Basic Principles and Mechanism of Antimicrobial Control
- 2. Basic Principles of Microbial Control 2
- 3. The Selection of Microbial Control Methods • Factors Affecting the Efficacy of Antimicrobial Methods ▫ Site to be treated Harsh chemicals and extreme heat cannot be used on humans, animals, and fragile objects Method of microbial control based on site of medical procedure 3
- 4. Relative susceptibilities of microbes to antimicrobial agents Figure 9.2 4
- 5. The Selection of Microbial Control Methods • Factors Affecting the Efficacy of Antimicrobial Methods ▫ Relative susceptibility of microorganisms Germicides classified as high, intermediate, or low effectiveness High-level kill all pathogens, including endospores Intermediate-level kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria Low-level kill vegetative bacteria, fungi, protozoa, and some viruses 5
- 6. Effect of temperature on the efficacy of an antimicrobial chemical Figure 9.3 6
- 7. The Selection of Microbial Control Methods • Methods for Evaluating Disinfectants and Antiseptics ▫ Phenol coefficient Evaluates efficacy of disinfectants and antiseptics by comparing an agent’s ability to control microbes to phenol Greater than 1.0 indicates agent is more effective than phenol Has been replaced by newer methods 7
- 8. The Selection of Microbial Control Methods • Methods for Evaluating Disinfectants and Antiseptics – Use-dilution test • Metal cylinders dipped into broth cultures of bacteria • Contaminated cylinder immersed into dilution of disinfectant • Cylinders removed and placed into tube of medium to see how much bacteria survived • Most effective agents entirely prevent growth at highest dilution • Current standard test in the U.S. • New standard procedure being developed 8
- 9. The Selection of Microbial Control Methods • Methods for Evaluating Disinfectants and Antiseptics ▫ Kelsey-Sykes capacity test Alternative assessment approved by the European Union Bacterial suspensions added to the chemical being tested Samples removed at predetermined times and incubated Lack of bacterial reproduction reveals minimum time required for the disinfectant to be effective 9
- 10. The Selection of Microbial Control Methods • Methods for Evaluating Disinfectants and Antiseptics ▫ In-use test Swabs taken from objects before and after application of disinfectant or antiseptic Swabs inoculated into growth medium and incubated Medium monitored for growth Accurate determination of proper strength and application procedure for each specific situation 10
- 11. Physical Methods of Microbial Control • Heat-Related Methods ▫ Effects of high temperatures Denature proteins Interfere with integrity of cytoplasmic membrane and cell wall Disrupt structure and function of nucleic acids ▫ Thermal death point Lowest temperature that kills all cells in broth in 10 min ▫ Thermal death time Time to sterilize volume of liquid at set temperature 11
- 12. Physical Methods of Microbial Control • Heat-Related Methods ▫ Moist heat Used to disinfect (kill organisms and remove spores), sanitize (kill organisms but not necessarily their spores), and sterilize (kill all organisms and spores) Denatures proteins and destroys cytoplasmic membranes More effective than dry heat Methods of microbial control using moist heat Boiling Autoclaving Pasteurization Ultrahigh-temperature sterilization 12
- 13. Physical Methods of Microbial Control • Heat-Related Methods ▫ Moist heat Boiling Kills vegetative cells of bacteria and fungi, protozoan trophozoites, and most viruses Boiling time is critical ▫ Different elevations require different boiling times Endospores, protozoan cysts, and some viruses can survive boiling 13
- 14. Physical Methods of Microbial Control • Heat-Related Methods ▫ Moist heat Autoclaving Pressure applied to boiling water prevents steam from escaping Boiling temperature increases as pressure increases Autoclave conditions – 121ºC, 15 psi, 15 min 14
