Control of Microbial Growth (PDF)

Control of Microbial Growth  Introduction  With the advent of the "Germ Theory" of Disease, the medical community gradually began to grow aware of the problem of nosocomial infections and that there was a need to practice "asepsis" in order to prevent contaminatio...

Control of Microbial Growth  Introduction  With the advent of the "Germ Theory" of Disease, the medical community gradually began to grow aware of the problem of nosocomial infections and that there was a need to practice "asepsis" in order to prevent contamination of wounds, dressings and surgical instruments.  Ignaz Semmelweis (1816-1865) and Joseph Lister (1827-1912), are considered to be important pioneers for the promotion of "asepsis"; working in a germ- free environment.  Semmelweiss - an Hungarian obstetrician, recognized (and enforced) the need for hospital staff to frequently wash their hands and take other precautions to minimize transmitting infections to their patients.  his interventions significantly reduced deaths due to "childbirth fever" a serious streptococcal infection.  Lister - a British physician, pioneered antiseptic surgery.  He performed surgery while using a mist of phenolic compounds and endorsed the treatment of dressings with carbolic acid.  He also promoted the heat sterilization of surgical instruments Microbial Control Ignaz Semmelweis (1816-1865) In 1847, Dr. Ignaz Semmelweis's close friend, Jakob Kolletschka, cuts his finger while he's doing an autopsy Kolletschka soon dies of symptoms like those of puerperal fever leading Ignaz Semmelweis to pioneer antiseptic policy – Chlorinated lime Joseph Lister (1827-1912) – Joseph Lister had been convinced of the importance of scrupulous cleanliness and the usefulness of deodorants in the operating room; and when, through Pasteur's researches, he realized that the formation of pus was due to bacteria, he proceeded to develop his antiseptic surgical method. – Carbolic acid (phenol) Control of Microbial Growth: Introduction Ø Early civilizations practiced salting, smoking, pickling, drying, and exposure of food and clothing to sunlight to control microbial growth. Ø Use of spices in cooking was to mask taste of spoiled food. Some spices prevented spoilage. Ø In mid 1800s Semmelweiss and Lister helped developed aseptic techniques to prevent contamination of surgical wounds. Before then: Ø Nosocomial infections caused death in 10% of surgeries. Ø Up to 25% mothers delivering in hospitals died due to infection Some Useful Terms Ø Sepsis Presence of pathogens in blood or tissues. Comes from Greek word for decay or putrid. Indicates bacterial contamination Ø Asepsis Absence of pathogens. Ex. Hand washing; use of sterile gloves, masks, gowns; sterilization of surgical equipment; use of disinfectants. Ø Antisepsis Prevention of infection. Ø Antiseptic technique Developed by Joseph Lister (1867). Use of antiseptics. Control of Microbial Growth: Aseptic techniques are used to prevent contamination of surgical instruments, medical personnel, and the patient during surgery. Aseptic techniques are also used to prevent bacterial contamination in food industry. Aseptic techniques  In Medicine:  In the Food Industry: - These techniques include: - Aseptic techniques Sterilization of include: Instruments Sterilization of Hand Hygiene Equipment Aseptic Packaging Use of Sterile Drapes Hygienic Practices Sterile Environment Controlled Environments  Sterile Technique Ø Practice of excluding all microorganisms from a particular area, so that the area will be sterile. Control of Microbial Growth: Definition of Terms Sterilization: Killing or removing all forms of microbial life (including endospores) in a material or an object. Heating is the most commonly used method of sterilization. Commercial Sterilization: Heat treatment that kills endospores of Clostridium botulinum the causative agent of botulism, in canned food.  Sterilization Ø Process of removing or killing all microorganisms and viruses on or in a product. www.kendall-ltp.com - Ensures complete destruction of all microorganisms, including cells, spores, and viruses. Examples of Sterilization Ø Dry heat Ø Autoclaving Ø Gas Ø Various chemicals Autoclave Ø Certain types of radiation Dry Heat Sterilization Control of Microbial Growth: Definitions Disinfection: Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases. Usually involves the removal of vegetative or non-endospore forming pathogens. May use physical or chemical methods.  Disinfectant: Applied to inanimate objects.  