ALU 301 Chapter 4 - An Overview of Infectious Diseases UPDATED
ACTUAL Questions and CORRECT Answers
1. Infections and infectious diseases have had a globe, killing uncounted millions,
major effect on humanity throughout the entire and fatal infections caused by rel-
history of our species. Until the 20th century, atively minor wounds and primitive
epidemics raged unchecked across the medical techniques were the norm
rather than the exception.
2. In the late 19th century Louis Pasteur and disease is caused by a microbe
Robert Koch developed the germ theory of dis- specific for that disease. Dr. Koch
ease. This theory postulated that each established four criteria, known as
Koch's Postulates, which are still
used to determine if a disease is
attributable to a particular microor-
ganism.
3. They are: 1. The same pathogen must be
found in all diseased individuals
with the same symptoms.
2. The pathogen must be isolated
from the individual with the disease
and grown in a culture.
3. The same disease must be in-
duced in an experimental ani-
mal by transfer of the cultured
pathogen.
4. After the disease develops, the
same pathogen must be isolated
from the experimental animal.
4. After Pasteur's and Koch's early discoveries, the course of infections included the
search for disease-causing microbes and for creation of vaccines and a greater
ways to combat them intensified. Early attempts understanding of the role of clean-
to stem the liness in the prevention of infection
,5. The first primitive vaccine was developed in pioneered the use of carbolic acid
1796 and was used to prevent smallpox. In the as an antiseptic both on his hands
mid-nineteenth century, Dr. Joseph Lister and as a dressing for wounds to
prevent infection.
6. However, the development of successful treat- antibiotic drug, a sulfonamide, was
ments to cure existing infections had to wait discovered. World War II acceler-
until the first half of the twentieth century. In ated the discovery of other an-
1935, the first effective tibiotics, such as penicillin and
cephalosporins.
7. Continued advances in the treatment of infec- 47 years. By 1950, it had increased
tious diseases have produced enormous bene- to 68 years.
fits. In 1900, the average life span in the United
States was only
8. That gain of 21 years was attributable almost en- substances, vaccines, and antibiot-
tirely to the successful treatment of infections. ic drugs that will combat infection
Research continues to the present day for even more effectively.
9. The native habitat, in which the infective agent 1. symptomatic individuals
lives and multiplies, is called a reservoir. There 2. carriers
are four types of reservoirs: 3. animals
4. water, food, soil, air, fomites (i.e.,
inanimate objects that carry dis-
ease-causing microbes).
10. By definition, infection occurs when there is en- external environment-i.e., the skin,
try and multiplication of a microorganism or conjunctiva, or mucous mem-
parasite in the body of a host. Entry usually oc- branes of the respiratory or uro-
curs through the parts of the body in contact genital tract. Microbes can be in-
with the haled, ingested, or injected into the
body.
,11. The infective organism can be acquired from microbe through a bite, but it can
another individual, an object, or from a vector. refer to any creature that transports
A vector is usually an insect that injects the the infective organism to the host.
12. A human host that is immunocompetent (i.e., cellular system (composed of
one whose immune system is functioning prop- macrophages, natural killer cells,
erly) has a variety of defenses against microbes, T-lymphocytes) and humoral sys-
from the cilia in the respiratory tract to the com- tem (composed of antibodies/im-
plex reactions of the immune system, i.e., the munoglobulins). Only if the de-
fense systems fail can microbes in-
vade the tissues of the host.
13. Infectious disease is a complex process. The mi- 1. Viruses must enter host cells in
crobes must invade, infect, and disrupt the cells order to reproduce.
of the host for disease to occur. For example: 2. Viruses often inhibit the immune
system.
3. Many bacteria produce toxins
that damage host cells.
4. Many diseases are caused by
pathogens growing in normally
sterile tissue.
5. The inflammatory response trig-
gered by the immune system com-
bating the disease is often respon-
sible for the signs and symptoms of
the disease.
14. A variety of different methods are used to directly or indirectly, the existence
identify the organisms causing an infection. All of the disease-causing bacteria,
demonstrate, either viruses, fungi, or parasites in the
body of the infected individual.
, 15. Direct detection methods use the microscope easier to see. There are many dif-
to view the microbe obtained in a tissue, body ferent stains and staining tech-
fluid, or excreta sample. Various stains are used niques. Two commonly used exam-
to make the organism ples are Gram stain and acid fast
stain.
16. Gram stain is used to differentiate between bac- thinner cell walls surrounded by
teria that have relatively thick cell walls and take an outer membrane that does not
up the stain readily (Gram-positive) and those stain (Gram-negative). Examples of
that have Gram-positive bacteria are strepto-
cocci and staphylococci.
17. Pseudomonas and E. coli are examples of staining dye even after be-
Gram-negative bacteria. Another staining tech- ing washed in an acid solvent,
nique uses acid-fast stain. This is used to identify i.e., acid-fast bacteria. Acid-fast
organisms that retain the stain helps identify Mycobacterium
species that cause tuberculosis and
leprosy.
18. Sometimes it is necessary to grow the microbe a gelatin-like medium, is used to
on an artificial culture medium in order to obtain culture bacteria since bacteria do
enough of the organism to identify it. Agar, not use it for food.
19. Culturing viruses requires using a medium of liv- sensitive to infection with the sus-
ing cells since viruses cannot replicate in vitro. A pected virus is used as the culture
single cell layer of living mammalian cells which medium. (Monkey kidney cells and
are chicken embryos are examples of
the cells used.)
20. Beside identifying the virus or bacterium, an- test the eflcacy of specific antibi-
other use of cultured microorganisms is to use otics, i.e. to test the microbe's sen-
them to sitivity to the drug.
