Substance Made By Any Microorganism Biology Essay


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Antibiotics are a preferred treatment for infections as previous remedies were harmful to the body as they had a high toxicity. Today's antibiotics have very few side affects, which may range from: nausea to an allergic reaction, they also can kill off normal defence bacteria found in the bowl and vagina, and a high effective target activity . The majority of antibiotics are manmade substances based on those found in nature. Some are still produced or extracted from living organisms. The production of antibiotics involves the screening of a wide range of microorganisms, testing them and eventually modifying them. Usually the making of antibiotics is carried out using fermentation under aerobic conditions.

Most anti-bacterial antibiotics are not affective against viruses, fungi, or other microbes. Anti-bacterial antibiotics are further categorized by how their target specificity works. Type 1) Narrow spectrum antibiotics target bacteria, such as Gram negative or Gram positive bacteria. Type 2) Broad spectrum antibiotics affect a wide range of bacteria.

The location of an infection, the ability of antibiotics to migrate to the infected site and the ability of a microbe to inactivate or excrete antibiotics gives rise to the variable environments that antibiotics work in. There are two main types of anti- bacterial antibiotics: 1) those that destroy the bacteria, bactericidal, this is often done by interfering with the structure of the cell wall of the bacteria and the making of important chemicals, 2) and those that prevent bacteria from multiplying, bacteriostatic, by interfering with genetic material. However these classifications are based on laboratory behaviour.

Antibiotics can be administered in a variety of ways: 1) intravenously, usually used in deep seated infections. 2) Orally. 3) topically, eye drops or ointments.

To test antibiotic resistance antibiotics are placed on paper discs and placed on a agar plate with a certain bacteria on, the antibiotics then diffuse out from antibiotic-containing disks and inhibit the growth of the bacteria, known as a zone of inhibition. This zone is then measured.


Antibiotic resistance: the ability of a microorganism to withstand the affects of antibiotics

Drug resistance: is the reduction in effectiveness of a drug in curing a disease or improving a patients symptoms. When the drug is not intended to it will inhibit a pathogen, then the term is equivalent to dosage failure or drug tolerance.

All antibiotic resistance is genetically based.

1) Some organisms inherit the resistance through:

Evolution: the changes in the inherital traits of a population of organisms from one generation to the next.

These changes are caused by a combination of: 1) reproduction and 2) selection, commonly known as the survival of the fittest. When a selection pressure is placed on a population, such as more competitors or the introduction of antibiotics, some organisms are more susceptible to antibiotic resistance than others, those with the desired trait survive or allow them to adapt while the weak dye off. The strong then go on to reproduce and pass on their preferred trait until the entire population survives.

This is a picture used to help describe how evolution alters resistancy. The top section shows a population of bacteria before being exposed to antibiotics. The middle section shows a population after the selection pressure, antibiotics have been introduced. And the last section shows the distribution / variety of resistance to the new generation.

2) Also some organisms become resistant through:

Mutations: the change in DNA sequence which codes for a particular protein. Mutations occur randomly and only in a small proportion of populations. There are four types of mutation: 1) deletion of a base 2) addition of a base 3) substitution of a base and 4) inversion of a base. These all result in a different protein being coded for and results in a different job being carried out within the cell.

3) Another factor contributing to the resistance of antibiotics is the bacterial Conjugation tube. This involves the horizontal transfer of genes, in the form of plasmids, from one bacteria to another. Similarly pieces of DNA carried on a bacterial virus can be transferred directly to naked DNA. This results in resistance being passed on to different bacteria.

4) Also it is known that the genetic interchange can take place between a very diverse number of organisms. Bacteria inhabit a global environmental pool in which resistant bacteria and those genes transferring antibiotic resistance between bacteria easily between people and animals. A continuous process of exchange of genes takes place within the microbial world. For example the resistance can be transferred from different ecological nieces', from those bacteria that live in humans to those that live in dogs. Genes carrying antibiotic resistance factors are easily able to spread if the host organism gains an evolutionary advantage in acquiring them.

A diagram to show how mutations introduce resistance

5) Antibiotic misuse also is a major contributor. Greater than 70% of antibiotics are fed to animals in the absence of disease. This encourages the chance of mutations to take place and for resistance to arise.

Each of these selection pressures encourage resistance and for the resistance to spread.

How to prevent resistance?

There is not much that can be done to try and prevent any type of resistancy. A few issues could be tackled: 1) rational use of antibiotics. This means antibiotics are only to be used in urgent cases. This will reduce the development of opportunistic bacterial resistance. 2) Try to discover vaccines for common illnesses which require antibiotics, as vaccines enhance the body's normal defence and do not suffer from resistancy.

The problem of antibiotic resistance has now become a major concern in medicine throughout the world. If this problem cannot be restored then who knows what untreatable super bug will be next?

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