- 15. The relationship between temperature and pressure Figure 9.5 15
- 17. Physical Methods of Microbial Control • Heat-Related Methods ▫ Moist heat Pasteurization Used for milk, ice cream, yogurt, and fruit juices Not sterilization ▫ Heat-tolerant microbes survive Pasteurization of milk ▫ Batch method ▫ Flash pasteurization (High temp, short time) ▫ Ultrahigh-temperature pasteurization (very high temp, very short time) 17
- 18. Pasteurization of milk Batch method • The batch method uses a vat pasteurizer which consists of a jacketed vat surrounded by either circulating water, steam or heating coils of water or steam. In the vat the milk is heated and held throughout the holding period while being agitated. The milk may be cooled in the vat or removed hot after the holding time is completed for every particle. 18
- 19. Pasteurization of milk Flash method • High Temperature Short Time (HTST) • Milk is heated to 72°C (161.6°F) for at least 15 seconds. • Used for perishable beverages like fruit and vegetable juices, beer, and some dairy products. Compared to other pasteurization processes, it maintains color and flavor better. • It is done prior to filling into containers in order to kill spoilage microorganisms, to make the products safer and extend their shelf life. Flash pasteurization must be used in conjunction with sterile fill technology. 19
- 20. Pasteurization of milk Ultrahigh-temperature method • Heating for 1-2 seconds at a temperature exceeding 135°C (275°F), which is the temperature required to kill spores in milk. • The most common UHT product is milk, but the process is also used for fruit juices, cream, soy milk, yogurt, wine, soups, and stews. • Can cause browning and change the taste and smell of dairy products. • UHT canned milk has a typical shelf life of six to nine months, until opened. 20
- 21. Physical Methods of Microbial Control • Heat-Related Methods ▫ Moist heat Ultrahigh-temperature sterilization 140ºC for 1 sec, then rapid cooling Treated liquids can be stored at room temperature 21
- 22. Physical Methods of Microbial Control • Heat-Related Methods ▫ Dry heat Used for materials that cannot be sterilized with moist heat Denatures proteins and oxidizes metabolic and structural chemicals Requires higher temperatures for longer time than moist heat Incineration is ultimate means of sterilization 22
- 23. Physical Methods of Microbial Control • Refrigeration and Freezing ▫ Decrease microbial metabolism, growth, and reproduction Chemical reactions occur slower at low temperatures Liquid water not available ▫ Psychrophilic microbes can multiply in refrigerated foods ▫ Refrigeration halts growth of most pathogens ▫ Slow freezing more effective than quick freezing ▫ Organisms vary in susceptibility to freezing 23
- 24. Physical Methods of Microbial Control • Dessication and Lyophilization ▫ Dessication is drying (98% of the water is removed) inhibits growth due to removal of water ▫ Lyophilization (freeze-drying) Substance is rapidly frozen and sealed in a vacuum Substance may also be turned into a powder ▫ Used for long-term preservation of microbial cultures Prevents formation of damaging ice crystals 24
- 25. The use of dessication as a means of preserving apricots Figure 9.8 25
- 26. Filtration equipment used for microbial control Figure 9.9 26
- 27. The role of HEPA filters in biological safety cabinets Figure 9.10 High-Efficiency Particulate Arresting (HEPA) air filters are used in medical facilities, automobiles, aircraft, and homes. The filter must remove 99.97% of all particles greater than 0.3 micrometer from the air that passes through. 27
- 28. Physical Methods of Microbial Control • Osmotic Pressure ▫ High concentrations of salt or sugar in foods to inhibit growth ▫ Cells in hypertonic solution of salt or sugar lose water ▫ Fungi have greater ability than bacteria to survive hypertonic environments 28