Antiseptic: Applied to living tissue (antisepsis).  Degerming: Mechanical removal of most microbes in a limited area. Example: Alcohol swab on skin. Disinfection and Antisepsis Ø Disinfection Ø Antisepsis Ø Removal of harmful Ø Removal of harmful organisms from organisms from the surfaces skin Ø Generally involves the Ø Use of a less harsh use of chemicals chemical substance Ø Example - Phenols Ø Antibacterial washes Antiseptic Ø chemical agents applied to skin and living tissues to prevent infection by killing or inhibiting pathogen growth Ø they also reduce the total microbial population. Decontamination Ø Inactivation or removal of both microbial toxins and the living microbial pathogens. Sanitization –Use of chemical agent on food-handling equipment to meet public health standards and minimize chances of disease transmission. E.g.: Hot soap & water. Reduction of microbial populations to levels considered safe by public health standards. -cidal or -static Ø -cidal (Latin cida,means to kill) Ø Bacteriocidal agent kills bacteria Ø -static (Greek statikos, causing to stand or stopping; to inhibit or prevent) Ø Bacteriostatic agent will only inhibit or prevent bacterial growth Ø Growth will resume after the agent is removed Control of Microbial Growth: Definitions Bacteriostatic Agent: An agent that inhibits the growth of bacteria, but does not necessarily kill them. Suffix stasis: To stop or steady. e.g., bacteriostatic and fungistatic. Germicide: An agent that kills certain microorganisms.  Bactericide: An agent that kills bacteria. Most do not kill endospores.  Virucide: An agent that inactivates viruses.  Fungicide: An agent that kills fungi.  Sporicide: An agent that kills bacterial endospores or fungal spores. Chemotherapy the use of chemical agents to kill or inhibit the growth of microorganisms within host tissue Factors influencing the effectiveness of antimicrobial treatment. 1. Number of Microbes (Population size): The more microbes present, the more time it takes to eliminate population. 2. Type of Microbes (Population Composition): Endospores are very difficult to destroy. Vegetative pathogens vary widely in susceptibility to different methods of microbial control. Microorganisms that form biofilms (protective layers) on surfaces are often more resistant to antimicrobials. 3. Environmental influences: Presence of organic material (blood, feces, saliva) tends to inhibit antimicrobials, pH etc. Control of Microbial Growth: Rate of Microbial Death Resistance to chemical Biocides 4. Duration of treatment or Time of Exposure: Chemical antimicrobials and radiation treatments are more effective at longer times. In heat treatments, longer exposure compensates for lower temperatures. 5.Concentration or intensity of an antimicrobial agent: Must be sufficient to kill or inhibit the microorganisms. 6.Temperature. An increase in the temperature at which a chemical acts often enhances its activity. Frequently a lower concentration of disinfectant or sterilizing agent can be used at a higher temperature. Other factors 7. Mode of Action: Different antimicrobials work in various ways (e.g., disrupting cell walls, inhibiting protein synthesis, or interfering with DNA replication). The mode of action must match the microorganism's vulnerabilities. 8. Site of Infection: The location of the infection can affect treatment efficacy. For instance, infections in areas with limited blood flow (like bones or heart valves) may be harder to treat due to poor antimicrobial penetration. 9. Host Factors: Immune System Status Age and Health Condition Allergies Other factors 10. Drug Interactions: Concurrent use of other medications can affect the absorption, metabolism, or elimination of antimicrobials, impacting their effectiveness. Some drugs may reduce the efficacy of antimicrobials or increase the risk of side effects. 11. Compliance: Patient adherence to the prescribed treatment regimen is critical. Missing doses, stopping treatment early, or incorrect administration can reduce effectiveness and contribute to resistance.  There are three general categories of microbial control agents: Ø Physical: Heat, freeze-drying, ultraviolet radiation and filtration are all physical control agents. Ø Chemical: Chemical agents of control, like the disinfectants Lysol or Clorox, destroy most vegetative cells and viruses. Ø Chemotherapeutic: are drugs used to treat patients diagnosed with an infectious disease (e.g., Antibiotics, Antifungals, Antivirals; Antiparasitics) Microbial Control Methods