Microbiology Chapter 9 Flashcards

Study Notes

Microbial Control Methods

Sterilization: Complete destruction of all microbial life including viruses; commonly applied to inanimate objects; methods include heat and chemicals called sterilants.
Disinfection: Reduces the number of viable microorganisms on inanimate surfaces to prevent infection; does not kill endospores; example: 5% bleach.
Antisepsis: Similar to disinfection but applied on living surfaces to destroy or inhibit pathogenic microorganisms; example: iodine used in hand washing.
Decontamination: Mechanical removal of most microbes from surfaces to minimize infection risk; involves cleaning processes such as sanitation and degermation.

Physical Agents of Microbial Control

Types include Heat (dry and moist) and Radiation.
Dry heat methods: Incineration sterilizes by burning; dry ovens expose items to high temperatures (150-180°C) for sterilization.
Moist heat: Steam under pressure (autoclaving) is effective for sterilization; boiling water is for disinfection (does not sterilize).

Chemical Methods of Microbial Control

Chemical agents: Includes both gases and liquids; can be used for sterilization, disinfection, or antisepsis.
Types of chemicals: Halogens (chlorine, iodine), alcohols (effective against vegetative forms), phenols (cellular poisons), and aldehydes (glutaraldehyde and formaldehyde for microbial control).

Mechanisms and Efficacy

Microbial control involves blocking synthesis, digesting, or damaging cell structures.
Logarithmic death: Microbial death occurs in a logarithmic fashion; affected by factors such as temperature and concentration of agents.

Germicides and Their Effects

Bactericides: Kill bacteria, not necessarily effective against endospores.
Sporicides: Specifically destroy bacterial endospores.
Virucides: Inactivate viruses through direct or indirect actions of oxygen.
Fungicides: Kill fungal spores, hyphae, and yeasts.
Activity depends on concentration; e.g., alcohol is effective at 50-70% for dissolving membrane lipids.

Resistance and Stability

Microbial resistance can develop against chemical agents; choosing effective agents includes ensuring they act rapidly at low concentrations without being toxic to human tissues.
Heavy Metals: Some, like mercury and silver, are effective but can pose toxicity risks and are neutralized by biological fluids.

Preservation Techniques

Lyophilization: Combines freezing and drying to preserve microbes for long periods.
Ultraviolet Radiation: Primarily for disinfection (kills DNA), safe for use in hospitals and water treatment.
Filtration: Removes microbes from liquids and air using membranes that allow fluid but not microorganisms to pass.

Temperature Effects

Elevated temperatures reduce microbial viability; methods such as pasteurization (flash and batch methods) disinfect beverages but do not kill all endospores.
Cold and desiccation: Slow microbial growth but do not necessarily kill microbes; freezing can preserve cultures.

pH Influence

Acids and alkalis can destroy or inhibit microbial cells at extreme pH levels; however, they have limited use due to harmful effects.

This comprehensive overview provides key terms and concepts vital for understanding microbial control methods and their applications in health and safety.

Description

Test your knowledge on key terms related to sterilization and disinfection in microbiology with these flashcards. This quiz covers definitions and processes essential for understanding microbial control methods.