- 29. Physical Methods of Microbial Control • Radiation ▫ Ionizing radiation Wavelengths shorter than 1 nm Electron beams, gamma rays Ejects electrons from atoms to create ions Ions disrupt hydrogen bonding, cause oxidation, and create hydroxide ions Hydroxide ions denature other molecules (DNA) Electron beams – effective at killing but do not penetrate well Gamma rays – penetrate well but require hours to kill microbes 29
- 30. Increased shelf life of food achieved by ionizing radiation Figure 9.11 30
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- 32. Physical Methods of Microbial Control • Radiation ▫ Nonionizing radiation Wavelengths greater than 1 nm Excites electrons, causing them to make new covalent bonds Affects 3-D structure of proteins and nucleic acids UV light causes pyrimidine dimers in DNA UV light does not penetrate well Suitable for disinfecting air, transparent fluids, and surfaces of objects 32
- 33. Physical Methods of Microbial Control • Biosafety Levels ▫ Four levels of safety in labs dealing with pathogens Biosafety Level 1 (BSL-1) Handling pathogens that do not cause disease in healthy humans Biosafety Level 2 (BSL-2) Handling of moderately hazardous agents Biosafety Level 3 (BSL-3) Handling of microbes in safety cabinets Biosafety Level 4 (BSL-4) Handling of microbes that cause severe or fatal disease 33
- 34. A BSL-4 worker carries Ebola virus cultures Figure 9.12 34
- 35. Chemical Methods of Microbial Control • Affect microbes’ cell walls, cytoplasmic membranes, proteins, or DNA • Effect varies with differing environmental conditions • Often more effective against enveloped viruses and vegetative cells of bacteria, fungi, and protozoa 35
- 36. Chemical Methods of Microbial Control • Phenol and Phenolics ▫ Intermediate- to low-level disinfectants ▫ Denature proteins and disrupt cell membranes ▫ Effective in presence of organic matter ▫ Remain active for prolonged time ▫ Commonly used in health care settings, labs, and homes ▫ Have disagreeable odor and possible side effects 36
- 37. Chemical Methods of Microbial Control • Alcohols ▫ Intermediate-level disinfectants ▫ Denature proteins and disrupt cytoplasmic membranes ▫ More effective than soap in removing bacteria from hands ▫ Swabbing of skin with 70% ethanol prior to injection 37
- 38. Chemical Methods of Microbial Control • Halogens ▫ Intermediate-level antimicrobial chemicals ▫ Believed to damage enzymes via oxidation or by denaturation ▫ Widely used in numerous applications Iodine tablets, iodophores, chlorine treatment, bleach, chloramines, and bromine disinfection 38
- 39. Pre-op preparation for hand surgery Figure 9.14 39
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- 41. Chemical Methods of Microbial Control • Oxidizing Agents ▫ Peroxides, ozone, and peracetic acid ▫ Kill by oxidation of microbial enzymes ▫ High-level disinfectants and antiseptics ▫ Hydrogen peroxide (H2O2) can disinfect and sterilize surfaces Not useful for treating open wounds due to catalase activity: the tissues convert it into H20 and 0ygen bubbles. ▫ Ozone treatment of drinking water ▫ Peracetic acid is an effective sporocide used to sterilize equipment 41
- 42. Chemical Methods of Microbial Control • Surfactants ▫ “Surface active” chemicals Reduce surface tension of solvents ▫ Soaps and detergents Soaps have hydrophilic and hydrophobic ends Good degerming agents but not antimicrobial Detergents are positively charged organic surfactants ▫ Quats (Quaternary ammonium cations) Low-level disinfectants; disrupts cell membranes Ideal for many medical and industrial applications Good against fungi, amoeba, and enveloped viruses, but not endospores, Mycobacterium tuberculosis and non-enveloped viruses. 42
- 43. Chemical Methods of Microbial Control • Heavy Metals ▫ Heavy-metal ions denature proteins ▫ Low-level bacteriostatic and fungistatic agents ▫ 1% silver nitrate to prevent blindness caused by N. gonorrhoeae ▫ Thimerosal used to preserve vaccines ▫ Copper inhibits algal growth 43
