BIOL-2420 FLASHCARDS: Exam #3

What are symptoms?

Subjective characteristics of disease felt only by the patient (cannot be measured)

What are some examples of symptoms?

Pain, nausea, fatigue, headache, malaise, etc.

What are signs?

Objective, measurable indicators of disease that can be observed by others

What are some examples of signs?

Fever, swelling, rash, vomiting, anemia, elevated white blood cell count, etc.

What is a syndrome?

A group of signs and symptoms that collectively characterize a specific disease or condition

What is an example of a syndrome?

AIDS - defined by the presence of HIV infection with specific opportunistic infections and decreased CD4 T-cell count

What is meant by an asymptomatic (subclinical) infection?

An infection lacking noticeable symptoms but still showing measurable signs of infection or transmissibility

What is a reservoir of infection?

Any site where a pathogen is maintained as a continual source of infection

What are the three main types of reservoirs?

Animal reservoirs, human carriers, and nonliving reservoirs

Describe animal reservoirs.

Wild or domestic animals that harbor pathogens naturally

Diseases spreading from animals to humans are called…

Zoonoses

What are some examples of zoonoses?

Rabies (dogs/bats), Lyme disease (deer/ticks), and plague (rodents/fleas)

How are zoonoses transmitted?

Direct contact, animal waste, ingestion of infected meat, or bites from arthropod vectors

Describe human carriers.

Infected individuals who harbor pathogens without showing symptoms but can infect others (e.g., Typhoid Mary with Salmonella typhi)

Describe nonliving reservoirs.

Soil, water, or food contaminated by feces or urine that harbor pathogens (e.g., Clostridium tetani spores in soil)

What are exotoxins?

Proteins secreted by living Gram-positive or Gram-negative bacteria that are highly toxic and have specific effects (e.g., neurotoxins, enterotoxins, etc.)

What are endotoxins?

The lipid A portion of lipopolysaccharide (LPS) in Gram-negative bacterial outer membranes, released upon cell death

____________ are highly toxic in small doses.

Exotoxins

____________ are less toxic, but can be fatal in large amounts.

Endotoxins

____________ are heat-labile (destroyed > 60 degrees Celsius).

Exotoxins

____________ are heat-stable, even at autoclave temperatures.

Endotoxins

____________ strongly stimulate antitoxin antibody formation.

Exotoxins

____________ produce weak immunity.

Endotoxins

What are some examples of exotoxins?

Botulinum toxin, tetanus toxin, and cholera toxin

What are some examples of endotoxins?

LPS released by E. coli or Salmonella during infection

What are resident microbiota?

Microbes that are part of the body’s normal flora throughout life and usually cause no harm; mostly commensal

What are transient microbiota?

Microbes that remain in or on the body for a short time, but do not persist

Where can transient microbiota be found?

In the same regions as resident microbiota (skin, mucous membranes, digestive tract, etc.)

Why can’t transient microbiota persist in the body?

They are outcompeted by resident microbes, eliminated by the immune system, or removed by chemical or physical body changes

What is an example of resident microbiota?

Staphylococcus epidermidis on the skin

What is an example of transient microbiota?

Temporary presence of E. coli on the hands after contact with contaminated surfaces

What is a virulence factor?

Any characteristic or structure of a microbe that contributes to its ability to cause disease (pathogenicity)

What are the major categories of virulence factors?

Adhesion factors, biofilms, extracellular enzymes, toxins, and antiphagocytic factors

What do adhesion factors do?

Allow microorganisms to attach to host cells and establish infection; include ligands and adhesins on bacterial/viral surfaces

What are some examples of adhesion factors?

Bacterial fimbriae, viral spikes, and glycocalyces used for attachment

What are biofilms and how do they contribute to virulence?

Organized communities of microbes attached to a surface that resist host defenses and antimicrobial agents (e.g., dental plaque)

What are extracellular enzymes and how do they enhance infection?

Secreted enzymes that dissolve body structures or chemicals, helping pathogens invade and evade defenses

What are some examples of extracellular enzymes?

Hyaluronidase, collagenase, and coagulase

Define toxins as virulence factors.

Chemicals produced by microbes that harm tissues or trigger damaging immune responses

What are antiphagocytic factors?

Substances or structures that prevent phagocytosis by host immune cells, allowing pathogens to survive longer

What are some examples of antiphagocytic factors?

Capsules that prevent recognition/engulfment and leukocidins that destroy white blood cells

What is biological transmission?

The active process in which an arthropod vector transmits pathogens and serves as a host for part of the pathogen’s life cycle

How do biological vectors transmit pathogens?

They bite the host, injecting pathogens during feeding or defecating near a bite wound

What are some examples of biological vectors?

Mosquitoes, ticks, and fleas

Mosquitoes spread…

Malaria (Plasmodium), dengue, and yellow fever

Ticks spread…

Lyme disease (Borrelia burgdorferi) and Rocky Mountain spotted fever (Rickettsia rickettsii)

Fleas spread…

Plague (Yersinia pestis)

What is mechanical transmission?

The passive transport of pathogens by arthropods on their body surfaces to food or hosts

Do mechanical vectors participate in the life cycle of the pathogen?

No - they only carry pathogens on their bodies

What are some examples of mechanical vectors?

