B5 communicable diseases Flashcards
What are communicable diseases?
Infectious diseases caused by pathogens that can be passed from person to person
What 3 factors can lead to good/ill health?
diet stress and life situations
Differences between bacteria and viruses
A virus is non-living and cannot be treated by antibiotics, they do not have a cell wall. Viruses are generally smaller and require a host to survive. A bacteria can be affected by antibiotics and can survive outside of a host. Bacteria can be free-living and do not require a host to reproduce. Viruses cause disease in every organism but can only infect living things.
How do bacteria and viruses reproduce?
Bacteria split into two (binary fission) and they produce toxins that harm cells and tissue
Viruses infect cells and reproduce inside of the damaged cell.
How are pathogens spread?
By air: they are spread from one organism to another via the air and droplet infection where they travel in droplets and are expelled from the body (eg cough) and infect other organisms.
Direct contact: happens a lot in plants, some diseases can enter through open wounds and sexual contact.
Water: water can harbour pathogens and so can food so they have to be cooked or cleaned to consume.
Bacteria culturing.
They need to grow in a culture medium, allows a liquid or gel to provide all the nutrients needed for bacteria to grow successfully. These must include: carbohydrates for energy, nitrogen for
protein synthesis, plus other minerals.
Agar plates are created by pouring hot molten agar into sterile
Petri dishes, which are then allowed to set. Bacteria can be spread onto the plates, and allowed to form
individual colonies of the specific bacterium.
Then you sterilise hands, surface petri dish and put an inoculating loop over a flame to sterilise it. When it has cooled use the loop and get the bacteria culture and move it in a zigzag shape across the jelly while keeping the lid partially over. Then seal it with two pieces of tape but leave oxygen to get in and store it upside down to stop condensation and place it in an incubator for the best temperature for the bacteria to grow.
What are the factors that affect bacterial growth?
temperature nutrients pH and oxygen levels.
What is the formula to calculate the number of bacteria in a population?
bacteria at the end of growth period= bacteria at the start of the growth period x 2^number of divisions
How to prevent bacterial growth?
raising or dropping temperature, uv light,chemicals such as disinfectants that kill on the surfaces, antiseptics that stop infections on the skin and antibiotics which stop bacteria IN the body
What did semmelweis discover?
Semmelweis realised the death rate among women giving birth in hospital was higher than among those giving birth at home. He believed this was because doctors often delivered babies after dissecting dead bodies. He then asked doctors to wash their hands and equipment in disinfectant and that stopped the death rate as the disease was spread from dead bodies to the mothers.
What is vaccination and how does it work?
Pathogens are microbes that cause diseases. Vaccines allow a dead or altered form of the disease causing pathogen to be introduced into the body without causing the disease. The pathogens that are introduced contain a specific
antigen. The antigen causes the body’s immune system, specifically the lymphocytes, to produce complementary antibodies, which target and attach to the antigen.
An altered form of a pathogen which cannot cause disease is injected into someone.
This causes lymphocytes to make and then release complementary antibodies to the specific antigen that was injected.
The antibodies attach to and clump the antigens together.
Phagocytes engulf the antigens to remove them from the body.
Some of the lymphocytes remain in the bloodstream as memory cells which can produce the specific antibody for the antigen.
If the body is infected by the real pathogen, the memory cells release antibodies to fight off the pathogen and quickly destroy it.
Problems with antibiotics
Commonly prescribed antibiotics are becoming less effective due to a number of reasons:
overuse of antibiotics
failing to complete the fully prescribed course by a doctor
use of antibiotics in farming
What happens when the patient doesn’t fully complete the antibiotic course?
Patients should always fully complete the prescribed course of antibiotics, every time they are taken. This ensures all bacteria are killed, and so none survive which can subsequently mutate and produce resistant strains. Patients begin to feel well after a few days of taking the medicine, and stop taking them. This is potentially very harmful, as random mutations can occur which can lead to antibiotic resistance. The resistant bacteria reproduce quickly, and the resistance spreads.
How to prevent antibiotic resistance?
Only take antibiotics when necessary.
Treat specific bacteria with specific antibiotics.
High hospital hygiene levels, including regular hand washing by staff and visitors.
Patients who are infected with antibiotic resistant strains of bacteria should be isolated from other patients
How was penicillin discovered?
The first antibiotic - penicillin - was discovered in 1928 by Alexander Fleming. He noticed that some bacteria he had left in a petri dish had been killed by naturally occurring Penicillium mould.
Since the discovery of penicillin, many other antibiotics have been discovered or developed. Most antibiotics used in medicine have been altered chemically to make them more effective and safer for humans.