Comparing the Optical Densities of Oral Bacteria Growth
in Humans, Felines and Canines
Mychal Hendrickson
Saint Martins University
Senior Seminar
Spring 2006
Dr. Margaret Olney and Dr. Mary Jo Hartman
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Table of Contents
Introduction…………………………………………………..pg. 1-7
Specific Goals………………………………………………..pg. 7
Proposed Research………………………………………….. pg. 8-10
Consent Form………………………………………………..pg. 11-13
Flow Chart…………………………………………………...pg. 14
Budget………………………………………………………..pg.15
Literature Cited………………………………………………pg. 16
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Abstract
In this study I hypothesized that humans would have the greatest amount of oral
bacteria growth compared with cats and dogs. Oral samples were collected from 30 cats,
30 dogs, and 30 humans. Bacterial samples were obtained from a combination of the
right and left upper canine teeth. These samples were placed in sterile nutrient broth and
were incubated at 37C. The optical densities were measured after 24-and 48-hours of
incubation. After the 24- hour incubation, all three species’ oral bacteria growth was the
same. It was found that dogs have the highest amount of oral bacteria growth, after 48hour incubation period, when compared to cats and humans (F=2.03, d.f.=2, p=0.014).
Introduction
Many people in the United States of America have cats or dogs as pets. Many of
these pet owners express their love for their pets in similar ways as they would towards
another human, with affection. Some pet owners even let their cat or dog lick them on
the face or hand. It is a personal preference whether a pet is allowed to kiss its owner.
Some people find it dirty and say that a pet’s mouth is full of bacteria that have the
potential to make them ill. Others believe that pets’ mouths are clean enough and that
the benefits of affection outweigh any risks. Since both cats and dogs lick themselves to
groom, there may be a meaningful amount of bacteria in the oral cavities of these
animals. However, research suggests that a human bite is more dangerous to a human
than a cat or dog bite (Allaker et al. 1997). Does being affectionate with our pets increase
the possibility of illnesses in humans, or are we humans exposing our pets to health risks?
Approximately 500 bacterial species are located within the human oral cavity
(Bachrach et al., 2003). These bacteria attach to the surface of teeth in a specific order.
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On the tooth’s surface are glycoproteins that are known as the acquired pellicle, as
described by Tannock (1995). Tannock describes the acquired pellicle as having a
negative charge, which attracts positively charged ions. The positively charged ions act
as a cloud and surround the acquired pellicle. These positively charged ions then attract
the negatively charged bacteria. Since the acquired pellicle has a negative charge and the
bacteria have a negative charge, they repel each other. The bacteria produce an
extracellular structure that can attach to the tooth’s surface (Tannock, 1995). These
attachments then become more permanent with the help of proline rich proteins.
Tannock (1995) suggests that the
proline rich proteins allow for the attachment of primary colonizers, which then produce
receptors to which the late colonizers attach. These layers of bacteria are known as
plaque. Cats, dogs, and humans all require regular dental hygiene, either home brushing
or a professional cleaning to remove plaque from the tooth’s surface. By understanding
the relationships between the amount of oral bacteria and species, safe and appropriate
methods of affection expression may be determined. This would provide a safe
environment for both humans and their pets.
Kroes et al. (1999) examined the bacterial diversity in the human oral cavity. By
using the definition of a phylotype differing by <1%, it was possible for Kroes et al. to
identify 59 different phylotypes. Phylotype is a commonly used term when classifying
and identifying bacteria. Despite the word’s popularity, it lacks a specific definition, but
for general practice it refers to the bacteria species differing by 1%. Through direct 16S
rDNA sequencing, Kroes et al, were able to identify 28 separate phylotypes. Within these
28 phylotypes, five separate divisions were seen that had not previously been identified.
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These unidentified phylotypes were then assigned numbers for identification purposes
and were then compared to known phylotypes in the clone libraries. The phylotype A-35
was 89.0% similar to its closest relative, which was a ruminal bacteria species.
