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19 – Pathogenic Gram-Positive Bacteria
Staphylococcus

1
...

a
...

b
...

i
...

2
...

a
...
Protein A coats the cell surface which interferes with phagocytic cells and
inhibits the complement cascade
...
Bound coagulase, converts fibrinogen to fibrin molecules and fibrin clots hide
the bacteria from phagocytes cells
...
Synthesized polysaccharide slime layers, inhibit leukocyte chemotaxis and
phagocytosis and facilitate attachment of staphylococcus to surfaces
...
Enzymatic Defenses
i
...
Aureus only) to trigger blood clotting
...
Hyaluronidase breaks down hyaluronic acid and enables the bacteria to spread
between the cells
...
Staphylokinase dissolves fibrin threads in blood clots and allows S
...

iv
...

v
...
Toxins
i
...

Exfoliative toxins cause skin cells to separate and slough off
...

Enterotoxin stimulates symptoms associated with food poisoning
...
Describe the symptoms and prevention of staphylococcal food poisoning
...
Food poisoning is due to ingestion of enterotoxin-contaminated food rather than the
invasion of bacteria
...
Symptoms, which include nausea, severe vomiting, diarrhea, headache, sweating, and
abdominal pain, usually appear within four hours following ingestion
...
Prevention methods include avoid leaving food at room temperature or warmer for
several hours
...
List and describe six pyogenic lesions caused by Staphylococcus aureus
...
Staphylococcal scalded skin syndrome is when the skin near the mouth becomes
reddened, spreads throughout the body, and then develops into large blisters
...

b
...
These vesicles usually crust over, making impetigo distinguishable from scalded
skin syndrome
...
Folliculitis is when a hair follicle becomes infected, causing it to become red, swollen,
and pus-filled
...
A sty is folliculitis that has occurred at the base of an eye lid
...
A furuncle, also known as a boil, is a large and painful nodular extension of folliculitis
into the surrounding tissue
...
Several furuncles together form a carbuncle
...

5
...

a
...
When carried into the blood, it causes fever, vomiting, a red
rash, low blood pressure, and loss of skin
...
Bacteremia is the presence of bacteria in the blood
...
About half of these
cases are acquired in hospitals
...
Endocarditis is when the bacteria attack the heart’s lining
...
It is a very
serious condition, as about 50% of patients do not survive
...
Pneumonia is caused when Staphylococcus enters the lungs
...
If this fluid is pus, the condition
is then called empyema
...
Osteomyelitis is when the bacteria invade a person’s bone
...

6
...

a
...

b
...
aureus bacterium
...
Coagulase-negative is usually S
...

c
...

7
...

a
...

i
...

b
...


c
...

Streptococcus

1
...

a
...

i
...

ii
...

iii
...

2
...

a
...

i
...

b
...
This then causes an
interference with opsonization and lysis, thus allowing the bacteria to prevent being
phagocytosed
...
Hyaluronic acid capsules help mask the bacteria from the body’s defenses
...

3
...
pyogenes in the body
...
The four enzymes and one toxin will be discussed here: streptokinases,
deoxyribonucleases, C5a peptidases, hyaluronidases, and pyrogenic toxins
...
There are two kinds of streptokinases that break down blood clots, in order to help
group A Streptococcus rapidly spread through infected tissue
...
There are also four kinds of deoxyribonucleases, which depolymerizes DNA that has
been released from dead cells
...

d
...

e
...

f
...
This causes fever, widespread rashes, and shock,
helping the bacteria spread
...
Describe seven diseases caused by S
...

a
...
Signs include high fever, cough, swollen lymph nodes, and tonsils which are red
and can have white patches
...
Scarlet Fever
i
...

ii
...
The tongue usually becomes

c
...


e
...


g
...
The rash disappears after about a week and is followed by
sloughing of the skin
...
A pyoderma (aka impetigo) is a confined, pus-producing lesion that usually
occurs on the exposed skin of the face, arms, or legs
...
After a pus-filled lesion breaks open, it forms a yellowish crust
...
This stage is highly contagious
...
When a streptococcal infection also involves surrounding lymph nodes and
triggers pain and inflammation, the condition is called erysipelas
...
This syndrome is when Group A streptococci spread from an initial site of
infection to a severe multisystem infections
...
Particularly seen in patients with HIV, cancer, heart disease, pulmonary
disease, or diabetes
...
Patients experience inflammation at sites of infection as well as pain,
fever, chills, malaise, nausea, vomiting, and diarrhea
...
It can lead to organ failure, shock—and over 40% of patients die
...
In this disease, streptococci enter the body through breaks in the skin, secrete
enzymes and toxins that destroy tissues, and eventually destroy muscle and fat
tissue
...
It also involves toxemia (toxins in the blood), failure of many organs,
and death of more than 50% of patients
...
This fever is when inflammation leads to damage of heart valves and muscle
...
Scientists suggest this is not caused directly by Streptococcus but instead is an
autoimmune response in which antibodies directed against streptococcal
antigens cross-react with heart antigens
...
This is when antibodies bound to the antigens of group A Streptococcus are not
removed from circulation but instead accumulate in the glomeruli of the
kidneys’ nephrons
...
Inflammation obstructs blood flow through the kidneys and leads to
hypertension (high blood pressure) and low urine output
...
Blood and proteins are often secreted in the urine
...
Discuss the epidemiology, diagnosis, treatment, and prevention of infections with S
...

