• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10

Comparing antiseptics

Extracts from this document...

Introduction

Analysis Comparing antiseptics An experiment was carried out measure the effectiveness of the antiseptics, tea tree oil and chlorhexidine on both Escherichia coli(gram negative) and Bacillus subtillis (gram positive) Once the plate had been incubated for one day (24 hours) at 30?C, the plates were analysed optically and the zones of inhibitions were measured using a metric ruler (mm), so that the average could be achieved and a justifiable conclusion to be made. E. coli and Bacilllis subtilis are Mesophiles which tolerate temperatures between 20 -40?C , temperatures above this would denature the protein structure of the microorganisms. The disc dipped in sterile water is shown as the control variable. This should not produce a zone of inhibition because the properties of water donot cause cell death to the bacterial cell wall. T-Test for the gram-negative bacteria (E.coli) Plate Zones of inhibition Diameter mm Chlorhexidine (y) Zones of inhibition Diameter mm Tea tree oil (x) Zones of inhibition Area mm2 Chlorhexidine Zones of inhibition Area mm2 Tea tree oil 1 15 20 225 400 2 15 24 225 576 3 16 20 256 400 4 14 16 196 256 5 16 15 256 225 6 16 17 256 289 7 15 20 255 400 8 15 17 255 289 Total 122 149 1924 2835 Mean 1 15.250 18.620 240.500 354.375 Mean 2 15.0 19.0 241 354 The effectiveness of the two antiseptics on E.coli (gram negative) was measured by carrying out a statistical T test. This was done to analyse, which active ingredient in the antiseptic was better in causing lysis (cell death), in the bacterium E. coli. The experiment was repeated eight times and the diameter of the zones of inhibition for tea tree oil and chlorhexidine were measured accordingly. Statistical T- test T = (x) - (y) (?x2/nx) - (x)2 + (?y/ny) - (y)2 nx - 1 ny-1 Null hypothesis - There is no significant difference between the two sets of results, due to chance. ...read more.

Middle

?x = 18 + 20 + 17 + 14 + 21 + 24 + 15 + 18 = 147 ?x2 = 324 + 400 + 289 + 196 + 441 + 576 + 225 + 324 = 2775 nx= 8 number of samples (x) = Mean of x is 147/8 = 18.375 18.0 (3.sf.) (x)2= 182 which is 324 (3.s.f) Calculations for the Chlorhexidine y = Chlorhexidine (mean of diameter) ?y = 24 + 23 + 15 + 20 + 23 + 26 + 21 + 22 = 174 ?y2 = 576 + 529 + 225 + 400 + 529 + 676 + 441 + 484 = 3860 ny = 8 samples (y) = Mean of y, therefore 174/8 = 21.75 22.0 (3.s.f) (y)2 = 222 which is 484 (3.s.f) Inserting the values of the Tea tree oil and the chlorhexidine into the statistical T- test equation T = (x) - (y) (?x2/nx) - (x)2 + (?y/ny) - (y)2 nx - 1 ny-1 Inserting the values for the Tea tree oil Step 1 2775/ 8 324 347 (?x2/nx) - (x)2 nx - 1 7 ?x2= 2775/8 =346.875 347 (3.s.f) nx = no. of samples which is 8 (x) = 18.0 (x)2 = 324 Inserting the values for the Chlorhexidine Step 2 3860 / 8 484 482 (?y2/ny) - (y)2 ny - 1 7 ?y2= 1924 ny = no. of samples which is 8 Therefore 3860/8 =482.5 (y) = 22.0 (y)2 = 484 It is now possible to add the values of the tea tree oil and the chlorhexidine. (?x2/nx) - (x)2 + (?y2/ny) - (y)2 nx -1 ny - 1 347 - 324 + 482 - 484 7 7 347 - 324 = 23 482 - 484 = -2 23 + -2 = 21 7 7 Step 3 It is now possible to add both the results for values for Tea tree oil and chlorhexidine into the statistical T -test equation. ...read more.

