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Infectious Diseases
Unit 5
5.1 Key Terms & Essential Questions
Antibody
Aseptic Technique
Bacillus
Bacteria
B Lymphocyte (B Cell)
Coccus
Contagious
Fungus
Gram Stain
Helminthes
Immunity
Infection
Microbiology
Phagocyte
Prion
Protozoan
Spirillum
T Lymphocyte (T Cells)
Transmission
Virus
1. How are infectious
diseases spread through
a population?
2. What is aseptic
technique?
3. How can an unknown
sample of bacteria be
identified?
4. How does the immune
system function to
protect the human body
from foreign invaders?
Infectious diseases
• Caused by the entrance and reproduction of
an infectious agent in a body
▫ Bacteria or virus
▫ The medical examiner who performed Anna Garcia’s
autopsy pulled copies of Anna’s medical records before
proceeding with the autopsy. Interestingly, the medical
examiner discovered that Anna had been hospitalized just
ten days prior to her death for a sickle cell crisis and
subsequently was treated for an infection that was most
likely acquired during her hospital stay. The medical
examiner then noted that a page of the medical history is
missing. Throughout this lesson, YOU will play the role of
medical detectives in order to investigate Anna’s mystery
infection. Ultimately, YOU will need to identify the exact
pathogen, or infectious agent, responsible for Anna’s
illness.
Influenza Outbreak (1918-1919)
Death and Devastation
• Deadliest in modern
history
• More died from the flu
than from World War I
▫ More than 25% of the
U.S. population became
sick
▫ 675,000 Americans died
during the pandemic
▫ All age groups were
affected, not just the
young and elderly
Spread of the Disease
• First observed in
Europe, the U.S. and
parts of Asia
▫ Swiftly spread around
the world
▫ Highest impact was
along shipping and
trade routes
▫ Spread quickly due to
worldwide travel of
troops returning from
WW1
▫ Estimates put the
worldwide death toll at
21,642,274
Cause of Death
• Extensive
hemorrhaging in the
lungs
• Patients literally
drowned in fluids
• Researchers later
discovered what made
the pandemic so
deadly
• In many victims, the
influenza virus had
invaded their lungs
and caused
pneumonia
Prevention
• Quarantine of
infected
individuals
• Mandatory use
of face masks by
all individuals
when out in
public
Public Service Announcements:
An important part of prevention
Public Service Announcements:
An important part of prevention
How are the diseases spread?
1.
▫
▫
2.
▫
▫
3.
4.
▫
▫
▫
From person-to-person
Potential to become epidemics.
Flu, colds, measles, small pox, and the plague
From animal-to-person
Zoonotic
Rabies, brucellosis (also known as undulant fever),
staphylcoccosis, and streptococcosis.
Through contaminated food, soil, water, or other
material
By disease vectors including:
Mosquitoes
Fleas
Ticks
How are people infected?
• Contact with infected
body fluids.
▫ Mucous from a cough
or sneeze, blood, feces
• Air, water, or food borne
infectious agent
• Contaminated surface
▫ Door knob
▫ Telephone
Long term effects of infection
• Bacterial and viral infections can damage the
heart tissue
• Viral infections can cause nerve damage
▫ suspected as a factor in the development of
chronic neuromuscular syndromes including
 Multiple sclerosis
 Fibromyalgia
 Chronic Fatigue Syndrome
• Both can lead to death
5.1.2: Infectious Disease Agents
• Begin your detective work by exploring the different
types of pathogens as well as examining specific
examples of each type in order to identify what is
plaguing Anna
▫
▫
▫
▫
▫
▫
bacteria
viruses
fungi
protozoa
helminthes
prions
• Investigate a variety of diseases caused by infectious
agents and use this information to determine the tests
you will need to perform in the subsequent activities to
fill in the missing pieces from Anna’s medical history
What are Viruses?
• Non-living particles that infect cells and cause disease
• Requires antivirals, antibiotics have no effect
• Very specific
▫ Must be able to attach to a cell to infect it
• Contain genetic material that mutate
▫ Causes a change in the characteristics of the virus
▫ Allowing the virus to attach to new types of cells
Viruses are not ALIVE!!!
