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Bohomolets Microbiology Lecture #7


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By Ms. Kostiuk from Microbiology department

Published in: Health & Medicine
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Bohomolets Microbiology Lecture #7

  1. 1. Antimicrobial medicines Principles of chemotherapy Antibiotics
  2. 2. Disinfection <ul><li>is the process that reduces the number of potential pathogens on a material until they no longer represent a hazard. </li></ul>
  3. 3. Asepsis <ul><li>asepsis refers to any practice that prevents the entry of infectious agents onto sterile tissues and thus prevent infection </li></ul>
  4. 4. Antisepsis <ul><li>is the complex of procedures of growth inhibition and reproduction potential pathogenic microorganisms on skin of mucous membrane </li></ul>
  5. 5. Categories antimicrobial agents based on their appsication Antibiotic Preserva-tive Sanitizer Antiseptic Disinfec-tant Term Penicillin, tetracycline Agent produced by microorganisms that inhibits or kills other microorganisms Lactic acid, benzoic acid, sodium chloride Agents that prevents microbial growth: often added to products such as foods and cosmetics to prevent microbial growth Ethanol A disinfectant that is used to reduce numbers of bacteria to levels judged safe by public health officials Soap, hydrogen peroxide, iodine, ethanol Agent that kills of prevents the growth of microorganisms on lining tissues Hypochlorite, formaldehyde Agent that kills microorganisms on inanimate objects Examples Description
  6. 6. The action of antimicrobial agents Cationic detergents Inactivates viruses so that they lose the ability to replicate Virucide Glutaraldehyde Agent that kills bacterial endospores Sporicide Formaldehyde, silver, mercury Chemical agent that specifically kills pathogenic microorganisms Germicide (microbicide) Ethanol Agent that kills fungi Fungicide Hypochlorite Agent that kills living organisms Biocide Chlorhexidine, ethanol Agent that kills bacteria Bactericide Examples Action Term
  7. 7. Antimicrobial agents Can kill or inhibit reproduction of agents of disease in the patient organism. Have selective influence upon microorganisms. Chemotherapeutic medicines Can kill or inhibit growth and development majority of microorganisms in space around patient, and microorganisms that are on human body surface Disinfectants and antiseptics
  8. 8. Classification of disinfectants based on their mode of action Phenolics, quaternary ammonium compounds (surface-active agents) Destroys cell membrane Halogens: iodine, iodophors, chlorine, chlorine compoynds Oxidize proteins Formaldehyde, glutaraldehyde, alcohols, dyes, mercurials, acids Coagulate proteins Type of disinfectant Mode of action
  9. 9. Chemotherapy <ul><li>is a method of therapy of infectious disease and cancer with chemical agents – chemotherapeutic medicines </li></ul>
  10. 10. Chemotherapeutic index <ul><li>Maximal tolerated dose is the most quantity of drug that not cause harmful effect in a patient . </li></ul><ul><li>Minimal curative dose is the least dose of drug that kill of inhibit reproduction of microorganisms </li></ul>Maximal tolerated dose Minimal curative dose > 3
  11. 11. Paul Ehrlich’s principles of chemotherapy <ul><li>Receptor interaction of drug and microorganism </li></ul><ul><li>Changing of chemical structure of drug causes change of its activity </li></ul><ul><li>Changing of drug structure can occur in microorganism’s cell, therapeutic effect can slacken or intensify during it </li></ul><ul><li>Microbes can develop drug resistance to medicine </li></ul><ul><li>The drug can be used only if its chemotherapeutic index is not less three. </li></ul>
  12. 12. Community interactions Mutualism Commensalism Parasitism Antagonism (competition) Synergism Predation
  13. 13. Antagonism (ammensalism) Antagonism is a form interaction between organisms when one microorganisms inhibits development of others <ul><li>Mechanisms of antagonism: </li></ul><ul><li>Competition for nutrient substrate (different spread of growth) </li></ul><ul><li>Excretion of acids, alcohols, ammonia by microorganisms-antagonist </li></ul><ul><li>Excretion antibiotics, bacteriocines by microorganisms-antagonist </li></ul><ul><li>Predation </li></ul>
  14. 14. Antibiotic <ul><li>Chemotherapeutic preparation produced by living organisms or their synthetic analogs that can selectively inhibit disease agents or inhibit growth tumor cells in patient organism </li></ul>
  15. 15. Characteristics of successful antimicrobial drugs <ul><li>Great activity against microbes </li></ul><ul><li>Selectively toxic to the microbe but nontoxic to host cells </li></ul><ul><li>Microbicidal rather than mocrobistatic </li></ul><ul><li>Relatively soluble and functions even when highly diluted in body fluids </li></ul><ul><li>Remains potent long enough to act and is not broken down or excreted prematurely </li></ul><ul><li>Not subject to the debelopment of antimicrobial resistance </li></ul><ul><li>Complements or assists the activities of the host’s defenses </li></ul><ul><li>Remains active despite the presence of large volumes of organic materials </li></ul><ul><li>It is readily delivered to the site of infection </li></ul><ul><li>Does not disrupt the host’s health by causing allergies or predisposing the host to other infections </li></ul>
