Microbial growth control Flashcards
What is sterilization?
Sterilization is the removal of all forms of microbial life, including bacteria, viruses, and spores.
What is the difference between disinfection and sanitization?
Disinfection refers to the destruction of pathogenic microbes, usually targeting vegetative (non-spore-forming) microbes. Sanitization reduces microbial counts to safe public health levels, commonly applied to eating utensils and surfaces to minimize disease transmission.
What is bacteriostasis?
Bacteriostasis refers to the inhibition of microbial growth without killing the microbes.
What are four factors that determine the effectiveness of antimicrobial treatments?
- Number of microbes
- Time of exposure
- Microbial environment (e.g., presence of biofilms, organic matter)
- Microbial characteristics (e.g., cell wall composition, resistance mechanisms).
What are the common actions/targets of antimicrobial agents?
- Alteration of membrane permeability – causes leakage of cellular contents.
- Damage to proteins – disrupts enzymatic functions and structure.
- Damage to nucleic acids – interferes with DNA replication and protein synthesis.
How does pasteurization control microbial growth?
Pasteurization applies limited heat treatment to reduce spoilage organisms and eliminate pathogenic microbes while allowing heat-tolerant microbes to survive without causing disease or significant spoilage.
What are two types of heat sterilization methods?
- Moist heat – Denatures proteins (e.g., autoclaving, boiling).
- Dry heat – Kills by oxidation (e.g., flaming, hot-air sterilization).
How does ionizing radiation control microbial growth?
Ionizing radiation damages DNA, causing lethal mutations that prevent microbial replication.
Why is filtration useful for microbial control?
Filtration removes microbes from liquids and air, making it useful for heat-sensitive solutions that cannot be sterilized by heat.
What is bacteriostatic and how does it inhibit microbial growth?
Bacteriostatic refers to treatments that inhibit microbial growth without killing the microbes. Low temperatures (e.g., refrigeration at 0–7°C) slow microbial metabolism, preventing reproduction and growth but not necessarily killing the microbes.
How does osmotic pressure prevent microbial growth?
High concentrations of salt or sugar create a hypertonic environment, drawing water out of microbial cells, causing plasmolysis and inhibiting growth.
Who is considered the ‘Father of Modern Surgery’ and why?
Joseph Lister is considered the ‘Father of Modern Surgery’ because he introduced aseptic techniques using phenol (carbolic acid) to reduce infections in surgical procedures.
What are the mechanisms of action for different types of chemical disinfectants?
- Phenolics (e.g., Triclosan) – Disrupt lipids in the plasma membrane.
- Halogens (Iodine, Chlorine) – Act as oxidizing agents, disrupting cell membranes.
- Alcohols (Ethanol, Isopropanol) – Dissolve membrane lipids and denature proteins.
- Heavy metals (Ag, Hg, Cu, Zn) – Denature proteins.
- Surfactants (Quats) – Denature proteins and disrupt plasma membranes.
What is the disk-diffusion method used for?
The disk-diffusion method evaluates disinfectants by placing disinfectant-soaked filter paper onto an inoculated agar plate. After incubation, the zone of inhibition around the filter paper indicates the disinfectant’s effectiveness.
What is an autoclave?
An autoclave is a device that uses steam under pressure to achieve sterilization. It raises the temperature above 100°C, effectively killing all microbes, including spores, by denaturing proteins and disrupting cellular structures.
What is batch pasteurization?
Batch pasteurization involves heating a liquid to 63°C for 30 minutes. This process kills many microbes except for heat-resistant ones, which are rarely pathogenic and prevents spoilage.
What is HSST pasteurization?
High-Temperature Short-Time (HSST) pasteurization involves heating to a much higher temperature for a short time (30 seconds). This process kills almost all microbes and is believed to influence nutrient availability.
Why are mycobacteria more resistant to microbial growth control?
Mycobacteria are more resistant to microbial growth control because they have a lipid-rich cell wall (acid-fast), which provides a protective barrier against many chemical and physical treatments.
Why is gram-negative bacteria more resistant to microbial growth control than gram-positive bacteria?
Gram-negative bacteria are more resistant to microbial growth control because they have an outer membrane that provides selective permeability, limiting the entry of antimicrobial agents.