Living Things
Viruses
Use and need energy
They don’t use neither need energy
The have a life span
They don’t have life span
They grow
They don’t' grow
They reproduce
REPLICATION, not reproduction
(inside another organism)
They develop
They don’t develop
They are organize
They aren’t organized
They are made up of cells
They are made up normally from a
genetic material and a capsid
They adapt to the environment
They adapt to the environment
• How Viruses Work NPR video
What are bacteria?
1. All are unicellular
2. All are prokaryotic - cells that lack nucleus
(no nuclear envelope) (PRO = NO nucleus)
3. All have cell walls
4. Reproduce via fission or budding
5. Can live in both aerobic (with O2) and anaerobic
(without O2) environments
6. Much larger than viruses
7. Usually have one of three different cell shapes:
coccus, sprillum, bacili
Endosymbiotic theory
Ex: Streptococcus
Ex: Lactobacillus
Ex: Spirillium
What shape?
bacillus
spirillu
m
coccus
coccus
bacillus
spirillu
m
5.1.2: Infectious Disease Agents:
Type of
Infectious
Agent
Bacteria
Viruses
Fungus
Protozoa
Helminthes
Prions
Disease
Examples
Modes of
Does the Agent
Transmission Require a Host
for
Reproduction?
How the
Agent is
Treated
Disease Cards
Tuberculosis (TB)
Type of Infectious Agent
Bacteria
Name of Infectious Agent
Mycobacterium tuberculosis
Symptoms of Disease
The symptoms of TB disease depend on where in the body the bacteria are
growing. Usually, TB bacteria grow in the lungs where they cause a bad cough that
lasts 3 weeks or longer, pain in the chest, and coughing up blood or the phlegm
from deep inside the lungs. Other symptoms include weakness, fatigue, weight
loss, no appetite, chills, fever, and sweating at night.
Diagnosis of Disease
Skin test, blood test, chest X-ray, and sputum culture.
Transmission of Disease
TB is spread through the air from one person to another. The TB bacteria are put
into the air when a person with TB disease of the lungs or throat coughs, sneezes,
speaks, or sings. People nearby may breathe in these bacteria and become
infected.
Treatment of Disease
Antibiotic treatment with isoniazid (INH), rifampin (RIF), or rifapentine (RPT).
Strep Throat
Type of Infectious Agent
Bacteria
Name of Infectious Agent
Streptococcus pyogenes
Symptoms of Disease
General symptoms include throat pain, difficulty swallowing, red and swollen tonsils
that often have white patches or streaks of pus on them, tiny red spots on the soft
or hard palate, swollen and tender lymph nodes in the neck, fever, headache, rash,
and fatigue.
Diagnosis of Disease
Throat culture, rapid antigen test, and/or rapid DNA test.
Transmission of Disease
Streptococcal bacteria are highly contagious. They can spread through airborne
droplets when someone with the infection coughs or sneezes, or through shared
food or drinks. You can also pick up the bacteria from a doorknob or other surface
and transfer them to your nose or mouth.
Treatment of Disease
Oral antibiotic treatment with penicillin, amoxicillin, erythromycin, or azithromycin.
Syphilis
Type of Infectious Agent
Name of Infectious Agent
Symptoms of Disease
Bacteria
Treponema pallidum
Primary syphilis – small sore on genitals
Secondary syphilis – Rash that begins on trunk and covers entire body and may
be accompanied by wart-like sores in the mouth or gential area. Muscle aches,
fever, sore throat and swollen lymph nodes are also common.
Latent syphilis – No symptoms
Tertiary or late syphilis – Brain, nerve, eye, heart, blood vessel, liver, bone, and
joint damage.
Diagnosis of Disease
Transmission of Disease
Blood test for presence of antibodies, fluid culture from sores, or spinal tap.
Spread through contact with an infected person's sore during sexual activity. The
bacteria enter your body through minor cuts or abrasions in your skin or mucous
membranes. Syphilis is contagious during its primary and secondary stages, and
sometimes in the early latent period. It is also spread through direct unprotected
close contact with an active lesion or through an infected mother to her baby
during pregnancy or childbirth.
