Important Factors For Antimicrobial Activity Biology Essay

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An antibiotic is a chemical compound that in high dilution hinders the growth and the survival of one or more species of microorganism.A drug is considered to have bacteriostatic or fungistatic activity when it inhibits the growth of bacteria or fungi respectively and bactericidal or fungicidal activity when it kills the bacteria or fungi. In vitro tests are used as screening procedure for new agents and for testing the susceptibility of individual isolates from infection to determine which of the available drug might be useful therapeutically.

Important factors for antimicrobial activity are size of the inoculums, metabolic state of microorganism, pH, temperature, and duration of interaction, concentration of the inhibitor and presence of interfering substance.

Antibacterial activity studies:

Literature survey reveals that the synthesis and evaluation of antibacterial activity of various 2-substituted benzimidazole derivatives. The development of resistant among various pathogenic microorganisms towards the antibiotics has increased the impetus for investigating new antimicrobial agent. When a compound are synthesized in the hope that one of them would be more effective than the existing one. The antimicrobial effectiveness of a compound can be evaluated by serial dilution method and cup plate method. Dilution susceptibility tests are used to determine the Minimum Inhibitory Concentration (MIC).

MIC is the lowest concentration of a drug that inhibits the growth of a particular organism under specific condition. The sensitivity of a compound against a particular organism can be studied by cup plate method.Initially the zone of inhibition method was carried out to evaluate the sensitivity of the organism were selected for determination of MIC.

CUP PLATE METHOD:

Cultivation of Microorganism for Antibacterial activity:

The following microorganisms were used to study the antibacterial activity.

Bacillus subtilis - Gram positive bacteria

Staphylococcus aureous - Gram positive bacteria

Escherichia coli - Gram negative bacteria

Salmonella typhi - Gram negative bacteria

Standard: Streptomycin (1000µg)

Solvent: DMF

All the test compounds were tested at 250 µg, 500 µg , and 1000 µg.

Preparation of the medium:

Composition of nutrient agar medium

Beef extract………..10g

Peptone……………..10g

Sodium chloride……..5g

Agar………………….20g

Purified water………1000ml

pH...............................7.2± 0.2

The medium was prepared by dissolving the specified quantity of the dehydrated medium in purified water by heating on a water bath and were dispensed in 100 ml volume conical flasks. The conical flasks were closed with cotton plugs and were sterilized by autoclaving at 121°C (15 lb psig) for 15 minutes.

The contents of the conical flasks were poured aseptically into sterile Petridishes are allowed to solidify. These sterilized Medias were used to subculture the bacterial culture.

Procedure:

Each Petridish was filled to a depth of 4-5 mm with a nutrient agar medium that was previously inoculated with suitable inoculums of suitable test organism, and then allowed to solidify. The petridish were specially selected with flat bottom and were placed on level surface so as to ensure that the layer of medium is in uniform thickness. The petridishes were sterilized at 160-170°C in hot air oven for 30 mins before use. Small sterile borer of uniform size was placed approximately at 10 cm height, having an internal diameter of approximately 6-8 mm and made of aluminium (or) stainless steel. Each plate was divided in to four equal portions along the diameter. To each portion one cylindrical cavity was made in medium with the help of sterile borer. Three cavities for test compounds and one cavity for the standard. The petridishes were incubated at 37°C for 18 hours. Diameter of the zone of inhibition was measured and the average diameter for each sample was calculated. The diameter obtained by the test sample was compared with that produced by standard Streptomycin.

Antifungal Activity Studies:

CUP PLATE METHOD:

Cultivation of Microorganism for Antifungal activity:

The following fungal strains were used to study the antibacterial activity.

1. C.raphigera

2. A.polytricha

Standard: Ketocanazole (1000mcg)

Solvent: DMF

All the test compounds were tested at 250 µg, 500 µg , and 1000 µg.

