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This assignment is about planning and designing practical experiment to carry out an investigation of how various antimicrobial agents' effect new strain of bacterium E.coli (Eschericia coli).

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BTEC National Diploma Applied Science UNIT TITLE: SCIENTIFIC METHODS UNIT NUMBER: 5 Assignment title- individual investigation (Antibiotics) This assignment is about planning and designing practical experiment to carry out an investigation of how various antimicrobial agents' effect new strain of bacterium E.coli (Eschericia coli). I chose antibiotics as antimicrobial agent to investigate the effects on new strain of E.coli, using clear zones. An antibiotic is any chemical compound used to kill or inhibit the growth of infectious organisms, particularly bacteria and fungi Aim The aim of this practical is, to investigate the action of selection of antibiotics on bacteria (E.coli). Hypothesis E.coli (bacterium) will be killed effectively, but this will depend on the type of antibiotic used, because there are 2 types of bacteria (Gram-positive and Gram-negative bacteria). E.coli is Gram-negative bacteria; this means it could be resistant or susceptible to some antibiotics. I think erythromycin, streptomycin, tetracycline and chloramphenicol will work well in this practical because they are all broad spectrum bacteria. Variable * E.coli was used for both dishes to keep the strain of bacteria same * Size of agar plates was also same to keep the size of clear zone to be measured the same. * 0.2cm3 of E.coli used for each plate * incubation temperature was constantly kept at 30oc * Sterilised syringes, forceps and loop are used for both dishes, so unwanted contamination is avoided. ...read more.


* By using match stick, the Bunsen burner was light and adjusted it to blue flame; this is the hottest and is done to make sure to avoid contaminations. Worked near Bunsen burner throughout the practical, again to avoid contamination. * A bottle containing E.coli was opened with little finger on other hand to avoid placing the lid on the bench * The bottle is then flamed at the neck for few seconds, by passing the opening through the Bunsen burner. This is done to produce an upward flow of air from the bottle so that any organism in the area will not fall into the bottle. * A sterilised syringe was used to transfer 0.2 cm3 of E.coli and placed in the centre of the agar plate. * A spreader that has been sterilised was used by dipping it in alcohol in a container and then the spreader was flamed over a Bunsen burner and allowed to burn and waited till it cooled down. * The sterilised spreader was used to spread the bacteria (E.coli) over the agar in the plate, until the bacteria was well spread over the agar * Forceps were sterilised by flaming it over Bunsen burner for few seconds * The sterilised forceps were used to place the antibiotic multi-test discs in the agar plate until flatly placed. ...read more.


May be if the concentration of E.coli increased and the whole practical is repeated again, the results may change and antibiotics such as chloramphenicol with average result of 2.85cm3 would kill bacteria better. In the experiment of some antibiotics overlapped, and because of this it was difficult to measure the area of no growth accurately and it could be measurements were done more than 24 hours. This can be avoided by placing each antibiotic disc on separate plate, so the overlapping of antibiotics will be well avoided. May be I didn't place the antibiotic multi-test disc in the agar plate flatly, and so the antibiotics didn't had good contact with the E.coli. Generally this practical can be improved with following extensions * One could have looked at different types of bacteria, for example one could have used gram-positive bacteria and used penicillin instead of gram-negative bacteria. * An effective antibiotic out of the eight antibiotics used in practical, could be used e.g. tetracycline which was most effective to the E.coli. * One can also use two different types of bacteria for example gram-positive bacteria and gram-negative bacteria and compare them to find out which one is resistant or susceptible to antibiotics. * Different antibiotics may work with different incubator temperature and may be if the temperature of the incubator is increased antibiotics such as chloremphenicol may work better with the E.coli. ...read more.

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