Microbiology Unit 4

Pathology

study of diseae

Infection

colonization of the body by pathogens

Disease

change from a state of health

Is it possible to have an infection without a disease?

Yes

Is it possible to have a disease without an infection?

Yes

Symbiosis

relationship between two organisms where at least one is dependent on the other

Communsalism (Symbiosis)

one benefits, the other unaffected

Mutualism (Symbiosis)

both organisms benefit

Parasitism (Symbiosis)

one benefits, the other suffers

Opportunistic pathogens

normal bacteria in the wrong environment

Transient microbiota

Bacteria you pick up from an outside environment and carry for several weeks

Koch’s Postulates (1)

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

Koch’s Postulates (2)

the pathogen must be isolated from the diseases host and grown in pure culture

Koch’s Postulates (3)

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

Koch’s Postulates (4)

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

Koch’s Postulates Exceptions

• One set of symptoms, many causes

• One pathogen, many symptoms

• Some pathogens are difficult to grow and isolate outside of host

• Unethical to infect healthy people with HIV just to prove it causes AIDS

Syndrome

A group of signs and symptoms

Signs

objective changes measures by a doctor

Symptoms

subjective changes not apparent to an observer

Noncommunicable disease

not spread from person to person
Ex. tetanus

Communicable disease

spread from person to person
Ex. tuberculosis

Contagious disease

easily spread from person to person
Ex. measles

Local infection

One area

Systematic infection

generalized, spread throughout body

Focal infection

infection in a second location

Incubation period

no signs or symptoms

Prodromal Period

mild signs or symptoms

Period of illness

most severe signs and symptoms

Period of decline

signs and symptoms

Period of convalescence

recovery but the body is still weak

Incidence

number of people who develop disease in a certain time period; spread of disease

Prevalence

number of people who have a disease at a specific time; commonness of disease

Sporadic

occasional disease in population

Endemic

constant disease in population

Epidemic

widespread disease in a population; more disease than expected

Pandemic

worldwide epidemic

Reservoirs

Source of disease organisms (where are they when they’re not in the patient?)
Human, animal, or nonliving

Contact transmission

contact from point A to B

Direct contact transmission

touching

Indirect contact transmission

touching what you touched (fomite~ the nonliving thing that is touched)

Droplet contact transmission

touching (or breathing) discharged droplets that travel only a short distance

Vehicle transmission

something brings the infectious agent to you (air, water, or food)

Air vehicle transmission

touching (or breathing) your discharged droplets that travel a long distance (>1m)

Vector transmission

spread of a pathogen via an animal, such as a mosquito, tick, flea, etc.

Mechanical vector transmission

Passive spread of infectious agent by a vector

Biological vector transmission

Spread of infectious agent by biologically involved vector

Epidemiology

the science of when and where disease occur

Founders of epidemiology

Snow, Semmelweis, Nightingale

Descriptive Epidemiology

Use data to determine cause (reservoir) of disease
Ex. Snow’s study of cholera

Analytical Epidemiology

Compares two groups of people to determine why one has a disease
Ex. Nightingale’s comparison of soldiers and civilians

Experimental Epidemiology

Change the conditions of one of two groups and observe spread of disease
Ex. a drug or vaccine study, Semmelweis’s hands

Epidemiology Organizations

CCDPH, CDC, WHO

Healthcare facilities are reservoirs for what?

Coagulase-negative staphylococci, gram-negative rods, staphylococcus aureus, C. difficile

Reasons for nosocomial infections

many microorganisms, weakened hosts, chain of transmission

Pathogen

organism that can cause disease

Pathogenicity

The ability to cause disease by overcoming host defense

Virulence

degree of pathogenicity

ID50

infectious dose for 50% of the population

LD50

lethal dose for 50% of population

Exotoxin

Proteins produced in cells and secreted or released upon death

Endotoxin

Lipids that are part of the outer membrane of Gram-negative bacteria

Viral Load

Number of viruses we are exposed to (infectious dose)

IgG

80% of serum antibodies, fights bacteria and viruses

IgM

first antibody produced during infection. Pentamer

IgA

Inhibits adhesion in membrane secretions. Dimer

IgD

Could be involved in B cell activation or inflammation

IgE

parasitic worms and allergic response, histamine