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Investigation - Examination of bacterial sensitivity on antibiotics.

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Investigation: Examination of bacterial sensitivity on antibiotics. Planning: (a) Introduction: The aim of this experiment is to see the effect of antibiotic on the growth and reproduction of three bacteria; Ecoli, Bacillus subtillis, Micrococcus luteus. (b) Apparatus: (i) 3 agar petridishes. (ii) 3 bacteria solution samples (Ecoli, bacillus, micrococcus). (iii) Marker pen. (iv) Alcohol. (v) Beaker. (vi) Glass spreader. (vii) 2ml Syringe. (viii) 3 antibiotic discs. (ix) Forceps (x) Bunsen burner. (xi) Sticky tape. (xii) Eye protection. (c) Method: (i) Take three petridishes and using the marker pen, mark each dish with your name, time and date, and the type of bacteria. (ii) Take one bottle of the samples of bacteria you want to inoculate e.g. Ecoli and using the 2ml syringe withdraw about 0.5ml of the bacteria. Note that before you withdraw the bacteria from the bottle, flame the neck of the bottle using the Bunsen burner, this is an aseptic technique. (iii) Using your syringe with the 0.5ml of Ecoli, add it to one of the petridish containing the agar and immediately place back the lid. (iv) To sterilise your glass spreader and forceps, put a little bit of alcohol in a beaker and place them in this alcohol. (v) Remove your glass spreader after some few minutes from the alcohol and pass it through a flame from the Bunsen burner. (vi) Use the sterilised glass spreader to spread the inoculated Ecoli in the petridish. (vii) After this, pass the glass spreader again through the flame before placing it back in the beaker with the alcohol. (viii) Take out the forceps in the alcohol and as before with the glass spreader, pass it through flame to sterilise. (ix) Use the sterilised forceps to pick the antibiotic disk. (x) ...read more.


2nd diameter (mm) 3rd diameter (mm) 4th diameter (mm) Average (mm) CD 0 0 0 0 0 PG 4.4 0 0 0 1.1 GM 0 1.9 2 0 0.975 T 0 0 0 0 0 TM 0 0 0 0 0 E 0 0 0 0 0 FC 0 0 0 0 0 SMX 0 0 0 0 0 (g) Review and evaluation of my experiment and result: (i) The results of my first experiment was inconclusive because there was no growth of bacteria on most part of the dish even the places without antibiotics. This was mainly because the bacteria samples we were given was not enough. But as shown in my result table, I repeated the experiment 4 times. (ii) From the result we can clearly see that not all of the antibiotics had effect on the growth of bacteria. The only antibiotic that heard effect on the growth of all the 3 bacteria was Gentamicin (GM). (iii) The Bacteria that was most affected by the antibiotics was Ecoli where 5 antibiotics stopped the growth of antibiotic. (iv) From my research I found out that PG that is penicillin had a very great effect on Bacillus and from my result this is not the case. This therefore means that there was something wrong most likely with the bacillus sample. (v) N.B. I have noticed from my result that penicillin had no effect on bacillus that is Gram positive, and from my research I found out that penicillin are active primarily against Gram positive because Gram-negative bacteria are impermeable. This means that I had not inoculated enough bacillus sample in to the nutrient agar. ...read more.


Major products that are either currently manufactured or are anticipated to be manufactured via genetically emerged microbes are hormones such as insulin and human growth hormone. N.B. Because of the high potential of economic value of pharmaceutical agent it can be anticipated that most of the new advancements will be in this field. (m) Conclusion on my results from both the table and the bar chart: * From the result in both the graph and the table we can see that even though that not all the antibiotics had effect on the bacteria some had effect on the growth of the bacteria on the agar and. We can safely say that antibiotics are chemical substances produced by certain microorganisms that are active against other microorgarnisms. * From the bar chart we can conclude that (i) Four antibiotics have effect on the growth of Ecoli and they are; CD, GM, T, E and FC. FC was the highest active on Ecoli because it had the largest diameter of0.95mm and that means that FC had killed the largest amount of Ecoli around it. (ii) Two antibiotics had effect on the growth of bacillus on the agar and they are; GM and T. GM had the largest diameter of 1.65mm and therefore was the most effective on halting the growth of bacillus on the agar. (iii) Finally also in micrococcus only two antibiotics had effect on its growth in the agar and they were; PG and GM. PG had the largest diameter of 1.1mm and therefore that means PG had killed most of the bacteria around it. Therefore from my result we can conclude that; * GM and T are broad-spectrum antibiotics because they act on both Gram positive and negative bacteria. * PG is a narrow spectrum antibiotic because it acts on a particular type of bacteria. ...read more.

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