MICRO 4/1 EXAM 3

Cysts of Protozoans: More difficult to eradicate compared to other types.
Mycobacterium: Contains mycolic acid in the cell wall, providing added resistance.
Bacterial Endospores: Among the hardest to destroy; they can survive severe conditions.
Prions: Misfolded proteins that induce misfolding of other proteins, causing diseases like Mad Cow Disease. They are rare but highly resistant to traditional sterilization methods.

Definition: Chemicals containing phenol or its derivatives.
Examples: Pine oil, clove oil (natural), Pine-Sol, and Lysol (synthetic).
Mechanism: Disrupts plasma membrane (PM) and proteins, effectively killing microorganisms.

Definition: Common disinfecting agents (most notably ethyl alcohol and isopropyl alcohol).
Mechanism: Disrupts PM but requires dilution in water for effectiveness.
Effective Concentration: 70% ethanol is commonly used over 100% because it penetrates membranes better.
Store-bought examples: Isopropyl alcohol (often diluted to 30% in store products).

Definition: Chemical elements like iodine, chlorine, bromine, and fluorine.
Mechanism: Acts as oxidizing agents and disrupts proteins through oxidation. Highly reactive.

Definition: Chemicals that generate hydroxyl radicals.
Examples: Hydrogen peroxide, ozone, and peracetic acid.
Applications: Hydrogen peroxide can be used in hospital settings, with ozone utilized in water treatment systems.

Definition: Chemicals that reduce surface tension (soap is the most common example).
Mechanism: Soap disrupts the PM due to its amphipathic nature (having both hydrophobic and hydrophilic sections).
Impacts: Effective at removing bacteria. Triclosan, once included in some soaps, has been removed due to concerns over antibiotic resistance.

Definition: Elements like copper, zinc, mercury, and silver.
Mechanism: Cause protein denaturation.
Applications: Silver nitrate is used in burn treatments; copper can be added to surfaces for antimicrobial properties.

Examples: Formaldehyde is a key example, known for its toxicity and protein denaturation ability.
Uses: Commonly used in isolation units to disinfect surfaces with its 37% solution.

Examples: Ethylene oxide and propylene oxide; highly effective in isolating diseases such as Ebola.
Mechanism: Gases fill spaces and crevices not reachable by conventional liquid disinfectants.
Risks: Highly flammable; used in special isolation units designed to accommodate their risks.

Types of Heat: Most efficient methods use moist heat like pressurized steam (autoclaving) or pressure cookers (for canning).
Applications: Used in sterilizing lab equipment or preserving food.
Pasteurization: Effective for reducing pathogens but does not sterilize.

Purpose: More for preservation than sterilization; slows microbial metabolism.
Applications: Bacteria can survive freezing if glycerol is present.

Purpose: Mechanical method of removing microorganisms from liquids that cannot be autoclaved.

Osmotic pressure: Used as a preservative method by creating hypertonic environments.
Radiation: Can disinfect materials that are sensitive to heat.

Defining Antibiotics: Definitions focus on their ineffectiveness against viruses; antibiotics work only on bacteria.
Forms of Antimicrobial Agents: Includes antivirals, antifungals, and antibiotics specifically for bacteria.

Penicillin: First antibiotic discovered by Alexander Fleming; observed effects of fungal growth preventing bacterial growth.
Mass Production: Significant during World War II due to a supply shortage of citric acid, leading Pfizer to produce penicillin.

Historical Timeline: Sulfonamides were the first mass-produced antibiotics (1936), leading to penicillin's use (1940).
Antibiotic Resistance: Resistance noticed as early as the late 1940s but became widespread later; the gap of antibiotic discovery from 1962 to 2000 impacted current antibiotic effectiveness.

Projected Statistics: Predictions indicate that by 2050, deaths from antibiotic-resistant infections might surpass cancer.
Demographics: Younger individuals are more affected by infections, whereas cancer predominantly affects older patients.

Broad Spectrum Antibiotics: Effective against a wide range of bacteria (both gram-positive and gram-negative).
Narrow Spectrum Antibiotics: More targeted, affecting fewer strains of bacteria.
Pros and Cons:
- Narrow Spectrum: Lesser impact on healthy microbiome; slower development of resistance.
- Broad Spectrum: Targets more bacteria quickly, useful when the pathogen is unidentified; however, it can harm healthy bacteria and promote antibiotic resistance.

Bactericidal vs. Bacteriostatic: Bactericidal antibiotics kill bacteria, while bacteriostatic ones inhibit growth/reproduction.

Beta-lactam Antibiotics: Characterized by their unique beta-lactam ring structure, necessary for their function (targeting bacterial cell walls).
Structural Modifications: R groups on penicillin can be altered to create new antibiotics with different properties (e.g. methicillin, ampicillin).
Generations of Antibiotics: The concept of first, second, and third generation reflects the evolution and adaptation of these drugs in response to resistance.

Selective Toxicity: Antibiotics must be toxic to bacteria without harming human cells; achieved by targeting unique bacterial features:
- Cell Walls: Bacterial cells have walls; human cells do not.
- Ribosomes: Different ribosomal sizes (70s in bacteria vs. 80s in humans).
- Metabolites: Enzymes specific to bacteria.
- Nucleic Acids: Target differences in replication/transcription mechanisms.