Phylotype A-36 was 89.4% similar to another ruminal bacteria species. Phylotypes A-38
and A-39 were 98% identical to each other and 93% identical to their closest relative,
Schwartiza succinivorans, which was isolated from the rumen of cows. Phylotype A-44
was identical to a bacterial species that had been isolated from abscesses. The phylotypes
A-33, A-34, A-72 and C-73 are all relatives of the Eubacteriumi saburreum. Phylotype
A-63 was most similar to Weeksella zoohelcum, which had been found in the canine
upper respiratory tract and has been cultured from human dog bite wounds.
While the study by Kroes et al. (1999) only dealt with the human oral cavity, it
showed the complexity and abundance of the microflora within the mouth. Kroes et al.
used the definition of a phylotype differing by >1%, rather then differing by 1%. This
difference of the definition resulted in many phylotypes that had previously not been
identified. This study also showed the relationship between bacteria and the species of
the host. Kroes et al. concluded that different host species have different locations of the
same or similar bacteria. This was observed in the phylotype A-63. In humans this
phylotype was found in the oral cavity, but in canines it was found in the upper
respiratory tract. It is determined that the location of the bacteria depends on the host
species and that different host species have the same or similar bacteria present.
Allaker et al. (1997) explored the oral microflora of canines in reference to the
bacteria found in bite wounds. The canine population used for this study included dogs
with no current oral health problems. For part one of the study, a sample size of 30 dogs
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was used. Part two of the study used a sample size of 34 dogs. It was found that, as the
age of the dog increased, so did the level of plaque. As the amount of plaque increased,
the amount of bacteria also increased. It was found that 44% of the dogs had
Porphyromonas intermedia present and 68% had Porphyromonas gingivalis present.
Allaker et al. (1997) concluded that P. gingivalis and P. intermedia are the main causes
of periodontal disease in both humans and canines.
The percentage of Eikenella corrodens in the canine mouth was 5%, but in the
human mouth it was 10-20%. E. corrodens was an important phylotype because of its
potential to be a pathogen in dog bite wounds found on humans. The higher percentage
of E. corrodens in humans than in dogs showed that a human bite can be more severe
than a canine bite (Allaker et al. 1997). This leads to a consensus that the human oral
cavity has more bacteria with the potential to cause illness.
Harvey et al. (1995) compared the subgingival bacteria found in felines and
canines. All of the 49 dogs and 40 cats that were tested had moderate to severe
gingivitis. The most abundant bacteria found were Actinomyces species (sp), Viridans
Streptococci, Staphylococcus sp., Fusobacterium sp., Porphyomonas gingivalis, and
Peptostreptococcus micros. There were a total of 272 feline isolates and 344 canine
isolates. Staphylococcus and Streptococcus sp. were the most abundant gram-positive
aerobes in both feline and canine samples. Unidentified gram-negative species were
reported at a level of 10% in canines and 9% in felines. Pasteurella multocida were
found in both, at levels of 2% for canines and 5% for felines. The most common grampositive anaerobe identified was Peptostreptococcus sp., which was seen at a level of 3%
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in canines and 2% in felines. Of the gram-negative anaerobes, the highest number seen
were Porphyromonas or Prevotella sp. at 17% in canines and 15% in felines.
Overall, Harvey et al. (1995) concluded that feline and canine oral floras were
very similar. Some of the organisms of the human oral flora are different than those
found in the feline and canine oral flora. An example of this was the Prophyromonas
gingivalis. In felines and canines, P. gingivalis was catalase-positive, but in humans it is
catalase-negative. This is due to a difference in the pH level of the oral cavities (Harvey
et al, 1995). The pH in the human oral cavity is 6.5-7, while in the feline and canine oral
cavities; it is 7.5-8 (Harvey et al, 1995).
