Infection and Disease

Dr. Allison Wiedemeier Allied Health Microbiology2016

Infection definition

colonization of the body by pathogens

Disease definition

an abnormal state when body is not functioning normally

What is a pathogen

a disease causing organism

Pathogenicity definition

a measurement of an organism’s potential to cause disease

Virulence definition

the degree of pathogenicity of an organism

What are normal microbiota

organisms that establish permanent residence but dont produce disease under normal body conditions

What are normal microbiota regions based on

nutrients, physical, chemical, and mechanical factors, and defenses of the host

Where do babies gain their microbiomes

in utero, birth, milk, caregivers, and the environment

How is a microbiome acquired in utero

the mother’s womb has her own microbiome

How is a microbiome acquired during birth

primarily by coming into contact with the mother's bacteria as it passes through the birth canal. For babies born via C-section, the initial microbiome comes more from the hospital environment and the mother's skin, which are different from the vaginal microbiota

How is a microbiome acquired by breast milk, compare it to formula

breast milk has a microbiome, but sterilized baby formula has none

How is a microbiome acquired from caregivers

family, siblings, and others share microbes with the baby

How is a microbiome acquired from the environment

baby can pick up microbes from anything it comes in contact with

Why would a doctor smear cesarean babies with vaginal canal bacteria?

because the baby did not pass through, missing the bacteria that could help shape its microbiome

Probiotics definition

live microbial cultures used to exert benefits to the host

What are opportunistic pathogens

under normal conditions they do not cause disease, but in a changed environment can cause disease

How do microbes cause disease

find a portal of entry, attaching firmly and negotiating the microbiome, surviving host defenses, causing damage/disease, exiting host

What is the first step in how microbes cause disease

gain entrance through a portal of entry

What are common portals of entry

skin, gastrointestinal tract, respiratory tract, urogenital tract

What is significant about the number of microbes in a disease

the likelihood of disease increases as the number of pathogens increases

ID50

the infection dose for 50 percent of population, how much needed to infect 50 percent of population

The lower the number, the more _____ the organism

virulent

LD50

the lethal dose for 50 percent of population

A bioweapon would need to be very ____

virulent

What is the second step in how microbes cause diease

adhere to host tissue

What are the ways a microbe adheres to host tissue

most methods are structures, some examples are fimbriae, hook/spirochete, and capsule

What is the third step in how a microbe causes disease

survives defenses, by producing antiphagocytic factors, means not going to be destroying

What are some ways microbes survive defenses

produce leukocidins (toxic to white blood cells), secrete slime layer or capsule to inhibit engulfing, survive inside phagocytes, and antigenic variation

What is antigenic variation

antigens on the surface of the microbe change enough that the immune system cannot recognize anymore, how we get new flu shots each year

What is the fourth step in how microbes cause disease

it actually causes disease/damage

How do microbes actually cause disease

microbes secrete enzymes and toxins, exoenzymes are produces by pathogens to break down tissues

What are the two types of toxins produces by microbes to cause disease

exotoxins and endotoxins, usually not both produced together

Exotoxin characeristics

most are enzymes, small amounts cause great harm, most come from gram positive only a few from gram negative, genes travel on plasmids then share them, soluble in body fluids, so easy to move through the body

Exotoxins definition

toxic substances released outside cell