Microbial Control Methods Quiz

Microbial Growth Control

• Correct terminology is essential for clarity in microbial control, especially among microbiologists and healthcare workers.
• Sterilization is the complete removal or destruction of all microbes, including viruses and bacterial endospores, on an object.
• Aseptic refers to an environment or procedure free from contamination by pathogens.
• Disinfection uses physical or chemical agents (e.g., UV light, alcohol) to inhibit or destroy pathogens on inanimate objects.
• Antisepsis is similar to disinfection but is applied to skin or tissue, using antiseptics that are typically less concentrated than disinfectants.
• Degerming removes microbes by scrubbing, often enhanced by soap or alcohol.
• Sanitization reduces pathogens in public areas to meet health standards.
• Pasteurization is a heat treatment to kill pathogens and reduce spoilage organisms in food and beverages.

Microbial Death Rates

• Microbial death is the irreversible loss of a microorganism's ability to reproduce in ideal conditions.
• The rate of microbial death is typically constant over time for a specific microorganism under specific conditions.
• A semilogarithmic graph, plotting microbial death rate, shows a straight line, confirming the constant nature of the death rate.

Action of Antimicrobial Agents

• Antimicrobial agents damage cell walls or cytoplasmic membranes.
• They can interfere with metabolism, affecting proteins and nucleic acids.
• Agents can alter cell wall and membrane function.
• They can damage nucleic acids by causing fatal mutations, thereby inhibiting protein synthesis.

Factors Affecting Efficacy

• The site to be treated (e.g., human tissue vs. inanimate objects) influences the choice of agent.
• Microorganism susceptibility varies across microbes.
• Environmental conditions (temperature, pH, etc.) affect agent effectiveness.
• Resistant microbes (e.g., bacterial endospores, mycobacteria, protozoan cysts) are more challenging to eliminate.

Environmental Conditions Affecting Microbial Control

• Higher temperatures increase the efficacy of antimicrobial methods.
• Acidic conditions enhance the effect of heat
• Organic materials interfere with penetration of heat, chemicals, and radiation.
• Pre-cleaning of surfaces, before sterilization or disinfection, increases the effectiveness of antimicrobial agents.

Biosafety Levels

• Four Biosafety Levels (BSLs) are defined by the CDC to ensure safety in labs handling pathogens.
• Each level determines the appropriate precautions, equipment, and facility design needed.

Physical Methods of Microbial Control

• Heat treatment (moist and dry heat) denatures proteins, disrupts cell walls/membranes, damages nucleic acids, and is effective in sterilization and food preservation.
• Cold temperatures slow microbial metabolism and growth.
• Desiccation (drying) inhibits microbial growth by removing water.
• Lyophilization (freeze-drying) preserves microbes long-term.
• Filtration removes microbes from fluids.
• Osmotic pressure creates a hypertonic environment and inhibits microbial metabolism.
• Radiation disrupts cell function through ionizing or nonionizing radiation.

Chemical Methods of Microbial Control

• Phenols and phenolics denature proteins and disrupt cell membranes.
• Alcohols denature proteins and disrupt membranes and are effective against bacteria, fungi, and enveloped viruses.
• Halogens (iodine, chlorine, bromine, and fluorine) damage proteins.
• Oxidizing agents kill microbes by oxidizing enzymes.
• Surfactants (soaps and detergents) decrease surface tension and disrupt cell membranes.
• Heavy metals denature proteins.
• Gaseous agents (ethylene oxide, propylene oxide) denature proteins and effectively sterilize heat-sensitive items.

Mechanism of Action of Oxidizing Agents

• Oxidizing agents kill microbes by oxidizing their enzymes, disrupting microbial metabolism.
• High-level disinfectants and antiseptics are particularly effective against anaerobic microorganisms.
• Hydrogen peroxide, ozone, and peracetic acid are examples of high-level disinfectants.

Antimicrobial Drugs

• Antibiotics are naturally produced by microorganisms.
• Semisynthetics are chemical modifications of antibiotics.
• Synthetics are entirely lab-developed.
• Antimicrobials can target cell wall synthesis, protein synthesis, cytoplasmic membranes, and metabolic pathways.

Methods for Evaluating Disinfectants and Antiseptics

• Higher concentrations ensure efficacy but can damage surfaces.
• The phenol coefficient compares a disinfectant's effectiveness to that of phenol.
• The use-dilution test measures the highest dilution that prevents microbial growth after incubation.
• The Kelsey-Sykes Capacity Test measures the time needed to reduce microbes by 90% (D-value).
• In-use tests measure efficacy on actual surfaces.

Resistance to Antimicrobial Drugs

• Resistance can develop in bacteria through genetic mutations or acquired resistance genes.
• Mechanisms include enzyme production, altered entry channels, target alteration, and metabolic pathway modification.

Multiple Resistance

• Multiple resistance occurs when pathogens are resistant to several drugs simultaneously.
• Cross-resistance occurs when resistance to one drug confers resistance to other drugs with similar structures.
• Strategies to prevent resistance include effective drug concentrations, combined therapy, and limited unnecessary use.

Antimicrobial Drug Targeting

• Bacteria can be targeted by inhibiting their cell wall synthesis, protein synthesis, or metabolic pathways.
• Viruses, protozoa and fungi can be targeted through various cellular actions.

Prevention of Virus Attachment, Entry, or Uncoating

• Virus-host attachment occurs via specific interactions, blocking sites prevents infection.
• Mechanism of action includes using analog compounds (e.g., pleconaril) of attachment receptors.
• Viral uncoating can be prevented, via a mechanism such as arildone.