A study by Elliott et al. (2005) explored the microbiota in the canine oral cavity
and compared it to the human oral cavity. This study showed that there was a
considerable difference between the bacteria found in the canine and human oral cavities.
The study took samples from the dental plaque of nine dogs and from the saliva of five
dogs. From these samples, a total of 339 bacterial isolates were found. Of these 339,
there were 84 separate phylotypes and 37 individual species that could be identified.
They found that only 28% of the phylotypes were indigenous to the oral microbiota of
humans. The 37 identified species, not including Staphylococcus, all were found in
samples from the plaque, but only 10 identified species were found from samples of the
saliva (Elliot et al., 2005). The only bacteria Elliot et al. (2005) were able to find in both
the plaque and saliva at >5% were species of Actinomyces. Actinomyces sp. composed
11.6% of the plaque and 25.5% of the saliva. Granulicatella sp. composed 16.5% and
Streptococcus sp. composed 18.2% of the bacteria found in the saliva. In the plaque,
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Porphyromonas sp. made up 20% and Neisseria species made up 10.3% of the total
bacteria found.
Through comparative 16S rRNA gene sequencing, Elliot et al. (2005) determined
that the bacteria found in canine and human oral cavities differed by 7%. These results
support those of a previous study (Harvey al., 1995) that found bacteria isolated from cats
and dogs differ from the bacteria found in humans. Species that are found in dogs are not
likely to be found in humans. Elliot et al. (2005) stated that similar species are present,
but there are considerable differences in the primary role of bacteria in each host. An
example of this is members of the Streptococcus genus; in human plaque S. sanguis is
present, but in canine plaque S. suis is present. It is believed that different species of
bacteria have different roles in the human and canine oral cavities. In the human oral
cavity, Streptococcus is a primary colonizer, but in the canine oral cavity, Granulicatella
sp. play the role of primary colonizers. The Granulicatella and Streptococci sp. are
closely related. Another difference between the canine and human oral cavities was the
presences of Fusobacterium sp. Fusobacterium sp. were found in human plaque, but
were not found in canine plaque. A close relative to the Fusobacterium, Filifacter sp.,
were detected in canine plaque.
The study by Goldstein et al. (1978) examined the bacteria present in human and
animal bites. Bite wounds were divided into 3 groups: 1) human bite; actual bite (HB)
and CFI (is a laceration over the third and fourth knuckle joints, usually occurring from
punching someone in the mouth, with a clenched fist), 2) dog bite (DB), and 3) other bite
(OB). A total of 73 people with bite wounds were examined. The total of human bites
received were 34; 18 were HB and 16 were CFI. Thirty-nine people had animal bites, 26
8
were DB and 13 were other bites (including 4 cat, 4 squirrel, 3 rodent, and 2 rattlesnake).
Six of the people (3 DB, 2 OB, and 1 HB) had neither anaerobic nor aerobic bacteria
isolated from their wounds (Goldstein et al., 1978). Thirty-four people (13 DB, 7 CFI, 8
HB, and 6 OB) had only aerobic bacteria isolated from the wounds (Goldstein et al,
1978). Goldstein et al., (1978) reported that S. aureus was the most frequent isolate. S.
aureus was found in 62-80% of the bite wounds and was most associated with infection
from human bites.
Goldstein et al. (1978) suggested that the human oral cavity had more bacteria
than a canine oral cavity. This conclusion was based upon the percentage of bites that
bacteria were isolated from. From the CFI bite wounds, 56% were infected with bacteria.
Fifty percent of the HB bite wounds were infected with bacteria and 38% of the DB
wounds were infected with bacteria. The highest percentage of bacteria of bite wounds
infected with bacteria was found to be from a type of human bite.
Previous studies have focused mainly on the specific types of bacteria in the oral
cavities of cats, dogs, and humans, rather than on which species has the highest amount
of oral bacteria. Based on the findings of the previously mentioned studies, I
hypothesized that humans would have more bacteria growth cultivated from their oral
cavities than felines or canines. My research quantified the amount of oral bacteria
growth from each of three host species: cats, dogs and humans.
