Chapter 9 Study Quiz

What is sterilization?

The removal or destruction of all microbes, including viruses and endospores, in or on an object.

What is disinfection?

The use of physical or chemical agents to inhibit or destroy microorganisms on inanimate objects.

What is antisepsis?

Reduction of microorganisms and viruses on living tissue.

What is degerming?

The mechanical removal of microbes by scrubbing.

What is sanitization?

The process of disinfecting places and utensils used by the public to reduce pathogen numbers.

What is pasteurization?

The use of heat to kill pathogens and reduce the number of spoilage microbes in food and beverages.

What is the difference between disinfection and sterilization?

Disinfection does not guarantee elimination of all pathogens; sterilization does.

What does the suffix "-cide" mean in microbial control?

Indicates killing of microbes (e.g., bactericide, fungicide).

What does the suffix "-static" mean?

Indicates inhibition of microbial metabolism and growth but not necessarily killing.

What are the modes of action of antimicrobial agents?

Damage to cell walls, disruption of cytoplasmic membranes, damage to proteins and nucleic acids.

Why is damage to cell walls harmful to microbes?

Cells become fragile and burst due to osmotic effects.

What does disruption of the cytoplasmic membrane cause?

Cell contents to leak out, resulting in death.

How do antimicrobial agents affect proteins?

Denature enzymes and structural proteins, impairing cell functions.

How can antimicrobial agents affect nucleic acids?

Mutations or inhibition of replication, transcription, or translation.

What environmental conditions affect microbial death rates?

Temperature and pH influence effectiveness of antimicrobial agents.

How does microbial load affect antimicrobial methods?

Higher microbial numbers require longer exposure to agents.

What are the most resistant microbial forms?

Bacterial endospores, Mycobacterium, cysts of protozoa, and prions.

Why are Gram-negative bacteria more resistant than Gram-positive?

They have an outer membrane that limits penetration of antimicrobial agents.

What are the four biosafety levels (BSLs)?

BSL-1: minimal precautions; BSL-2: restricted access; BSL-3: containment cabinets, respiratory protection; BSL-4: full suits, airlocks, isolation.

What are physical methods of microbial control?

Heat (moist and dry), refrigeration, freezing, desiccation, filtration, osmotic pressure, radiation.

How does moist heat kill microbes?

Denatures proteins and destroys membranes via boiling, autoclaving, pasteurization.

What are the typical conditions for autoclaving?

121°C, 15 psi, 15 minutes.

Why is autoclaving effective?

It uses steam under pressure to kill all microbes including endospores.

What is pasteurization used for?

To kill pathogens and reduce microbial numbers in food and beverages without affecting taste.

What are the main pasteurization methods?

Batch: 63°C for 30 min; Flash: 72°C for 15 sec; UHT: 135°C for 1 sec.

What is dry heat used for?

Sterilizing materials that can't be sterilized with moist heat, like powders or oils.

How does refrigeration inhibit microbial growth?

Slows metabolism and reproduction of microbes.

What is desiccation?

Removal of water to inhibit microbial growth.

What is lyophilization?

Freeze-drying to preserve microbial cultures.

What does filtration do?

Physically separates microbes from air or liquids using filter membranes.

What is HEPA filtration?

High-Efficiency Particulate Air filters used in biosafety cabinets and hospitals to remove airborne microbes.

How does osmotic pressure inhibit microbes?

High salt or sugar concentrations cause cells to lose water, inhibiting growth.

What are the types of radiation used for microbial control?

Ionizing (X-rays, gamma rays) and nonionizing (UV light).

How does ionizing radiation work?

Damages DNA and cellular structures via production of free radicals.

How does nonionizing radiation (UV) work?

Causes thymine dimers in DNA, inhibiting replication.

What are chemical methods of microbial control?

Phenols, alcohols, halogens, oxidizing agents, surfactants, heavy metals, aldehydes, enzymes, gases.

How do phenols and phenolics work?

Denature proteins and disrupt cell membranes; effective even in presence of organic matter.

How do alcohols control microbes?

Denature proteins and disrupt membranes; most effective at 70–90%.

What are halogens used for?

Disinfection and antisepsis (e.g., iodine, chlorine, bromine, fluorine).

How does chlorine kill microbes?

Forms hypochlorous acid which denatures proteins.

What are oxidizing agents?

Peroxides, ozone, and peracetic acid—oxidize microbial enzymes.

What are surfactants?

Soaps and detergents that reduce surface tension and mechanically remove microbes.

How do heavy metals act as antimicrobial agents?

Bind to proteins, denature them (e.g., silver, mercury, copper).

How do aldehydes work?

Cross-link functional groups in proteins and nucleic acids (e.g., glutaraldehyde, formaldehyde).

How do gaseous agents sterilize?

Ethylene oxide, propylene oxide disrupt proteins and DNA; used in enclosed chambers.

What are antimicrobial enzymes?

Enzymes like lysozyme and prionzyme that digest microbial cell components.

What is lysozyme used for?

Breaking down bacterial cell walls, especially in Gram-positive bacteria.

What is prionzyme used for?

Removing prions from surgical instruments.

What factors affect the efficacy of antimicrobial agents?

Number and type of microbes, concentration of agent, contact time, temperature, pH, and presence of organic matter.

What is the phenol coefficient?

A comparison of a disinfectant's ability to that of phenol.

What are use-dilution tests?

Assess effectiveness of disinfectants on surfaces contaminated with dried bacteria.

What are Kelsey-Sykes capacity tests?

Determine appropriate contact time for disinfectants under realistic conditions.

What is in-use testing?

Evaluates effectiveness of disinfectants in actual clinical settings.

What is the decimal reduction time (D value)?

Time required to kill 90% of microbial population under specific conditions.