ANTIBIOTICS (and their misuse)

What are Antibiotics?

Antibiotics are mainly organic compounds (usually with synthetic modifications to increase potency) used to kill or disable invading bacteria.
There are two main types of antibiotics:
Bactericidal Antibiotics - These kill bacteria. For instance, Penicillin inhibits cell wall formation, thus is toxic to bacterial cells.
Bacteriostatic Antibiotics - These inhibit bacterial proliferation, thus allowing the host’s immune system to overpower the stalled cells. An example is Tetracycline.

Wonder Drug.
First accidentally discovered in 1928 by Alexander Fleming when a dish in which he was growing staphylococcus bacteria became contaminated with Penicillium mould. Fleming noticed a substance coming from the mould was destroying the bacteria.

This substance, later named penicillin, remained unused until 1940 when it was isolated and purified by Howard Florey and Ernst Chain. It was able to treat meningitis, gonorrhoea, syphilis and many other infections successfully with little or no harm to the infected person.

Advances in medical science and new techniques, soon allowed new antibiotics and modifications to earlier ones, giving the world powerful new bacteria fighting drugs - Many diseases could be all but eradicated - An erroneous assumption!

Unfortunately, as early as 1950s and 1960s, antibiotic-resistant stains of mutated bacteria had been detected - The warning signs had already appeared!

Antibiotic Resistance.
The increase in antibiotic resistant bacteria is largely due to the widespread use of antibiotics in medicine, animal care, and agriculture. Doctors often prescribe antibiotics on demand. These prescriptions are often inappropriate, as when the illness is caused by a viral or other non-bacterial infection. This overuse of antibiotics contributes directly to the rapid emergence of resistant bacteria strains.

Additionally, patients often fail to complete the full course of treatment. In this case, the disease agents are attacked with a sub-therapeutic dosage that often fails to completely eliminate the infecting bacteria. The surviving bacteria, those most resistant to treatment, are left alone to proliferate and possibly cause a subsequent infection that will be harder to treat.

In the non-industrial or "Third-World, drugs are less stringently controlled. Thus the rate of improper usage is high in these countries due to a lack of patient knowledge.

Farming and agriculture.
Forty percent of the antibiotics manufactured in the United States are given to animals. Most of this is mixed into the food of livestock in small dosages. This practice is meant to promote growth in the animals. However, treatment with low doses of antibiotics over extended periods of time, develops and promotes resistant strains of bacteria. These resistant strains may then be spread to humans through contact with the animals or through the consumption of undercooked meat.

An aerosol form of antibiotics is sprayed on fruit orchards. The dosage is sufficiently high to kill all bacteria on the trees when they are sprayed. However, low doses of the aerosol sprays reach plants other than the targets. The low doses create selective pressure for resistant bacteria, promoting the growth of resistant strains on these other plants. The resultant antibiotic resistant bacteria may contaminate the human food chain, ultimately ending up in the human digestive system where a problematic infection may occur.

Also, small amounts of the antibiotic spray may form a lasting residual layer on the treated fruit, killing sensitive bacteria but allowing bacteria with a resistance advantage to slowly proliferate and end up in the human food chain. At its core, the resistance problem is due to a lack of incentive for individuals using antibiotics to consider the negative social implications of antibiotic use.

The possibility for individual benefit from antibiotic use in medicine, animal care and agriculture is great and, for most, outweighs social consequences leading to the overuse of these drugs. The problem is compounded by the lack of new antibiotics to attack bacteria in different ways to circumvent the resistance genes.

Resistance Genes.
Found in the bacterial genome that protect bacteria against the inhibitory effects of antibiotics, these genes allow the bacteria to continue to proliferate unaffected by the drug. Resistance genes may encode enzymes to degrade the antibiotic or may code for mutations which alter the antibiotic’s binding site on the bacterial cell, effectively eliminating the drug’s target.
The resistance gene may code for a mutated membrane transport protein that prevents the antibiotic from entering the bacterial cell. Alternatively, the resistance gene might create a pump to export antibiotics immediately upon entry into the cell, preventing the antibiotic from finding its intracellular target.

Resistance Genes evolve in two ways:
Vertical evolution - Random mutation passed on to subsequent generations.
Horizontal evolution - Genes exchanged or acquired from nearby bacteria.

Vancomycin.
Known as a "last resort" antibiotic, vancomycin is no longer able to cope with some bacterial strains. VRE (Vancomycin-Resistant Enterococci) and MRSA (Methicillin-Resistant Staphylococcus Aureus) are two examples. Antibiotic combinations are used in these circumstances, with some limited success.
Colloidal silver has been shown to kill both MRSA and VRE in laboratory tests.

New antibiotics are currently being developed, but wont be available for some years. Meanwhile, researchers are studying alternatives including ionic colloidal silver.

Link - Technical information on antibiotics and their resistance.