Chain of Infection
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any microbe capable of producing a disease.
- 1. Bacteria: simple, ONE-CELLED microbes with double cell-membrane that protect them from harm; REPRODUCE RAPIDLY.
- **considered as one of the MOST COMMON cause of fatal disease.
- ☆ classified according to:
- A. SHAPE:
- a. cocci -spherical shaped
- b. bacilli -rod-shaped
- c. spirilla -spiral-shaped
- B. NEED OF O2:
- a. aerobic
- b. anaerobic
- C. RESPONSE TO STAINING:
- a. gram (+) or (-)
- b. acid-fast
- D. MOTILITY:
- a. non-motile
- b. motile
- E. TENDENCY TO CAPSULATE:
- a. encapsulated
- b. capsulated
- F. CAPACITY TO FORM SPORES:
- a. spore-forming
- b. nonspore-forming
3. Viruses: smallest known microbes.
- 2. Spirochete: a bacterium with flexible, slender, undulating spiral rods that posses cell wall. Three forms of spirochete:
- a. treponema
- b. leptospira
- c. borilia
They cannot replicate independently of the host's cell;
rather they invade and stimulate the host's cell to participate in the formation of additional viruses.
5. Chlamydiae: smaller than rickettsiae but larger than viruses;
- 4. Rickettsiae: small, gram (-) bacteria-like microbes that can induce life-threatening infections. They require a host's cell for replication (like viruses); transmitted through a bite ARTHROPOD CARRIERS like lice, fleas, ticks.
- *DISEASES: Rocky mountain spotted fever, typhus fever and Q fever.
common cause of infection of the urethra, bladder fallopian tubes and prostate gland. Common: transmitted through sexual contact.
live in organic matter, water, animals and plants; seen almost everywhere on earth. thrive either inside or outside of the boy; may be beneficial or harmful. Fungi are beneficial in manufacturing cheese, yogurt, beer, wine and certain drugs.
7. Protozoa: much larger than bacteria; simplest singled-cell organism.
Parasitic protozoa absorb nutrients from the body of the host.
8. Parasites: live on or inside other organisms (called "host") at the expense of those organisms.
They don't kill the host,
but take only the nutrients they need.
Reservoir of infection: environment or object in which an organism lives and survives.
- HUMAN RESERVOIR:
- a. frank cases of the very ill
- b. ambulatory or sub-clinical
- c. CARRIERS:
- 1. INCUBATORY CARRIER:
- -a person who is incubating the illness.
- 2. CONVALESCENT CARRIER:
- -a person who is at the RECOVERY STAGE of the illness but continues to shed pathogenic organisms.
- 3. INTERMITTENT CARRIER:
- -a person who OCCASIONALLY sheds pathogenic microorganisms.
- 4. CHRONIC or SUSTAINED CARRIER:
- -a person who ALWAYS HAS the infectious organism in his/ her system.
Portal of exit:
- -the path or way through which the organism leaves the reservoir. Usually, this is where the organism grows. The common portal exits are the:
- a. resp system
- b. GUT
- c. GIT
- d. skin and mucus membrane
- e. placenta (in transplacental transmission)
Mode of Transmission:
- -is the means by which the infectious agent passes through from the portal of exit of the reservoir to the susceptible host.
- *EASIEST TO BREAK IN THE CHAIN OF INFECTION.
- 4 MODES IN TRANSMITTING INFECTIONS:
- 1. CONTACT TRANSMISSION:
- -most COMMON.
- 3 types:
- a. Direct contact: person-to-person.
- b. Indirect contact: person comes in contact with a contaminated object.
- c. Droplet spread: transmission through contact with resp secretions when the infected person coughs, sneezes or talks. Microbes in droplets can travel up to three feet (one meter). The organism is not suspended in the air but settles on a surface.
- 2. AIR-BORNE TRANSMISSION:
- -occurs when fine microbial particles or dust particles containing microbes remain suspended in the air for a long period of time. Infectious disease is spread by air current and is inhaled by a susceptible host.
- 3. VEHICLE TRANSMISSION:
- -transmission of dse through articles or substance that harbor the organism.
- 4. VECTOR-BORNE TRANSMISSION:
- -occurs when intermediate carriers. such as fleas, flies and mosquitoes, transfer the microbe to another living organism.
Portal of Entry:
-an organism gains entrance into the susceptible host. The microbe use the same avenues when they exit the reservoir.
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