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129 Cards in this Set

  • Front
  • Back
What is infection the result of?
the result of an interaction between an organism and a host
What types of organisms can cause infection?
– Viruses
– Bacteria
– Fungi
– Protozoa
– Helminths (worms)
What two types of infectious organisms are parasites?
Protozoa and Helminths
What are a few examples of infectious diseases?
– Cholera (bacteria)
– Malaria (protozoa)
– Tuberculosis (bacteria)
– Leprosy (bacteria)
-- The Smallpox Virus
What is the only infection that has been eradicated world wide by vaccination (was declared eradicated in 1980)?
What virus is smallpox caused by?
The variola virus.
What are the symptoms of smallpox?
• Two weeks after infection: high fever and flu-like symptoms
• Within 4 more days the smallpox rash develops, first as red spots on the tongue and mouth
• The rash spreads to the skin, mostly the face, hands, and feet
• Within 2 weeks the rash starts to form scabs which fall and leave scars
• The rash also appears inside the body
• When in vital organs, it can cause death, mostly through interfering with breathing
• Historically, it is fatal about 30% of the time
Where is death from infectious diseases more common?
Death from infectious diseases is more common in developing countries with dense populations and poor sanitation.
What does the process of prevention and treatment of infectious diseases include in developing countries?
The progress in prevention and treatment of infectious diseases includes:
• Sanitary living conditions
• Clean water
• Uncontaminated food
• Vaccinations
• Antimicrobials (antibiotics)
T/F In the US, infectious diseases other than AIDS are a major cause of death.
false - they are not a major cause of death
How many infections result in hospitalization and death each year in the USA?
An estimated 2 million infections occur in hospitals each year, causing about 90,000 deaths (mainly from pneumonia, influenza, and HIV).
What changes the prevalence of infectious disease?
Vaccines and antimicrobials changed the prevalence of infectious disease.
What are examples of infectious diseases that are hard to control?
– Mutant strains of bacteria that are resistant to antibiotics have emerged
– New diseases have developed, such as:
• The global spread of AIDS
• Legionnaires’ disease
• Hantavirus
• Bird flu
Why does the human body provide an appropriate environment for microorganisms?
The human body provides a hospitable environment for microorganisms, supplying them with the appropriate :
– Nutrients
– Temperature
– Humidity
T/F The human gut is colonized by a large variety of microorganisms that make up the normal human flora
Why is the normal human flora beneficial?
– They produce enzymes that facilitate digestion of complex molecules
– They fight and prevent colonization by harmful microorganisms
T/F The flora is kept outside the body’s tissues by the intact skin and mucosal epithelium.
True - Otherwise, the immune system would attack them
How many possible relationships can exist between humans and organisms?
What are the five relationships that can exist between humans and organisms?
Mutualism, Symbiosis, Commensalism, Opportunism, and Pathogenicity.
What kind of relationship between a human and organism benefits both the human and the organism?
What type of relationship between a human and organism benefits the human, does not harm the organism?
What type of relationship between a human and organism benefits the organism, does not harm the human?
What type of relationship between a human and organism occurs when a benign organism becomes pathogenic due to immunodeficiency of the human?
What type of relationship between a human and organism benefits the organism but harmful to the human?
How many pathogenic organisms enter the body?
Pathogenic organisms may enter the body through:
– Direct contact (wound)
– Inhalation
– Ingestion
– Animal or insect bites
How is an infection able to spread?
The infection is spread by the ability of the pathogen to:
– Attach to cell surface
– Release enzymes that dissolve protective barriers
– Escape the action of phagocytes
– Resist the effect of low pH
One a microorganism penetrates the body's first line of defense, what response is initiated?
Once a microorganism penetrated the first line of defense and invaded the tissues, the inflammatory response is initiated
In the inflammatory response, what kills the microorganism?
In the inflammatory response, neutrophils and later macrophages, phagocytose (attack, engulf, and destroy) the microorganism
What response follows the inflammatory response?
The immune response.
What cells produce antibodies against both organisms and their toxins?
What attack the microorganisms directly or by recruiting macrophages?
T/F Many pathogens have devised ways of preventing destruction by the immune system.
T/F Bacterial and viral pathogens use the same mechanisms to prevent destruction by the immune system.
False - they use different mechanisms.
Bacteria are small (eukaryotes/prokaryotes).
Are bacteria aerobic or anaerobic?
Are bacteria motile or immotile?
What are the three shapes that bacteria can be?
Spherical (cocci), Rod-like (spirochete), and spiral (vibrio, spirillum, spirochete).
Are bacteria gram negative or gram positive?
What is the name of the dye used to determine whether a bacteria is gram negative or positive?
Crystal Violet (gentian)
What color to gram positive bacteria turn under the gram stain?
