Chapter 14 - Disease and Pathology

Pathogen

disease causing microorganism 

human pathogen

special properties that allow them to invade the body or produce toxins

intoxication

when a pathogen produc

disease

the ability of a pathogen to overcome your body’s defenses - leads to disease state

disease state

abnormal state in which part of or all of the body is not properly adjusted or is incapable of performing normal functions (change in the health state) 

infection

the invasion and growth of a pathogen in the body 

the colonization of the pathogen causes disease

host

the organism that shelters and supports the growth of the pathogen 

pathology

study of disease

etiology

cause of disease

pathogenesis

development of disease

normal microbiota

microorganisms that establish permanent colonies inside of the body without producing disease (resident microbes)

colonization in and on the surface of the body occurs

soon after birth 

placental microbiome 

vaginal delivery 

transient microbiota

visiting microbes

microbes that are present and then disapear 

microbial antagonism

prevent pathogens from causing infection through the process of competitive exclusion (there’s only room for one of us) 

symbiosis

living together

commensalism

one organism benefits and the other is unaffected

mutualism

both organisms benefit

parasitism

does not include normal microbiota, one organism benefits, but the other is harmed (disease state) 

opportunistic microorganisms 

microorganisms that do not cause disease under normal conditions, but can cause disease under special conditions

• e.coli

• candida albicans

• skin bacteria

e.coli

gi tract - normal but cause UTI when they get into the urinary tract 

candida albicans

yeast infections - under normal conditions there is no disease state, special conditions that lead to overgrowth can lead to disease state

skin bacteria

on skin surface - normal, under the skin (dermal layer or below) - can cause disease state 

cooperation

associated with disease state 

one microorganism makes it possible for another microorganism to cause disease or produce severe symptoms 

what are koch’s postulates

criteria that established that specific microbes specific disease - determines etiology

koch’s postulates requirements

1: the same pathogen must be present in every case of the disease 

2: the pathogen must be isolated in pure culture

3: the pathogen that was isolated must cause disease in a healthy, susceptible lab animal 

4: the pathogen must be reisolated from the inoculated lab animal 

exceptions to koch’s postulates

• viruses and some bacteria cannot be grown on artificial media (tissue culture, etc)

• some diseases have unequivocal signs and symptoms (tetanus) 

• some diseases may be caused by a variety of microbes (pneumonia, nephritis, meningitis) 

• some pathogens cause several different diseases (streptococcus pyogenes) 

• some pathogens cause disease in human only (HIV) 

symptoms

subjective changes in body function

sign

measurable changes

diagnosis

identification of the disease/ pathogen

syndrome

a specific group of symptoms and/or signs that always accompanies a specific disease

communicable disease

transmitted directly or indirectly from one host to another 

contagious disease

able to spread easily and rapidly from one person to another 

noncommunicable disease

disease is caused by a microbe that normally grows outside of the human body 

not able to be transmitted from one host to another 

occurrence is reported by

incidence and prevalence in defined population

incidence

new cases

prevalence

number of people who already have the disease

sporadic

popping up in few people, not spreading

endemic

high in a specific area, high prevalence

epidemic

spreads rapidly through population

high incidence

pandemic

epidemic that spreads to multiple geographical locations across the gloce

acute disease

has a beginning and end, can cause severe symptoms but it is not lingering 

chronic disease 

lower severity, longer duration 

subacute 

between acute and chronic - more than acute 

latent

present but dormant, can reoccur

herd immunity

• presence of immunity to a disease in most of the population 

• usually accomplished through immunization 

• dependent on the immune response to the pathogen 

• harder to establish in quickly mutated pathogens

local infection

small area of the body

systemic infection

spread through the body, circulatory system

primary infection

acute infection causing initial illness

secondary infection

a second infection in a weakened host due to primary infection

subclinical infection

inapparent, no signs or symptoms of disease

reservoir

source of pathogen

transmission

can be direct or indirect

invasion

multiplication

pathogenesis

injury to the host

predisposing factors

factors that make the body more susceptible to disease 

• gender/sex

• climate

• age

• fatigue

• inadequate nutrition 

• genetics

• primary infection

incubation period

initial infection

first appearance of signs and symptoms

pathogen is multiplying

host has recognized pathogen

depends on microbe and hosts resistance to microbe

prodromal period

appearance of first mild symptoms and signs

general symptoms 

not specific disease 

relatively short 

period of illness

disease at its height

signs and symptoms of disease 

period of decline

signs and symptoms begin to subside

most vulnerable to secondary infection 

period of convalescence

body returns to pre diseased state

humans as reservoirs of disease 

can have the disease or can be carriers of the pathogen

STI

Typhoid mary

animals/insects as reservoirs of disease 

animal carries the disease

ex: rabies, plague, lyme disease, malaria

zoonoses

disease that affects a wild or domestic animal and can be transmitted to a human

animal also gets sick

pathogen that wouldn’t usually impact a human but mutates and now infects humans

• Bird flu

• swine flu

nonliving reservoirs

soil and water

clostridium tetani (tetanus) - soil

cholera - water

uncooked food

direct transmission

• direct contact 

• fomite 

• droplet transmission 

direct contact

close contact between reservoir and host

congenital - mother to fetus/newborn

fomite

inanimate objects

indirect contact 

ex: fungal disease on a towel 

droplet transmission

saliva or mucus in coughing or sneezing, droplet nuclei only travel a short distance 

vehicle transmission

by medium such as air, water, or food

• airborne transmission

• foodborne transmission 

airborne transmission 

droplets of dust that travels a distance of GREATER than 1 meter

foodborne transmission

cross-contamination

fecal oral

arthropods

insects that act as vectors for pathogens

mechanical transmission

biological transmission

mechanical transmission

passive transmission

fly on food

biological transmission

active transmission

ex: bite 

Healthcare associated infections (HAIs)

nosocomial

infections acquired in healthcare settings 

microbes in hospitals

normal microbiota - introduced to other parts of body and leads to infection (opportunistic)

• surgical procedures 

• catheterization 

antibiotic resistance 

Immunosuppressed host examples 

burns 

surgical wounds 

disease

standard precaution to control HAIs

washing hands

wearing lab coat

transmission based precautions to control HAIs

specific to pathogen

mask, proper cleaning and handling of equipment