1 / 23

Physical and Chemical Control of Microbes

Physical and Chemical Control of Microbes. Relative resistance of microbes. Highest resistance Bacterial endospores prions Moderate resistance Mycobacterium tuberculosis Protozoan cysts Non-enveloped viruses Least resistance most vegetative cells Fungal spores enveloped viruses

mkelley
Download Presentation

Physical and Chemical Control of Microbes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physical and Chemical Control of Microbes

  2. Relative resistance of microbes • Highest resistance • Bacterial endospores • prions • Moderate resistance • Mycobacterium tuberculosis • Protozoan cysts • Non-enveloped viruses • Least resistance • most vegetative cells • Fungal spores • enveloped viruses • Protozoan trophozoites

  3. Terms • Sterilization– A process that destroys all microbes, including endospores. • Disinfection– A process to destroy most microbes, not endospores. • Antisepsis – Disinfectants applied directly to exposed body surfaces • -cide: the agent will kill the organism • (e.g.,bacteriocide, viricide, fungicide). • - static: the agent will inhibit the growth of the organism • (e.g., bacteriostatic, fungistatic).

  4. Factors that influence action of antimicrobial agents: • Number of microbes • Nature of microbes in the population • Concentration or dosage of agent • Mode of action of the agent

  5. Methods of Control • Chemical • Halogens • Alcohols • Aldehydes • Ethylene Oxide • Physical • Heat • Radiation • Filtration

  6. 1.Heat • denaturation of proteins • Moist Hat • Dry heat

  7. Moist heat • Autoclave 15 psi / 121oC /15-20min • sterilization • Protein coagulation = 15 psi http://www.frankshospitalworkshop.com/equipment/autoclaves_equipment.html

  8. Intermittent sterilization • Tyndallization , by john tyndal • unpressurized steam at 100oC 15-20 min for 3 days • a process that kills spore-forming microorganisms, involves exposing the material to elevated temperatures (killing the vegetative cells) • then incubation at 37C (to allow spores to germinate to form new vegetative cells) • and then exposure to elevated temperatures again (to kill the newly germinated vegetative cells) • used to sterilize heat-sensitive materials or to kill particularly resistant endospores.

  9. Pasteurization • Invented by Louis Pasture 72°C for 15 seconds 135°C for 2-3 s 63°C for 30 minutes

  10. Dry heat Dry heatusing higher temperatures than moist heat. • bacteria incinerator – ~800 oC combusts & dehydrates cells • dry ovens – 160 °C for 2 hours - coagulate proteins

  11. Methods of Control • Chemical • Halogens • Alcohols • Aldehydes • Ethylene Oxide • Physical • Heat • Radiation • Filtration

  12. 2.Radiation • Ionizing radiation – deep penetrating power, breaks DNA, • gamma rays, X-rays • used to sterilize medical supplies & food products • Nonionizing radiation – little penetrating power to sterilize air, water & solid surfaces • UV light creates thymine dimer, which interfere with replication

  13. Gamma rays X rays UV light

  14. 3.Filtration • physical removal of microbes by passing a gas or liquid through filter • used to sterilize heat sensitive liquids & air in hospital isolation units & industrial clean rooms

  15. Chemical control • Halogens • Alcohols • Aldehydes • Ethylene Oxide (Gas)

  16. 1. Halogens • Chlorine – Cl2, hypochlorites (chlorine bleach), • Disinfectant water supply • Iodine - I2, iodophors (betadine) • Iodopovidone (Povidone-iodine)is an antiseptic used for skin disinfection before and after surgery. • Denature proteins

  17. 2.Alcohols • Ethyl, isopropyl in solutions of 70% • Act as surfactants dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi • Not sporicidal

  18. 3. Aldehydes • Glutaraldehyde & formaldehyde ( formalin) kill by alkylating protein , DNA and RNA. • glutaraldehyde in 2% solution (Cidex) used as sterilant for heat sensitive instruments • formaldehyde - disinfectant, preservative , toxicity limits use

  19. 4.Ethylene Oxide • colorless gas that is flammable and explosive. • sporicidal • The main disadvantages associated with ETO are the lengthy cycle time (~14h) , the cost, and its potential hazards to patients and staff but it can sterilize heat- or moisture-sensitive medical equipment . (CDC)

  20. Others • Hydrogen Peroxide (H2O2) 3% • Phenolics : Phenol , Lysol , tricolsan • Chlorhexidine

  21. Cold temperatures • slows the growth of microbes • refrigeration 0-15oC & freezing <0oC • used to preserve food, media and cultures

  22. Desiccation or drying • gradual removal of water from cells, leads to metabolic inhibition • Lyophilization “freeze-drying” a process in which water is removed from a product after it is frozen

More Related