Podcast
Questions and Answers
What is the function of helicase in DNA replication?
What is the function of helicase in DNA replication?
- Unzips DNA (correct)
- Seals gaps in DNA
- Adds mRNA
- Builds DNA strands
What enzyme builds DNA strands during replication?
What enzyme builds DNA strands during replication?
- DNA polymerase (correct)
- Ligase
- RNA polymerase
- Helicase
What is the role of ligase in DNA replication?
What is the role of ligase in DNA replication?
- Adding primers to DNA
- Sealing gaps in DNA (correct)
- Building DNA strands
- Unzipping DNA
What does it mean for DNA replication to be 'semi-conservative'?
What does it mean for DNA replication to be 'semi-conservative'?
Which enzyme is responsible for making mRNA from DNA during transcription?
Which enzyme is responsible for making mRNA from DNA during transcription?
What cellular structure reads mRNA to assemble proteins?
What cellular structure reads mRNA to assemble proteins?
Which molecule delivers amino acids to the ribosome for protein synthesis?
Which molecule delivers amino acids to the ribosome for protein synthesis?
What is the term for a change in the nucleotide sequence of DNA?
What is the term for a change in the nucleotide sequence of DNA?
What type of mutation does NOT change the amino acid sequence?
What type of mutation does NOT change the amino acid sequence?
Which of the following mutations results in a stop codon being introduced too early?
Which of the following mutations results in a stop codon being introduced too early?
What kind of mutation involves a shift in the reading frame of a gene?
What kind of mutation involves a shift in the reading frame of a gene?
What is one potential cause of mutations?
What is one potential cause of mutations?
What does the Ames test primarily detect?
What does the Ames test primarily detect?
What is the term for the uptake of free DNA by bacteria?
What is the term for the uptake of free DNA by bacteria?
Which process involves the transfer of DNA via a virus?
Which process involves the transfer of DNA via a virus?
What is the transfer of DNA between bacteria via a pilus called?
What is the transfer of DNA between bacteria via a pilus called?
What is the process that destroys all microbes?
What is the process that destroys all microbes?
What is the process that reduces pathogens on surfaces called?
What is the process that reduces pathogens on surfaces called?
What is the term for the process of making something safe for skin by reducing pathogens?
What is the term for the process of making something safe for skin by reducing pathogens?
What are the standard autoclave conditions?
What are the standard autoclave conditions?
How does an autoclave work to sterilize?
How does an autoclave work to sterilize?
Which of the following is a common item treated in an autoclave?
Which of the following is a common item treated in an autoclave?
What temperature and time are used in pasteurization?
What temperature and time are used in pasteurization?
What is the main purpose of pasteurization?
What is the main purpose of pasteurization?
Which of the following is a halogen used as a disinfectant?
Which of the following is a halogen used as a disinfectant?
What is the effective range of alcohol concentration for disinfection?
What is the effective range of alcohol concentration for disinfection?
How do Quats (Quaternary Ammonium Compounds) work?
How do Quats (Quaternary Ammonium Compounds) work?
Which of the following is an advantage of using Quats?
Which of the following is an advantage of using Quats?
What type of disinfectant is hydrogen peroxide?
What type of disinfectant is hydrogen peroxide?
What is the function of a 1 micron filter?
What is the function of a 1 micron filter?
What does HEPA filter remove?
What does HEPA filter remove?
How does UV radiation kill bacteria?
How does UV radiation kill bacteria?
What is a common effect of cold temperatures on microbes?
What is a common effect of cold temperatures on microbes?
What is the mechanism of action for penicillin?
What is the mechanism of action for penicillin?
Which drug class inhibits protein synthesis?
Which drug class inhibits protein synthesis?
How does ciprofloxacin work?
How does ciprofloxacin work?
What is the mechanism of action for sulfa drugs?
What is the mechanism of action for sulfa drugs?
Enzymes that inactivate penicillin are called:
Enzymes that inactivate penicillin are called:
What is a mechanism of antibiotic resistance where bacteria pump the drug out of the cell?
What is a mechanism of antibiotic resistance where bacteria pump the drug out of the cell?
What is the Kirby-Bauer test used for?
