Published on March 1, 2014
Learning Goals: To understand the means by which bacterial disease spreads. To a understand variety of diseases caused by bacteria. To examine a variety of protists.
How do bacteria cause disease? • Bacteria can cause disease in humans if: 1. They can enter a person who acts as a host 2. They can reproduce in the host 3. They act adversely on the tissue of the host. Task: List several ways in which bacteria can be transmitted to a person.
Transmission to a host • Transmission of bacteria (and other pathogens) occurs by: a) From one person to another through droplets if an infected person coughs, sneezes or comes into body contact b) Contaminated water and food c) Carried from one host to another by a vector (an animal host such as a mosquito, rat or fly) A carrier of a disease is someone who has the disease, be shows no symptoms, so passes it on to others unaware of doing so.
Reproduction of bacteria • In order to reproduce, bacteria need an environment with adequate nutrients and water, and an appropriate temperature and pH. • When conditions are favourable, bacteria reproduce very quickly, about every 20 minutes or so. Task: Work out how many bacteria could be made in a school day.
Bacteria effects on tissues Flesh eating bacteria Tumours caused by exotoxins Bacteria can damage the host in several ways: 1. By producing enzymes that break down or digest tissues. 2. By producing poisonous toxins. a) Exotoxins are released into the surroundings by bacteria as they grow. Exotoxins are some of the most lethal substances known, and can (i) inhibit protein synthesis; (ii) Damage cell membranes or disrupt transport of materials across cell membranes; or (iii) Interfere with normal nerve function. Toxins retains their destructive powers after the bacteria dies.
b) Endotoxins are derived from the lipopolysaccharide layer in the cell wall of Gram-negative bacteria and are released after the cell lyses (breaks open). Bacterial endotoxins can lead to diabetes Meningococcemia uses up the bodies clotting factor resulting in mass haemorrhaging Endotoxins resist the body’s defence system better than exotoxins.
Treatment of bacterial diseases • Chemotherapy is the term used when a disease is treated with chemicals. • Many chemicals are produced, or have been extracted from bacteria and fungi to fight disease-causing agents. • Naturally occurring compounds which kill bacteria are called antibiotics. • Some drugs are narrow-spectrum and act against a limited variety or microorganisms. • Other drugs are broad-spectrum and act against many different kinds of pathogens.
• Broad-spectrum antibiotics are useful when the doctor is not sure which bacterium is causing an infection. • Sensitivity tests are carried out to determine which drug is most effective against the infecting bacteria. • A drug should be selectively toxic – it should kill the infecting cells without destroying the host cells. • Some drugs have adverse effects (side effects) on a host.
2. Protoctista • Protoctistans/protozoans are unicellular eukaryotic organisms. • Most species are harmless. • Many species are very useful and live in close association with other organisms in a mutualistic relationship. • They range in length from 0.1 to 2mm and vary greatly in shape.
Examples of pathogenic protozoa include: a. Entamoeba histolytica • This affects ±50 million people worldwide. • It is found in drinking water. • In the colon the organisms actually bore their way into the bowel wall, and cause ulcerations, severe bloody diarrhoea called dysentery, and abdominal pain. • Some of the amoeba can inter the blood stream where they can spread to other tissues, such as the liver, lungs and brain.
b. Trichomonas vaginalis This is a single cell flagellum parasite that lives in the female vagina and the male urethra. This STD is often asymptomatic but usually causes vaginitis or urethritis. It can live for up to 24 hours outside of a host in water, semen or urine.
c. Trypanosoma gambiense More than 66 million people in 36 countries of sub-Saharan Africa suffer from human African trypanosomiasis (HAT). There are two forms of African sleeping sickness, caused by two different sub-species. Both are transmitted to humans through the bite of a tsetse fly. When untreated, HAT ultimately ends in death.
d. Giardia lamblia This is found in contaminated water supplies. Contamination occurs from human faeces, poor hygiene or water-borne transmission. It causes low-grade intestinal problems in humans, and is difficult to eliminate from the body.
Pages in category "Bacterial diseases" The following 138 pages are in this category, out of 138 total. This list may not reflect recent changes . ...
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Englisch-Deutsch-Übersetzung für bacterial disease im Online-Wörterbuch dict.cc (Deutschwörterbuch).