ACTUAL Questions and CORRECT Answers
1. Infections and infectious diseases have had a globe, killing uncounted millions,
major effect on humanity throughout the entire and fatal infections caused by rel-
history of our species. Until the 20th century, atively minor wounds and primitive
epidemics raged unchecked across the medical techniques were the norm
rather than the exception.
2. In the late 19th century Louis Pasteur and disease is caused by a microbe
Robert Koch developed the germ theory of dis- specific for that disease. Dr. Koch
ease. This theory postulated that each established four criteria, known as
Koch's Postulates, which are still
used to determine if a disease is
attributable to a particular microor-
ganism.
3. They are: 1. The same pathogen must be
found in all diseased individuals
with the same symptoms.
2. The pathogen must be isolated
from the individual with the disease
and grown in a culture.
3. The same disease must be in-
duced in an experimental ani-
mal by transfer of the cultured
pathogen.
4. After the disease develops, the
same pathogen must be isolated
from the experimental animal.
4. After Pasteur's and Koch's early discoveries, the course of infections included the
search for disease-causing microbes and for creation of vaccines and a greater
ways to combat them intensified. Early attempts understanding of the role of clean-
to stem the liness in the prevention of infection
,5. The first primitive vaccine was developed in pioneered the use of carbolic acid
1796 and was used to prevent smallpox. In the as an antiseptic both on his hands
mid-nineteenth century, Dr. Joseph Lister and as a dressing for wounds to
prevent infection.
6. However, the development of successful treat- antibiotic drug, a sulfonamide, was
ments to cure existing infections had to wait discovered. World War II acceler-
until the first half of the twentieth century. In ated the discovery of other an-
1935, the first effective tibiotics, such as penicillin and
cephalosporins.
7. Continued advances in the treatment of infec- 47 years. By 1950, it had increased
tious diseases have produced enormous bene- to 68 years.
fits. In 1900, the average life span in the United
States was only
8. That gain of 21 years was attributable almost en- substances, vaccines, and antibiot-
tirely to the successful treatment of infections. ic drugs that will combat infection
Research continues to the present day for even more effectively.
9. The native habitat, in which the infective agent 1. symptomatic individuals
lives and multiplies, is called a reservoir. There 2. carriers
are four types of reservoirs: 3. animals
4. water, food, soil, air, fomites (i.e.,
inanimate objects that carry dis-
ease-causing microbes).
10. By definition, infection occurs when there is en- external environment-i.e., the skin,
try and multiplication of a microorganism or conjunctiva, or mucous mem-
parasite in the body of a host. Entry usually oc- branes of the respiratory or uro-
curs through the parts of the body in contact genital tract. Microbes can be in-
with the haled, ingested, or injected into the
body.
,11. The infective organism can be acquired from microbe through a bite, but it can
another individual, an object, or from a vector. refer to any creature that transports
A vector is usually an insect that injects the the infective organism to the host.
12. A human host that is immunocompetent (i.e., cellular system (composed of
one whose immune system is functioning prop- macrophages, natural killer cells,
erly) has a variety of defenses against microbes, T-lymphocytes) and humoral sys-
from the cilia in the respiratory tract to the com- tem (composed of antibodies/im-
plex reactions of the immune system, i.e., the munoglobulins). Only if the de-
fense systems fail can microbes in-
vade the tissues of the host.
13. Infectious disease is a complex process. The mi- 1. Viruses must enter host cells in
crobes must invade, infect, and disrupt the cells order to reproduce.
of the host for disease to occur. For example: 2. Viruses often inhibit the immune
system.
3. Many bacteria produce toxins
that damage host cells.
4. Many diseases are caused by
pathogens growing in normally
sterile tissue.
5. The inflammatory response trig-
gered by the immune system com-
bating the disease is often respon-
sible for the signs and symptoms of
the disease.
14. A variety of different methods are used to directly or indirectly, the existence
identify the organisms causing an infection. All of the disease-causing bacteria,
demonstrate, either viruses, fungi, or parasites in the
body of the infected individual.
, 15. Direct detection methods use the microscope easier to see. There are many dif-
to view the microbe obtained in a tissue, body ferent stains and staining tech-
fluid, or excreta sample. Various stains are used niques. Two commonly used exam-
to make the organism ples are Gram stain and acid fast
stain.
16. Gram stain is used to differentiate between bac- thinner cell walls surrounded by
teria that have relatively thick cell walls and take an outer membrane that does not
up the stain readily (Gram-positive) and those stain (Gram-negative). Examples of
that have Gram-positive bacteria are strepto-
cocci and staphylococci.
17. Pseudomonas and E. coli are examples of staining dye even after be-
Gram-negative bacteria. Another staining tech- ing washed in an acid solvent,
nique uses acid-fast stain. This is used to identify i.e., acid-fast bacteria. Acid-fast
organisms that retain the stain helps identify Mycobacterium
species that cause tuberculosis and
leprosy.
18. Sometimes it is necessary to grow the microbe a gelatin-like medium, is used to
on an artificial culture medium in order to obtain culture bacteria since bacteria do
enough of the organism to identify it. Agar, not use it for food.
19. Culturing viruses requires using a medium of liv- sensitive to infection with the sus-
ing cells since viruses cannot replicate in vitro. A pected virus is used as the culture
single cell layer of living mammalian cells which medium. (Monkey kidney cells and
are chicken embryos are examples of
the cells used.)
20. Beside identifying the virus or bacterium, an- test the eflcacy of specific antibi-
other use of cultured microorganisms is to use otics, i.e. to test the microbe's sen-
them to sitivity to the drug.