Methods
Preparation of nutrient broth:
The first step was to prepare the nutrient broth tubes. Nutrient broth (Ward’s)
was prepared in liter quantities. For each 1-liter of nutrient broth prepared, 8 grams of
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powered nutrient broth was added to 1-liter of distilled water. The powered nutrient
broth was dissolved in the water with a stir bar. Next, 10 ml of nutrient broth solution
was added to each of the 90 test tubes. These tubes were loosely capped and autoclaved
for 15 minutes at 121C at 15 psi, using a Tuttnauer 2540E autoclave. Immediately after
autoclaving, the caps were tightened on the tubes to prevent contamination, and the tubes
were stored at 4C until use.
Subject Recruitment:
There were a total of 90 participants that met the criteria of not having received a
professional dental cleaning two days prior to participation in the study (Stanley and
Reysenbach, 2002). Participation was on a volunteer basis and required signing a
consent form. Two different consent forms were used, one for the humans (Appendix 1)
and one for the cats and dogs (Appendix 2). Subjects were recruited from the Saint
Martin’s community and the surrounding areas of Pierce and Thurston counties. These
participants were divided into 3 groups: humans, canines and felines.
Obtaining samples:
One oral sample was obtained from 30 humans, 30 canines and 30 felines, for a
total of 90 samples. When samples were collected, the investigator wore latex gloves to
avoid the unwanted transfer of bacteria between subject and investigator. The samples
were obtained through oral swabbing in two different locations of the mouth. The two
locations for swabbing were the outside surfaces of both the right and left maxillary
canine teeth (Harvey et al., 1995), (Fig. 1).
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Figure 3. The right and left maxillary canine teeth that samples were obtained from.
These two locations provided the most bacteria and easiest access
(Jones Animal Hospital, personal communication, 2003). To ensure sample sizes were
the same, each sterile, cotton swab was used to obtain a sample using the same method.
First, the right maxillary canine tooth was swabbed quickly in 5 complete circles across
the surface of the tooth. The cotton swab was rotated and used to immediately wipe the
left maxillary canine tooth in 5 complete circles across the width of the tooth and was
placed in a sterilized tube of broth.
Before obtaining the samples from humans, the subjects rinsed their mouths for
30 seconds with water (Hitch et al., 2004). This was done to reduce the chance of
contamination from tooth brushing and food particles. After waiting 2 minutes, to ensure
the bacteria had recolonized on the tooth’s surface (Stanley and Reysenbach, 2002), the
tooth was swabbed using the procedure described above.
The canine and feline samples were obtained from the same locations in the
mouth and in the same manner as the human samples. The only exception was that I
rinsed the tooths’ surfaces, since a dog and cat cannot do this alone. I used a needle-less
syringe and rinsed both teeth with 3 cc of water. In order to have cooperation from the
animal when obtaining the sample, specific holds were used to prevent the cat or dog
from scratching or biting me. These two holds were not harmful for the animal. They
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only prevented movements of their heads and mouths. The cat was held by the scruff of
the neck, while lying on its side with the back legs held to prevent the cat from scratching
(Jones Animal Hospital, personal communication, 2003). The dog was held with one arm
around the neck of the dog, holding the head close to the body of the holder (Jones
Animal Hospital, personal communication, 2003). I wore long sleeves, pants and latex
gloves.
Transportation of samples:
First, I prepared empty sterilized test tubes. This was done in a similar manner as
the broth tube preparation. One hundred loosely capped, empty test tubes were
autoclaved at 15 minutes at 121C at 15 psi. Immediately after being removed from the
autoclave, the caps were tightened to ensure sterilization until use.
