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is a disturbance in the equilibrium resulting in pathogenic microbes multiplying in the tissues.
is the pathologic state that results when the infection damages or disrupts tissues and organs
are microbes that are present on the body for a period of and rapidly lost (not infection)
being used to identify the microbial profile inside and on humans
Human Microbiome Project
human host benefits from bacterial biota. Biota can produce vitamins, help digest lactose or prevent the overgrowth of harmful microorganisms by releasing bacteriocins
Natural part of the bacterial flora in the human body and have a symbiotic bacteria-host relationship with humans.
a microbe whose relationship with its host is parasitic and results in infection and disease
Type and severity of infection depend on pathogenicity of the organism and the condition of its host. how virulant is it, does it reproduce quickly?
cause disease when defenses are compromised (host said to be immunocompromised)
1. The degree of pathogenicity
2. Determined by its ability to
A. establish itself in the host
B. cause damage
any characteristic or structure of the microbe that contributes to its virulence (contributes to establishment or ability to cause disease)
already existing on or in the body (normal biota or latent infection)
infectious agent comes from the body
Infections by birth canal (TORCH)
2. other diseases (hepatitis, HIV, clamidia)
4. Cytomeglovirus (mumps)
5. Herpes complex
Becoming established: 3 steps
1. portals of entry (skin, gastrointestinal, respiratory, urogenital) - outside environment
2. Attaching to the host (adhesion) - fimbrae, surface proteins, adhesive slimes or capsules.
3. Surviving host defenses (phagocytes, some use anti-phagocytic factors
antiphagocytic factors: Leukocidins
toxic to white blood cells, produced by Streptococcus and Staphylococcus
antiphagocytic factors: Extracellular Enzymes
Break down and inflict damage on tissues or dissolve the host's defense barriers
ex. mucinase, keratinase, collagenase. some react with components of blood
toxinoses in which the toxin is spread by the blood from the site of infection (tetanus and diphtheria)
general state in which microorganisms are multiplying in the blood and are present in large numbers
an individual who inconspicuously shelters a pathogen and spreads it to others without any notice
a live animal that transmits an infectious agent from one host to another
Majority are arthropods
Larger animals can also be vectors
actively participates in a pathogen's life cycle. (ex. mosquito, bites, feces, regurgitate blood)
some of part of life cycle of MO takes place
an infection indigenous to animals but naturally transmissible to humans
ex. rabies, yellow fever
when an infected host can transmit the infectious agent to another host and establish infection in that host
Transmission can be direct or indirect
Contagious agent: highly communicable
1. does not arise through transmission of the infectious agent from host to host
2. Acquired through some other, special circumstance (ex. cut)
3. Compromised person invaded by his or her own microbiota
4. Individual has accidental contact with a microbe in a nonliving reservoir
1. Vehicle: any inanimate material commonly used by humans that can transmit infectious agents (food, water, biological products, fomites)
- Contaminated objects (doorknobs, telephones, etc.)
- Food poisoning
- Oral-fecal route
2. Air as a vehicle
- Indoor air
- Droplet nuclei
developed a standard for determining causation that would stand the test of scientific scrutiny
1. Find evidence of a particular microbe in every case of a disease
2. Isolate that microbe from an infected subject and cultivate it in pure culture in the laboratory
3. Inoculate a susceptible healthy subject with the laboratory isolate and observe the same resultant disease
4. Reisolate the agent from this subject
total number of existing cases w/ respect to the population
= (total number of cases in population / total number of persons in population) x 100 = %
the number of new cases over a period of time
= number of new cases / total number of susceptible persons
disease that exhibitsa a relatively steady frequency over a long time period in a particular geographic locale (ex. lyme disease = found where ticks are located)
revalence of an endemic or sporadic disease is increasing beyond expectations. clusters of breakouts
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