  16. 16. Classification based on type of antibiotic action <ul><li>Microbistatic (bacteriostatic, fungistatic) agents prevent the growth of microorganisms (bacteria, fungi) </li></ul><ul><li>Microbicidal agent (bactericide, virucide, fungicide) kills microorganisms (bacteria, viruses, fungi) </li></ul>
  17. 17. Categories based on group of organisms that produce of antibiotics Polmyxyn Bacteria Lysocim Animals Imanin, salvin, Plants Streptomycin , tetracycline Actinomycetes Penicillin , cephalosporin Fungi Antibiotics Producers
  18. 18. Classification of antibiotics based on spectrum of action <ul><li>Narrow-spectrum agents are effective against a limited array of different microbial types ( examples: bacitracin inhibit certain gram-positive bacteria ) </li></ul><ul><li>Broad-spectrum agents are active against a wider range of different microbes ( example – tetracycline that affect upon gram-positive and gram-negative bacteria, rickettsias, mycoplasmas) </li></ul>
  19. 19. Primary sites of action of antimicrobic drugs
  20. 20. Modes of action of antimicrobial medicines Amphotericin B, nystatin Antifungal activity Polymyxin Antibacterial activity Alteration of cell membrane function Rifampin Inhibition of RNA synthesis Quinolones Inhibition of DNA synthesis Sulfonamides, trimethoprim Inhibition of nucleotide synthesis Inhibition of nucleic acid synthesis Chloramphenicol, erythromycin Inhibition of protein synthesis Penicilins, cephalosporins Inhibition of cell wall synthesis Drugs Mechanism of action
  21. 21. Types of cell wall synthesis inhibition <ul><li>Inhibit polymerization of peptidoglican </li></ul><ul><ul><li>Penicillins </li></ul></ul><ul><ul><li>Cephalosporins </li></ul></ul><ul><ul><li>Carbapenems </li></ul></ul><ul><ul><li>Monobactams </li></ul></ul><ul><li>Inhibit the synthesis of dipeptide </li></ul><ul><ul><li>Cycloserine </li></ul></ul><ul><li>Inhibit transport of murein components to the assembly place </li></ul><ul><ul><li>Bacitracin </li></ul></ul><ul><li>Block the formation of precursors subunit (muramic acid, pentapeptide, and slucosamine) </li></ul><ul><ul><li>Vancomycin </li></ul></ul>
  22. 22. Inhibition of cell wall synthesis
  23. 23. Mode of action of antibiotics that inhibit protein synthesis
  24. 24. Mode of action of antibiotics that inhibit protein synthesis Clindami-cin Primarily bacteriostatic Blocks peptide bond formation 50 S Erythro- mycin Primarily bacteriostatic Blocks translocation 50 S Chloram-phenicol Both Blocks peptidyltransferase 50 S Tetracyc-lines Bacteriostatic Blocks tRNA binding to ribosome 30 S Aminogly-cosides Bactericidal Blocks functioning of initiation complex and causes misreading of mRNA 30 S Example Type of action Mode of action Riboso-mal subunit
  25. 25. Alteration of cell membrane function Polymyxin Cytoplasm Membrane The detergent action of polymyxin
  26. 26. Microbial resistance to drugs is a possibility of microorganisms to grow and in presence of antibiotic
  27. 27. Specific mechanisms of drug resistance <ul><li>Synthesis of enzymes that inactivate the drug (a) </li></ul><ul><li>Decrease in cell permeability and uptake of the drug </li></ul><ul><li>Change in the number or affinity of the drug receptor sites </li></ul><ul><li>Modification of an essential metabolic pathway (b) </li></ul>
  28. 28. Types of drug resistance <ul><ul><li>Natural </li></ul></ul><ul><ul><li>Acquired </li></ul></ul><ul><ul><ul><li>Mutation </li></ul></ul></ul><ul><ul><ul><li>Recombination </li></ul></ul></ul><ul><ul><ul><li>Transferred with plasmids and transposons </li></ul></ul></ul>
  29. 29. Natural selection and drug resistance
  30. 30. Suppression and alteration of the normal microflora by antimicrobics
  31. 31. Method of testing for the drug susceptibility of microorganisms <ul><li>Qualitative. Diffusion methods </li></ul><ul><li>Quantitative. Method of serial dilutions </li></ul>
  32. 32. Diffusion test for investigation of susceptibility of microorganisms to antibiotics
  33. 33. Tube dilution test Minimal inhibitory dose (MID) is a lowest concentration of drug that inhibits the growth of the microorganisms.
  34. 34. Antiviral therapy Ribavarin Respiratory syncytial Amantadine Influenza A Dideoxyinosine, zidovudine Human immunodeficiency Acyclovir, foscarnet Herpes simplex  -interferon Hepatitis B or C Ganciclovir, foscarnet Cytomegalovirus Medication Virus
  35. 35. Modes of action of antiviral medicines Inhibit viral DNA synthesis by reacting with DNA polymerases Acyclovir, ribavarin, ganciclovir Inhibits reverse transcriptase by attaching to its phosphate receptors Foscarnet Inhibits function of viral mRNA or degrades mRNA  -interferon Prevents assembly of the viral core protein Amantadine Mode of action Medicine