Gram-positive organisms stain purple-black (thicker wall)
What color to gram negative bacteria turn under the gram stain?
pink because of the endotoxins
What are examples of gram positive bacteria?
Staphylococci ("staph"),
streptococci ("strep")
What are examples of gram negative bacteria?
Gonococci (venereal disease),
meningococci (bacterial meningitis)
What are the three bacterial survival mechanisms?
Rapid proliferation, Protective coating, and some gram negative bacteria produce toxins that injure cells (endotoxins).
What kind of survival mechanism of bacteria is the following: some bacteria proliferate faster than the immune system can respond (~ 1 week)
For example, some bacteria can produce pneumonia that may kill an individual within 2 days
Rapid proliferation
What kind of survival mechanism of bacteria is the following: some bacteria have a coating that protects them from being phagocytosed
a. Thick covering made from polysaccharides or proteins
b. Waxy capsule
Protective coating
What kind of bacterial survival mechanism is the following: – Contained in the cell walls of Gram-negative bacteria
– Are released during destruction of the bacteria
– Can cause anaphylactic shock because they:
• Activate the inflammatory response
• Increase vasodilation and vascular permeability, which may result in decreased blood volume, hypotension, and shock
– Other actions of endotoxins:
• Produce fever (pyrogenic bacteria)
• Some bacteria (group A streptococci) produce toxins that are destructive to the skin (flesh-eating bacteria)
Endotoxins produced by gram negative bacteria
What kind of microorganism has the following characteristics?:

– Intracellular parasites
– They take over the metabolic machinery (protein production) of host cells and use it for their own survival and replication
• The infected cell is usually destroyed
– Have no metabolic organelles and thus have no metabolism
– Do not produce toxins
What kind of infection has the following characteristics:

– More common in humans than bacterial infection
– Ranges in severity from the common cold to cancer and AIDS
Viral Infection
How do viruses resist phagocytosis?
viruses resist phagocytosis because of their extremely small size
How do viruses bypass defense mechanisms?
Viruses bypass many defense mechanism by developing intracellularly, thus they hide within tissues and away from normal inflammatory and/or immune responses
T/F Viruses spread from cell to cell.
T/F Most of the time the antibody response cures the infection (neutralizes the virus) so the viral disease is self-limiting.
Are viruses capable of independent reproduction?
No, Their replication depends totally on the host cell.
How many cycles does the replication of viruses have?
What is the first cycle of replication of viruses?
Absorption - – Infection begins with a virus binding to specific receptors on the plasma membrane of host cells
– A particular virus will infect only host cells that have receptors for it
Example: the influenza virus binds to receptors on epithelial cells of the respiratory tract and causes symptoms of upper respiratory tract infection
What is the second cycle of replication of viruses?
Penetration – Once the virus binds to the receptor it will weaken the the plasma membrane and penetrate the cell
What is the third cycle of replication of viruses?
Uncoating – Viruses contain their genetic material in a form of DNA or RNA
– The genetic material is protected by a protein coat
– Uncoating is the removal of the coat
– Uncoating must happen (in the cytoplasm of the host cell) before the virus can replicate
What is the fourth cycle of replication of viruses?
Replication – Viruses make multiple copies of their genetic material
• DNA viruses: replicate in the host’s nucleus
• RNA viruses (except influenza and retroviruses): replicate
in the cytoplasm of the infected cells
• Retroviruses: convert their RNA to DNA and then replicate
in the nucleus (like HIV)
What is the fifth cycle of replication of viruses?
Assembly (maturation) – After copying its genetic material, the virus uses the host cell’s
organelles to make its own proteins
– New viruses are assembled in the host cell’s cytoplasm
What is the sixth cycle of replication of viruses?
Release – The new viruses are released from the cell for transmission of the
viral infection to other host cells
– Frequently the host cell is destroyed during the release of the new viruses
T/F Some viruses integrate their DNA into the host cell’s DNA, which passes the virus to all its daughter cells.
What kind of viruses stay dormant (latent) in the host cell’s DNA until it enter its reproductive cycle, usually due to a stimulus such as stress, hormonal changes, or disease?
Viruses that integrate their DNA into the host cell’s DNA, which passes the virus to all its daughter cells.
What are the harmful effects of viruses inside host cells?
1. Causing the host cell to stops its own protein synthesis
2. Destroying the plasma membrane of host cells when released in large quantities
3. Expressing viral antigens (on the host cell’s plasma membrane) that identify the host cell as foreign and cause the immune system to attack it (such as with hepatitis B)
4. Transforming the host cell into cancerous cell, resulting in uninhibited growth (cervical cancer)
5. Promoting secondary bacterial infection of the host cells damaged by the virus (pneumonia)
What are relatively large organisms with thick walls made of polysaccharides?
