Amensalism

One of the partners is inhibited, while the other is not affected in any significant way.

Commensalism

One of the organisms benefits, and the other is unaffected.

Mutualism

Benefits both organisms.

Predation

Between two organisms of unlike species in which one of them acts as predator that captures and feeds on the other organism that serves as the prey

Parasitism

One organism gains and tho other is harmed.

Normal Microbiota

Permanently colonize the host

Transient Microbiota

Colonize the host for days weeks or months

How do Normal Microbiota protect?

Competetive Exclusion

Compete for nutrients

Alter conditions such as pH, available oxygen

Produce harmful substances

What is Competetive Exclusion?

Covers binding sites so pathogens can't bind

Probiotics

Addition of microbes to the diet in order to provide health benefits beyond basic nutritional value

Benefits of Probiotics?

Restore friendly bacteria in digestive tract

Aid in digestion and absorption of nutrients

Promote proper elimination of waste

Prebiotics

Selectively stimulate bacteria of color and improve health of host

Infection

Colonization of the body by pathogens

Disease

Impairment of normal state of an organizm or any of it's components that hinders the performance of vital functions

Infectious Disease

Disease that is caused by microorganisms

Non communicable disease

Not transmitted from one host to another

Communicable disease

Spread from one host to another

Contagious disease

Easily spread from one host to another

Symptom

Change in body function that is felt as a result of disease

sign

change in body that can be measured or observed as a result of disease

syndrome

A specific group of signs and symptoms that accompany a disease

Acute infections

short duration

may develop long lasting immunity

result in productive infections

disease symptoms result from tissue damage and infection of new cells

Persistent infections

viruses continually present in host

Persistent infections caused by?

Integration of viral genome into host genome

decrease of antigenicity of virus

mutation to less virulent and slower reproducing form

three categories of persistent infections

latent

chronic

slow

Latent infections

infection is followed by a symptomless period.

During latency what happens?

Virus stops reproducing and remains dormant for some time, Symptoms antivirus -antibodies, and viruses are not detectable.

Reactivation of a latent virus

Infectious particles are again detected

symptoms may be different than originally

Chronic Infections

Infectious virus can be detected at all times

i.e. Hepatitis

During a chronic infection is the disease always present?

No. may be absent or present or may develop late

i.e. Hepatitis

Slow Infections

Infectious agent gradually increases in amount over a long period of time

During a slow infection are symptoms always apparent?

no, during the increase they may not be apparent

i.e. retrovirus or prions

Classifications of Disease

(5)

Sporadic

Outbreak

Endemic

Epidemic

Pandemic

Sporadic

Occurs occasionally in a population (irregular)

Outbreak

Sudden and unexpected occurrence of disease usually focal or in a limited segment of the population.

Endemic disease

Constantly present in a population

Epidemic disease

Acquired by many hosts in a given area in a short time

Pandemic Disease

Increase in disease occurrence within large population over wide region

Disease Incidence

Fraction of a population that contracts a disease during a specific time.

Disease Prevalence

Fraction of a population having a specific disease at any given time.

Koch's Postulates :

Same pathogen must be present in every case of the disease

Pathogen must be isolated from the diseased host and grown in pure culture

pathogen from the pure culture must cause the disease when it is inoculated into a healthy susceptible laboratory animal

pathogen must be isolated from the inoculated animal and must be shown to be the original organism

What disease did Koch search the link between organism and disease?

Anthrax and Bacillus anthracis

What is unculturable taxa

organism cannot survive outside the host

True or false - Pathogens can cause only one type of disease

False. some pathogens can cause several disease conditions

True or False - Some pathogens cause disease only in humans

True. HIV

Source of pathogen

Location from which pathogen is transmitted to host

Reservoir of pathogen

Site or natural environmental location in which pathogen is normally found - can also be the source

Carrier

infected host

Casual carrier

harbors pathogen for a short time

Chronic carrier

Harbors pathogen for long periods of time (months, years, life)

Incubatory carrier

harbors pathogen, but is not yet ill

Active carrier

Has overt clinical case of disease

Convalescent carrier

has recovered from disease, but continues to harbor large numbers of the pathogen

Healthy carrier

harbors pathogen, but is not ill

Animal reservoir

transmission from animal to human, can be direct or indirect

Vectors

Organisms that spread disease from one host to another

Water

Air

Soil

Food

What are the four main routes of pathogen transmission?

Contact

Airborne

Vehicle

Vector-borne

Direct contact transmission

person to person or person to source or reservoir

Indirect contact

Involves an intermediate such as tissues, bedding, utensils, ,etc. (fomite)

Droplet spread

large particles that travel (>5 Micro meter travel < 1 meter)

Airborne transmission

droplet is suspended in air and travels > 1 meter

Can remain airborne for hours or days and travel long distances,

Vehicle transmission

Vehicles are inanimate materials or objects involved in pathogen transmission, (water, food)

Vector Borne Transmission

External (mechanical) transmission

Passive carriage of pathogen on body of vector

No growth of pathogen during transmission

Vector Borne Transmission

Internal Transmission

Carried within Vector

Horborage transmission

Pathogen does not undergo changes within vector

Biologic transmission

pathogen undergoes changes within vector

Active escape

movement of pathogen to exit

Passive escape

Excretion in feces, urine, droplets, saliva or desquamated cells

How to control epidemics?

(3 part answer)

Reduce or eliminate source or reservoir of infection

Break connection between source and susceptible individual

Reduce number of susceptible individuals

Nosocomal Infection

Acquired as a result of a hospital stay

What % of hospital patients are affected by nosocomial infections??

5-15%

What bacteria usually cause nosocomial infections?

Normal microbiota