Chp 15 Worksheet Flashcards
Communicable disease
A disease that can be transmitted from one person to another (e.g., influenza, tuberculosis).
Noncommunicable disease. Ex.s?
A disease that cannot be transmitted from one person to another (e.g., acne, diabetes).
Contagious disease. Ex.s?
A communicable disease that is easily spread from one person to another (e.g., chickenpox, measles).
Examples of communicable diseases.
Influenza, tuberculosis, herpes.
Examples of noncommunicable diseases
Acne, diabetes, heart disease.
Examples of contagious diseases
Chickenpox, measles, COVID-19.
Portal of entry
The site through which a pathogen enters the host (e.g., skin, mucous membranes, respiratory tract).
Portal of exit
The site through which a pathogen leaves the host (e.g., respiratory secretions, blood, feces).
Parenteral route
The entry of pathogens through breaks in the skin or mucous membranes, such as wounds, insect bites, or needle pricks.
Infection
The colonization and multiplication of a pathogen in or on a host.
Disease
The damage or impairment of the host’s normal functions as a result of the infection.
Symptom
Subjective characteristics of a disease felt only by the patient (e.g., pain, nausea, fatigue).
Sign
Objective manifestations of a disease that can be observed or measured by others (e.g., swelling, fever, rash).
Resident microbiota
Microorganisms that constantly live on or in the body and are typically harmless or beneficial.
Transient microbiota
Microorganisms that temporarily colonize the body but do not establish long-term residence; often includes pathogens.
Steps in pathogenesis
- Exposure/contact, 2. Adhesion, 3. Invasion, 4. Infection.
Koch’s Postulate 1
The suspected pathogen must be found in every case of the disease and not in healthy individuals.
Koch’s Postulate 2
The suspected pathogen must be isolated and grown in pure culture.
Koch’s Postulate 3
The cultured/suspected pathogen must cause the same disease when inoculated into a healthy host.
Koch’s Postulate 4
The pathogen must be re-isolated from the inoculated host and be identical to the original pathogen.
Purpose of Koch’s Postulates
To establish a causal relationship between a specific pathogen and a specific disease.
Limitations of Koch’s Postulates
Some pathogens cannot be grown in pure culture (e.g., viruses, certain bacteria); some diseases are caused by multiple pathogens or factors; ethical concerns prevent the use of human hosts for testing.
ID50 (Infectious Dose 50)
The number of pathogen cells or virions required to cause infection in 50% of exposed hosts.
LD50 (Lethal Dose 50)
The number of pathogen cells or virions required to kill 50% of exposed hosts.
How ID50 and LD50 are determined
Using animal models.
Benefits of virulence factors
Help microbes adhere to host cells, invade host tissues, evade the host immune system, and cause damage to the host.
Importance of adhesion in infection
Adhesion allows pathogens to attach to host cells, which is the first step in colonization and infection.
Hyaluronidase
Breaks down hyaluronic acid in connective tissue, allowing pathogens to spread.
Collagenase
Breaks down collagen in connective tissue, facilitating tissue invasion.
Exotoxin
Secreted toxins that cause damage to host cells.
Cytotoxin
A type of exotoxin that kills host cells.
Neurotoxin
A type of exotoxin that disrupts nerve function.
Enterotoxin
A type of exotoxin that affects the intestines, causing diarrhea.
Endotoxin
Not secreted; part of the outer membrane of Gram-negative bacteria, causing inflammation and fever.
Lipopolysaccharide (LPS)
A type of endotoxin that triggers a strong immune response.
Steps in AB toxin activity
- The B subunit binds to host cell receptors. 2. The toxin is internalized by the host cell. 3. The A subunit is released and exerts its toxic effect (e.g., disrupting protein synthesis or cell signaling).
Steps in botulinum toxin activity
- The toxin binds to nerve cells at the neuromuscular junction. 2. It is internalized into the nerve cell. 3. The toxin blocks the release of acetylcholine, preventing muscle contraction and causing paralysis.
Five stages of infectious disease
- Incubation period, 2. Prodromal period, 3. Illness, 4. Decline, 5. Convalescence.
Incubation period
Time between infection and the appearance of symptoms.
Prodromal period
Early, mild symptoms appear.
Illness
Disease is most severe, with clear signs and symptoms.
Decline
Symptoms begin to subside as the immune system responds.
Convalescence
The body returns to its pre-diseased state.
Four ways virulence factors promote infection
- Adhesion, 2. Invasion, 3. Immune evasion, 4. Toxin production.
How capsules act as virulence factors
Capsules protect pathogens from phagocytosis by the host immune system, allowing them to evade detection and destruction.
Antigenic variation
The ability of a pathogen to alter its surface proteins, allowing it to evade the host immune system.
Antigenic variation in Neisseria
Neisseria (e.g.,Neisseria gonorrhoeae) can change the expression of its surface proteins (pili and outer membrane proteins) through genetic recombination, allowing it to evade the immune system.
Antigenic drift
Small, gradual changes in viral surface proteins due to mutations.
Antigenic shift
Sudden, major changes in viral surface proteins due to reassortment of genetic material between different viral strains.
Why influenza viruses are prone to antigenic shift
Influenza viruses have segmented genomes, which allows for the exchange of genetic material between different strains, leading to major changes in surface proteins.
Why influenza A is more prone to antigenic shift than influenza B
Influenza A infects a wider range of hosts (including humans, birds, and pigs), increasing the chances of genetic reassortment. Influenza B primarily infects humans and is less prone to shift.
Local infection
Infection that is a small area of the body, usually around the portal of entry.
Focal infection.
A localized infection spreads to a confined secondary location.
Systemic infection.
Infection that affects the entire body.
Primary and secondary infections.
One pathogen infects first and causes an infection which makes the individual more susceptible to infection by another subsequent pathogen.
Are all infections communicable?
No; sometimes humans are a ‘dead end’ host.
