CHAPTER 10

What are the main types of symbioses between microbes and human hosts?

Mutualism, commensalism, and parasitism.

Where do most microbes in the human body reside?

In the gastrointestinal tract, particularly the large intestine.

Which microbes are commonly found on the skin and in the nasal passages?

Staphylococcus.

Where is Escherichia primarily found in the human body?

In the gastrointestinal tract.

What type of relationship do resident microbiota have with their human host?

Primarily mutualistic or commensalistic.

What benefits do resident microbiota provide to the host?

Competing with pathogens, aiding in digestion, and producing essential vitamins.

What factors can prevent transient microbiota from permanently colonizing?

Competition from resident microbiota, elimination by the host's immune system, and changes in environmental conditions.

How do infants acquire their normal microbiota at birth?

Through contact with the mother's vaginal and fecal microbiota during vaginal delivery or from the environment and skin microbiota during C-section.

What factors influence the composition of normal microbiota throughout life?

Diet, age, geographical location, hygiene practices, antibiotic use, stress, hormonal changes, and exposure to environmental microbes.

What conditions provide opportunities for pathogens to infect humans?

Immunosuppression, breaches in physical barriers, changes in normal microbiota, malnutrition, stress, and exposure to virulent pathogens.

What are the three main reservoirs for pathogens?

Humans, animals (zoonoses), and non-living environments (e.g., soil, water).

What is the primary reservoir for HIV?

Humans.

What is the primary reservoir for Lyme disease?

Small mammals (especially mice) and deer.

What is the term for individuals who can transmit a pathogen without showing symptoms?

Asymptomatic human carriers.

What are the three main portals of entry for pathogens?

Skin, mucous membranes, and the parenteral route.

What is the most common portal of entry for human pathogens?

The respiratory tract.

What are attachment proteins also known as?

Adhesins.

What does morbidity refer to?

The incidence of disease in a population.

What does mortality refer to?

The incidence of death in a population.

What is contamination in the context of microbes?

The mere presence of microbes in or on the body or an inanimate object.

What is the definition of infection?

When microbes overcome the host's defenses, multiply, and cause damage to tissues.

What is pathogenicity?

The ability of a microorganism to cause disease.

What do Koch's Postulates establish?

A causal relationship between a microbe and a specific disease.

What is the first criterion of Koch's Postulates?

The microorganism must be found in abundance in all organisms suffering from the disease.

What are some difficulties in establishing the etiology of disease?

Some pathogens cannot be cultured, some diseases are caused by multiple pathogens, and asymptomatic carriers exist.

What are five key virulence factors?

Adhesins, exoenzymes, toxins, antiphagocytic factors, and mechanisms for evading the immune system.

What does hyaluronidase do?

Breaks down hyaluronic acid, allowing pathogens to spread through tissues.

What are exotoxins?

Proteins secreted by living bacteria that are highly toxic and specific in their effect.

What primary effects do endotoxins produce?

General systemic physiological effects such as fever and inflammation.

What is the function of bacterial capsules?

Prevent phagocytes from adhering and engulfing the bacteria.

What is the difference between signs and symptoms in disease?

Signs are objective manifestations, while symptoms are subjective characteristics felt by the patient.

Name the five stages of infectious disease.

Incubation period, prodromal period, illness, decline, and convalescence.

What is direct disease transmission?

Immediate physical contact between an infected host and a susceptible host.

How does contact transmission differ from vehicle transmission?

Contact transmission involves direct or indirect physical contact, while vehicle transmission occurs via inanimate reservoirs.

What distinguishes biological vectors from mechanical vectors?

Biological vectors transmit pathogens and serve as hosts for their multiplication, while mechanical vectors carry pathogens without being infected.

What is the vector for malaria?

The mosquito.

What defines nosocomial infections?

Infections acquired by patients during a stay in a hospital or healthcare facility.

What is the most effective way to minimize nosocomial infections?

Proper hand hygiene.