Download Doctor, Doctor, Give me the Cure Lab Report

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Nicole Christian
Kylie Martinod
Biology Lab
28 October 2014
Doctor, Doctor, Give me the Cure Lab Report
Hypothesis:
The catfish were infected by a bacterial infection that is best prevented by
ampicillin.
Methods:
During week one, 5 petri plates were prepared by isolating the bacteria samples
using the serial dilution method of 10^-4 concentration. Then a sample from pond 16 was
placed on a petri dish, and a sample from pond 22 was placed on the remaining 4 petri
dishes. To transfer the bacteria onto the plate correctly, the streaking method was used.
Then the antibiotics penicillin, ampicillin, and colistin sulfate were added to different
petri dishes containing the pond 22 sample. Then all samples were covered and left alone
until week two.
During week two, each petri dish was examined under a microscope and the
bacteria were classified by their forms, margins, and elevations. After this was recorded
the samples were put through gram staining. If the bacteria tested negative their color
would be pink, and if the bacteria tested positive their color would be purple. These
results were also recorded.
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Results:
In Table 1, pond 16’s data points show that is has 2 morphotypes of bacteria.
Morphotype A was not treated with an antibiotic, had a cell shape of coccus, colony color
of white, colony elevation of convex, colony margins of entire, colony form of circular,
and a negative gram stain. Morphotype B was not treated with an antibiotic, had a cell
shape of bacillus, colony color of white, colony elevation of convex, colony margins of
entire, colony form of circular, and a positive gram stain.
In Table 2, pond 22’s data points show that is has 7 morphotypes of bacteria.
Morphotype C’s cell shape was coccus, it’s colony color was white, colony elevation was
raised, colony margins were entire, colony form was circular, it’s gram stain was positive
and it was not treated with an antibiotic. Morphotype D’s cell shape was coccus, colony
color was red, colony elevation was raised, colony margin was undulate, colony form was
spindle, it’s gram stain was positive and it was not treated with an antibiotic. Morphotype
E’s cell shape was coccus, colony color was pink, colony elevation was raised, colony
margin was undulate, colony form was spindle, it’s gram stain was negative, and it was
not treated with an antibiotic. Morphotype F’s cell shape was coccus, colony color was
white, colony elevation was convex, colony margin was entire, colony form was circular,
it’s gram stain was positive, and it was treated with an antibiotic. Morphotype G’s cell
shape was coccus, colony color was red, colony elevation was raised, colony margin was
undulate, colony form was spindle, it’s gram stain was negative, and it was treated with
an antibiotic. Morphotype H’s cell shape was coccus, it’s colony color was pink, colony
elevation was raised, colony margin was undulate, colony form was circular, it’s gram
stain was negative, and it was treated with an antibiotic. Morphotype I’s cell shape was
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bacillus, colony color was red, colony elevation was raised, colony margin was undulate,
colony form was spindle, it’s gram stain was negative, and it was treated with an
antibiotic.
Picture 1 shows the 4 petri dishes of pond 22’s samples, one with no antibiotic,
and the other 3 that were treated with colistin sulfate, ampicillin, and penicillin. It shows
over what quadrants the bacteria grew.
I chose to use these tables because the objective of the lab was to compare the
petri dishes from each pond to discover the infectious agent. I thought that the best way
to do this was to make two separate tables of each pond to more easily compare them and
find the answer.
Discussion:
This is experiment does support my hypothesis. When the petri dishes were
examined underneath the microscope, only bacteria were found, no viruses. It can be
concluded from this that the catfish were infected by a bacterial infection. From the
pictures, it is shown that the sample of bacteria from pond 22 that was treated with
ampicillin showed the least amount of growth. From this, it is clear that ampicillin is the
antibiotic suited to kill the infectious agent. The infectious agent is morphotype F, as it is
the only morphotype in pond 22 that is most similar to the morphotype found in pond 16.
As evidenced in Tables 1 and 2, the morphotype A in pond 16 and Morphotype F in pond
22 have the same cell shape, colony color, colony elevation, colony margin, and colony
form. Their only difference is the gram stain. Considering all of the other similarities it is
most likely that these are the same type of bacteria, and the difference in gram stain is
due to human error. Since both pond 16 and pond 22 were infected with the same disease,
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and these bacteria are the only ones so similar, it can be concluded that morphotype F is
the infectious agent.
All of the data collected in this lab was based off of observations, leaving a lot of
room for human error. The images seen in the microscope will never perfectly match the
pictures in the lab manual; so multiple people could see the same thing as a different
morphotype, making the observations not completely reliable. On top of this, there is a
large risk of foreign bacteria entering the petri dishes from either the desk, or the air if the
lid was left off for too long. If foreign contamination did occur, then a lot of the
morphotypes recorded could potentially not even be from the ponds, and thus useless.
To control the infectious agent, Finney town Catfish Co. should put into effect
decontamination procedures such as hand hygiene and safe antibiotic use when dealing
with their other ponds to contain the bacteria and prevent spreading. (Gould, Dinah) To
save money on antibiotics for future baby fish, sanitizing the fish tank is very necessary.
To do this, they must remove the fish from the tank so they are not killed and then
destroy the bacteria with heat, which is the most rapid way of killing them (Gould,
Dinah) As for decontaminating the infected fish, the effective antibiotic was determined
above as ampicillin. When distributing this antibiotic it should not be dumped into the
ponds, but fed to the fish through their food (Cabello, Felipe). This way even the fish’s
feces will carry some of the antibiotic and kill any remaining bacteria in the tank
(Cabello, Felipe). However, this antibiotic should be distributed sparingly and not all at
once because it is quite possible for the bacteria to mutate and develop antibiotic-resistant
bacteria, which could be very harmful for all involved (Cabello, Felipe). Only in doing
this do they have a hope of saving their company.
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Morphotype
ID
Pond ID
A
B
Antibiotic
16 N
16 N
Cell Shape
Colony
Color
Colony
Elevations
Colony
Margins
Colony
Forms
Gram Stain
coccus
bacillus
white
white
convex
convex
entire
entire
circular
circular
negative
positive
Table 1: Pond 16
Picture 1: Bacterial
Growth
Morphotype
ID
Pond ID
C
D
E
F
G
H
I
22
22
22
22
22
22
22
Antibiotic
Cell Shape
Colony
Color
Colony
Elevations
Colony
Margins
Colony
Forms
Gram Stain
N
N
N
Y
Y
Y
Y
coccus
coccus
coccus
coccus
coccus
coccus
bacillus
white
red
pink
white
red
pink
red
raised
raised
raised
convex
raised
raised
raised
entire
undulate
undulate
entire
undulate
undulate
undulate
circular
spindle
spindle
circular
spindle
circular
spindle
positive
positive
negative
positive
negative
negative
negative
Table 2: Pond 22
Works Cited
Cabello, Felipe. (2006). Heavy use of prophylactic antibiotics in aquaculture: a
growing problem for human and animal health and for the environment. Environmental
Microbiology: 1137-1144.
Gould, Dinah. (2004). Bacterial infections: antibiotics and decontamination.
Nursing Standard. 18, 40, 38-42.
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