1. ANTIMICROBIAL THERAPHY prepared by Miss Rashidah Hj Iberahim

2. Antimicrobial theraphy in daily life prepared by Miss Rashidah Hj Iberahim

3. Content Overview of the mechanism of action of antimicrobial drugs Antimicrobial sensitivity test Mechanism of antibiotic resistance prepared by Miss Rashidah Hj Iberahim

4. Introduction  Discovered by Paul Ehrlich (chemical killing pathogenic m/org wtout injuring the host) Antimicrobial theraphy Chemotheraphy  Antibiotic (antibiosis) – chemical (against life)  2 types synthetic semisynthetic prepared by Miss Rashidah Hj Iberahim

6. General properties Selective toxicity The spectrum of activity Modes of action Side effects Resistance of m/org prepared by Miss Rashidah Hj Iberahim

7. PART 1 – GENERAL PROPERTIES prepared by Miss Rashidah Hj Iberahim

8. Selective toxicity To way of actions internal (eat) external (topical) Internal – should be selective toxicity (harm to microbes not the host cell) Most of the antibiotic act depending on 2 levels - toxic dosage level (cause host damage) - therapeutic dosage level ( eliminates the pathogenic organism) prepared by Miss Rashidah Hj Iberahim

9. Relationship of antibiotic and host Measured by chemotherapeutic index – max dose ÷ min dose = range 1 till 8 kg bw kg bw 8 = > effective, < toxic 1 = > toxic, < effective Eg. arsenic, mercury, antimony = toxic and effective towards pathogen Eg. Treatment for worm infection = damage to parasites and host prepared by Miss Rashidah Hj Iberahim

10. The spectrum of activity prepared by Miss Rashidah Hj Iberahim

11. Modes of action 1.Inhibition of cell wall synthesis 2.Disruption of cell membrane function 3.Inhibition of protein synthesis 4.Inhibition of nucleic acid synthesis 5.Action as antimetabolites prepared by Miss Rashidah Hj Iberahim

12. 1. Inhibition of cell wall synthesis Normal mechanism, the peptidoglycan can helps to maintain the osmotic pressure of the cell Allow the membrane of the effected microbe to rupture and release the cell content Usually affecting Gram positive bacteria Examples – penicillin, bacitracin, vancomycin and cephalosporin All the respective antibiotic contain β-lactam ring that attach to enzyme and cross-link with peptidoglycan However, those lack with peptidoglycan (Fungi and Archaea) were unaffected prepared by Miss Rashidah Hj Iberahim

13. 2. Disruption of cell membrane function Dissolve the membrane of interfere with the movement of substances into or out of the cells Polypeptide antibiotic (Polymyxins) act on bacteria as detergent and distort bacterial cell membranes by binding with the phospholipid bilayer Effects on Gram negative bacteria (rich with phospholipids) prepared by Miss Rashidah Hj Iberahim

14. Cont. Polyene antibiotic (amphotericin B) Bind to particular sterols, present in the membranes of fungal and animal cell Polymyxins – do not act on fungi Polyenes - do not act on bacteria prepared by Miss Rashidah Hj Iberahim

15. 3. Inhibition of protein synthesis Basically protein synthesis requires DNA, RNA and ribosomes (bacterial – 50S + 30S / animal – 60S + 40S) Prevent the growth of microbes by disrupting ribosomes or otherwise, interfering with the process of translation Thru selective toxicity (respective attack) Examples: Streptomycin – from amino acids and glycosidic bonds that act on 30S portion interfering the translation process Tetracycline Erythromycin, chloramphenicol – act on 50S portion and interfering the growing of polypeptide prepared by Miss Rashidah Hj Iberahim

16. 4. Inhibition of nucleic acid synthesis Interfere with the synthesis RNA (transcription) or DNA (replication) and disrupt the formation these molecules contain The enzyme used by bacterial and animal cells to synthesize nucleic acids provide a means selective action of antimicrobial agents Example: rifamycin family (transcription), quinolones (DNA replication) and metronidazole Bind to a bacterial RNA polymerase and inhibit RNA synthesis prepared by Miss Rashidah Hj Iberahim

17. 5. Action as antimetabolites Affect normal metabolites by competitively inhibiting microbial enzymes or by being erroneously incorporated into important molecules such as nucleic acids prepared by Miss Rashidah Hj Iberahim

