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.

 Introduction

Antibiotics are chemicals that are produced by micro-organisms like fungi, which are discovered by a scientist called Louis. They are capable of destroying and disrupting the growth of other micro-organisms mostly by bacteria.

There are 2 types of antibiotics, biocidal and biostatic agents. Biocidal agents kill bacteria and these are streptomycin and penicillin, while biostatic agents only effect the growth and multiplication of micro-organisms, these are chloramphenicol, erythromycin and tetracycline.  

Antibiotic are classified into 2 main types (spectrum):---

Broad spectrum - Broad spectrum antibiotic kills wide range of bacteria

Narrow spectrum- kills limited group of bacteria.

-Penicillin (PG, 1unit) - is first antibiotic produced; This antibiotic is active gram-positive bacteria only, so this means PG is not effective on gram-negative bacteria. PG kills bacteria by targeting their cell wall and it destroys by controlling the formation of peptide links of the bacteria burst open and then it destroys the bacteria. PG is used against anthrax, tetanus diphtheria and many more.

-Chloramphenicol (C, 25ug) - this is an early antibiotic and works by blocking protein synthesis in bacteria. It is used against pneumonia and typhoid.  

-Erythromycin (E, 5ug)) – this is broad spectrum antibiotic, this destroying the plasmid chromosomal of bacteria. It is used to treat patients with a condition which is resistant to the penicillin.

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-Fusidic acid (FC, 10ug) - fusidic acid is a narrow spectrum bacteria used to treat the infection on skin, this also works by blocking protein synthesis in a bacteria

-Methicilin (MT, 10ug) - 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.  

-Streptomycin(S 10ug)- is almost used for the treatments of tuberculosis. This antibiotic binds on bacterial ribosome by interfering with it and ...

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