What is the Kirby-Bauer test used for?
What does the zone of inhibition indicate in the Kirby-Bauer test?
What does the zone of inhibition indicate in the Kirby-Bauer test?
Which two types of alcohol are commonly used as disinfectants?
Which two types of alcohol are commonly used as disinfectants?
What did Griffith's experiment demonstrate?
What did Griffith's experiment demonstrate?
What did Avery's discovery determine?
What did Avery's discovery determine?
What does the E-test determine?
What does the E-test determine?
How is the MIC determined in a broth dilution test?
How is the MIC determined in a broth dilution test?
Which of the following is considered a sterile site in the human body?
Which of the following is considered a sterile site in the human body?
Where is normal flora typically found in the body?
Where is normal flora typically found in the body?
Which stage of disease occurs immediately after the incubation period?
Which stage of disease occurs immediately after the incubation period?
What is a fomite?
What is a fomite?
Which of the following is a possible reservoir for pathogens?
Which of the following is a possible reservoir for pathogens?
Which of the following is a common healthcare-associated infection (HAI)?
Which of the following is a common healthcare-associated infection (HAI)?
Which characteristic describes exotoxins?
Which characteristic describes exotoxins?
What part of Gram-negative bacteria is endotoxin?
What part of Gram-negative bacteria is endotoxin?
What is the function of adhesins?
What is the function of adhesins?
How do capsules contribute to bacterial virulence?
How do capsules contribute to bacterial virulence?
What does antigenic variation allow a pathogen to do?
What does antigenic variation allow a pathogen to do?
What is a gene?
What is a gene?
What is a plasmid?
What is a plasmid?
Which of the following describes a bacterial chromosome?
Which of the following describes a bacterial chromosome?
What does a bacteriophage infect?
What does a bacteriophage infect?
What is the primary function of a cytokine?
What is the primary function of a cytokine?
What does PAMP stand for?
What does PAMP stand for?
What recognizes PAMPs?
What recognizes PAMPs?
Which of these is an inflammatory cytokine?
Which of these is an inflammatory cytokine?
What is opsonization?
What is opsonization?
What is the function of the MAC?
What is the function of the MAC?
What is the correct order of disease stages?
What is the correct order of disease stages?
What is the name for the measure of the lowest concentration of a drug that stops growth?
What is the name for the measure of the lowest concentration of a drug that stops growth?
What is Candida Auris?
What is Candida Auris?
Exotoxins are secreted by which of the following?
Exotoxins are secreted by which of the following?
What is the purpose of coagulase?
What is the purpose of coagulase?
What is kinase?
What is kinase?
CSF stands for:
CSF stands for:
Where is lipopolysaccharide found?
Where is lipopolysaccharide found?
Botulinum toxin is:
Botulinum toxin is:
What does it mean for transformation to occur?
What does it mean for transformation to occur?
What is the point where bacterial growth touches the strip called?
What is the point where bacterial growth touches the strip called?
Flashcards
Semi-conservative DNA replication
Semi-conservative DNA replication
Each strand of DNA serves as a template for a new strand.
Helicase
Helicase
Unzips DNA, separating strands.
DNA polymerase
DNA polymerase
Builds new DNA strands.