These empty sterilized tubes were used to transport the feline and canine samples
back to the lab. In order to control the premature growth of bacteria, the swab was placed
in the empty sterilized tube and stored on a shelf in a cooler while being transported back
to the lab (for no longer than 4 hours before incubation). The shelf in the cooler ensured
that the samples would not freeze, but would maintain a temperature of 11C to avoid
unwanted bacteria growth. Upon returning to the lab, the swab from each tube was then
placed into a sterilized nutrient broth tube and then incubated.
Incubation and optical density:
Each test tube containing a sample was loosely capped and incubated for 24 and
48 hours at 37 C. Both the 24 and 48 hour time periods were used to show the growth of
bacteria over time. This allowed for bacteria growth in a similar environment to where it
was cultivated. The Spectronic 20D+ spectrophotometer was set to measure the optical
12
density at the standard wavelength of 686 nm for each of the broth tubes (Allaker et al.,
1997). The spectrophotometer was cleaned by using distilled water and a lint free tissue.
The machine was zeroed and blanked using sterile nutrient broth without a swab. Each
sample was transferred into a disposable cuvette (Sargent Welch) and then placed into
the spectrophotometer. The optical densities were measured for each sample. Data
analysis compared the data of the three groups using a one-way analysis of variance test
(ANOVA). If there was a significant difference at  =0.05, a Tukey’s test (Minitab®,
2005), to compare each group to each other.
Results
The collected oral samples were incubated at 37C and the optical densities were
recorded measuring the absorbance after both 24-hour and 48-hour incubations. The
samples from the 24-hour time period were low, < 0.015 absorbance (Fig. 1). The
samples from the 24-hour time period were analyzed using a one-way ANOVA
(Minitab). The ANOVA showed that there was no significant difference between the oral
bacteria growth in cats, dogs, and humans after 24 hours of growth (F= 2.03, d.f= 2, p=
0.138), (Fig.1).
0.16
0.14
absorbance
0.12
0.1
0.08
0.06
0.04
0.02
0
cat
Dog
Species
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Human
Figure 1. The means of oral bacteria growth in 30 cats, 30 dogs, and 30 humans after 24-hour incubation
time period, measured the absorbance (shown on the y-axis) with the spectrophotometer. The x-axis
represents the host species of oral bacteria. Error bars represent one standard deviation
The 48- hour time period, had bacteria growth ranging from 0.3 to 0.5. The samples of
the 48- hour time period were analyzed using a one-way ANOVA test (Minitab®, 2005).
This ANOVA showed that there was a significant difference between the oral bacteria of
cats, dogs, and humans (F=2.03, d.f.=2, p=0.014), (Fig. 2).
0.6
0.5
Absorbance
0.4
0.3
0.2
0.1
0
cat
Dog
Human
Species
Figure 2. The means of oral bacteria growth in 30 cats, 30 dogs, and 30 humans after 48-hour incubation
time period, measured by the absorbance with the spectrophotometer. Error bars represent one standard
deviation. The Y-axis (absorbance) ranges from zero to 0.60. The x-axis represents the host species of oral
bacteria.
A Tukeys multiple comparisons test compared the groups to each other and showed a
difference at a confidence level of 98.06%. This showed that the difference was between
the dogs and the humans. The dogs had the highest amount of oral bacteria growth, when
compared to humans (Fig. 2). The cats’ oral bacteria growth was not significantly
different from the humans or dogs oral bacteria growth.
Discussion
Results included both the 24-hour and 48-hour optical density measurements of
absorbance from swabs of oral cavities of 30 dogs, 30 cats and 30 humans. At the 2414
hour time period, there was no significant difference between the three groups. The 48hour time period showed that the amount growth from samples from the dogs’ oral cavity
was statistically greater than the amount found in humans (P= 0.014). This failed to
support my hypothesis that humans would have more oral bacteria growth cultivated
from their oral cavity than felines or canines.
Within the 24-hour incubation period, bacteria growth occurs in all three species
and ranges in growth from 0.02 to 0.14. All three species had low bacteria growth after
the 24- hour incubation period. The 48-hour incubation period showed that all three
species had bacteria growth. The bacteria growth ranged in absorbance from 0.3
(humans) to 0.5 (dogs).