What are the two ways in which fungi grow?
1. Single-celled yeast (aerobic) or
2. Multi-celled molds (anaerobic)
What kind of fungi can exist in either single celled or multi-celled form?
Dimorhphic fungi
T/F Fungi are motile.
False - they are not motile.
How to fungi reproduce?
Simple division or budding.
What are diseases caused by fungi called?
Where do most pathogenic fungi grow?
Most pathogenic fungi grow on (or near) the skin or mucous membranes.
How severe of a disease to fungi generally cause?
Mild or superficial
Fungi that invade the skin (or hair or nails) are called what?
What are the diseases the fungi case on the skin (or hair or nails) called?
tineas (ringworm)
What is a common symptom of fungal infections?
Itching is intense and cracking of the tissue can lead to secondary bacterial infection.
T/F Deep fungal infections involving internal organs can be life threatening and are most common as opportunistic infection.
T/F Fungi causing superficial infection enter the body through either inhalation or open wounds
False - Fungi causing deep infection enter the body through either inhalation or open wounds.
T/F There is no fungi that are part of the normal body's flora.
False - there are some fungi that are part of the body's flora.
T/F In pH or use of antibiotics (that kill the “good” bacteria, which inhibit candida growth) permit rapid proliferation of candida, leading to yeast infections (either superficial or deep infections).
What kind of fungi release toxins that are damaging to connective tissue?
pathogenic fungi
How are fungi diagnosed?
Microscopic observation.
What are important in fighting fungal infection?
Phagocyctes and T-Lymphocytes.
What vaccines are available to treat fungal infections?
T/F The anti-fungal drugs used to treat deep systemic infection are good for the host.
False - they are harmful to the host.
What are the clinical manifestations of infection?
– Fever (the hallmark of most infectious diseases)
– Fatigue
– Malaise
– Weakness
– Aching
– Loss of concentration
– Loss of appetite
What are innate countermeasures against infection?
The body’s own response against pathogens. The most potent innate response is granuloma, isolating the infection and preventing its spread.
What type of countermeasure against infection has the following characteristics?
- destroy the pathogen once the disease process has started
• Destroy the pathogen once the disease process has started
• Mostly against bacteria
– Act by preventing the function of enzymes or cellular structures unique to the specific bacteria
• There are not many successful antiviral antimicrobials because viruses use the metabolism and enzymes of the host cells
Antimicrobials (antibiotics)
What type of countermeasure against infection have the following characteristics?
prevent the pathogen from initiating disease
• Induce immune responses under conditions that will not result in disease
– Some individuals cannot produce a protective immune response and will be susceptible to getting full blown infection from the vaccine
– The immune response from vaccination is generally short-lived so booster shots are needed at times to produce large numbers of memory cells and protective antibodies
What type of countermeasure against infection has the following characteristics:
– Contain live but weakened (attenuated) viruses
– Express antigens but are not strong enough to cause infection (unless the immune system is compromised)
– Flu vaccines must be given every year because the new virus is very distinct from the previous years’ strains
Viral vaccines
What kind of countermeasure against infection has the following characteristics?
– Contain killed bacteria or extracts of bacterial antigens
– Vaccines against toxins contain toxoids (detoxified toxins that still express the antigens)
– Diphtheria, cholera, and tetanus are examples of organisms that do not enter the body but produce toxins that result in life threatening diseases
Bacterial vaccines
T/F Microorganisms make mechanisms to fight against the immune system.
What disease/virus has the following characteristics:
– A virus that directly attacks the immune system, destroying T-cytotoxic and T-helper cells
– Thus, the virus suppresses the immune response against itself
– Secondarily, it suppresses immune responses against other pathogens and opportunistic organisms
What kind of pathogenic adaptation has the following characteristic:
– Some bacteria have done this and developed resistance against particular antibiotics
• These mechansisms usually produce enzymes that breaks down the structure of the drug, penicillin for example
– In the last decade, multiple antibiotic-resistant bacteria that develop resistance to almost all currently available antibiotics, have appeared
• The streptococcus which causes pneumonia, meningitis, and ear infection is now penicillin resistant in 30% of the population
– Also drug-resistant gonorrhea, malaria, salmonella, and staphylococcus infections have increased
T/F Multiple-drug-resistant organisms appeared because of overuse of antibiotics.
T/F Overuse of antibiotics can lead to destruction of the normal flora, allowing the selective overgrowth of the drug-resistant strains of pathogens that were previously kept under control by the normal flora.
T/F Individuals commonly do not comply with instructions to complete the 10 days of antibiotics, which allows the selective resurgence of more resistant organisms.
Immunodeficiency is a result of impaired function of what components?
– B lymphocytes
– T lymphocytes
– Phagocytes
– Complement
What is the main cause of immunodeficiency?