Treatment of Disease
Antibiotic treatment with penicillin.
Giardiasis
Type of Infectious Agent
Protozoa
Name of Infectious Agent
Giardia lamblia parasite
Symptoms of Disease
A gastrointestinal disease with water, sometimes foul-smelling diarrhea that may
alternate with soft, greasy stools, fatigue, abdominal cramps and bloating, belching
gas with a bad taste, nausea, and weight loss.
Diagnosis of Disease
The infection is diagnosed with a stool sample.
Transmission of Disease
Giardia parasites live in the intestines of people and animals. Before the microscopic
parasites are passed in stool, they become encased within hard shells called cysts,
which allows them to survive outside the intestines for months. Once inside a host,
the cysts dissolve and the parasites are released. Infection occurs when you
accidentally ingest the parasites. This can occur by swallowing contaminated water,
by eating contaminated food, or through person-to-person contact.
Treatment of Disease
Administration of medications specific to giardia infection (including metronidazole,
tinidazole, nitazoxanide, and paromomycin).
Malaria
Type of Infectious Agent
Protozoa
Name of Infectious Agent
Plasmodium parasite
Symptoms of Disease
Malaria causes damage to red blood cells which can cause serious and sometimes
fatal complications. The disease is characterized by recurrent attacks with moderate
to severe shaking chills, high fever, profuse sweating as the body temperature falls,
headache, nausea, vomiting, and diarrhea.
Diagnosis of Disease
Blood test for the parasite.
Transmission of Disease
Microscopic parasites transmit the disease from person to person. A mosquito
becomes infected by feeding on a person who has malaria and then transmits the
malaria parasites to the next person the mosquito bites. Malaria can also be
transmitted from mother to unborn child, through infected blood transfusions, and by
sharing infected needles.
Treatment of Disease
Administration of antimalarial drugs.
Cryptosporidiosis
Type of Infectious Agent
Protozoa
Name of Infectious Agent
Cryptosporidium parvum parasite
Symptoms of Disease
A gastrointestinal disease whose symptoms include watery diarrhea, dehydration,
weight loss, stomach cramps or pain, fever, nausea, and vomiting.
Diagnosis of Disease
The infection can be diagnosed with an acid-staining test which identifies
cryptosporidium under the microscope or a stool culture.
Transmission of Disease
The infection begins when you ingest the parasite which then travels to your intestinal
tract and settles into the walls of your intestines. You can become infected with
cryptosporidium by touching anything that has come in contact with contaminated
feces. Methods of infection include swallowing or putting something contaminated in
your mouth, drinking contaminated water, swimming in contaminated water and
accidentally swallowing some of it, touching your hand to your mouth if you had comes
into contact with a contaminated surface, or having close contact with other infected
people or animals.
Treatment of Disease
Administration of anti-parasitic drug, anti-motility agents to slow down the movements
of the intestines, and fluid replacement therapy.
Creutzfeldt-Jakob Disease (CJD)
Type of Infectious Agent
Prion
Name of Infectious Agent
CJD Prion
Symptoms of Disease
CJD is marked by rapid mental deterioration, usually within a few months. Initial signs
and symptoms typically include personality changes, anxiety, depression, memory
loss, impaired thinking, blurred vision, insomnia, difficulty speaking, difficulty
swallowing, and sudden jerky movements. As the disease progresses, mental
symptoms worsen and people eventually lapse into a coma.
Diagnosis of Disease
Doctors commonly use an EEG, MRI, spinal fluid tests, and/or tonsil biopsies to
diagnose the disease.
Transmission of Disease
CJD disease is caused by an abnormal version of a kind of protein called a prion.
Normally the proteins are harmless, but when they’re misshapen they become
infectious and can cause major problems on normal biological processes. Most people
with CJD develop the disease for no apparent reason, but others who develop the
disease have a family history of the disease or test positive for a genetic mutation
associated with CJF. A small number of people have developed CJD after being
exposed to infected human tissue during a medical procedure. This happens because
standard sterilization methods do not destroy abnormal prions.
Treatment of Disease
No effective treatment exists for Creutzfeldt-Jakob disease or any of its variants.
