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. Antibiotics from Actinomycetes Actinomycetes are soil bacteria They produce compounds that inhibit other microorganisms Competition for food and space in the soil environment 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

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

18. 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.

19. Control of Microbial Growth- Growth Curve

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

21. Chemical agents Agent Mechanism of Action Use PeroxygensOxidationsUse in wounds and abrasions AlcoholsProtein denaturationSkin disinfection Organic acidsDisrupt proteins- low pH Used to control moleds DetergentsDisrupts cell membranes Disinfection Halogens derivative Iodine Chlorine Inhibits protein action in bacteria Surface area disinfection

22. 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

23. Chemical agents Torr solution Chlorox solution Mouth wash Lysol solution Other

24. 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

25. Chemical Agent Activity Assay OrganismAntisepticDisinfectant E. coli SA Other