Ligase
Ligase
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Transcription
Transcription
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Translation
Translation
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Silent Mutation
Silent Mutation
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Missense Mutation
Missense Mutation
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Nonsense Mutation
Nonsense Mutation
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Frameshift Mutation
Frameshift Mutation
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Transformation (in bacteria)
Transformation (in bacteria)
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Transduction (in bacteria)
Transduction (in bacteria)
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Conjugation (in bacteria)
Conjugation (in bacteria)
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Sterilization
Sterilization
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Disinfection
Disinfection
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Antiseptics
Antiseptics
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Autoclave
Autoclave
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Pasteurization
Pasteurization
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Halogens (as disinfectants)
Halogens (as disinfectants)
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Alcohols (as disinfectants)
Alcohols (as disinfectants)
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Quats (as disinfectants)
Quats (as disinfectants)
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Peroxides (as disinfectants)
Peroxides (as disinfectants)
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1 micron filter
1 micron filter
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How alcohols work
How alcohols work
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Radiation (UV)
Radiation (UV)
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Ionizing Radiation
Ionizing Radiation
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Cold
Cold
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Penicillin
Penicillin
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Drug resistance mechanism of efflux
Drug resistance mechanism of efflux
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Broth dilution test for MIC
Broth dilution test for MIC
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Normal flora locations
Normal flora locations
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Transmission routes
Transmission routes
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Descriptive Epidemiology
Descriptive Epidemiology
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Experimental Epidemiology
Experimental Epidemiology
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Exotoxins
Exotoxins
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Adhesins (fimbriae)
Adhesins (fimbriae)
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Swab Plate Evenly
Swab Plate Evenly
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E-test
E-test
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Sterile Sites
Sterile Sites
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Disease Stages
Disease Stages
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Reservoirs
Reservoirs
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HAI Organisms
HAI Organisms
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Gene
Gene
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Plasmid
Plasmid
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Chromosome
Chromosome
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Bacteriophage
Bacteriophage
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Cytokine
Cytokine
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PAMP
PAMP
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PRR
PRR
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IL-1, TNF-alpha
IL-1, TNF-alpha
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Opsonization
Opsonization
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MAC
MAC
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Clostridium difficile
Clostridium difficile
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Candida Auris
Candida Auris
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Alcohols
Alcohols
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Griffith’s Experiment
Griffith’s Experiment
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Avery’s Discovery
Avery’s Discovery
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Study Notes
DNA Replication
- DNA replication is semi-conservative, meaning each strand serves as a template for a new strand
- Key enzymes in DNA replication include:
- Helicase: Unzips the DNA double helix
- DNA polymerase: Builds the new DNA strands
- Ligase: Seals gaps in the newly synthesized DNA
Transcription
- RNA polymerase is the enzyme responsible for making mRNA from a DNA template
Translation
- Ribosomes read mRNA sequences
- tRNA molecules deliver corresponding amino acids to build a protein
Prokaryotes vs. Eukaryotes
- Prokaryotes
- Lack a nucleus
- Transcription and translation occur simultaneously
- Eukaryotes
- Transcription occurs in the nucleus
- Translation occurs in the cytoplasm
Types of Mutations
- Silent mutation: No change in the amino acid sequence