18. Side effects Most of the host will show adverse effects such as toxicity, allergy and disruption of normal microflora Most of the antibiotic acts on pathogen, and also the normal flora Leads to superinfections will happens where the normal flora will demolished and no host defends in particular area prepared by Miss Rashidah Hj Iberahim

19. Resistance of m/org Antibiotic resistance can be a result of horizontal gene transfer, and also of unlinked point mutations in the pathogen genome and a rate of about 1 in 10 8 per chromosomal replication.horizontal gene transferpathogengenome The antibiotic action against the pathogen can be seen as an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce. They will then pass this trait to their offspring, which will result in a fully resistant colony. prepared by Miss Rashidah Hj Iberahim

21. The four main mechanisms: 1.Drug inactivation or modification: e.g. enzymatic deactivation of Penicillin G in some penicillin-resistant bacteria through the production of β-lactamases.Penicillin Gβ-lactamases 2.Alteration of target site: e.g. alteration of PBP—the binding target site of penicillins—in MRSAand other penicillin-resistant bacteria.PBPMRSA 3.Alteration of metabolic pathway: e.g. some sulfonamide- resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acids in bacteria inhibited by sulfonamides. Instead, like mammalian cells, they turn to utilizing preformed folic acid.sulfonamidepara-aminobenzoic acidfolic acidnucleic acids 4.Reduced drug accumulation: by decreasing drug permeability and/or increasing active efflux(pumping out) of the drugs across the cell surface.permeabilityefflux prepared by Miss Rashidah Hj Iberahim

22. Diagram of resistance prepared by Miss Rashidah Hj Iberahim

23. History of resistance The first antibiotic, penicillin, was discovered in 1929 by Sir Alexander Fleming, who observed inhibition of Staphylococci on an agar plate contaminated by aPenicillium mold prepared by Miss Rashidah Hj Iberahim

24. In simple words.. Hereditary drug resistance (R) factors are carried by plasmids and transposons Resistance may be due to enzymatic destruction of a drug, prevention of penetration of the drug to its target site, cellular or metabolic changes at target sites, or rapid efflux of the antibiotic Resistance can be minimized by the discrimination use of drugs in appropriate concentrations and dosages prepared by Miss Rashidah Hj Iberahim

25. Examples Staphylococcus aureus Pseudomonas aeruginosa Streptococcus and Enterococcus Clostridium difficile Salmonella and E. Coli Acinetobacter baumannii prepared by Miss Rashidah Hj Iberahim

26. PART 2 – DETERMINING MICROBIAL SENSITIVITY prepared by Miss Rashidah Hj Iberahim

27. 1.The Disk Diffusion Method Also known as Kirby-Bauer method The sensitivity compared by size of inhibition zone around the disk referred to a table of standard measurements prepared by Miss Rashidah Hj Iberahim

28. The sensitivity level prepared by Miss Rashidah Hj Iberahim

29. 2. The Dilution Method Constant inoculum is placed into broth cultures or well wt differing known quantities of chemotherapeutic agents 2 level of determination: MIC (minimum inhibitory concentration) - lowest concentration of growth / no growth at all MBC (minimum bactericidal concentration) – lowest cont. in which subculturing of broth yields no growth prepared by Miss Rashidah Hj Iberahim

31. 3. Serum Killing Power To determine the capability of antibiotic in killing the pathogen By adding bacterial suspension to the patient’s serum that already taken the antibiotic for certain period of time prepared by Miss Rashidah Hj Iberahim

32. 4. Automated Methods prepared by Miss Rashidah Hj Iberahim

33. Antibacterial agents Refer to : slide on modes of action prepared by Miss Rashidah Hj Iberahim

34. Antifungal Imidazoles and Triazoles Polyenes Griseofulvin Other agents prepared by Miss Rashidah Hj Iberahim

35. Antiviral agents Purine and Pyrimidine Analogs Amantadine Interferons and Immunoenhancers prepared by Miss Rashidah Hj Iberahim

36. Antiprotozoan agents Quinine Chloroquine and Primaquine Metronidazole Other agents prepared by Miss Rashidah Hj Iberahim

37. Antihelminthic agents Niclosamide Mebendazole Other agents prepared by Miss Rashidah Hj Iberahim

38. Homeworks Please study regarding each of the antimicrobial agents listed in this lecture. Focus on the mechanism of actions, resistances and laboratory diagnostic. prepared by Miss Rashidah Hj Iberahim

39. THE END prepared by Miss Rashidah Hj Iberahim