Ascariasis
Type of Infectious Agent
Helminth
Name of Infectious Agent
Ascariasis worm
Symptoms of Disease
After the ascariasis eggs are ingested, they hatch in the intestines and sometimes
migrate through the bloodstream or lymphatic system into the lungs. An intestinal
infection can cause abdominal pain, nausea and vomiting, diarrhea or blood stools,
and/or fatigue. A lung infection can cause persistent cough, shortness of breath, and/or
wheezing.
Diagnosis of Disease
Infection is identified by stool tests, blood tests, and/or imaging tests.
Transmission of Disease
A person must come into contact with soil mixed with human feces that contains
ascariasis eggs.
Treatment of Disease
Administration of anti-parasite medications.
Trichinosis
Type of Infectious Agent
Helminth
Name of Infectious Agent
Trichinella roundworm
Symptoms of Disease
When a person swallows trichinella larvae encased in a cyst, the digestive juices
dissolve the cyst, releasing the parasite into the body. The larvae then penetrate the
intestine, where they mature into adult worms and mate. At this stage, symptoms
include diarrhea, abdominal cramps, and malaise. Later the adult female worms
produce larvae that penetrate the intestinal wall, enter the bloodstream, and burrow
into muscle or other tissue. This causes high fever, muscle pain and tenderness,
swelling of the eyelids or face, weakness, headache, and sensitivity to light.
Diagnosis of Disease
Initial diagnosis relies on physical examination of the classic signs and symptoms,
blood samples, and a muscle biopsy.
Transmission of Disease
People get trichinosis when they eat undercooked meat — such as pork, bear,
walrus, or horse — that is infected with the immature form (larvae) of the trichinella
roundworm.
Treatment of Disease
Administration of anti-parasite (anti-helminthic) medication.
Tapeworm
Type of Infectious Agent
Helminth
Name of Infectious Agent
Tapeworm
Symptoms of Disease
Intestinal infections cause nausea, weakness, loss of appetite, abdominal pain,
diarrhea, weight loss and inadequate absorption of nutrients from food. Invasive
infections result in fever, cystic masses or lumps, allergic reactions to the larvae,
bacterial infections, and neurological symptoms including seizures.
Diagnosis of Disease
Stool sample analysis, blood test, and/or imaging exam.
Transmission of Disease
Consumption of food or water contaminated with feces from a person or animal with
tapeworm or ingestion of larvae cysts in meat or muscle tissue of an animal with a
tapeworm infection.
Treatment of Disease
Administration of oral medications that are toxic to the adult tapeworm (including
praziquantel, albendazole, and nitazoxanide).
Common Cold
Type of Infectious Agent
Virus
Name of Infectious Agent
Rhinovirus
Symptoms of Disease
Symptoms include: runny or stuffy nose, itchy or sore throat, cough, congestion,
slight body aches or a mild headache, sneezing, watery eyes, a low-grade fever, and
mild fatigue.
Diagnosis of Disease
Physical examination.
Transmission of Disease
The virus enters your body through your mouth or nose. The virus can spread
through droplets in the air when someone who is sick coughs, sneezes, or talks. But
it also spreads by hand-to-hand contact with someone who has a cold or by using
shared objects, such as utensils, towels, toys, or telephones. If you touch your eyes,
nose, or mouth after such contact or exposure, you're likely to "catch" a cold.
Treatment of Disease
There is no cure for the common cold. Over-the-counter cold treatments do not treat
the cold but can sometimes relieve symptoms. These include pain relievers,
decongestants, and cough syrups.
Flu
Type of Infectious Agent
Virus
Name of Infectious Agent
Influenza
Symptoms of Disease
Symptoms include fever, aching muscles (especially in the back, arms, and legs), chills
and sweats, headache, dry cough, fatigue and weakness, and nasal congestion.
Diagnosis of Disease
Physical examination.
Transmission of Disease
Flu viruses travel through the air in droplets when someone with the infection coughs,
sneezes, or talks. You can inhale the droplets directly, or you can pick up the germs
from an object — such as a telephone or computer keyboard — and then transfer them
to your eyes, nose, or mouth.
