Bacteria and Disease: Transmission, Pathogenicity
Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), Chameleon
Transmission of Bacteria and Disease
We often assume that all bacteria are harmful, but there are many uses for bacteria, and every healthy person has natural flora - bacteria lining the skin the gut and digestive tract.
Bacteria that cause harm are described as pathogenic. There are numerous ways that pathogenic bacteria can be transmitted to us. In the table below we will take a two examples.
|Salmonella||Food - mainly eggs and egg products.||This bacteria infects the colon and lower intestine. The response to this is to increase fluid production which results in diarrhoea. This can cause dehydration, so sufferers must drink a lot of water and replace salts, it also makes absorbing antibiotics difficult.|
|Escherichia coli||Water contaminated with faeces.||E. coli is a bacteria naturally occurring in the human gut, but some strains are pathogenic. This also results diarrhoea, and can be fatal. In developing countries, over 5 million children die a year from diarrhoea because of poor sanitation.|
Contamination of food and water can be prevented by basic hygiene. Food-borne infection is prevented:
- 1Inspecting farms to ensure animals do not carry diseaseAdvertisement
- 2Washing food properly.
- 3Cooking food thoroughly.
- 4Wear protective clothing where food is being both produced and prepared.
Water-borne infections are prevented by treating the water before it is ingested by people. To reduce the millions of deaths in developing countries, infrastructure to provide clean water is desperately needed.
Pathogenicity is the ability of the bacteria to cause disease. The most dangerous bacteria have a high pathogenicity. There are a number of features that can make a bacteria more pathogenic.
- 1Molecules in their cell wall can bind to molecules on the host's cell membranes.How easily the bacteria can attach and enter the host is important.
- 2Receptors vary from individual to individual, so some people may be more susceptible to diseases than others.
- 3Many pathogenic bacteria produce toxins - chemicals that have a harmful effect on the body.
- 4Exotoxins are produced by living bacteria and can have varying affects.
- 5Tetanus is caused by Clostridium tetani which releases toxins in to the nervous system that cause involuntary muscle contractions.
- 6These are what cause fever and aches.'Endotoxins are compounds in bacterial cell walls that only have an effect when the cell dies and is broken down.
- 7Large numbers of bacteria may be required to cause infection, as is the case with Salmonella enteritidis (10 million), however another species of salmonella only needs be present in small numbers to cause typhoid fever.
- 8A bacterium that can break into one of the body's major transport systems (blood or lymphatic, will be very invasive.The invasiveness of a bacteria is its ability to spread within the host.
Milk is vulnerable to contamination during collection and storage, and is an excellent medium for growth. The flash pasteurization method is the most common for destroying micro-organisms. Milk is heated to 72o C for 15 seconds, then rapidly cooled to 3oC. The heat kills many pathogens and the rapid cooling prevents those resistant to heat, from dividing rapidly. The milk now must be kept refrigerated and can last for several days. The flash pasteurization process has little effect on the flavour or nutritional value of milk.
Another method of heat treating milk is ultra-high temperature processing, where the milk is heated to 135°C for 1 or 2 seconds. This is more effective and means the milk can be stored for several months. This treatment, however, has more of an effect on the nutritional content of the milk (mainly vitamins).
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Categories : Micro
Recent edits by: Taylor (ScienceAid Editor), Jamie (ScienceAid Editor)