Objectives come from your Unit 3 sheet  and the content/examples come from the PowerPoints .
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UNIT 3 COMPLETE STUDY GUIDE
(Based strictly on your slides + objectives)
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CHAPTER 11 — CONTROLLING MICROBIAL GROWTH
Difference Between Antisepsis, Disinfection, Sanitization, Sterilization, Degerming, Decontamination
Sterilization
Complete destruction of all microbial life including viruses and endospores.
Examples from slides:
• Surgical instruments
• Syringes
• Packaged foods
Endospores must be destroyed for something to be considered sterile. 
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Disinfection
Destroys most vegetative pathogens on nonliving surfaces.
Examples:
• Disinfecting medical equipment
• Hospital surfaces
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Antisepsis
Use of antimicrobial chemicals on living tissue.
Examples:
• Skin prep before surgery
• Cleaning wounds
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Degerming
Mechanical removal of microbes by scrubbing.
Example:
• Handwashing
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Sanitization
Reduces microbial numbers to public health safe levels.
Examples:
• Cleaning food preparation surfaces
• Restaurant sanitation
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Decontamination
General removal of microbes from objects or surfaces.
Example:
• Cleaning contaminated hospital equipment
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Difference Between Static and Cidal
Cidal
Kills microbes.
Example
Bactericidal antibiotics.
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Static
Stops growth but does not kill.
Example
Bacteriostatic antibiotics.
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Variables That Influence Effectiveness of Antimicrobial Methods
1. Population size
Large populations require more time to kill.
2. Nature of microbes
Some microbes are more resistant.
Example:
Bacterial endospores.
3. Temperature
Higher temperature increases killing.
4. Concentration of agent
5. Contact time
6. Organic matter present
Example:
Blood or mucus interfering with disinfectants.
7. Mode of action of agent
8. Biofilms
Biofilms protect microbes from antimicrobials. 
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Most Resistant vs Least Resistant Microbes
Most resistant:
Bacterial endospores
Reason:
Thick protective layers.
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Less resistant:
• Mycobacteria
• Gram-negative bacteria
• Gram-positive bacteria
• Fungi
• Viruses
Endospores are the target of sterilization methods. 
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Mechanisms of Antimicrobial Agents
Agents work by damaging:
Cell wall
Example
Detergents and alcohol disrupt cell wall.
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Cell membrane
Effects
• Loss of permeability
• Leakage of molecules
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Proteins
Agents denature proteins.
Examples
• Heat
• Alcohol
• Strong acids
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DNA and RNA
Example
Radiation damaging DNA.
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Practical Concerns When Choosing Control Method
Consider:
• Does item require sterilization or disinfection?
• Can item tolerate heat, pressure, radiation, chemicals?
• Cost effectiveness
• Safety
• Ability of agent to penetrate surfaces. 
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PHYSICAL AND MECHANICAL METHODS
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Pasteurization vs Sterilization
Pasteurization:
Reduces microbial numbers but does not sterilize.
Used for:
Milk and beverages.
Sterilization:
Destroys all microbes including endospores.
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Boiling
Kills many pathogens but may not destroy endospores.
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Autoclaving
Uses steam under pressure.
Conditions from slides:
121°C
15 minutes
15 psi
Mechanism:
Denatures proteins and disrupts metabolism. 
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Most Rigorous Heat Method
Incineration (dry heat)
Burns microbes completely.
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Ionizing Radiation vs UV Radiation
Ionizing radiation
Examples:
Gamma rays
X-rays
Effect:
Destroys DNA and proteins.
Highly penetrating.
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UV radiation
Example:
Germicidal lamps.
Mechanism:
Forms pyrimidine dimers (thymine dimers).
Effect:
DNA replication blocked. 
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Filtration
Removes microbes from liquids or air.
Examples:
• Water purification
• Milk filtration
• Air filtration systems
• HEPA filters
• N95 masks
HEPA filters remove 99.97% of particles. 
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Osmotic Pressure
High salt or sugar removes water from microbes.
Examples:
Salt:
Cured meats
Sugar:
Jams and jellies
Causes plasmolysis and prevents growth. 
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Cold and Drying
Cold:
Slows microbial metabolism but rarely kills microbes.
Drying (desiccation):
Removes water necessary for microbial metabolism.
Example:
Freeze drying (lyophilization). 
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CHEMICAL METHODS
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Characteristics of Good Chemical Antimicrobials
• Rapid action
• Effective at low concentrations
• Broad spectrum
• Stable
• Non-toxic to tissues
• Affordable
• Effective in presence of organic matter 
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Major Chemical Agents
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Halogens
Examples:
• Chlorine
• Iodine
Common example:
Household bleach (sodium hypochlorite)
Mechanism:
Oxidizes cellular molecules and damages enzymes. 
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Phenols
Mechanism:
Disrupt cell membranes and denature proteins.
Examples:
Phenolic disinfectants.
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Alcohols
Examples:
• Ethanol
• Isopropanol
Mechanism:
Denature proteins and disrupt membranes.
Common use:
Hand sanitizers.
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Quats
Quaternary ammonium compounds.
Mechanism:
Disrupt membranes.
Example:
Lysol wipes
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Peroxides
Example:
Hydrogen peroxide.
Mechanism:
Forms reactive oxygen molecules that damage cells.
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Detergents / Surfactants
Mechanism:
Break down lipid membranes.
Examples:
Soap and cleaning detergents. 
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CHAPTER 12 — ANTIBIOTICS
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Alexander Fleming
Discovered penicillin in 1928 from the fungus Penicillium. 
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Characteristics of a Good Antimicrobial Drug
• Selective toxicity
• High therapeutic index
• Targets unique microbial structures
• Effective against pathogen
• Minimal harm to microbiota 
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Selective Toxicity
Ability of a drug to kill microbes without harming host cells.