- Missense mutation: Results in a wrong amino acid being incorporated
- Nonsense mutation: Introduces a stop codon prematurely, truncating the protein
- Frameshift mutation: Shifts the reading frame, altering the entire amino acid sequence downstream
Causes of Mutations
- Radiation
- Chemicals
- Copying errors during DNA replication
Ames Test
- Used to detect the mutagenic potential of chemicals
DNA Sharing in Bacteria
- Transformation: Uptake of free DNA from the environment
- Transduction: Transfer of DNA via a virus
- Conjugation: Transfer of DNA via a plasmid through a pilus
Griffith's Experiment
- Demonstrated transformation
- Dead virulent bacteria + live harmless bacteria = disease (proved transformation)
Avery's Discovery
- Identified DNA as the genetic material
Microbial Control - Definitions
- Sterilization: Destroys all microbes
- Disinfection: Reduces pathogens on surfaces
- Antiseptics: Safe for use on skin
Autoclave Conditions
- 121°C, 15 psi, for 15 minutes
- Denatures proteins via steam heat
- Used for liquids, glassware, surgical tools, and some plastics
- Time can vary from 20-45 minutes
Pasteurization
- 72°C for 15 seconds (does not boil)
- Kills pathogens, slows spoilage, but doesn't stop it completely
Disinfectant Categories & Examples
- Halogens
- Bleach
- Effective against bacteria, viruses, and fungi
- Do not kill all endospores or cysts
- Alcohols
- Isopropanol
- Ethanol
- Effective range: 60-70% (with water for protein denaturation)
- Quats (Quaternary Ammonium Compounds)
- Benzalkonium chloride
- Disrupt membranes
- Non-corrosive, non-staining, no strong fumes, inexpensive, and easy to use
- Some microbes (e.g., Pseudomonas) can grow in quats
- Peroxides
- Hydrogen peroxide
- Filters
- 1 micron: Removes protozoa and most bacteria
- HEPA: Filters air in rooms
- N95: Filters air for individual breathing
How Disinfectants Work
- Alcohols: Denature proteins and dissolve lipids (effective against envelope viruses)
- Autoclave: Steam denatures proteins
Radiation (UV)
- Damages DNA via thymine dimers
Ionizing Radiation
- Forms toxic oxygen via ionized water and damages DNA
Cold
- Slows metabolism and prevents reproduction
Filtration
- Physically removes microbes from liquid or air
Antimicrobial Drugs - Common Drug Classes
- Penicillin: Cell wall inhibitor (e.g., for strep infections)
- Tetracycline: Protein synthesis inhibitor (e.g., for acne)
- Ciprofloxacin: DNA replication inhibitor (e.g., for UTIs)
- Sulfa drugs: Folic acid synthesis inhibitor
Resistance Mechanisms
- Drug inactivation: Beta-lactamase inactivates penicillin
- Drug efflux: Pumps drug out of the cell (e.g., tetracycline resistance)
- Blocked entry: Modified porins in Gram-negative bacteria
- Target alteration: Changes in ribosomes (e.g., tetracycline, aminoglycoside resistance)
Testing Methods – Kirby-Bauer
- Measures the zone of inhibition around antibiotic disks
E-test (Epsilometer test)
- Determines the Minimum Inhibitory Concentration (MIC)
- A plastic strip with a gradient of antibiotic concentrations is placed on an agar plate with bacteria
- As the bacteria grow, an elliptical zone of inhibition forms around the strip.
- The point where bacterial growth touches the strip indicates the MIC—the lowest concentration of the drug that inhibits visible bacterial growth
Broth Dilution
- Determines the lowest concentration to stop growth (MIC)
- Bacteria exposed to serial dilutions of drug in 96-well plate
- MIC is the lowest concentration with no visible growth
Antimicrobial Drug Examples
- Penicillin: Inhibits cell wall synthesis, used for streptococcal infections; resistance via beta-lactamase
- Tetracycline: Inhibits protein synthesis, used for acne and respiratory infections; resistance via efflux pumps
- Ciprofloxacin: Inhibits DNA replication, used for UTIs and anthrax; resistance via altered target sites
- Sulfa drugs: Inhibits folic acid synthesis, used for UTIs and respiratory infections; resistance via altered target sites
- Common sensitivity tests include Kirby-Bauer, E-test, and Broth dilution
Epidemiology - Normal Flora Locations
- Skin
- GI tract
- Mouth
- Throat
Sterile Sites in Body
- Blood
- CSF
- Lungs
Disease Stages
- Incubation → Prodromal → Illness → Decline → Convalescence
Transmission Routes
- Airborne
- Foodborne
- Vector
- Fomite
- Direct contact
Reservoirs
- Human
- Animal
- Soil
- Water
HAI (Healthcare-Associated Infection) Organisms & Diseases
- Clostridium difficile: Endospores, causes diarrhea
- Candida Auris: Drug-resistant yeast
- MRSA, E. coli, Pseudomonas: pneumonia, wounds, UTIs
Key Organisms and Characteristics
- Clostridium difficile
- Gram-positive bacterium
- Forms endospores, anaerobic
- Causes severe diarrhea, colitis
- Candida auris
- Fungal yeast
- Drug-resistant, invasive
- Causes bloodstream, wound, and ear infections
- MRSA (Staph. aureus)
- Gram-positive bacterium
- Methicillin-resistant
- Causes pneumonia and wound infections
- Escherichia coli
- Gram-negative bacterium
- Normal flora, opportunistic
- Causes UTIs, pneumonia, and wound infections
- Pseudomonas aeruginosa
- Gram-negative bacterium
- Resistant and forms biofilms
- Causes pneumonia (esp. in CF), UTIs, and wounds
Descriptive vs. Experimental Epidemiology
- Descriptive Epidemiology
- Goal:Describe disease patterns (who, where, when)
- Design: Observational
- Questions: Who is affected? When and where?
