Lab 13' Microbes from your body

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Lab 13. Microbes from your body
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Commensalism

• Non-harmful coexistence
• Interaction between two living organisms,
• one organism benefits
• the other is neither harmed nor helped

http//hthbiotech.sandiegostc.org/boat_channel/ani
mals/w-barnacle.gif
http//www.nearctica.com/ecology/pops/commens.htm
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Mutualism

• Beneficial coexistence
• Interaction between two living organisms, both
  benefit

http//www.dimijianimages.com/More-page5-mutualism
s/3-way-mutualism.jpg
http//www.orn.mpg.de/knauer/bshary/bsharyr.jpg
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Parasitism

• Harmful coexistence
• Interaction between two living organisms,
• one organism benefits
• the other is harmed
• There is no advantage for the parasite in
  causing too much damage resulting in the death of
  the host

lamprey
dracunculus
http//www.nwrc.usgs.gov/world/images/lamprey.jpg
http//ryoko.biosci.ohio-state.edu/parasite/pictu
res/dracunculus_3.gif
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Normal bacterial flora

• Internal tissue
• Free of microorganisms ? sterile
• Surface tissue
• Skin, mucosa
• In contact with outside bacteria
• Normal bacteria found there normal flora
• Digestive tract is considered to belongs to the
  exterior
• Because has 2 openings (beginning and end)
• Many of the normal flora are either
  non-pathogenic or only opportunistic pathogens

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Hemolysis

• Some bacteria have the ability to break down red
  blood cells
• This characteristic can be used for bacteria
  identification
• Stretococcus spp.

http//gold.aecom.yu.edu/id/micro/hemolysisabg-72.
jpg
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Alpha hemolysis

• Incomplete hemolysis
• Greenish darkening of the agar under the colonies
• Displayed by Streptococcus pneumoniae
• Caused by peroxide produced by the bacteria

http//gold.aecom.yu.edu/id/micro/hemolysis.htm
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Beta hemolysis

• Complete hemolysis, giving a clear zone with a
  clean edge around the colony.
• Streptococcus pyogenes
• Caused by the presence of hemolysine

http//gold.aecom.yu.edu/id/micro/hemolysis.htm
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Gamma hemolysis

• No hemolysis
• No change in the blood agar around the colony
• Ex enteroccocus faecalis

http//gold.aecom.yu.edu/id/micro/hemolysis.htm
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Coagulase plasma
S aureus ()

• Some microbes contains enzymes that will cause
  blood to clot.
• The test is done by adding a loopful of colony to
  a tube of plasma (blood that contains the
  clotting factors but no red or white blood
  cells).
• Positive test is the solidification (clotting) of
  the plasma.

S epidermidis (-)
http//student.ccbcmd.edu/courses/bio141/labmanua/
lab15/images/coagpos.JPG
http//student.ccbcmd.edu/courses/bio141/labmanua/
lab15/coagnegse.htm
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Objective1 Swab of your throatIndividual

• Using the sterile swab
• Swab your throat or your neighbor throat (do not
  touch the swab with your tongue)
• Plate on a sheep blood agar
• Incubate at 37oC in a Candle jar
• Next lab determine Hemolysis
• Do a catalase test for your throat bacteria
• Put few colonies on the slide
• Add peroxide

www.indstate.edu/thcme/micro/throat.htm
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Objective 2 Alpha and beta hemolysis

• Divide a Sheep Blood Agar (SBA) plate in half (in
  team)
• Make a lawn of S. pyogenes on one half
• Make a lawn of S. pneumoniae on the other half
• On each half place one disk A and one disk P
  using sterile forcep
• A contains Bacitracin
• P contains Optichin
• Incubate all blood plate in candle jar at 37

S. pneumoniae
S. pyogenes
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Objective 2 Alpha and beta hemolysis
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Objective 3 Swab of your skin

• Take one MSA plate (each person)
• Wet a swab with sterile saline
• Swab your skin
• Inoculate on one half of the plate
• Inoculate the other half with S. aureus Using the
  loop
• Next lab you will do a Gram stain of each half
  (taking a representative colony)
• If you have yellow colonies in the plate
• Inoculate a coagulase plasma with your bacteria
• If you do not have yellow colonies in the plate
• Inoculate a coagulase plasma with S. aureus
• Incubate at 37oC
• Determine coagulation of plasma

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Objective 4 Bacteria from your mouth

• Spit into a paper cup
• Try to get 1-2 ml
• Using the sterile 1ul calibrated loop (blue
  plastic)
• Streak down the center of a sucrose blood plate
• Take loop and go back and forth through original
  streak
• Incubate in candle Jar
• Next lab record your observations

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Objective 4 Bacteria from your mouth