The main cause is disruption of lymphocyte function.
What is a clinical hallmark of immunodeficiency?
The clinical hallmark of immunodeficiencies is a tendency to develop severe infections, either unusual or recurrent.
How many infections to pre-school aged children have on average per year?
6-12 infections.
How many infections to adults have per year on average?
2-4 infections.
• If an individual has severe and frequent bouts of pneumonia, otitis media, sinusitis, bronchitis, meningitis, or opportunistic infections they are suspect of having what?
What type of immunodeficiency is characterized by the following:
Caused by a genetic anomaly
– Develops before birth
– May be related to genetic disorders
– The dysfunction may be due to:
• Impaired lymphocytes development (T, B, or both)
• Impaired lymphocyte maturation due to dysfunction in lymphoid organs (thymus, bone marrow)
– Symptoms include repeated infections, chronic diarrhea, pneumonia, skin rashes and failure to thrive.
Congenital (primary) immunodeficiency
What type of immunodeficiency is characterized by the following:
Caused by aging (normal changes) or by illness (such as cancer or viral infection)
• Develop after birth, not related to genetic disord
Acquired (secondary) immunodeficiency
What are the two types of immunodeficiencies?
Congenital and Acquired
What conditions are associated with secondary or acquired immunodeficiencies?
1. Pregnancy
2. Infancy
3. Aging
4. Down syndrome
5. Infections (rubella, CMV, measles, leprosy, tuberculosis, etc.)
6. Malignancies (Hodgkins disease, leukemia, myeloma, etc.)
7. Nutritional deficiencies (protein, zinc, vitamins, starvation)
8. Stress (surgical or emotional trauma)
T/F Periods of major stress (loss of loved ones) and minor stress (final exams) may be associated with infections and malignancies.
There are connections between the immune system and the what two other systems? The connections are characterized by the following:
• Many lymphoid organs are innervated and thus are affected by nerve stimulation
• Lymphocytes have receptors for various stress hormones and neurotransmitters and thus are affected by these chemicals.
Nervous and Hormonal systems.
What kind of trauma can cause an immunodeficiency?
Burn victims are associated with decreased what?
1. Neutrophil function
2. Complement plasma protein levels
3. Cell-mediated immunity
4. Primary humoral response (secondary humeral responses are normal)
What are a few examples of iatrogenic conditions causing immunodeficiencies?
– Drugs used in chemotherapy suppress blood cell formation in the bone marrow
– Radiation suppresses fast proliferating cells (T & B)
– Other drugs such as analgesics, anticovulsants, antihitamine, antimicrobials, and tranquilizers may induce responses that destroy mature granulocytes
– Surgery and anesthesia can suppress both T and B cell function causing transient, severe lymphopenia (up to 1 month after surgery)
What diseases can cause immunodeficiencies?
diabetes, cirrhosis, sickle cell anemia
What is AIDS best known as?
The best-known example of acquired dysfunction of the immune system.
What is a viral disease caused by the human immunodeficiency virus (HIV), a retrovirus?
What cells does HIV attack and deplete?
T-helper cells
What do T-helper cells do?
T-helper cells facilitate both cell-mediated and humoral-mediated immune responses and secrete lymphokines that coordinate the immune response.
Why is HIV so life threatening?
HIV infection greatly compromises the immune system, making the infected individual susceptible to life-threatening infections and malignancies. It destroys the T-helper cells.
What is a receptor on the surface of T-helper cells that acts as the primary receptor for HIV?
What lymphocytes does HIV primarily affect?
The virus infects primarily CD4-positive T-helper lymphocytes.
What system also expresses the CD4 receptor and thus can be infected by HIV?
The nervous system
T/F The HIV virus can stay dormant for years.
Once HIV is activated, what does it do to the cells it invades?
Once activated, it proliferates inside the infected cell resulting in lysis and death of these cells.
In 1995 what became the #1 killer of individuals between the ages of 25-44?
How many new HIV infections occur annually?
40,000 new HIV infections occur each year in the United States, about 70 percent among men and 30 percent among women.
What sex is affected the greatest by AIDS?
Men. About 70 percent among men and 30 percent among women.
By 1998, how many healthcare workers had become infected by AIDS?
About 40,000 total.
About how many health care professionals became infected with HIV accidently while working with a patient with AIDS?
At least 54 were infected while caring for patients with HIV (accidentally stuck with a needle).
What should people with recurrent infections undergo?
Individuals with recurrent infections (the most common symptom of immunodeficiency) should undergo blood tests and laboratory evaluation of their immune system.
What is the medical treatment for immunodeficiencies?
– For deficient antibody production: replacement therapy of missing immunoglobulins with commercial γ-globulin preparation
– For lymphocyte deficiencies: transplants of bone marrow and fetal liver or thymus from a donor