BIOL 2420 (Microbiology) - Chapter 14: Determinants of Disease and Epdemiology (Lecture #4)

Mutualism

the way two organisms of different specie biologically interact in a relationship in which each individual derives a benefit

Commensalism

a class of relationship between two organisms where one organism benefits without affecting the other

Parasitism

a non-mutual relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host

infection

multiplication of a microbe in a host

microbial antagonism

natural flora protects the host by competing with and edging out many pathogens

normal flora

permanent species

transient flora

microbes that can sometimes be cultured from body surfaces, but aren’t permanent residents

sites that harbor normal flora

skin, upper respiratory tract, GI tract, outer opening of urethra, external genitalia, vagina, external ear canal, external eye

the steps of infection

contact → infection → disease

contact

exposure to microbes

infection

penetrate defenses, enter tissues, and multiply

disease

the infection damages or disrupts tissues and organs

Examples of portals of entry

ear, broken skin, insect bites, the anus, the conjunctiva of the eye, the nose, mouse, placenta, vagina, penis, urethra

pathology

study of disease

etiology

cause of the disease

etiologic agent

the microbe that causes the disease

pathogenesis

manner in which a disease develops

pathogenic microbe 

microbe that has the capacity to produce disease

virulence

refers to the degree of pathogenicity

reservoir

the primary habitat in the natural world from which a pathogen originates

source

the individual or object from which an infection is actually acquired

carrier

an individual who inconspicuously shelters a pathogen and spreads it to others without any notice 

types of asymptomatic carriers

incubation, convalescent, chronic and passive carriers

Zoonosis

an infection indigenous to animals but naturally transmissble to humans

vector

a live animal that transmits an infectious agent from one host to another

Patterns of transmissions (contact) 

Direct (Kissing/Touching), Droplets, Vertical, and Vector

Patterns of transmissions (indirect)

Fomites, Food/Water, Air

types of adherence

fimbriae, capsules, spikes

benefits of deeper tissue

escape the hosts’ defenses, little competition and nutrient-rich

examples of exoenzymes

streptokinase, hyaluronidase, catalase, hemolysins, leukocidins

types of bacterial toxins

exotoxins, endotoxins

exotoxins

proteins secreted from the pathogens

method of evasions for capsule pathogens

difficult to engulf

method of evasions for exoenzymes

leukocidins

antigenic varitation

some microbes mutate and change their surface antigens so that the immune system does not recognize them

stages of infectious disease

incubation period → prodromal period → Illness → Decline → Convalescence

incubation period

time between infection and the appearance of signs and symptoms

prodromal phase

short period during which nonspecific, often mild, symptoms such as malaise and headache sometimes appear

invasive phase

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

decline phase 

symptoms begin to subside as the host defenses and the effects of treatment if being administered finally overcome the pathogen

convalescence period

tissues are repaired, healing takes place, and the body regains strength and recovers

sign

any objective evidence of disease as noted by an observer

symptom

the subjective evidence of disease as sensed by the patient

syndrome

when a disease can be identified by a certain complex of signs and symptoms

asymptomatic infection

acute disease

develops rapidly and runs its course quickly

chronic disease

develops more slowly, is usually less severe, and persists for a long period

local infection

confined to a specific area

systemic infection

generalized infection; affects most of the body

septicemia

pathogens are present in and multiply in the blood

primary infection

initial infection in a previously healthy person

secondary infection

follows a primary infection

superinfection

secondary infection that results from the destruction of normal microflora and often follows the use of broad-spectrum antibiotics

mixed infection

caused by several species of organisms present at the same time

communicable

disease spreads from one host to another

Noncommunicable

disease not spread from one host to another

contagious

diseases that spread easily from one host to another

epidemiology

the study of the frequency and distribution of disease and other health-related factors in defined human populations

descriptive epidemiology

collection and analysis of data

analytical epidemiology

comparison of a diseased group and a healthy group

experimental epidemiology

controlled experiments

epidemic

a pattern of disease transmission that affects many members of a population within a short time

pandemic

an epidemic that spreads worldwide

endemic

disease exhibits steady frequency over a long time period in a particular area; numbers generally stay too low to constitute a public health concern

sporadic

diseases occurring only occasionally in a population

reportable diseases

diseases that by law, must be reported to the authorties

prevalence

the total number of existing cases with respect to the entire population

incidence

the number of new cases over a certain time period

mortality rate

the total number of deaths in a population due to a certain disease

morbidity rate

the number of persons afflicted with infectious diseases

nosocomial infections

infectious diseases that are acquired or develop during a hospital stay