Summary of Infectious Diseases Viruses ● Describe how a virus reproduces inside a cell. Viruses can only reproduce in living cells. A particular strain of virus may only attack specific cells - but these may be plant cells, animal cells or bacterial cells. For example, common colds are caused by viruses which attack cells in the respiratory system. These are the main stages: 1. 2. 3. 4. the virus attaches itself to a specific host cell (the cell in which it will reproduce) the virus injects its genetic material into the host cell the host cell uses the genetic material to make new viruses the host cell splits open, releasing the viruses ● Explain the two ways white blood cells can kill pathogens. ingest pathogens and destroy them produce antibodies to destroy pathogens produce antitoxins that neutralise the toxins released by pathogens Note that: the pathogens are not the disease - they cause the disease white blood cells do not eat the pathogens - they ingest them antibodies and antitoxins are not living things - they are specialised proteins ● Explain how we become immune to a disease and how a vaccine works. Vaccines greatly reduce the risk of infection by working with the body's natural defenses to safely develop immunity to disease. To understand how vaccines work, it is helpful to first look at how the body fights illness. When germs, such as bacteria or viruses, invade the body, they attack and multiply. ● Describe how Edward Jenner discovered the vaccine. This paper explores the history of vaccines and immunization, beginning with Edward Jenner’s creation of the world’s first vaccine for smallpox in the 1790s. We then demonstrate that many of the issues salient in Jenner’s era—such as the need for secure funding mechanisms, streamlined manufacturing and safety concerns, and deep-seated public fears of inoculating agents—have frequently reappeared and have often dominated vaccine policies. We suggest that historical awareness can help inform viable long-term solutions to contemporary problems with vaccine research, production, and supply. Bacteria Describe how bacteria reproduce ● Bacteria can reproduce very quickly given the right conditions, such as warmth, moisture and suitable nutrients. Huge numbers of bacteria can be grown commercially in large containers called fermenters. Smaller numbers can be cultured in the lab by growing them on agar plates Describe how bacteria can become resistant to antibiotics. ● Bacterial strains can develop resistance to antibiotics. This happens because of natural selection. In a large population of bacteria, there may be some cells that are not affected by the antibiotic. These cells survive and reproduce, producing even more bacteria that are not affected by the antibiotic. Comment on the benefits and limitations of antibiotic use. ● Antibiotics are substances that kill bacteria or prevent their growth. They do not work against viruses. It is difficult to develop drugs that kill viruses without damaging the body’s tissues. ● Outline Fleming's role in the discovery of antibiotics (Penicillin). ● The first a ntibiotic, penicillin, was discovered by Alexander Fleming in 1928. 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 of those used in medicine have been altered chemically to make them more effective and more safe for humans. Microbes and Pathogens Define they terms microorganisms, microbes and pathogens. Pathogens: Pathogens are microorganisms that cause infectious disease. Bacteria and viruses are the main pathogens. Microbes: a microorganism, especially a bacterium causing disease or fermentation. Microorganism- a microscopic organism, especially a bacterium, virus, or fungus. Outline the 4 main types of pathogens (bacteria, viruses, fungi and protozoa) and give examples of diseases caused by them. Fungi Bacteria – Virus – Protozoa - Our Body's Defences ● Outline the barriers to the entry of microbes into our body (skin, mucus, tears, stomach acid) ● Outline the necessity of personal hygiene. Defenses Against Infection. Natural barriers and the immune system defend the body against organisms that can cause infection. Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid. Also, the normal flow of urine washes out microorganisms that enter the urinary tract. ● Natural barriers and the immune system defend the body against organisms that can cause infection. ● Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach ● ● ● ● acid. Also, the normal flow of urine washes out microorganisms that enter the urinary tract. Usually, the skin prevents invasion by microorganisms unless it is damaged—for example, by an injury, insect bite, or burn. Mucous membranes, such as the lining of the mouth, nose, and eyelids, are also effective barriers. Typically, mucous membranes are coated with secretions that fight microorganisms. For example, the mucous membranes of the eyes are bathed in tears, which contain an enzyme called lysozyme that attacks bacteria and helps protect the eyes from infection. The airways filter out particles that are present in the air that is inhaled. The walls of the passages in the nose and airways are coated with mucus. Microorganisms in the air become stuck to the mucus, which is coughed up or blown out of the nose. Mucus removal is aided by the coordinated beating of tiny hairlike projections (cilia) that line the airways. The cilia sweep the mucus up the airways, away from the lungs. The digestive tract has a series of effective barriers, including stomach acid, pancreatic enzymes, bile, and intestinal secretions. These substances can kill bacteria or prevent them ● from multiplying. The contractions of the intestine (peristalsis) and the normal shedding of cells lining the intestine help remove harmful microorganisms. The urinary tract also has several effective barriers. The bladder is protected by the urethra, the tube that drains urine from the body. In males older than 6 months, the urethra is long enough that bacteria are seldom able to pass through it to reach the bladder, unless the bacteria are unintentionally placed there by catheters or surgical instruments. In females, the urethra is shorter, occasionally allowing external bacteria to pass into the bladder. In ● ● both sexes, when the bladder empties, it flushes out any bacteria that reach it.
