Download Bacteria are Everywhere

Bacteria are
Everywhere
By: Lauren Senter
Dr. Hamrick
STEP Program at
Campbell University
Overview

Part 1
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Part 2
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Places we find bacteria
Identification
Control
Part 3
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Detection in drug products
Places we find bacteria:
Hands
 Throat
 Nose
 Food

Hand Washing Experiment

This experiment shows how bacteria normally
lives on your skin. When you wash your
hands, you remove the surface bacteria that
can make you sick but it will not kill or remove
all the bacteria on your skin.
 To do this experiment:
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–
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Make imprint of hand on an agar plate before
washing hands.
Then make an imprint of hand after washing
hands thoroughly with soap and water.
Incubate until the bacteria grows.
Bacteria in the Throat


For this experiment, we
were able to look at and
see the different types
of bacteria in the throat.
To do this experiment:
–
–
Gently rub the back of
throat with a sterile
cotton swab.
Then rub the bacteria
onto a rich media.
Bacteria in the Nose


In this experiment, we
were looking for a
specific kind of bacteria.
In this experiment:
–
–
Using a sterile cotton
swab, gently rub the
inside of one nostril.
Then rub the bacteria
onto an agar plate and
incubate for 2 to 3 days.
Mannitol Salt agar
Bacteria in Food

In this experiment, we were looking for
different types of bacteria in the foods we
might eat.
 To do this experiment:
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–

Grind up alfalfa sprouts into a fine liquid.
Plate dilutions of the liquid, and incubate to grow
up the bacteria.
One of the plates was labeled TNTC (or too
numerous to count).The other plate had a
total of 165 colonies
–
82,500,000 bacteria in a gram of alfalfa sprouts.
Identifying Bacteria

When we find bacteria, there are a number of
ways to find out what kinds of bacteria we
have.
Gram positive
Gram negative
rods
Cocci (spheres)
Cocci (spheres)
rods
Easy to grow
Hard to grow
Bacillus subtilis
Cells in chains
catalase negative
Streptococcus pneumoniae
E. coli
Haemophilus influenzae
Cells in clusters
catalase positive
Staphylococci
Coagulase positive
Staphylococcus aureus
Coagulase negative
Staphylococcus epidermidis
Flow chart for
identifying
microorganisms
Identifying Bacteria

Gram Staining is the first step in figuring out
what kind of bacteria you are dealing with.
 Gram Staining determines whether the
bacteria is gram positive, which consists of a
cell membrane and a thick cell wall, or gram
negative, which consists of an inner
membrane, a thinner cell wall, and an outer
membrane.
Gram-negative
Gram-positive
Cell
membrane
Cytoplasm
Cell
membrane
Outer
membrane
Cytoplasm
Periplasmic
space
Peptidoglycan
Peptidoglycan
Don’t Mess Up!

It is important for the bacteria
to be a pure culture before
putting in a test tube or
running any test.
–

1

2
4
3
Single colony purification
If you have a mixture of
bacteria when you run
biochemical test they might
appear positive even if some
bacteria are negative.
It will cause you to mess up
when classifying the
bacteria.

Catalase Test


Hydrogen peroxide is a
good chemical for killing
bacteria.
Catalase is a bacterial
enzyme that converts
hydrogen peroxide into
water and oxygen.
To do this experiment:
–
–
–
Use a loop to remove a
little bit of bacteria from
the plate and smear it
onto a microscope slide.
Add 1 drop of hydrogen
peroxide. If the organism
produces a catalase,
rapid bubbling will occur.
This test helps to
recognize if the gram +
bacteria is Streptococci
or Staphylococci.
Coagulase Test



We did a third test to
determine if the
bacteria were
coagulase positive or
coagulase negative.
Coagulase is a
bacterial enzyme that
clots (or coagulates)
plasma products.
This test would tell us if
the Gram +, catalase +,
bacteria were
Staphylococcus aureus
or Staphylococcus
epidermidis.
Clinical sample
Gram positive
Gram negative
rods
Cocci (spheres)
Cocci (spheres)
rods
Easy to grow
Hard to grow
Bacillus subtilis
Cells in chains
catalase negative
Streptococcus pneumoniae
E. coli
Haemophilus influenzae
Cells in clusters
catalase positive
Staphylococci
Coagulase positive
Staphylococcus aureus
Coagulase negative
Staphylococcus epidermidis
Flow chart for
identifying
microorganisms
Control
Bacteria in the wrong place can make
us sick, therefore we have several ways
to eliminate or control bacteria.
 Some of the ways we can control
bacteria are:

–
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Antibiotics
UV light
Antibiotics
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Antibiotics kill bacteria.
Different bacteria show different susceptibilities to
different antibiotics.
To do this experiment:
–
–
Lay little discs with antibiotics in them on plates
inoculated with bacteria.
Incubate and you are able to see the different
susceptibilities of the bacteria to the medicines.
Resistant
Sensitive

UV Light

UV light damages bacterial
DNA. Different bacteria
have different
susceptibilities to UV Light.
To do this experiment:
–
–
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Swab half of each of 4 plates
with a spore-forming bacteria,
and the other half with a nonspore forming bacteria.
Place one plate (marked 0
min) into the incubator. Place
the remaining plates into the
hood under the UV light with
their lids off. Place the
sunglasses over the plate
labeled 5min.
Leave the plates in the hood
for the allotted time, then take
them out and put them into
the incubator.


Results
0min. :All bacteria grew.
1min. :Bacillus subtilis is
able to form spores. Spores
are more resistant to UV
damage, but some of the
bacteria were killed.
–


Without the ability to
produce spores most of the
bacteria in the lower part of
the plate were killed by the
UV light.
3min. :A little more of the
Bacillus continues to die off.
The non-spore forming
bacteria is almost completely
dead.
5min. :Most of all bacteria
are dead except for where
the sunglasses were
sitting.The sunglasses
protected both kinds of
bacteria from the UV light.
Detection

To do this experiment:
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Grow up Bacillus subtilis as your test bacteria.
Generate a growth curve and add small amounts
of bacteria to the media.
The plan was to then add small amounts of
Bacillus to a drug preparation and pass through
the filter.
Then add media to the filters and wait for the
growth of the bacteria.
~117 ~12
~117
~12
Steritest

Add drug
preparation
(containing bacteria)
to the filter unit
 Add media and
incubate
 Each filter unit in this
test received 2.4 x
104 bacteria.
Sum Up

From doing these
experiments, I
have learned that
bacteria are
everywhere and
sometimes they
belong;
sometimes they
don’t!