- 44. Chemical Methods of Microbial Control • Aldehydes ▫ Compounds containing terminal –CHO groups ▫ Cross-link functional groups to denature proteins and inactivate nucleic acids ▫ Glutaraldehyde disinfects and sterilizes ▫ Formalin used in embalming and disinfection of rooms and instruments 44
- 45. Chemical Methods of Microbial Control • Gaseous Agents ▫ Microbicidal and sporicidal gases used in closed chambers to sterilize items ▫ Denature proteins and DNA by cross-linking functional groups ▫ Used in hospitals and dental offices ▫ Disadvantages Can be hazardous to people Often highly explosive Extremely poisonous Potentially carcinogenic 45
- 46. Chemical Methods of Microbial Control • Enzymes ▫ Antimicrobial enzymes act against microorganisms ▫ Human tears contain lysozyme Digests peptidoglycan cell wall of bacteria ▫ Enzymes to control microbes in the environment Lysozyme used to reduce the number of bacteria in cheese Prionzyme can remove prions on medical instruments 46
- 47. Chemical Methods of Microbial Control • Antimicrobials ▫ Antibiotics, semi-synthetic, and synthetic chemicals ▫ Typically used for treatment of disease ▫ Some used for antimicrobial control outside the body 47
- 48. Chemical Methods of Microbial Control • Development of Resistant Microbes ▫ Little evidence that products containing antiseptic and disinfecting chemicals is beneficial to human or animal health ▫ Use of such products promotes development of resistant microbes 48
- 49. Antimicrobial Agents • Chemicals that affect physiology in any manner • Chemotherapeutic agents ▫ Drugs that act against diseases • Antimicrobial agents ▫ Drugs that treat infections 49
- 50. The History of Antimicrobial Agents • Semi-synthetics ▫ Chemically altered antibiotics that are more effective than naturally occurring ones • Synthetics ▫ Antimicrobials that are completely synthesized in a lab 50
- 51. Mechanisms of Antimicrobial Action • Key is selective toxicity • Antibacterial drugs constitute largest number and diversity of antimicrobial agents • Fewer drugs to treat eukaryotic infections (protozoa, fungi, helminthes) • Even fewer antiviral drugs 51
- 52. Mechanisms of Antimicrobial Action • Inhibition of bacterial wall synthesis • Disruption of existing cytoplasmic membranes • Inhibition of Protein Synthesis • Inhibition of Nucleic Acid Synthesis • Inhibition of Metabolic Pathways • Prevention of Virus Attachment 52
- 53. Basic Principles of Microbial Control • Action of Antimicrobial Agents ▫ Alteration of cell walls and membranes Cell wall maintains integrity of cell Cells burst due to osmotic effects when damaged Cytoplasmic membrane controls passage of chemicals into and out of cell Cellular contents leak out when damaged Non-enveloped viruses have greater tolerance of harsh conditions 53
- 54. Mechanisms of Antimicrobial Action • Inhibition of Cell Wall Synthesis ▫ Inhibition of bacterial wall synthesis Most common agents prevent cross-linkage of NAM- NAG subunits Beta-lactams are most prominent in this group Functional groups are beta-lactam rings Beta-lactams bind to enzymes that cross-link NAM- NAG subunits Bacteria have weakened cell walls and eventually lyse 54
- 55. Mechanisms of Antimicrobial Action • Inhibition of Cell Wall Synthesis ▫ Inhibition of synthesis of bacterial walls Semi-synthetic derivatives of beta-lactams More stable in acidic environments More readily absorbed Less susceptible to deactivation More active against more types of bacteria Simplest beta-lactams – effective only against aerobic Gram-negatives 55
- 56. Mechanisms of Antimicrobial Action • Inhibition of Cell Wall Synthesis ▫ Inhibition of synthesis of bacterial walls Vancomycin and cycloserine Interfere with particular bridges that link NAM subunits in many Gram-positives Bacitracin Blocks secretion of NAG and NAM from cytoplasm Effective against Gram positives Isoniazid and ethambutol Disrupt mycolic acid formation in mycobacterial species 56
