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Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
Chemical control part2
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Chemical control part2

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For BIO120lec1 2011-2012

For BIO120lec1 2011-2012

Published in: Health & Medicine
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  • 1. Chemical controlMicrobial control part 2 Lani Manahan January 27,2012
  • 2. Chemical Agents 1. PHENOLICS 2. ALCOHOLS 3. HALOGENS 4. HEAVY METALS 5. QUATERNARY AMMONIUM COMPOUNDS 6. ALDEHYDES 7. STERILIZING GASES
  • 3. Chemical Agents Chemical agent Effectiveness against Endospores Mycobacteria Phenolics Poor Good Quats None None Chlorines Fair Fair Alcohols Poor Good Glutaraldehyde Fair Good
  • 4. PHENOLICS• First widely used antiseptic and disinfectant• Joseph Lister (1867): reduced the risk of infection during operations• Act by denaturing proteins and disrupting cell membranes• Phenol / Phenolics: Lysol • Bisphenols: Hexachlorophene, Triclosan
  • 5. PHENOLICSPHENOLICS• ADVANTAGES: effective in the presence of organic material and remain active on surfaces long after application• DISADVANTAGE: disagreeable odor and can cause skin irritation and in some instances brain damage (hexachlorophene)
  • 6. ALCOHOLS • Ethanol, Isopropanol (70-80% concentration)• Act by denaturing proteins and possibly by dissolving membrane lipids• 10-15 soaking in alcohol is sufficient to disinfect thermometers and small instruments
  • 7. HALOGENS• Iodine – Kills by oxidizing cell constituents and iodinating cell proteins – Kill spores at high concentrations – DISADVANTAGE: a stain may be left (answer = iodophor)• Chlorine – Usually for water supply – Kills by oxidation of cellular materials and destruction of vegetative bacteria, fungi – Will not kill spores – Death within 30 minutes
  • 8. HEAVY METALS• Mercury, Arsenic, Zinc, Copper• Used as germicides• How do they Kill: – Heavy metals combine with proteins, often with their sulfhydryl groups and inactivate them – May also precipitate cell proteins
  • 9. QUATERNARY AMMONIUM COMPOUNDS• DETERGENTS – Amphipathic (both polar and non-polar ends) – Kill by disrupting microbial membranes and denature proteins – ADVANTAGE: stable, non-toxic – DISADVANTAGE: inactivated by hard water Soap Degerming Acid-anionic Sanitizing detergents Quaternary ammonium Bactericidal, Denature proteins, compounds disrupt plasma membrane Cationic detergents
  • 10. ALDEHYDES• FORMALDEHYDES – Very reactive molecules that combine with proteins and inactivate them – Sporicidal and can be used as sterilants
  • 11. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESSPHENOL COEFFICIENT TEST – Best-known disinfectant screening test – Potency of a disinfectant is compared with that of phenol – The highest dilution that killed bacteria after a 10 minutes exposure are used to calculate phenol coefficient – The higher the phenol coefficient value, the more effective the disinfectant under this conditions• The reciprocal of the appropriate test disinfectant dilution is divided by that for phenol to obtain the coefficient• Example: phenol dilution = 1/90 and the maximum effective dilution for disinfectant X = 1/450• Phenol coefficient = 5
  • 12. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESSTHE USE DILUTION TEST – Metal rings dipped in test bacteria are dried – Dried cultures placed in disinfectant for 10 min at 20°C – Rings transferred to culture media to determine whether bacteria survived treatment
  • 13. EVALUATION OF ANTIMICROBIAL AGENT EFFECTIVENESS• Disk diffusion
  • 14. ChemotherapyChemotherapeutic agent: Antibiotic
