Chapter 11: Interactions Between Microbes and Humans

Vocabulary practice flashcards covering the human microbiome, bacterial pathogenesis, disease stages, transmission types, epidemiology, and healthcare-associated infections from Chapter 11.

Human Microbiome (Normal Flora)

The sum total of all microbes living in and on a human being.

Microbial Antagonism

The ability of non-pathogenic microbes to keep potentially dangerous pathogens in check by competing with them for resources and space.

Colonized Bacteria

Microbes that live permanently in or on a host for long periods of time, such as permanent staphylococci strains living on normal human skin.

Transient Bacteria

Microbes that interact with the body in a quick, non-permanent way, often picked up from the environment and quickly lost or washed away.

Infectious Disease

Any condition caused by a microbe where normal structures or functions of the body are damaged or impaired.

True Pathogens

Organisms that can cause disease in healthy individuals a high percentage of the time.

Opportunistic Pathogens

Organisms of generally low virulence that only cause infection when a person is immunocompromised or when there is a disruption in the microbiome.

Pathogenicity

An organism's general ability to cause disease (yes or no).

Infectivity

How easily an organism can spread and cause disease.

Virulence

How severe or serious the disease is that an organism causes.

Exogenous Pathogen

A pathogen originating from outside the body, such as one inhaled from someone else's cough.

Endogenous Pathogen

A pathogen already existing inside the body (from the normal flora) that shifts to cause harm, such as gut bacteria entering the urinary tract to cause a UTI.

Infectious Dose (ID)

The number of organisms that must gain entry into a host to cause disease.

Adhesion

The process by which microbes firmly establish themselves in or on the host using structures like capsules or fimbriae to prevent being washed away.

The Trojan Horse Strategy

An evasion mechanism in which certain bacteria survive inside white blood cells after being engulfed, utilizing the immune cell as a hideout.

Direct Damage

Tissue harm caused directly by microbial enzymes or toxins, such as tetanus neurotoxin over-activating motor neurons.

Indirect Damage

Harm caused by the host's own overreacting immune response to an infection rather than by the microbe alone.

Sign of Disease

A measurable and observable change in the body evaluated by a healthcare provider or observer.

Symptoms of Disease

Subjective feelings experienced by the patient that cannot be directly observed or measured by others.

Syndrome

A specific group of signs and symptoms that consistently accompany a particular disease, helping clinicians identify what is wrong.

Incubation Period

The time from initial contact with a pathogen to the appearance of first symptoms, during which the patient feels normal while the microbe multiplies.

Prodromal Period

A short period of $1$ to $2\text{ days}$ characterized by general, non-specific symptoms such as feeling tired or achy.

Acute Phase

The height of an infection where symptoms are most severe and specific to the particular disease.

Convalescent Period

The period where the immune system or medicine begins taking over, symptoms decline, and the patient regains strength, but remains most susceptible to a secondary infection.

Continuation Period

A stage involving long-term or permanent damage where the disease never truly goes away entirely, which does not happen with every infection.

Reservoir

The primary natural habitat of a potential pathogen where it lives and multiplies, classified as either living or non-living.

Carrier State

A situation where a pathogen lives as part of a human's microbiome without causing that specific host harm, but can still be passed on to others.

Direct Transmission

Microbial spread from one host to another via touching, kissing, or direct droplet contact from sneezing.

Indirect Transmission

Microbial spread occurring through contact with contaminated inanimate surfaces (fomites like doorknobs) or consumption of contaminated food.

Vector-borne Transmission

Transmission of an infectious agent involving an insect or animal vector, such as mosquitoes transmitting malaria.

Communicable Disease

A disease that can easily transition from one host to another.

Non-communicable Disease

A disease that does not spread easily from person to person, usually picked up from the environment or non-living sources.

Healthcare-Associated Infection (HAI)

An infectious disease acquired as a direct result of a stay in a hospital or healthcare facility.

Epidemiology

The study of the frequency and distribution of disease within populations.

Reproductive Rate ($R$)

The rate at which a microbe spreads through a population.

Herd Immunity

A condition occurring when a significant portion of a population becomes immune to a disease, thereby protecting vulnerable, non-immune individuals.

Clostridioides difficile (C. diff)

A major HAI strongly associated with long-term broad-spectrum antibiotic use that wipes out protective gut flora, leading to severe bowel inflammation and watery diarrhea that can cause bowel perforation.

Fecal Microbiota Transplants (FMT)

A unique treatment utilized to restore healthy gut microbiome competition in patients suffering from Clostridioides difficile infections.