Houseflies and cockroaches

Houseflies spread…

Foodborne infections like Salmonella and E. coli

Cockroaches spread…

Shigella and other foodborne bacteria

What are the five stages of infectious disease in order?

1. Incubation period

2. Prodromal period

3. Illness

4. Decline

5. Convalescence

What happens during the incubation period?

This is the time between infection and the appearance of the first signs/symptoms; in this phase, the pathogen is establishing itself, but there are no symptoms yet

What occurs in the prodromal period?

This is a short phase characterized by mild, general symptoms such as malaise, muscle aches, or fatigue

What occurs during the illness phase?

The disease is the most severe during this phase; signs and symptoms are at their peak and the immune system is fully engaged

What occurs during the decline phase?

Symptoms subside as the immune response or treatment reduces pathogen numbers

What occurs during the convalescence phase?

The patient recovers and their tissues are repaired, however the pathogen may still be present and transmissible in some cases

What is an epidemic?

A disease that occurs at a greater frequency than usual in a specific area or population

What is an example of an epidemic?

The Ebola outbreak in West Africa

What is a pandemic?

A worldwide epidemic that occurs on multiple continents simultaneously

What is an example of a pandemic?

The global outbreak of COVID-19

What is a sporadic disease?

A disease that occurs only occasionally and irregularly, without a predictable pattern

What is an example of a sporadic disease?

Tetanus

What is an endemic disease?

A disease that is constantly present in a population or region at a stable rate

What are some examples of endemic diseases?

Malaria in parts of Africa; common cold in the United States

What is an acute disease?

A disease characterized by symptoms that develop rapidly and run their course quickly

What are some examples of acute diseases?

Influenza and strep throat

What is a sub-acute disease?

A disease characterized by symptoms that are between acute and chronic in speed and duration

What is an example of a sub-acute disease?

Bacterial endocarditis

What is a chronic disease?

A disease that develops slowly and lasts long-term, often with milder symptoms

What are some examples of chronic diseases?

Tuberculosis and hepatitis B

What is a latent disease?

A disease that appears long after infection; the pathogen remains inactive for a period of time

What are some examples of latent diseases?

Herpes simplex virus and shingles (Varicella-zoster)

What is a primary infection?

The initial infection caused by a pathogen in a host

What is an example of a primary infection?

A cold caused by rhinovirus

What is a secondary infection?

An infection following a primary infection; often caused by opportunistic pathogens

What is an example of a secondary infection?

Pneumonia after influenza

What is an opportunistic pathogen?

Normal microbiota or environmental microbes that cause disease when the immune system is compromised or when introduced to an unusual site

What is an example of an opportunistic pathogen?

Candida albicans causing yeast infections after antibiotic use

What is a nosocomial infection?

An infection acquired in a healthcare setting, such as a hospital, nursing home, or clinic

What is the most effective way to reduce the spread of nosocomial infections?

Proper and frequent handwashing

What is an exogenous nosocomial infection?

A pathogen that is acquired from the healthcare environment

What is an endogenous nosocomial infection?

A pathogen that develops from the patient’s own microbiota

What is an iatrogenic nosocomial infection?

A pathogen that results from a medical procedure

What is a nosocomial superinfection?

A pathogen that develops when the patient’s normal microbiota is disrupted by antimicrobial therapy

What are some examples of nosocomial infections?

Pseudomonas infections in burn patients, Staphylococcus aureus surgical wound infections, and Clostridium difficile diarrhea following antibiotic use

What type of acquired immunity does vaccination produce?

Artificially acquired immunity (because the body is exposed to antigens through vaccination and actively mounts its own immune response)

How does vaccination work to create immunity?

It introduces antigens from a pathogen (dead, weakened, or a part of the pathogen) to stimulate the body’s adaptive immune system to produce memory cells without causing disease

How is acute immunization different from passive immunotherapy?

Acute immunization (like vaccination) stimulates the body to produce its own antibodies, while passive immunotherapy provides preformed antibodies from another person or animal for immediate but temporary protection

What are the long-term effects of vaccination?

Long-term or even lifelong protection due to the formation of memory B and T cells that quickly respond upon future exposure to the same pathogen

What is herd immunity?

Occurs when a large proportion of a population is immune (usually through vaccination), reducing the overall spread of infection and protecting individuals who are not immune

How does herd immunity protect unvaccinated individuals?

When enough people are immune, chains of infection are interrupted, making it unlikely for an infectious disease to spread

What is an attribute of a population with herd immunity?

Disease prevalence is significantly reduced, and outbreaks are rare or mild because most people are protected

Why is hard immunity important for public health?

It protects vulnerable individuals who cannot be vaccinated (such as infants, elderly, or immunocompromised people)

What is an attenuated (live) vaccine?

It uses pathogens with reduced virulence (weakened forms) that still replicate slightly and stimulate a strong immune response

Attenuated (live) vaccines are composed of…

Modified live microbes

What are some examples of attenuated (live) vaccines?

MMR (measles, mumps, and rubella), Varicella (chickenpox), and Yellow fever

What is a key feature of attenuated (live) vaccines?

They may provide contact immunity (spread to close contacts and immunize them)

What is an inactivated (killed) vaccine?

It contains whole dead microbes or subunit vaccines made from parts of microbes that cannot replicate