- 57. Mechanisms of Antimicrobial Action • Inhibition of Cell Wall Synthesis ▫ Inhibition of synthesis of bacterial walls Prevent bacteria from increasing amount of peptidoglycan Have no effect on existing peptidoglycan layer Effective only for growing cells 57
- 58. Mechanisms of Antimicrobial Action • Disruption of Cytoplasmic Membranes ▫ Some drugs form channels through cytoplasmic membrane and damage its integrity ▫ Amphotericin B attaches to ergosterol in fungal membranes Humans somewhat susceptible because cholesterol similar to ergosterol Bacteria lack sterols; not susceptible 58
- 59. Mechanisms of Antimicrobial Action • Disruption of Cytoplasmic Membranes ▫ Azoles and allyamines inhibit ergosterol synthesis ▫ Polymyxin disrupts cytoplasmic membranes of Gram-negatives Oral form is toxic to human kidneys, so only used topically ▫ Some parasitic drugs act against cytoplasmic membranes 59
- 60. Which topical ointment is best? • Neomycin is an aminoglycoside antibiotic (disrupts protein synthesis). It has excellent activity against Gram-negative bacteria, and has partial activity against Gram-positive bacteria. • Polymixin disrupts bacterial cell membranes by interacting with its phospholipids. They are selectively toxic for Gram-negative bacteria. • Bacitracin disrupts cell wall synthesis. Its action is on Gram-positive organisms. It can cause contact dermatitis and cross-reacts with allergic sensitivity to sulfa-drugs. • Which topical ointment is best: Neomycin or Triple Antibiotic (contains all three) 60
- 61. Basic Principles of Microbial Control • Action of Antimicrobial Agents ▫ Damage to proteins and nucleic acids Protein function depends on 3-D shape Extreme heat or certain chemicals denature proteins Chemicals, radiation, and heat can alter or destroy nucleic acids Can produce fatal mutants Can halt protein synthesis through action on RNA 61
- 62. Mechanisms of Antimicrobial Action • Inhibition of Protein Synthesis ▫ Prokaryotic ribosomes are 70S (30S and 50S) ▫ Eukaryotic ribosomes are 80S (40S and 60S) ▫ Drugs can selectively target translation ▫ Mitochondria of animals and humans contain 70S ribosomes Can be harmful 62
- 63. Mechanisms of Antimicrobial Action • Inhibition of Protein Synthesis ▫ Aminoglycosides: excellent against Gram negatives, partially effective against Gram positives amikacin (Amikin®) gentamicin (Garamycin®) kanamycin (Kantrex®) neomycin (Mycifradin®) streptomycin tobramycin (TOBI Solution®, TobraDex®) 63
- 64. Antimicrobial inhibition of protein synthesis Figure 10.4 64
- 65. Mechanisms of Antimicrobial Action • Inhibition of Nucleic Acid Synthesis ▫ Several drugs block DNA replication or mRNA transcription ▫ Drugs often affect both eukaryotic and prokaryotic cells ▫ Not normally used to treat infections ▫ Used in research and perhaps to slow cancer cell replication 65
- 66. Nucleotides and some of their antimicrobial analogs Figure 10.7 66 Nucleotides
- 67. Acyclovir • Acyclovir is used to decrease pain and speed the healing of herpes sores or blisters in people who have varicella (chickenpox), herpes zoster (shingles; a rash that can occur in people who have had chickenpox in the past), and first-time or repeat outbreaks of genital herpes (a herpes virus infection that causes sores to form around the genitals and rectum from time to time). • Acyclovir is also sometimes used to prevent outbreaks of herpes sores in people who are infected with the virus. • Acyclovir disrupts nucleic acid function. It works by stopping the spread of the herpes virus in the body. Acyclovir will not cure herpes or protect others from catching it. 67
- 68. Mechanisms of Antimicrobial Action • Inhibition of Nucleic Acid Synthesis ▫ Quinolones and fluoroquinolones Act against prokaryotic DNA gyrase (enzyme that is needed for DNA to unwind during replication) ▫ Inhibitors of RNA polymerase (enzyme used during transcription) ▫ Reverse transcriptase inhibitors Act against an enzyme HIV uses in its replication cycle Does not harm people because humans lack reverse transcriptase 68