- Tools: Case reports, surveillance, epidemic curves
- Example: Tracking measles outbreak in a school
- Data Collection: Often retrospective or real-time
- Use: Generate hypotheses
- Experimental Epidemiology
- Goal: Test hypotheses about causes or treatments
- Design: Controlled experiment
- Questions: Does X cause Y? Does a treatment work?
- Tools: Clinical trials, randomized controlled trials
- Example: Testing a new vaccine in two randomized groups
- Data Collection: Prospective (follows subjects forward in time)
- Use: Confirm or refute hypotheses
Virulence & Pathogenicity - Toxins
- Exotoxins: Secreted, very toxic (e.g., botulinum toxin)
- Endotoxins: LPS of Gram-negatives, weakly toxic
Virulence Factors
- Adhesins (fimbriae): Attachment
- Capsules: Evade immune system
- Enzymes (coagulase, kinase): Damage tissues
- Antigenic variation (e.g., HIV, Trypanosoma)
- Invasion into host cells
Virulence Factors - Examples
- Adhesins (fimbriae)
- Surface structures for attachment
- E. coli, Neisseria gonorrhoeae
- Helps microbes stick to host tissues
- Capsules
- Polysaccharide coating that hides the cell
- Streptococcus pneumoniae
- Prevents phagocytosis by immune cells
- Enzymes
- Coagulase (clots), kinase (spreads infection)
- Staphylococcus aureus
- Disrupts tissues or evades immune response
- Antigenic variation
- Alters surface proteins to avoid detection
- HIV, Trypanosoma
- Evades immune memory and prolongs infection
- Invasion
- Forces entry into host cells
- Salmonella, Listeria
- Hides inside host cells, avoids immune attack
Key Vocabulary
- Gene: Segment of DNA with instructions to make a specific protein or functional RNA
- Plasmid: Small, circular piece of DNA in bacteria, separate from the chromosome, carries extra genes like antibiotic resistance
- Chromosome: Large, organized structure of DNA containing many genes
- Bacteriophage: Virus that infects bacteria
- Cytokine: Immune signaling molecule
- PAMP (Pathogen-Associated Molecular Pattern): Pathogen signal recognized by host
- PRR (Pattern Recognition Receptor): Host receptor for PAMP
- IL-1, TNF-alpha: Inflammatory cytokines
- Opsonization: Tags microbes for phagocytosis
- MAC: Membrane attack complex, lyses microbes
Kirby-Bauer Disk Diffusion Test Steps
- Prepare a bacterial lawn
- Use a sterile swab to evenly spread the test bacterium over the entire surface of a Mueller-Hinton agar plate
- Let the plate dry
- Allow the plate to sit for about 5–10 minutes so moisture absorbs
- Place antibiotic-impregnated disks
- Use sterile forceps or a disk dispenser, place antibiotic disks evenly spaced on the agar surface
- Gently press each disk to ensure full contact
- Invert and incubate the plate
- Turn the plate upside down and incubate at 35–37°C for 16–18 hours
- Measure zones of inhibition
- After incubation, use a ruler or caliper to measure the diameter (in mm) of the clear zones around each disk
- Interpret results
- Compare measurements to a standard chart to determine if the bacterium is: Susceptible (S), Intermediate (I), or Resistant (R) to the antibiotic
Spectrophotometer
- Measures turbidity to estimate bacterial growth
Disinfectant Lab
- Halogens
- Example: bleach, iodine
- Mode of Action: oxidizes cell components
- Effectiveness: Very effective
- Phenolics
- Example: Lysol
- Mode of Action: disrupts membranes, denatures proteins
- Effectiveness: Moderately effective
- Alcohols
- Example: Ethanol, isopropanol
- Mode of Action: Denatures proteins, dissolves membranes
- Effectiveness: Effective (requires water)
- Quats (Quaternary ammonium)
- Example: Benzalkonium chloride
- Mode of Action: Disrupts membrane integrity
- Effectiveness: Less effective against gram-negatives
- Peroxides
- Example: Hydrogen peroxide
- Mode of Action: Forms reactive oxygen species (ROS)
- Effectiveness: Highly effective (broad spectrum)
- Heavy Metals
- Example: Silver nitrate
- Mode of Action: Inactivates proteins
- Effectiveness: Effective but less commonly used
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