Conclusion

Chlorhexidine on the other hand seems to work better on the gram-positive bacteria rather than on the gram-negative bacteria. " Treatment with Chlorhexidine on gram positive bacteria (Bacillus substilis) had a mean diameter of 22.0mm, whereas on the gram negative bacteria (E.coli) the mean diameter value of 15.0mm" This resistance arises because E.coli are able to produce specific enzymes for destroying the active properties of chlorhxidine glucanoate and due to the plasmids that may be carried. These plasmids are extra chromosomal pieces of DNA, which code for the resistance to a number of antibiotics. Resistance can be developed within the bacterium's chromosome. This happens because gram-negative bacteria are generally more resistant to the antiseptic properties of chlorhexidine. The main active property in chlorhexidine, 'chlorhexidine glucanoate' is slow acting antiseptic and its chemistry is not as complex as terpine-4-ol, resulting in the development of resistant strains of an organism in otherwords enables development of resistant enzymes in E.coli. The plasmid DNA carries the resistance and can developed within the bacterium's chromosome. The antimicrobial agents such as the chlorhexidine glucanoate naturally act selectively on specific types of organisms or on specific strain of organism. This action of selectivity favours the survival of organisms that either escape full-strength assault, or those capable of resisting the assault. It seems from the practical investigation I have carried that the E.coil (gram negative) was able to resist full assault of the chlorhexidine, while the Bacillus subtillus (gram positive) endured the full effect of the active ingredient in chlorhexidine and produced less resistance to the antiseptic. Using scientific knowledge, It could be that the outer membrane of gram-negative bacteria (E.coli) however acted as a barrier (layer of peptidoglycan is protected by a complex membrane including lipopolysaccarides, lipids and phospholipids, which limits the entry of many chemically unrelated types of antibacterial agents such as the chlorhexidine gluconate. This could also be a partial reason why the chlorhexidine worked better in gram-positive bacteria, than that of the gram negative. Donald Blankson-Hemans A2 Biology coursework ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Living Things in their Environment section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Living Things in their Environment essays

  1. Marked by a teacher

    The effects of disinfectants and antibacterial soap on bacterial growth

    5 star(s)

    If we were merely repeating our experiment, there would still be several necessary changes. We made an error in not filtering the bouillon broth after it cooled and before it was autoclaved, because the broth had residue and chunks of fat floating in it that inhibited our observations of whether

  2. Marked by a teacher

    Research question - Is using dogs for work ethical?

    5 star(s)

    that animal testing is appropriate and all of the people who don't have a dog believe that it is appropriate. Do dogs sometimes show human behaviours? The above graph shows that all the people who took my questionnaire believe that dogs show human behaviours.

  1. Marked by a teacher

    A2 Biology Coursework -Investigation into the effect of different concentrations of antibiotics on the ...

    4 star(s)

    I repeated this step for all the rest of the test tubes using 2 different cuvettes, one for the blank solution and the other for the solution which was in the test tubes (I washed the cuvette after each test tube to reduce contamination and distortion of light absorbency values)

  2. This assignment is about planning and designing practical experiment to carry out an investigation ...

    - these antibiotics are not inactivated by enzymes and so they are used to treat which other penicillins are incapable of countering. -Novobiocin (NO, 5ug)- NO is effective against some Gram-positive and negative bacteria, but it is no longer used and have no medical reference.

  1. Micro-organisms,most effective antibiotic to act against the two types of bacterium: E.coli and B.subtilis.

    I then inverted the bottle four times slowly and carefully 7. Next I took one of the sterile Petri dishes I was provided with and snipped the sellotape on the side facing away from me. I had to make sure I didn't open the Petri dish in case any dust would get in.

  2. An investigation into the antibiotic effects of penicillin and streptomycin on the bacterium Escherichia ...

    Gram-negative bacteria when developed, such as ampicillin which can treat both Gram-positive bacteria and Gram-negative. Penicillin works by forming peptidoglycan cross links in the bacterial wall, which causes the cell wall to weaken when it tries to divide, causing cytolysis.

  1. Science Chemistry Casestudy

    contaminated by pesticides, animals can also be exposed to pesticides by breathing pesticide spray, or absorbing pesticides through their skin. Eating other animals that have been exposed to pesticides can poison predators such as hawks and owls. [5] * What health problems are associated with exposure to pesticides?

  2. Monitoring an Organism

    If I have monitored them at night then my results would be complete. Bonobos are generally quite peaceful primates and therefore my results shows that it has less aggressiveness compare to the chimpanzee. In fact bonobos are completely opposite to the chimpanzees.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work