Treatment of Disease
Bed rest and hydration is usually the only treatment needed. Antiviral medications can
be prescribed if taken soon after symptoms begin. These drugs may shorten the illness
by a day or so and help prevent serious complications.
Rotavirus
Type of Infectious Agent
Name of Infectious Agent
Symptoms of Disease
Virus
Rotavirus
Symptoms begin with a fever, followed by three to eight days of watery diarrhea and
vomiting. The infection can cause abdominal pain as well. In adults who are
otherwise healthy, a rotavirus infection may cause only mild signs and symptoms —
or none at all.
Diagnosis of Disease
Diagnosed via a physical exam. Stool sample may be analyzed to confirm the
diagnosis.
Transmission of Disease
Rotavirus is present in an infected person's stool several days before symptoms
appear and for up to 10 days after symptoms subside. The virus spreads easily
through hand-to-mouth contact throughout this time — even if the infected person
doesn't have symptoms. Not washing your hands after using the toilet or changing a
child’s diaper can cause the virus to spread to anything you touch, including food,
toys, and utensils. If another person touches your unwashed hands or a
contaminated object and then touches his or her mouth, an infection may follow.
Sometimes rotavirus spreads through contaminated water or infected respiratory
droplets coughed or sneezed into the air.
Treatment of Disease
There is no treatment for a rotavirus infection. The infection usually resolves within
three to eight days. Primary treatment involves the prevention of dehydration.
Histoplasmosis
Type of Infectious Agent
Fungus
Name of Infectious Agent
Histoplasma capsulatum
Symptoms of Disease
Several types of histoplasmosis exist. The mildest form produces no signs or
symptoms, but severe infections can be life-threatening. Symptoms of the infection
include fever, chills, headache, muscle aches, dry cough, and chest discomfort.
Sometimes the infection causes joint pain and a rash.
Diagnosis of Disease
Inspection of lung secretions, blood or urine, biopsied lung tissue, and/or bone
marrow.
Transmission of Disease
Histoplasmosis is caused by the reproductive cells (spores) of the fungus. The
histoplasmosis fungus thrives in damp soil that's rich in organic material, especially
the droppings from birds and bats The spores are extremely light and float into the
air when dirt or other contaminated material is disturbed, so infection is most
commonly transmitted during cleanup or demolition projects and to farmers and
landscapers.
Treatment of Disease
Treatment usually isn't necessary if you have a mild case of histoplasmosis. But if
your symptoms are severe or if you have the chronic or disseminated forms of the
disease, you'll likely need treatment with one or more antifungal drugs.
Ringworm (Tinea corporis)
Type of Infectious Agent
Fungus
Name of Infectious Agent
Dermatophytes
Symptoms of Disease
A circular rash on the skin that’s red and inflamed around the edge and healthy looking
in the middle; slightly raised expanding rings of red, scaly skin on the trunk or face;
and/or a round, flat patch of itchy skin.
Diagnosis of Disease
Skin scrapings or samples from the infected area are taken and looked at under a
microscope.
Transmission of Disease
Ringworm is contagious and can be spread in the following ways: direct, skin-to-skin
contact with an infected person; touching an animal with ringworm; contact with
objects or surfaces that an infected person or animal has recently touched or rubbed
against; or contact with infected soil.
Treatment of Disease
Administration of a prescription-strength topical antifungal or oral medication.
Athlete’s Foot (Tinea pedis)
Type of Infectious Agent
Fungus
Name of Infectious Agent
Dermatophytes
Symptoms of Disease
Symptoms include itching, stinging, and burning between the toes; itching, stinging,
and burning on the soles of the feet; itchy blisters; cracking and peeling skin,
especially between the toes and on the soles of the feet; excessive dryness of the
skin on the bottoms or sides of the feet; and/or toenails that are thick, crumbly,
ragged, discolored, or pulling away from the nail bed.
Diagnosis of Disease
Skin scrapings or samples from the infected area are taken and viewed under a
microscope.
Transmission of Disease
Athlete's foot thrives in thick, tight shoes that squeeze the toes together and create
warm, moist areas between them. Damp socks and shoes and warm, humid
conditions also favor the organisms' growth. The fungus is transmitted by sharing
clothes or shoes with someone who has the fungal infection or walking barefoot in
public areas where the infection can spread.
