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Chemotherapeutic and Chemical Agents

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.

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Chemotherapeutic and Chemical Agents

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  1. Chemotherapeutic and Chemical Agents Microbiology 156

  2. Antibiotics • Drugs that interfere with bacterial cell metabolism • They produce a bacteriocidal or bacteriostatic effect on prokaryote cells

  3. 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.

  4. Antibiotics inhibit the growth of other microorganisms

  5. 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

  6. Two Pioneers in Chemotherapeutic agents

  7. Penicillin – The first • Effects the synthesis of the peptidoglycans cell wall • Makes the bacteria vulnerable to the phagocytes in the immune system

  8. Chemical structure of antibiotics based upon the original penicillin

  9. Actinomycetes are soil bacteria They produce compounds that inhibit other microorganisms Competition for food and space in the soil environment Antibiotics from Actinomycetes Selman Waksman, Rutgers University, NJ

  10. Streptomycin

  11. Inhibition of bacterial growth by soil bacteria

  12. 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

  13. 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

  14. 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

  15. Determination of antibiotic resistance or sensitivity

  16. Chemical agents • Incubate the plates for 24 hours • Measure the diameter of the plate to determine efficacy of the chemical agents

  17. 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.

  18. Control of Microbial Growth- Growth Curve

  19. Heat- Destruction of bacterial cells Autoclave – heat under pressure • 121 0C at 15 psi for 15 minutes Boiling • For more than 30 minutes

  20. Chemical agents

  21. 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

  22. Chemical agents • Torr solution • Chlorox solution • Mouth wash • Lysol solution • Other

  23. 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

  24. Chemical Agent Activity Assay

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