- 69. Mechanisms of Antimicrobial Action • Inhibition of Nucleic Acid Synthesis ▫ Nucleotide analogs Interfere with function of nucleic acids Distort shapes of nucleic acid molecules and prevent further replication, transcription, or translation Most often used against viruses Effective against rapidly dividing cancer cells 69
- 70. Nucleotides and some of their antimicrobial analogs Figure 10.7 70 Nucleotides
- 71. Mechanisms of Antimicrobial Action • Inhibition of Metabolic Pathways ▫ Antimetabolic agents can be effective when pathogen and host metabolic processes differ ▫ Quinolones interfere with the metabolism of malaria parasites ▫ Heavy metals inactivate enzymes ▫ Some agents disrupt glucose uptake by many protozoa and parasitic worms ▫ Some drugs block activation of viruses 71
- 72. Mechanisms of Antimicrobial Action • Inhibition of Metabolic Pathways ▫ Antiviral agents can target unique aspects of viral metabolism Amantadine, rimantadine, and weak organic bases prevent viral uncoating ▫ Protease inhibitors interfere with an enzyme that HIV needs in its replication cycle 72
- 73. Mechanisms of Antimicrobial Action • Prevention of Virus Attachment ▫ Attachment antagonists block viral attachment or receptor proteins ▫ New area of antimicrobial drug development 73
- 74. Clinical Considerations in Prescribing Antimicrobial Drugs • Ideal Antimicrobial Agent ▫ Readily available ▫ Inexpensive ▫ Fast-acting ▫ Chemically stable during storage ▫ Easily administered ▫ Nontoxic and nonallergenic ▫ Selectively toxic against wide range of pathogens ▫ Capable of controlling microbial growth while being harmless to humans, animals, and objects 74
- 75. Clinical Considerations in Prescribing Antimicrobial Drugs • Spectrum of Action ▫ Number of different pathogens a drug acts against Narrow-spectrum effective against few organisms (Gram positive bacteria only) Broad-spectrum effective against many organisms (Gram positive and Gram negative bacteria) May allow for secondary or superinfections to develop Killing of normal flora reduces microbial antagonism 75
- 76. Spectrum of action for selected antimicrobial agents Figure 10.8 76
- 77. Clinical Considerations in Prescribing Antimicrobial Drugs • Efficacy ▫ Ascertained by Diffusion susceptibility test Minimum inhibitory concentration test Minimum bactericidal concentration test 77
- 78. Diffusion Susceptibility Test: Zone of inhibition Figure 10.9 78
- 79. Minimum inhibitory concentration test Figure 10.10 79
- 80. A minimum bactericidal concentration test Figure 10.12 80
- 81. Clinical Considerations in Prescribing Antimicrobial Drugs • Routes of Administration ▫ Topical application of drug for external infections ▫ Oral route requires no needles and is self- administered ▫ Intramuscular (IM) administration delivers drug via needle into muscle ▫ Intravenous (IV) administration delivers drug directly to bloodstream ▫ Must know how antimicrobial agent will be distributed to infected tissues 81
- 82. Effect of route of administration on chemotherapeutic agent Figure 10.13 82
- 83. Clinical Considerations in Prescribing Antimicrobial Drugs • Safety and Side Effects ▫ Toxicity Cause of many adverse reactions poorly understood Drugs may be toxic to kidneys, liver, or nerves Consideration needed when prescribing drugs to pregnant women ▫ Allergies Allergic reactions are rare but may be life threatening Anaphylactic shock 83
- 84. Side effects resulting from toxicity of antimicrobial agents Figure 10.14 84
- 85. Clinical Considerations in Prescribing Antimicrobial Drugs • Safety and Side Effects ▫ Disruption of normal microbiota May result in secondary infections Overgrowth of normal flora causing superinfections Of greatest concern for hospitalized patients 85
- 86. Resistance to Antimicrobial Drugs • The Development of Resistance in Populations ▫ Some pathogens are naturally resistant ▫ Resistance by bacteria acquired in two ways New mutations of chromosomal genes Acquisition of resistance genes (R-plasmids) via transformation, transduction, and conjugation 86