Treatment of Disease
Administration of antifungal medication.
5.1.1 Contagious: Are you patient zero?
Outbreak: Anatomy of an epidemic
Infection & Disease
• Pathogen- infectious agent
responsible for disease
• Infection- pathogen invades
and begins growing within a
host
• Disease- occurs if and when
the invasion and growth of
a pathogen impair bodily
functions
• To cause disease pathogens
must
1.
2.
3.
4.
Enter the host body
Adhere to specific cells
Invade and colonize
tissues
Inflict damage
• Enter through openings to the body: mouth, eyes, nose,
genital openings, breaks in the skin
• Cause disease by
▫ Destroying cells of infected organisms by breaking the
cells down for food
▫ Releases toxins (poisons) which destroy cells of infected
organism
• Must have access to new hosts to spread
Highly contagious and virulent
Contagious
• Infectious agents that are easily transmitted
Virulent
• Infectious agents that are very likely to cause disease
once transmitted
The most troublesome infectious agents
• Highly contagious and virulent
5.1.3: Isolating Bacteria
• Patient samples contain
a mix of bacteria
• Bacteria grow in groups
called colonies
• On a growth media
called agar
• Isolation of individual
colonies is necessary to
study all of the possible
pathogenic organisms
for identification tests
5.1.3 Colony Morphology
• http://www.microbelibrary.org/images/shoeb/c
olonial%20morphology.html
• Shape
• Margin
• Optical Properties
• Pigment
• Elevation
• Texture
Colony
Shape
Colony
Margin
Optical Properties
Colony Pigment
Colony Elevation
Colony Texture
•
•
•
•
Soft
Granular
Tenacious
Mucoid
Bacterial Isolation
• A sample of each colony
type streaked onto an
agar plate to physically
separate the colonies
• You will isolate bacterial
colonies from four
samples, including
Anna’s, and then
complete a gross
examination of the
colonies from Anna’s
sample
Kocuria rhizophila
• Coccoid
• halotolerant (acid
tolerant)
• Gram-positive
• mammalian skin,
soil, fermented
foods, clinical
specimens, fresh
water and marine
sediments
Kocuria rosea
• Gram-positive
bacteria
• Widespread in nature
• Commonly found
along with coagulasenegative Staphylococc
us spp. on the skin of
humans and
mammals.
Stigmatella aurantiaca
• Rod shaped
• Typically
measuring about
5–8 μm long and
0.7–0.8 μm wide
• Gram negative
• Fruiting bodies
• Found on rotting
wood or fungi and
soil
Stigmatella aurantiaca
Kocuria rhizophila
Kocuria rosea
Anna’s Sample
5.1.3 Bacterial Morphology Results
Species
Size
Margins
Elevation
Color
Anna’s Sample
Small
Wavy/Irregular
Raised
Red/Pink
K. rhizophilia
Small
Smooth
Convex
White/Yellow
K. roseus
Small
Smooth
Convex
Pink
S. aurantiaca
Small
Smooth
Convex
Yellow
Career Journals
•
•
•
•
•
•
Microbiologist
Epidemiologist
Medical Laboratory Technician
Pick 2
Any format
Due Friday April 25th
5.1.4 Gram Staining: Gram (+) & Gram (-)
• Bacteria can divided
into 2 main groups
• Based on reaction to
Gram stain (set of
dyes)
▫ Hans Christian Gram
(1800s)
▫ Remains first step in
classifying bacteria
 Purple- Gram positive
 Pink- Gram negative
• Based on the ability of the bacterial cell wall to
retain the crystal violet dye
• It is retained or not is dependent on the type of
bacterial cell
Gram positive bacteria differ from Gram negative bacteria in
the structure of their cell walls. The cell walls of Gram
positive bacteria are made up of 20x more peptidoglycan, a
polymer made of sugar and amino acids- which absorbs and
retains crystal violet dye
Gram Stain Process
1. Heat fix the slide so that bacterial cells are fixed to the
slide.
2. Flood the slide with crystal violet dye.
▫ The individual crystal violet ions penetrate the thick
peptidoglycan layer of the cell as well as the plasma
membrane.