Having completed the experiment, I have determined that I would change the
method of obtaining the samples. Rather than using only plaque samples, I would use a
combination of plaque and saliva to better represent the oral bacteria population. This is
because of the small surface area of the cat’s teeth, which provided fewer bacteria than a
tooth with a larger surface area. Additional studies could include growing the oral
bacteria on agar plates and then counting the colonies of bacteria growth.
Another change I would make to the methods is more precise incubation periods.
The incubation period was not exactly 24 and 48 hours, but rather 24  4 hours and 484
hours. This is because of the availability of the spectrophotometer and lab room. My
data collection began using the digital spectrophotometer and to maintain consistency, all
data collections were obtained from this spectrophotometer. Many of my colleagues
were also using this spectrophotometer and sharing had to occur, which allowed for nonprecise incubation times. The open hours of the lab room also effected the incubation
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time periods, some samples would not reach the full 24 or 48-hour incubation time before
the lab closed and therefore data collection was done prematurely. I noticed that the
incubator was constantly being opened, due to the high number of people using it. From
frequent opening, the incubator may not have maintained a temperature of 37C, which
may have lowered the amount of bacteria growth, therefore affecting my data.
The last change I would make involves the blanking of the spectrophotometer.
For the blank, I used sterile nutrient broth. This is a potential source of error, because
there was not a sterile swab within the sterile nutrient broth tube used for blanking the
spectrophotometer. If there had been, it could have controlled for the possibility of
contamination from swab fibers and ensured that the absorbance measured only the
absorbance of bacteria (Steve Parish, personal communication, 2007).
My study compared the oral bacteria growth in cats, dogs, and humans and is just
a step in the direction of gaining knowledge of safe affection expression between humans
and their pets. In order to fully understand what appropriate is, many further studies are
needed.
Acknowledgements
I would like to thank Dr. Mary Jo Hartman and Dr. Margaret Olney for their
consent support and help throughout this experiment. I would also like to thank Cheryl
Guglielmo for her assistance in the lab. I would like to thank Jeremy Boje and my
colleagues for assisting me in the lab room during weekend hours.
(Appendix 1)
Consent to Act as a Human Subject in an Experimental Study
Description:
The purpose of this research is to compare the quantities of oral bacteria found in humans, dogs,
and cats. Two samples from each participant will be taken. The participants will include 50 humans, 50
16
cats, and 50 dogs. The duration of participation is approximately 10 minutes on one day. It will then be
determined who has the most bacteria located in the mouth.
Risks and Benefits:
There is minimal risk to you. As the investigator, I will follow proper microbiological safety
procedures to prevent the transfer of bacteria between the subjects and the investigator. This will be done
with the use of latex gloves, a lab coat, safety goggles, sterilized swabs and proper hand washing
techniques.
Alternative Treatments:
There are no alternative treatments in this study.
New Information:
New information gained during the time the research is in progress and which is relevant to
participation will be provided.
Cost and Payments:
There are no costs or payments associated with participation in this study. All costs not related to
the research will be charged to me just as though I were not part of this study.
Confidentiality:
This research is strictly for educational purposes and complete confidentiality will be maintained.
After signing the consent form, the samples obtained from you, will be assigned a number and further
reference to the samples will be made using this number. The signed consent forms will be stored in a
locked file in the Vice President of Academic Affairs Office at Saint Martins University.
Right to Refuse or to End Participation:
I understand that I can choose to end my participation in this study, at any time without further
consequences to myself.
Voluntary Consent:
I certify that I have read and understand the above statements. My signature below represents my
voluntary participation in this study. I will be given a copy of this consent form. If I have any questions
about the research, I can contact Mychal Hendrickson. Any questions concerning my rights as a participant,
will be answered by the Office of the Vice President for Academic Affairs (360-438-4310).
