Microorganisms Flashcards
Define “disease”
A condition with a specific cause in which part or all of the body functions abnormally
How do microorganisms cause diseases?
Bacteria: Release toxins when they multiply which affect cells in the region of infection
Virus: Affect the metabolic systems of the cell. The genetic material of the virus takes over the cell and instructs it to produce more viruses
Fungi: Hyphae secrete digestive enzymes that break down the tissues; can physically damage tissues/cause an allergic reaction
Protozoa: No set pattern
Three basic shapes of bacteria:
Spirals, rods, and spheres
The process by which bacteria reproduce:
Binary fission
Where can bacteria be cultured?
Agar jelly or broth
Stages of the bacterial growth curve
LAG PHASE: adjusting to the new environment
GROWTH PHASE: division of bacteria
STATIONARY PHASE: rate of growth of new cells equals the rate of death of cells
DEATH PHASE: more and more cells die
What limiting factors cause the stationary and death phase?
The build-up of toxins/ poisonous waste products
Using up nutrients and oxygen
What’s a parasite?
An organism that lives in or on another organism, called its host and causes it harm
The course of a disease:
Infection period ➡ Incubation period ➡ Symptoms
Means of infection:
- Droplets (respiratory diseases)
- Drinking contaminated water (colonize in regions of the gut)
- Eating contaminated food (regions of the gut)
- Direct contact (skin infection or other diseases)
- Sexual intercourse (STDs)
- Blood-to-blood contact (STDs)
- Animal vectors
Define “syndrome”
A set of symptoms caused by a medical condition
Role of T-helper cells:
To help other lymphocytes to become active and start fighting infections
A typical infection with HIV involves this course:
- The virus makes DNA from the RNA. It gets incorporated into the DNA of the T-helper cell.
- At some point the HIV DNA gets activated and instructs the T-helper to make HIV proteins and more RNA.
- The HIV proteins and the RNA are assembled into new virus particles.
- Some of the HIV proteins end up as antigens on the surface of the lymphocyte which are recognized by the immune system as foreign and so the lymphocyte is destroyed by the immune system.
- The assembled virus particles escape into other lymphocytes. The cycle repeats for as long as the body can replace the lymphocytes that have been destroyed. Eventually, the body will not be able to do so.
- The number of viruses in the blood increases and HIV may infect other areas of the body. The immune system is severely damaged, and other pathogens infect the body. The person usually dies due to opportunistic infections
What is the latency period?
The period during which the body can replace the lymphocytes as quickly as they are being destroyed. Shows no symptoms at the time
The main ways HIV is transmitted are:
Unprotected sexual intercourse
Blood to blood contact (infected needles)
How can the transmission of HIV be reduced?
Using condoms
Using new, sterile needles
Limiting the no. of sexual partners
Testing the blood used for transfusions
The incubation period for the Ebola virus:
2 to 21 days (not infectious)
Symptoms of Ebola:
Fever Muscle pain Headache Sore throat Vomiting Diarrhea Rash Damaged liver and kidney Internal and external bleeding Low WBC and platelet count
How can direct contact cause Ebola?
Through broken skin and mucus membranes (mouth and intestine)
Through infected surfaces eg. bedding
Prevention and control methods for Ebola:
- Reduce the risk of transmission from animals (eg. thoroughly cooking meat)
- Reduce the risk of transmission from infected people (eg. wearing gloves, protective clothing, washing hands)
- Reduce the risk of transmission from sexual intercourse
- Containing the outbreak (isolating people, monitoring patient contacts, having testing facilities, safe burial)
Treatment for the symptoms of the Ebola disease:
ORH: a solution of salts and glucose dissolved in sterile water
The microorganism that causes cholera:
Vibrio cholerae
How can cholera be transmitted?
- Through contaminated drinking water
- Infected people are handling food
- Undercooked seafood caught in water polluted with sewage
The incubation period for cholera:
A few hours to a few days