3. Rinse with water.
4. Flood the slide with iodine.
▫ (+) The iodine ions penetrate the cell wall and bind
with the crystal violet.
▫ (-) The iodine ions and crystal violet react, forming a
crystal violet-iodine complex that is a very large
molecule and is insoluble in water.
5. Rinse with water.
6. Decolorize the slide with alcohol.
▫ (+) The alcohol causes water to leave the cell wall.
Because of its larger size, the crystal violet-iodine
complex is blocked from moving easily through the cell
wall and thus is prevented from leaving the cell.
▫ (-) The alcohol disrupts and dissolves the outer
membrane. Therefore the big crystal violet-iodine
complex is able to leave the cell.
7. Rinse with water.
▫ (+) The crystal violet-iodine complex is still stuck
inside the cell. The cell is therefore stained purple.
▫ (-) The crystal violet-iodine complex is washed away,
leaving colorless, unstained cells.
8. Flood the slide with Safranin dye
Transfer
Fix
Crystal Violet Dye (sit for 1m)
Rinse
Iodine (sit for 1m)
Rinse
Alcohol (rinse for 15-30s)
Rinse
Safranin (sit for 30s)
Gram (+) Bacteria
▫ Safranin penetrates the
cell, but since it is a
lighter color than the
crystal violet-iodine
complex, it is not
visualized over the
purple color of the
crystal violet-iodine
Gram (-) Bacteria
▫ Safranin penetrates the
cell and stains the cell a
reddish-pink color
5.1.4 Gram Staining
1.
2.
3.
4.
5.
6.
7.
Cells Alive Website: Examine bacterial structure
Draw and label bacteria cell
Include function
Skip.
Completed.
Completed.
Slides: Cocci Gram positive, Cocci Gram negative,
bacillus, salmonella spp.
8. Sketch: Always label and include name and
magnification
9. Slides: E. coli, Streptococci spp.
10. Sketch and Record Shape and Gram Status
Design your own Bacteria Experiment
• In your journal…
▫ Write your research question
 Antibacterial soap
 Hand sanitizer
 Test different surfaces
▫ Write your hypothesis
▫ Describe your experiment
 Each person has 1 petri dish
and 2 sterile swabs
 Can work alone or with a
partner
▫ Include a data table
 How will you measure your
results?
 What data will you collect?
• Get my OK
• Proceed!!!
Bacteria Experiment: Record Growth
• After 24 hours
▫ Diagram each dish/section
 Draw exactly what it looks
like
 Include measurements of
each colony
 Take notes on appearance
• After 72 hours
▫ Return to diagram after 24
hours
▫ Add additional growth and
measurements in a different
color
5.1.5 Bacterial Identification
• Identification based on many factors
▫
▫
▫
▫
Cell and colony morphology
Chemical composition of cell walls
Biochemical activities
Nutritional requirements
• Most definitive way to identify bacterial species
▫ Determine what growth media the bacteria will grow on
▫ Identify the end products of their metabolic processes
 Wastes they excrete
▫ Many tests are performed
• Anna’s bacterial sample is a Gram negative rodshaped bacteria
▫ You will analyze the results of various biochemical tests
▫ To identify the unknown bacterial species
Biochemical Tests Performed on Anna’s Sample
Type of test performed:
Result:
Ornithine Decarboxylase Test
Positive
Citrate Test
Positive
VP test
Positive
Oxidase Test
Negative
Lysine Decarboxylase Test
Positive
H2S Test
Negative
Pigmentation
Red
Glucose Fermentation Test
Positive
Lactose Fermentation
Negative
Indole Test
Negative
Urease Test
Negative
Nitrate Reduction
Positive
Arabinose Test
Negative
Motility Test
Positive
Gelatin Hydrolysis
Positive
Catalase Test
Positive
Serratia marcescens
• It is motile
• Discovered by Bartolomeo Bizio in 1819. Named
after Italian physicist named Serratia.
• Found in places such as dirt, supposedly “sterile”
places, and the subgingival biofilm of teeth.
• pH levels 5-9
• Commonly found in patients with catheters.
• Look on wikipedia lol

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