__________
Date
_________________________________________________
Subject Signature
Witness
Investigator’s Certification:
I certify that I have explained to the above individual the purpose of the experiment along with
having witnessed the above signature.
___________
Date
___________________________________________________
Investigator
(Appendix 2)
Consent to Act as an Animal Subject in an Experimental Study
Description:
17
The purpose of this research is to compare the quantities of oral bacteria found in humans, dogs,
and cats. Two samples from each participant will be taken. The participants will include 50 humans, 50
cats, and 50 dogs. The duration of participation is approximately 10 minutes on one day. It will then be
determined who has the most bacteria located in the mouth.
Risks and Benefits:
There is minimal risk to your pet. As the investigator, I will follow proper microbiological safety
procedures to prevent the transfer of bacteria between the subjects and the investigator. This will be done
with the use of latex gloves, a lab coat, safety goggles, sterilized swabs and proper hand washing
techniques.
Alternative Treatments:
There are no alternative treatments in this study.
New Information:
New information gained during the time the research is in progress and which is relevant to
participation will be provided.
Cost and Payments:
There are no costs or payments associated with participation in this study. All costs not related to
the research will be charged to me just as though I were not part of this study.
Confidentiality:
This research is strictly for educational purposes and complete confidentiality will be maintained.
After signing the consent form, the samples obtained from your pet, will be assigned a number and further
reference to the samples will be made using this number. The signed consent forms will be stored in a
locked file in the Vice President of Academic Affairs Office at Saint Martins University.
***********************************************************************
Right to Refuse or to End Participation:
I understand that I can choose to end my pet’s participation in this study, at any time without
further consequences to myself or my pet.
Voluntary Consent:
I certify that I have read and understand the above statements. My signature below represents my
voluntary participation in this study. I will be given a copy of this consent form. If I have any questions
about the research, I can contact Mychal Hendrickson. Any questions concerning my rights as a participant,
will be answered by the Office of the Vice President for Academic Affairs (360-438-4310).
__________
Date
________________________________________
Owner’s Signature
Pet’s Name
_________________________________
Witness
Investigator’s Certification:
I certify that I have explained to the above individual the purpose of the experiment along with
having witnessed the above signature.
___________
Date
___________________________________________________
Investigator
Literature Cited
Allaker, R., Young, K., Langloris, T., Rosayro, R., Hardie, J. 1997. Dental plaque of the
dog with reference to fastidious and anaerobic bacteria associated with bites.
Journal of Veterinary Dentistry. 14:127-130.
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Elliott, R., Wilson, M., Buckley, C., Spratt, D. 2005. Cultivable oral microbiota of
domestic dogs. J. Clinical Microbiology. 11: 5470-5476.
Goldstein, E., Citron, D., Wield, B., Blachman, U., Sutter, V., Miller, T., Finegold, S.
1978. Bacteriology of human and animal bite wounds. Journal of Clinical
Microbiology. 8: 667-672.
Harvey, C., Thornsberry. C., Miller, B. 1995. Subgingival bacteria-comparison of culture
results in dogs and cats with gingivitis. Journal of Veterinary Dentistry. 12: 147150.
Hitch, G., Pratten, J., Taylor, P. 2004. Isolation of bacteriophages from the oral cavity.
Letters in Applied Microbiology. 39:215-219.
Kroes, I., Lepp, P., Relman, D. 1999. Bacterial diversity within the human subgingival
crevice. Proceedings of the National Academy of Sciences of the United States of
America. 96:14547-14552.
Minitab Release 14.20.2005. Minitab Inc.
Stanley, J., Reysenbach, A. 2002. Biodiversity of microbial life. Ajoln Wiley and Sons,
Inc., New York, pp.317-318.
Tannock, G. 1995. Normal Microflora: an Introduction to Microbes Inhabiting the
Human Body. Chapman and Hall, London, pp. 51-54.
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