a
...

b
...

i
...

c
...

d
...

e
...
Sometimes
vancomycin is prescribed
...


Prevention of Streptococcus agalactiae infection includes a prophylactic administration
of penicillin at birth
...


6
...
(include Streptococcus mutans in your list of species to know for this group;
it’s a (the) major species causing dental caries)
...
Viridans streptococci are alpha-hemolytic streptococci that are not part of any
Lancefield group
...
Viridans streptococci normally inhabit the mouth, pharynx, GI tract, genital tract, and
urinary tract of humans
...
Diseases include dental caries on teeth
...
Once in the blood, they can cause meningitis and endocarditis
...
Streptococcus mutans is a major species causing dental caries as well
...
Describe how the structure of Streptococcus pneumonia affects is pathogenicity
...
Virulent strains of S
...

b
...

i
...

Bacillus

1
...

a
...
anthracis cause disease because they contain multiple copies of
another plasmid coding for anthrax toxins
...
The toxin genes are “turned on” by bicarbonate, a molecule found in blood
...
List three methods of transmission of anthrax
...
Humans contract the disease Anthrax from infected animals in 3 ways:
i
...

ii
...

iii
...

3
...

a
...

b
...
However, the nodule quickly spreads into a swollen, black, crusty ulcer
...

c
...
These endospores
then germinate in the lungs, where they secrete toxins that are absorbed by the
bloodstream, causing toxemia
...
This type of anthrax is the most dangerous
...
Identify the mechanisms accounting for the pathogenesis of Clostridium perfringens infections
...
Clostridium perfringens produces 11 toxins that lyse erythrocytes and leukocytes, which
then increase the bacteria’s vascular permeability, which leads to a reduction of blood
pressure, all of which causes irreversible damage
...
It can divide rapidly, thus allowing it to spread across the body very quickly, especially
once it has become vascularly permeable
...
Discuss the role of antimicrobial drugs in the development of gastrointestinal diseases caused by
Clostridium difficile
...
Under normal conditions, C
...

b
...
difficile to
become an opportunistic pathogen
...
With the balance disturbed, C
...

3
...

a
...

b
...

c
...

4
...

a
...
Occur via eating improperly canned-foods or preserved fish
...
Infant botulism
i
...

ii
...

c
...
Contamination of a wound by endospores
...
Describe how mice are used in the diagnosis of botulism
...
First, specimens of food, feces or blood serum are divided into two portions
...
Botulism antitoxin is mixed with one portion and then inoculated into one of two mice
...
With the uninoculated portion put into the other mice
...
If the mice receiving the antitoxin survive, while the other mice die, then the botulism
diagnosis is confirmed
...
Describe the pathogenesis of Clostridium tetani, and the disease and epidemiology of tetanus
...
C
...

b
...

i
...
With inhibition blocked, muscles are signaled to contract
simultaneously
...
Opposing contractions can be so severe that they break bones
...
Typically the initial sign of tetanus is tightening of the jaw and neck muscles

then heartbeat irregularities, fluctuations in blood pressure, and extensive
sweating
...

Mycoplasmas

1
...

2
...

3
...

4
...

a
...

Diphtheria

1
...

a
...

b
...

Mycobacterium

1
...

a
...

b
...

2
...
tuberculosis and its subsequent action within the human body
...
It is transmitted via airborne droplet nuclei containing bacteria enter the respiratory
tract of an exposed individual and are deposited in the lung alveoli
...
Discuss the diagnosis, treatment, and prevention of tuberculosis
...
A tuberculin skin test is used to screen patients for possible exposure to tuberculosis
...
In this test, cell wall antigens from M
...

ii
...

b
...

c
...
tuberculosis
...
Best chance of treatment is a combination of isoniazid (INH), rifampin, pyrazinamide,
and either streptomycin or ethambutol for two months, followed by INH and rifampin
alone for four more months
...
In countries where tuberculosis is common, health care workers immunize patients with
BCG vaccine

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