Interactions Between Microbes and Humans

This set of vocabulary flashcards covers the fundamental concepts of microbial interactions with humans, including infection stages, virulence factors, disease transmission, and epidemiology metrics.

Infectious Disease

The disruption of a tissue or organ caused by microbes or their products.

Normal Biota (Normal Flora)

Microorganisms that live in or on the human body, forming commensal or mutualistic relationships with their hosts.

Microbial Antagonism

The generally antagonistic effect good microbes have against pathogenic microorganisms by using up nutrients, limiting attachment points, or creating hostile chemical environments.

True Pathogens

Microbes that can cause disease in healthy persons with normal immune defenses, such as Ebola and Influenza.

Opportunistic Pathogens

Microbes that cause disease when host defenses are compromised or when they become established in a part of the body that is not natural.

Virulence

The severity of the disease caused by a microbe, which depends on its ability to establish itself in the host and cause damage.

Virulence Factors

Specific traits such as plasmids, flagella, pili, fimbriae, and toxins that contribute to a microbe's ability to cause disease.

Exogenous Microbes

Microbes that originate from a source outside the body, such as the Influenza virus.

Endogenous Microbes

Microbes that are already existing in or on the body, such as Clostridium difficile.

Infectious Dose ($ID$)

The minimum number of microbes necessary to cause an infection; microorganisms with smaller doses, like Tuberculosis ($10$ cells), have greater virulence.

Adhesion

The process by which microbes attach to host cells or tissues using pili, fimbriae, surface proteins, adhesive capsules, or glycoprotein spikes.

Phagocytes

White blood cells which engulf and destroy pathogens by means of antimicrobial chemicals and enzymes.

Leukocidin

Toxins produced by bacteria, such as Staphylococcus, to destroy leukocytes (white blood cells).

Coagulase

An extracellular enzyme that accelerates the coagulation (clotting) of blood to keep bacteria hidden from the immune system.

Kinase

An extracellular enzyme that dissolves blood clots, freeing bacteria to spread to other tissues.

Exotoxins

Toxins produced by gram-positive bacteria that are secreted into host tissue.

Endotoxins

Lipopolysaccharides that are part of the outer cell membrane of gram-negative bacteria and are released into host tissues often when the bacteria die or divide.

Alpha-hemolysins

Exotoxins that partially break down hemoglobin and produce a greenish ring around colonies in blood agar.

Beta-hemolysins

Exotoxins that completely break down hemoglobin and leave a clear ring around colonies in blood agar.

Sign

Objective evidence of disease as noted by an observer, such as a seizure, redness, or sneezing.

Symptom

Subjective evidence of disease as sensed by the patient, such as fatigue, headache, or nausea.

Incubation Period

The time between infection and the appearance of signs and symptoms.

Prodromal Phase

A short period during which nonspecific, often mild, symptoms occur.

Invasive Phase

The period during which the individual experiences the typical signs and symptoms of the disease.

Convalescence Period

The stage where tissues are repaired, healing takes place, and the body recovers strength.

Communicable Disease

An infectious disease that is spread from one host to another.

Direct Transmission

The transfer of an infectious agent from a reservoir to a susceptible host by skin-to-skin contact, kissing, sexual intercourse, or droplet spread.

Indirect Transmission

The transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects (vehicles), or animate intermediaries (vectors).

Fomites

Inanimate objects such as handkerchiefs, bedding, or surgical scalpels that may indirectly transmit an infectious agent.

Vectors

Animate intermediaries such as mosquitoes, fleas, and ticks that may carry an infectious agent.

Healthcare-associated Infections ($HAIs$)

Infections resulting from germs entering the body during medical care, such as catheter-associated urinary tract infections or surgical site infections.

Epidemiology

The study of factors and mechanisms involved in the frequency and spread of diseases and other health-related problems within populations.

Incidence Rate

The number of NEW cases of a disease contracted within a set population during a specific period.

Prevalence

The TOTAL number of people infected within the population at any given time.

Morbidity Rate

The rate at which persons are afflicted with infectious diseases.

Endemic Disease

A disease that is constantly present in a certain population or region with relatively low spread.

Epidemic Disease

A disease characterized by a sudden increase in cases spreading through a large population like a country.

Pandemic Disease

A sudden increase in disease cases spreading through several countries, continents, or the whole world.