  • 15. ANTIBIOTICS• An antibiotic is a product produced by a microorganism or a similar substance produced wholly or partially by chemical synthesis, which in low concentrations, inhibits the growth of other microorganisms – Antibiotics are medicines used to treat infections caused by bacteria only – Infections are usually caused by bacteria or viruses – Antibiotics, therefore, do not cure all infections – Many infections like the common cold, flu, mild sore throat or diarrhea are caused by viruses
  • 16. ANTIBIOTICSTestsSusceptibility 1. Broth dilution - MIC test 2.Agar dilution - MIC test
  • 17. ANTIBIOTICS Minimal Inhibitory Concentration (MIC) 32 ug/ml 16 ug/ml 8 ug/ml 4 ug/ml 2 ug/ml 1 ug/ml Sub-culture to agar medium MIC = 16 ug/ml
  • 18. ANTIBIOTICSTestsSusceptibility3. Agar diffusion  Kirby-Bauer Disk Diffusion Test
  • 19. ANTIBIOTICSTestsSusceptibility“Kirby-Bauer Disk-plate test”Diffusion depends upon:1. Concentration (cont’d)2. Molecular weight3. Water solubility4. pH and ionization5. Binding to agar
  • 20. ANTIBIOTICS Susceptibility Tests “Kirby-Bauer Disk-plate test” (cont’d) Zones of Inhibition (~ antimicrobial activity) depend upon: 1. pH of environment 2. Media components – Agar depth, nutrients 3. Stability of drug 4. Size of inoculum 5. Length of incubation 6. Metabolic activity of organisms
  • 21. Antibiotic Mechanisms of Action Alteration of Cell Membrane Polymyxins Bacitracin Neomycin Transcription Translation Translation
  • 22. • When bacteria are exposed to an antibiotic, they either die or adapt• Those that survive carry genes that protect them against the antibiotic and pass those genes on to other bacteria• Since bacteria multiply very quickly and can be easily spread among people, resistant bacteria can easily occur in places like hospitals and nursing homes, where a lot of people are gathered and antibiotic use is high
  • 23. ANTIBIOTICS Emergence of Antimicrobial Resistance Susceptible Bacteria Resistant Bacteria Resistance Gene Transfer New Resistant Bacteria
  • 24. Selection for Antimicrobial- Resistant Strains Resistant Strains Rare Antimicrobial Exposure Resistant Strains Dominant
  • 25. ResistancePhysiological Mechanisms 1. Lack of entry – tet, fosfomycin 2. Greater exit – efflux pumps – tet (R factors) 3. Enzymatic inactivation – bla (penase) – hydrolysis – CAT – chloramphenicol acetyl transferase – Aminogylcosides & transferases 4. Altered target – RIF – altered RNA polymerase (mutants) – NAL – altered DNA gyrase – STR – altered ribosomal proteins – ERY – methylation of 23S rRNA 5. Synthesis of resistant pathway – TMPr plasmid has gene for DHF reductase; insensitive to TMP
  • 26. Mechanism of ActionCELL WALL SYNTHESIS INHIBITORS Resistance to β-Lactams – Gram pos. (cont’d)
  • 27. Mechanism of ActionCELL WALL SYNTHESIS INHIBITORSResistance to β-Lactams – Gram neg. (cont’d)
  • 28. Danger of spread of antibiotic resistant bacteria
  • 29. Danger of spread of antibiotic resistant bacteria• Antibiotics revolutionised medicine• The first antibiotic, penicillin, was discovered by Alexander Fleming in 1929• It took less than 20 years for, bacteria to show signs of resistance• Staphylococcus aureus, which causes blood poisoning and pneumonia, started to show resistance in the 1950s• Today there are different strains of S. aureus resistant to every form of antibiotic in use (MRSA)
  • 30. Danger of spread of antibiotic resistant bacteria
