Chemotherapeutic and Chemical Agents Microbiology 156.

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Chemotherapeutic and Chemical Agents Microbiology 156

Transcript of Chemotherapeutic and Chemical Agents Microbiology 156.

Chemotherapeutic and Chemical Agents

Microbiology 156

Antibiotics

Drugs that interfere with bacterial cell metabolism

They produce a bacteriocidal or bacteriostatic effect on prokaryote cells

Origin of Antibiotics

These are agents that have been synthesized by bacteria or fungi against other organisms

Example – Penicillin was isolated from the mold Penicillium notatum. It was first observed by Alexander Fleming and later purified by Howard Florey.

Antibiotics inhibit the growth of other microorganisms

Mode of Action

Interfere with the synthesis of the cell wall( peptidoglycans)

Disruption of the cell membrane Inhibition of folic acid Interference with protein synthesis Interference with nucleic acid

synthesis Ribosomal interference

Two Pioneers in Chemotherapeutic agents

Penicillin – The first

Effects the synthesis of the peptidoglycans cell wall

Makes the bacteria vulnerable to the phagocytes in the immune system

Chemical structure of antibiotics based upon the original penicillin

Antibiotics from Actinomycetes

Actinomycetes are soil bacteria

They produce compounds that inhibit other microorganisms

Competition for food and space in the soil environmentSelman Waksman,

Rutgers University, NJ

Streptomycin

Inhibition of bacterial growth by soil bacteria

Pharmacology

Synthetic drugs are designed based upon the structure of molecules produced in nature by bacteria

They are then tested for their antimicrobial activity – in vitro and in vivo

KirbyBauer

The determination of antibiotic sensitivity or resistance

Sensitivity – The organisms growth is inhibited by the presence of the antibiotic

Resistance – The organism has a means of interfering with the mode of action of the antibiotic

Kirby Bauer

Plate bacteria on Mueller Hinton Agar Plate

Distribute bacteria evenly over the surface of the agar

Place discs impregnated with antibiotic on the agar at indicated spots.

Incubate

Determination of antibiotic resistance or sensitivity

Chemical agents

Incubate the plates for 24 hours Measure the diameter of the plate to

determine efficacy of the chemical agents

Determination of resistance or sensitivity Measure the diameter of the ring

around the disc Compare the measurement in mm

with the table in your lab manual, page 284. Table 44.2

Record your results in Table on page 287.

Control of Microbial Growth- Growth Curve

Heat- Destruction of bacterial cells

Autoclave – heat under pressure 121 0C at 15 psi for 15 minutesBoiling For more than 30 minutes

Chemical agentsAgent Mechanism of

ActionUse

Peroxygens Oxidations Use in wounds and abrasions

Alcohols Protein denaturation

Skin disinfection

Organic acids Disrupt proteins- low pH

Used to control moleds

Detergents Disrupts cell membranes

Disinfection

Halogens derivative IodineChlorine

Inhibits protein action in bacteria

Surface area disinfection

Chemical Agents- Agar Plate sensitivity assay Plate the bacteria by spreading it

evenly across the Mueller- Hinton agar.

Dip sterile filter discs into chemotherapeutic agents.

Carefully place the discs in indicated spots on the agar plate

Chemical agents

Torr solution Chlorox solution Mouth wash Lysol solution Other

Determination of activity

Measure the zone of inhibition around the disc to determine if the antiseptic or disinfectant had sufficient activity to inhibit the growth of the bacteria in your study

Chemical Agent Activity AssayOrganism Antiseptic Disinfectant

E. coli

SA

Other