D.6+Antibacterials

toc **D.6 Antibacterials **

D.6.1
**Outline the historical development of penicillin** **Antibacterials**: Chemicals which prevent the growth and multiplication of bacteria   
 * Antibiotics**: Chemicals usually produced by microorganisms which act against other microorganisms
 * Paul Ehrlich, a German scientist of the late 19th Century, introduced the concept of the ‘magic bullet’. The ‘magic bullet’ is a chemical designed to target select pathogenic (disease causing) cells, without affecting their host cells. This was part of the treatment of syphilis (a bacterial disease) with an arsenic compound.
 * [[image:http://www.rpsgb.org.uk/informationresources/museum/exhibitions/exhibition04/images/paul_ehrlich.jpg width="210" height="210" align="right"]]In the 1890's scientists found that certain types of fungi killed bacteria. (Below is an image of penicillium notatum
 * In 1928 the Scottish microbiologist Alexander Fleming accidentally discovered that a mold (penicillium notatum) growing on a petri-dish inhibited bacteria growth. He concluded that the mold had produced a compound which he called penicillin. This discovery was not pursued further.
 * Australian bacteriologist Howard Florey and German biochemist Ernst Chain isolated the antibacterial agent produced by the mold in 1940. Chain also worked out how to isolate and concentrate penicillin as well as theorized its structure (later confirmed by x-ray crystallography done by Dorothy Hodgkin)
 * In 1941, a patient was treated with penicillin to combat an infection. There was a significant improvement in his conditions. However, Florey and Chain did not have sufficient supply to cure him, and the patient died. Later, they began to produce the antibiotic in bulk by growing the mold in large tanks containing corn-steep liquor.
 * Mass development of penicillin was undertaken in the United States and increased quantities reduced the death toll of the Second World War (1944), where many soldiers suffered from bacterial infections caused by open war wounds. The three scientists (Fleming, Florey and Chain) were awarded the 1945 Nobel Prize in Medicine for their discovery.



**Major contributions of Florey and Chain**

overcame the problems with isolating penicillin (producing it in concentrated form) showed that penicillin was harmless on mice developed techniques to purify penicillin (to eliminate the impurities that caused side effects) first to use penicillin on a human grew penicillin in large enough quantities to treat humans

D.6.2
<span style="color: rgb(0, 0, 255); font-size: 110%;">**Explain how penicillins work and discuss the effect of modifying the side chain** <span style="font-family: Verdana,Geneva,sans-serif;"> <span style="font-family: Verdana,Geneva,sans-serif;">
 * <span style="font-family: Verdana,Geneva,sans-serif;">There are two types of bacteria: [|gram positive] and [|gram negative].
 * <span style="font-family: Verdana,Geneva,sans-serif;">Gram positive bacteria have a simple cell wall while gram negative bacteria have complex many layered cell walls. Some antibiotics are ineffective because it is difficult to penetrate the outer layer of gram negative bacteria.
 * Structural formula of penicillin**
 * <span style="font-family: Verdana,Geneva,sans-serif;">Different types of penicillin vary in their R group (side chain). Modifying the R group changes the bacteria destroying ability of the penicillin.
 * How penicillin destroy bacteria**
 * 1) <span style="font-family: Verdana,Geneva,sans-serif;">Prevents cell wall formation so cell shape can't be maintained
 * 2) <span style="font-family: Verdana,Geneva,sans-serif;">Water enters the cells
 * 3) <span style="font-family: Verdana,Geneva,sans-serif;">The cells burst and the bacteria die.

<span style="font-family: Verdana,Geneva,sans-serif;">The structure of penicillin affects its ability to work in different environments. Different R groups side chains changes its activity.

The First Penicillin was called Penicillin G. However it was deactivated by stomach acid so, the benzene side chain was modified to form the modern form of [|Penicillin V] (regular broad spectrum antibiotic prescribed today), which is acid resistant, more soluble in water and is resistant to penicillinase. Penicillinase is an enzyme produced by bacteria that deactivates penicillin preventing it from destroying bacteria.
 * [[image:Penicillin_V_structure.jpg width="337" height="177" caption="Penicillin V" link="http://http://en.citizendium.org/wiki/Penicillin_V"]]

Broad vs. Narrow Spectrum Antibiotics**
 * <span style="font-family: Verdana,Geneva,sans-serif;">Narrow spectrum antibiotics effective against certain types/strains bacteria leaving other unharmed. The specific bacteria is identified with a blood or urine test so the specific antibiotic can be identified and prescribed.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Broad spectrum antibiotics - effective against a wide range of types and strains of bacteria, including helpful/beneficial ones (disadvantage). Blood/urine test not required. Can be brought over the counter.

<span style="font-family: Verdana,Geneva,sans-serif;">D.6.3
<span style="font-family: Verdana,Geneva,sans-serif;"><span style="color: rgb(0, 0, 255); font-size: 110%;">**Discuss and explain the importance of patient compliance and the effects of penicillin over prescription** <span style="font-family: Verdana,Geneva,sans-serif;"> To effectively treat diseases such as tuberculosis, it is important for the patients to adhere strictly to a treatment regime involving a combination of several drugs, to prevent the development of further resistance. Also, some people are allergic to some or all forms of penicillin. Symptoms include skin rashes and fever. In more serious cases, anaphylactic shock, which is sometimes fatal, can occur. Therefore, an allergy to penicillin is always required to be filled out on medical consent forms.
 * Problems with Penicillin Over Prescription**
 * <span style="font-family: Verdana,Geneva,sans-serif;">Makes pencillin less effective, so larger doses are needed
 * <span style="font-family: Verdana,Geneva,sans-serif;">Destroys [|useful/beneficial bacteria]
 * <span style="font-family: Verdana,Geneva,sans-serif;">Allows for more resistant strains to build up
 * <span style="font-family: Verdana,Geneva,sans-serif;">Superbugs, bacteria that are resistant to antibiotic are becoming more of a health problem. Examples of these include Staphylococcus aureus, and the penicillin vancomycin to which it may soon become resistant.
 * <span style="font-family: Verdana,Geneva,sans-serif;">Antibiotics given to farmed animals to prevent the risk of disease (e.g. cows, pigs, chicken, shrimp) are passed on through meat and dairy products to humans, causing the development of more resistant bacteria.
 * Patient compliance**

<span style="font-family: Verdana,Geneva,sans-serif;">Neuss, Geoffrey. __IB Diploma Programme Chemistry Course Companion.__ Oxford: Oxford University Press, 2007. Bro wn, Catra and Mike Ford. __Standard Level Chemistry.__ Heinemann Baccalaureate, 2008. <span style="font-family: Verdana,Geneva,sans-serif;">Derry, Lanna, Maria Connor and Carol Jordan. __Chemistry for use for the IB Diploma Standard level.__ Melbourne: Pearson Education, 2008.