Preparation of the medium:

Composition of nutrient agar medium

Sabraoud Dextrose broth...........64gm

Distilled water............................1000ml

pH...............................................7.2± 0.2

The medium was prepared by dissolving the specified quantity of the dehydrated medium in purified water by heating on a water bath and were dispensed in 100 ml volume conical flasks. The conical flasks were closed with cotton plugs and were sterilized by autoclaving at 121°C (15 lb psig) for 15 minutes.

The contents of the conical flasks were poured aseptically into sterile Petri dishes are allowed to solidify. These sterilized medias were used to subculture the fungal culture.

ROCEDURE:

Each Petridish was filled to a depth of 4-5 mm with a nutrient agar medium that was previously inoculated with suitable inoculums of suitable test organism, and then allowed to solidify. The petridish were specially selected with flat bottom and were placed on level surface so as to ensure that the layer of medium is in uniform thickness. The petridishes were sterilized at 160-170°C in hot air oven for 30 mins before use. Small sterile borer of uniform size was placed approximately at 10 cm height, having an internal diameter of approximately 6-8 mm and made of aluminium (or) stainless steel. Each plate was divided in to four equal portions along the diameter. To each portion one cylindrical cavity was made in medium with the help of sterile borer. Three cavities for test compounds and one cavity for the standard. The petridishes were incubated at 37°C for 18 hours. Diameter of the zone of inhibition was measured and the average diameter for each sample was calculated. The diameter obtained by the test sample was compared with that produced by standard Ketocanazole.

Table: Antifungal activity of Benzimidazole Derivatives

Compound

Concentration

(µg)

Zone of Inhibition

C.raphigera

A.polytricha

A

250

500

1000

23

24

25

24

25

26

B

250

500

1000

22

24

24

24

26

28

C

250

500

1000

24

26

28

19

22

27

D

250

500

1000

21

23

24

21

22

25

E

250

500

1000

23

25

26

20

22

24

F

250

50

1000

23

24

26

25

26

27

G

250

500

1000

23

24

27

19

22

25

H

250

500

1000

22

23

24

16

20

24

Std

Ketocanazole

1000

26

30

Introduction to Medicinal Chemistry

The subject of medicinal chemistry explains the design and production of compounds that can be used for the prevention, treatment or cure of human and animal diseases. Medicinal chemistry includes the study of already existing drugs, of their biological properties and their structure-activity relationships. Medicinal chemistry was defined by IUPAC specified commission as "it concerns the discovery, the development, the identification and the interpretation of the mode of action of biologically active compounds at the molecular level".Medicinal chemistry covers the following stages:

(i) In the first stage new active substances or drugs are identified and prepared from natural sources, organic chemical reactions or biotechnological processes. They are known as lead molecules.

(ii) The second stage is optimization of lead structure to improve potency, selectivity and

to reduce toxicity.

(iii) Third stage is development stage, which involves optimization of synthetic route for bulk production and modification of pharmacokinetic and pharmaceutical properties of active substance to render it clinically useful. Medicinal chemistry is the application of chemical research techniques to the synthesis of pharmaceuticals. During the early stages of medicinal chemistry development, scientists were primarily concerned with the isolation of medicinal agents found in plants. Today, scientists in this field are also equally concerned with the creation of new synthetic compounds as drugs. Medicinal chemistry is almost always geared toward drug discovery and development. Medicinal chemists apply their chemistry training to the process of synthesizing new pharmaceuticals. They also work on improving the process by which other pharmaceuticals are made. Most chemists work with a team of scientists from different disciplines, including biologists, toxicologists, pharmacologists, theoretical chemists, microbiologists, and bio pharmacists. Together this team uses sophisticated analytical techniques to synthesize and test new drug products and to develop the most cost-effective and eco-friendly means of production.

Medicinal

Chemistry

The focus on development of new synthetic drug compounds has resulted in the Incorporation of many other disciplines, such as biochemistry and molecular biology, into medicinal chemistry.These areas include biology, computer aided drug design , X-ray crystallography metabolism and pharmacokinetics, legal and regulatory affairs, clinical, franchise management, pharmaceutics and process research chemistry.

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