Example:
Penicillin targets bacterial cell walls, which human cells lack.
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Susceptibility Tests
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Kirby-Bauer
Disc diffusion test.
Antibiotic discs placed on bacterial culture.
Zone of inhibition measured.
Results:
Sensitive
Resistant 
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MIC
Minimum inhibitory concentration.
Smallest drug concentration preventing visible growth.
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MBC
Minimum bactericidal concentration.
Smallest concentration that kills bacteria.
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Therapeutic Index
TI = toxic dose / therapeutic dose
Example from slides:
TI of 10 safer than TI of 1.1. 
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Antibiotic Mechanisms
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Cell Wall Inhibitors
Example:
Penicillin
Mechanism:
Prevents cross-linking of NAM-NAG peptidoglycan.
Cell bursts due to osmotic pressure.
Other examples:
• Methicillin
• Cephalosporins 
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Cell Membrane Disruption
Examples:
• Polymyxin
• Daptomycin
• Colistin
Mechanism:
Creates pores causing leakage. 
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Protein Synthesis Inhibitors
Example:
Tetracycline
Mechanism:
Blocks 30S ribosomal subunit.
Other examples:
• Erythromycin
• Azithromycin
• Chloramphenicol 
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DNA / RNA Inhibitors
Example:
Fluoroquinolones
Examples:
• Ciprofloxacin
• Levofloxacin
Mechanism:
Inhibit DNA gyrase.
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Metabolic Pathway Inhibitors
Example:
Sulfa drugs
Block folic acid synthesis.
Example drug:
Bactrim. 
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Drugs for Eukaryotic Pathogens
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Antifungals
Examples:
• Fluconazole
• Amphotericin B
• Azoles
Target ergosterol in fungal membranes.
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Antiprotozoal Drugs
Examples:
• Metronidazole
• Chloroquine
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Antihelminthic Drugs
Examples:
• Pyrantel
• Mebendazole
• Ivermectin 
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Antiviral Drugs
Targets:
• Viral attachment
• Viral transcription/translation
• Viral assembly or release
Examples:
Acyclovir
Blocks viral DNA replication.
Tamiflu
Prevents influenza virus release. 
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HIV Drugs
Target steps in HIV replication:
1 Reverse transcriptase
2 Integrase
3 Protease
4 Viral attachment
Combination therapy prevents resistance.
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Antibiotic Resistance
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How Resistance Develops
• Mutation
• Natural selection
• Overuse of antibiotics
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Mechanisms of Resistance
• Drug-destroying enzymes
• Efflux pumps
• Target modification
• Reduced permeability 
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CHAPTER 13 — MICROBIOTA
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Normal Microbiota
Microorganisms living on body surfaces without causing disease.
Examples from slides:
Skin:
Staphylococcus epidermidis
Gut:
Escherichia coli
Breast milk microbes:
• Bifidobacterium
• Lactobacillus
• Streptococcus
• Clostridium 
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Benefits of Microbiota
• Produce vitamins
• Digest food
• Stimulate immune system
• Produce neurotransmitters
• Prevent pathogen colonization 
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Dysbiosis
Imbalance in microbiota.
Associated diseases:
• Diabetes
• Obesity
• Cancer
• Asthma
• Allergies
• Heart disease 
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Microbiota Development
Microbiota develop:
1 During birth
2 Through breast milk
3 Environmental exposure
Stable microbiome forms by age 3.
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Probiotics vs Prebiotics
Probiotics:
Live microbes that improve microbiota.
Example:
Yogurt.
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Prebiotics:
Food that feeds beneficial microbes.
Examples:
• Garlic
• Onions
• Asparagus
• Agave
• Artichokes 
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Fecal Microbiota Transplant
Transfer of microbiota from healthy donor.
Used for:
Clostridioides difficile infections
Success rate:
70–90%. 
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Virulence Factors
Examples:
Adhesion structures:
Capsules, fimbriae
Exoenzymes:
Hyaluronidase
Coagulase
Biofilms increase resistance. 
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Toxins
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Exotoxins
Secreted protein toxins.
Examples:
• Cytotoxins
• Neurotoxins
• Enterotoxins
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Endotoxins
Found in gram-negative bacteria.
Example:
LPS containing lipid A.
Effects:
• Fever
• Inflammation
• Shock 
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CHAPTER 14 — EPIDEMIOLOGY
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Epidemiology
Study of disease frequency, distribution, and control in populations. 
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Epidemiological Terms
Index case:
First identified patient.
Incidence:
Number of new cases.
Prevalence:
Total existing cases.
Mortality rate:
Deaths in a population.
Case fatality rate:
Deaths among infected individuals. 
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Disease Occurrence
Sporadic:
Random cases.
Endemic:
Constant presence.
Outbreak:
Localized increase.
Epidemic:
Large regional increase.
Pandemic:
Worldwide epidemic. 
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Healthcare-Associated Infections (HAIs)
Common examples:
• CAUTI
Catheter-associated urinary tract infection
• CLABSI
Central line bloodstream infection
• Surgical site infections
• Ventilator associated infections 
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Causes of HAIs
• Low patient immunity
• Antibiotic resistant organisms
• Invasive procedures
• Healthcare worker transmission
Example:
Healthcare workers moving between patients. 
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Prevention of HAIs
• Medical asepsis
• Surgical asepsis
• Universal precautions
• Infection control officers
Examples:
• Needlestick precautions
• Surface decontamination
• Barrier protection 
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If you want, I can also give you the 20–30 questions your professor is MOST likely to put on the exam from these slides.
Micro professors tend to repeat the same exact conceptual questions every semester, and your slides have some really obvious ones.
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