body parts) indirectly by touch or food intermediate ex: fly
  • Biologic vector: a site where pathogen multiplies/ plays part in life cycle, transmits by biting or touch ex: mosquito/tick
• Types of disease frequency

  • Endemic: steady and predictable frequency over time tied to a particular area
  • Epidemic: a disease outbreak, rapidly spreading in limited region
  • Sporadic: occasional cases are reported at irregular times in different locations
  • Pandemic: disease outbreak crossing country, and spreading to multiple regions
• Prevalence rate

  Total # of cases in a population (formula: # of total cases/total population x 100)
• Incidence rate

  Total # of new cases in a population (formula: # of new cases/ total population x 100)
• Cohort study

  • Follow test subjects & control group in real time (prospective) test group has been exposed to the same variable, while control group haven't. Ability to evaluate a rare risk factor
• Case control study

  • Retrospective, looking back in time, ability to evaluate a rare outcome
• Glycocalyx

  • Capsule
  • Slime layer
• How glycocalyx helps bacteria survive in a host


  Helps cells adhere to surfaces and can help establish biofilm
• How biofilm helps bacteria survive

  Biofilm is a thick layer composed of microbes that aggregate through fimbriae, pili, slime layers or capsules hard to penetrate through
• Cell wall make-up


  • Gram +: cell wall (thick peptidoglycan layer) & cell membrane
  • Gram -: cell wall (thin peptidoglycan) inner & outer plasma membrane
  • Acid-Fast +: used on mycobacterium cells, contain mycolic acid + lipid based dye called carbol-fuschin
• Gram stain

  1. Primary stain: crystal violet

  2. Decolorizer: alcohol (95% ethanol)

  3. Counterstain: safranin
• False +

  Gram -'s appear purple (+) because there was under decolorization
• False -

  Gram +'s appear pink (-) due to over decolorization
• Why use counterstain

  Gram - does not take up crystal violet, would be clear if no counterstain is used
• What you see with a Gram + if you stop after decolorizing

  Purple (no change)
• What you see with a Gram - if you stop after decolorizing

  Clear, no color
• Endotoxin

  Gram - endotoxins/lipid A, released when bacteria die or cell is damaged
• Exotoxin

  Gram + exotoxins (cytotoxin, enterotoxins, neurotoxins) released continuously
• Mycobacterium vs. Mycoplasma

  Mycobacterium contain mycolic acid, Mycoplasma lack cell wall
• Active diffusion

  Requires energy as it goes from low concentration to high concentration (against the concentration gradient)
• Passive diffusion

  Does not require energy as molecules go from high to low (with concentration gradient)
• Osmosis

  Diffusion of water
• Iso/Hypo/Hypertonic

  • Hypotonic: movement of water outside to inside (solute concentration high inside cell) cells swell and lyse, represents overhydrated person
  • Isotonic: solute concentration is the same within and out, no net movement
  • Hypertonic: movement of water inside to outside (solute concentration high outside cell) cells shrink and crenate, represent dehydrated person (loss of water to outside environment)
• FTM (fluid thioglycollate media)

  Determines oxygen tolerance
• Obligate aerobes

  Growth at top of FTM
• Obligate anaerobes


  Growth at bottom of FTM
• Facultative anaerobes

  Growth throughout FTM, more at top
• Types of symbiotic relationships


  • Mutual: both members benefit (ex: e.coli)
  • Commensal: one benefits, other is neither harmed or benefited (ex: staph)
  • Amensal: one member is harmed, however does not benefit the other (ex: penicillium and staph)
  • Parasitic: parasite benefits, host is harmed (ex: tapeworm)
• Calculating number of cells

  You have 9 bacteria cells in a sample. This bacteria's generation time is 15 minutes. After 2 hours, how many cells are present? 2,304 (formula: # x 2 (ex))
• Differences between alpha, beta & gamma hemolysis

  • Alpha - partial lysis of rbc, pea brown color
  • Beta - complete lysis, golden brown color
  • Gamma - no lysis, shadow
• BSL 1-4


  • BSL-1: normal flora (ex:e.coli) that do not cause disease in healthy individuals. Handwashing & disinfecting
  • BSL-2: moderately hazardous microbes (ex: MRSA) precautions with sharps & aerosols
  • BSL-3: requires safety cabinets with HEPA filters & negative pressure entry (microbes don't leave room) (ex: mycobacterium tuberculosis)
  • BSL-4: severe/ fatal disease causing microbes (ex: ebola) use sealed airlocks & "space suits"
• Sulfas


  Bactrim & gastrinsin, the inhibition of PABA binding causes no folic acid to be produced in bacteria
• Tetracycline


  Antibiotic that stains teeth and stunts bone growth in children
• Black box warning

  Can cause rhabdomyolysis, cardiovascular kidney conflicts, include nalidixic acid & cipro
• Cell wall synthesis inhibitors (the beta-lactam family)

  • Penicillin
  • Cephalosporin
  • Monobactams
  • Carbapenems
• Beta Lactamase

  Enzyme some bacteria produce that deactivates the beta-lactam ring
• Augmentin


  Antibiotic that can inhibit beta lactamase
• Rifampin


  Antimicrobial that can cause orange tears as a side effect
• Kirby-Bauer method


  Used to evaluate plates and determine sensitivity or resistance to antibiotics, larger zone of inhibition diameter = more effective