  • 31. Where do we get antibiotic resistant bacteria• If a patient taking a course of antibiotic treatment does not complete it• Or forgets to take the doses regularly, then resistant strains get a chance to build up• When antibiotics are used on a person, the numbers of antibiotic resistant bacteria increase in other members of the family• In places where antibiotics are used extensively e.g. hospitals and farms antibiotic resistant strains increase in numbers
  • 32. Antimicrobial Resistance Among Pathogens Causing Hospital-Acquired Infections Methicillin (oxacillin)-resistant Vancomycin-resistant Staphylococcus aureus enterococci 30 60 Percent Resistance 25 Percent Resistance 50 20 40 15 30 10 20 10 5 0 0 89 90 91 92 93 94 95 96 97 98 99 00 89 90 91 92 93 94 95 96 97 98 99 00 19 19 19 19 19 19 19 19 19 19 19 20 19 19 19 19 19 19 19 19 19 19 19 20 Non-Intensive Care Unit Patients Intensive Care Unit PatientsSource: National Nosocomial Infections Surveillance (NNIS) System
  • 33. Antimicrobial Resistance Among Pathogens CausingHospital-Acquired Infections 3rd generation cephalosporin- Fluoroquinolone-resistant resistant Klebsiella pneumoniae Pseudomonas aeruginosa 30 14 Percent Resistance 25 Percent Resistance 12 20 10 8 15 6 10 4 5 2 0 0 89 90 91 92 93 94 95 96 97 98 99 00 89 90 91 92 93 94 95 96 97 98 99 00 19 19 19 19 19 19 19 19 19 19 19 20 19 19 19 19 19 19 19 19 19 19 19 20 Non-Intensive Care Unit Patients Intensive Care Unit PatientsSource: National Nosocomial Infections Surveillance (NNIS) System
  • 34. Myths & Facts aboutAntibiotics andRespiratory Illness
  • 35. Myths and Facts• Myth: Taking antibiotics means I or my child can return to work or childcare sooner• Fact: Antibiotics do not shorten the duration of viral illnesses Everyone should stay home until they are fever-free and well enough to participate in activities whether they have a viral or bacterial illness.
  • 36. Myths and Facts• Myth: Cold and flu symptoms will feel better or get better faster on antibiotics• Fact: Antibiotics cannot ease the symptoms of viral illnesses; these infections resolve on their own Children and adults need extra rest and care, extra fluids…not antibiotics, symptomatic relief is helpful
  • 37. Myths and Facts• Myth: Illnesses with the same symptoms require antibiotics• Fact: Illnesses with similar symptoms can be caused by different germs Let a healthcare provider decide if the illness is caused by a virus or bacteria - and if antibiotics are needed
  • 38. Myths and Facts• Myth: If I take an antibiotic, I won’t spread my illness to others• Fact: Viral illnesses (colds, flu, etc.) usually spread from person to person before the onset of symptoms; before a person appears ill Antibiotics cannot stop the spread of viral illnesses
  • 39. How do we Stop AntibioticMisuse?• Don’t ask for antibiotics – let your doctor decide if you need them• Always take antibiotics exactly as prescribed• Finish the whole prescription - do not stop when you feel better• Never save antibiotics for a future illness – or share with others
  • 40. ANTIMICROBIAL RESISTANCE:KEY PREVENTION STRATEGIES Susceptible Pathogen Antimicrobial-Resistant Pathogen Pathogen Prevent Prevent Transmission Infection Antimicrobial Infection Resistance EffectiveOptimize Use Diagnosis and Treatment Antimicrobial Use
  • 41. 12 Steps to Prevent AntimicrobialResistance: Hospitalized Adults Use Antimicrobials Wisely Prevent Infection 5. Practice antimicrobial control 1. Vaccinate 6. Use local data 7. Treat infection, not 2. Get the catheters out contamination 8. Treat infection, not colonization 9. Know when to say “no” to vanco Diagnose and Treat Infection Effectively 10. Stop treatment when infection is cured or unlikely 3. Target the pathogen Prevent Transmission 4. Access the experts 11. Isolate the pathogen 12. Contain the contagion

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