- 87. The development of a resistant strain of bacteria Figure 10.15 87
- 88. Resistance to Antimicrobial Drugs • Mechanisms of Resistance ▫ At least six mechanisms of microbial resistance Production of enzyme that destroys or deactivates drug Slow or prevent entry of drug into the cell Alter target of drug so it binds less effectively Alter their metabolic chemistry Pump antimicrobial drug out of the cell before it can act Mycobacterium tuberculosis produces MfpA protein Binds DNA gyrase preventing the binding of fluoroquinolone drugs 88
- 89. How -lactamase renders penicillin inactive Figure 10.16 89
- 90. Resistance to Antimicrobial Drugs • Multiple Resistance and Cross Resistance ▫ Pathogen can acquire resistance to more than one drug ▫ Common when R-plasmids exchanged ▫ Develop in hospitals and nursing homes Constant use of drugs eliminates sensitive cells ▫ Superbugs ▫ Cross resistance 90
- 91. Resistance to Antimicrobial Drugs • Retarding Resistance ▫ Maintain high concentration of drug in patient for sufficient time Kills all sensitive cells and inhibits others so immune system can destroy ▫ Use antimicrobial agents in combination Synergism vs. antagonism 91
- 92. Example of synergism between two antimicrobial agents Figure 10.17 92
- 93. Resistance to Antimicrobial Drugs • Retarding Resistance ▫ Use antimicrobials only when necessary ▫ Develop new variations of existing drugs Second-generation drugs Third-generation drugs ▫ Search for new antibiotics, semi-synthetics, and synthetics Bacteriocins Design drugs complementary to the shape of microbial proteins to inhibit them 93
- 94. Vaccination • Vaccine – use the immune system to protect against infectious disease • Types of vaccines ▫ attenuated (weakened) microbe; virulence factors are removed ▫ heat-killed / chemically killed microbe ▫ toxoids • Passive versus Adaptive vaccination ▫ passive – immune system products from another mothers milk (presence of IgA) gamma-globulin (anti-bee venom, anti-hepatitis A, etc) ▫ active – stimulate individuals immune system to produce memory cells 94
- 95. Effect of smallpox vaccine 95 Initial “modern” vaccine: 1796.
- 96. U.S. cases against diseases for which there are vaccines. 96 SSPE: sub-acute sclerosing panencephalitis (late stage measles)
- 97. • Why Your Cellphone Has More Bacteria Than a Toilet Seat • By Susan E. Matthews, MyHealthNewsDaily Staff Writer | LiveScience.com – 3 hrs ago • http://news.yahoo.com/why-cellphone-more- bacteria-toilet-seat-124147769.html 97
- 98. • Cellphones carry 10 times more bacteria than most toilet seats, so it shouldn't be surprising that a man in Uganda reportedly contracted Ebola after stealing one. • He stole the phone from a quarantined ward of a hospital, near the site of a recent Ebola outbreak. • While toilets tend to get cleaned frequently, because people associate the bathroom with germs, cellphones and other commonly handled objects — like remote controls— are often left out of the cleaning routine. • Cellphones pick up germs all the time; some people talk on their phone on toilets. 98
- 99. • However, the amount of germs on a phone isn't a problem — it’s the sharing of phones between people. Without sharing, each phone carries just one set of germs, and won't get its owner sick. • The problem with phones is that we're in constant contact with them, and they spend a lot of time in close proximity to our faces and mouths. • And, because it's an electronic device, most people are hesitant about cleaning them. 99
- 100. • This is also this case with remote controls, which, are also often used by people when they're sick. • Remotes are more frequently shared, too, so they're usually even worse than phones for spreading germs. • Other common culprits that are hotspots of unseen disease include office phones, shopping carts and the first-floor buttons of elevators. 100
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