뒤로Comprehensive Study Notes: Bacteriology, Bacterial Genetics, Pathogenesis, and Control
스터디 가이드 - 스마트 노트
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Bacteriology: Taxonomy and Classification
Three Domain and Five Kingdom Systems
The classification of microorganisms is fundamental to microbiology, enabling the identification and study of pathogens. - Three Domain System: Bacteria, Archaea, Eukarya. - Five Kingdom System: Animals, Plants, Fungi, Protista, Prokaryote (Monera). - Hierarchy: Domain → Kingdom → Phylum/Division → Class → Order → Family → Genus → Species. - Importance of Strain Identification: Different strains may have varying pathogenicity and treatment implications (e.g., E. coli).
Prokaryotes vs. Eukaryotes
Understanding cellular differences is crucial for diagnosis and treatment. - Prokaryotes: No membrane-bound nucleus, single chromosome, usually unicellular, partial genetic recombination, smaller ribosomes (70S), lack organelles. - Eukaryotes: Membrane-bound nucleus, multiple chromosomes, multicellular, meiosis and gamete fusion, larger ribosomes (80S), organelles present.
Bacterial Cell Structure and Function
Architectural Regions
Bacterial cells are organized into appendages, cell envelope, and cytoplasmic components.
Appendages
- Flagella: Motility, sometimes adhesion. - Fimbriae: Adhesion, biofilm formation, virulence factor. - Pili: DNA transfer (conjugation), adhesion. 
Cell Envelope
- Glycocalyx: Capsule (rigid, virulence factor) or slime layer (diffuse, aids in adherence). - Cell Wall: Peptidoglycan structure with N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). - Gram Positive: Thick peptidoglycan, teichoic acids, stains purple, more susceptible to penicillin. 
- Gram Negative: Thin peptidoglycan, outer membrane, lipopolysaccharides (LPS), porins, less susceptible to penicillin. 
Cytoplasmic Components
- Nucleoid: Aggregated DNA. - Plasmids: Extra-chromosomal DNA, often carry resistance genes. - Ribosomes: Protein synthesis, target for antibacterial drugs. - Endospores: Survival under hostile conditions, resistant to heat, drying, chemicals.
Cell Membrane Functions
The bacterial cell membrane is essential for various cellular processes. - Nutrient uptake and transport - Electron transport - Energy production - Secretion of enzymes and toxins 
Bacterial Identification and Classification
Phenotypic Characteristics
- Morphology: Cocci (spherical), Bacilli (rod), Spirilla (spiral), Vibrio (curved rod), Spirochete (flexible spiral), Branching filaments. - Colony Morphology: Shape, size, color, margin, elevation, texture.
Serotyping and Antibiogram
- Serotyping: Uses antibody interactions to identify bacteria. - Antibiogram: Determines antibiotic sensitivity/resistance.
Classification by Oxygen Use
- Obligate Aerobes: Require O2, aerobic respiration. - Obligate Anaerobes: Killed by O2 derivatives, anaerobic respiration or fermentation. - Facultative Anaerobes: Grow with or without O2. - Aerotolerant Anaerobes: Can grow in O2, obligate fermenters. - Microaerophiles: Require low O2 concentration.
Biofilm Formation and Bacterial Relationships
Biofilm Formation
Biofilms are complex communities of bacteria that are highly resistant to treatment. - Stages: Initial attachment, irreversible attachment, maturation I, maturation II, dispersion. - Advantages: Protection from antimicrobials, increased virulence, genetic exchange. 
Bacterial Genetics and Gene Expression
Genome Organization
- Genome: Total genetic material. - Genotype: Genetic makeup. - Phenotype: Observable traits. - Operon: Multiple genes transcribed from a single promoter (polycistronic mRNA).
DNA Structure and Replication
- Nucleotide: Phosphate, deoxyribose sugar, nitrogenous base (A, T, G, C). - Base Pairing: A-T, G-C.
Central Dogma
The flow of genetic information is from DNA to RNA to protein. - Transcription: DNA → mRNA. - Translation: mRNA → Protein. - Codons: Triplet bases in mRNA specify amino acids. 
Genetic Transfer in Bacteria
- Plasmids: Self-replicating, may integrate into genome, carry resistance genes. - Transposons: Mobile DNA segments, "jumping genes." - Pathogenicity Islands: Multiple genes that confer pathogenic traits. - Bacteriophages: Bacterial viruses, can mediate gene transfer.
Horizontal Gene Transfer
Bacteria acquire new genes via transformation, transduction, and conjugation. 
Mode | Factors Involved | Direct/Indirect | Products |
|---|---|---|---|
Conjugation | Donor cell with pilus, fertility plasmid | Direct | Drug resistance, toxin production |
Transformation | Free donor DNA, competent recipient | Indirect | Capsule, unlimited with cloning |
Transduction | Bacteriophage carrier | Indirect | Toxins, drug resistance |
Bacterial Pathogenesis
Patterns of Infection
- Localized: Confined to specific tissue. - Systemic: Spreads to multiple sites. - Focal: Breaks loose from local infection.
Disease Progression
- Incubation: Time from exposure to symptoms. - Prodromal: Early symptoms. - Period of Invasion: High multiplication, greatest virulence. - Convalescent: Recovery phase. 
Virulence Factors
Virulence factors promote colonization, survival, and host damage. 
Adherence and Invasion
- Adherence: Fimbriae, pili, capsules, adhesin proteins. 
- Invasion: Exoenzymes break down cell cement, hyaluronidase and collagenase allow deeper tissue invasion. 
Spread and Survival
- Coagulase: Forms blood clots for protection. - Streptokinase: Dissolves clots for spread. 
Damage to Host
- Spreading Factors: Enzymes and toxins cause tissue necrosis. - Toxins: Exotoxins (A-B toxins), endotoxins (LPS). 
- Membrane Disruption: Pore-forming toxins and phospholipases disrupt cell membranes. 
Control of Microbes
Terminology
Term | Definition | Example |
|---|---|---|
Decontamination | Destruction/removal of undesirable microbes | Asepsis, disinfection |
Antiseptic | Chemicals applied to body surfaces | Iodophor, chlorhexidine |
Disinfection | Destruction of vegetative pathogens | 5% bleach, boiling water |
Sterilization | Removal/destruction of all viable microbes | Autoclaving, ionizing radiation |
Physical Methods
- Dry Heat: Incineration, hot air oven. - Moist Heat: Boiling, autoclaving (sterilizes). - Radiation: Ionizing (sterilizes), nonionizing (disinfects surfaces). - Filtration: Removes microbes from air/liquids.
Chemical Methods
- Alcohols: Used at 70% for optimal effectiveness. 
Evaluation of Antimicrobial Agents
- Disk Diffusion (Kirby-Bauer Test): Measures zone of inhibition for different agents. 
Antibacterial Therapy
Therapeutic Index and Drug Properties
- Therapeutic Index (TI): Ratio of toxic dose to minimum effective dose. - Desirable Properties: Selective toxicity, solubility, minimal resistance, minimal side effects, stability.
Mechanisms of Drug Action
- Protein Synthesis Inhibitors: Act on ribosomes. - Cell Wall Inhibitors: Block synthesis and repair. - Folic Acid Synthesis Inhibitors: Block metabolic pathways. - Cell Membrane Inhibitors: Cause loss of permeability. - DNA/RNA Inhibitors: Inhibit replication and transcription. 
Bacterial Infections: Cardiovascular, Nervous, Skin, Respiratory, and Urogenital Systems
Cardiovascular Infections
- Bacteremia: Bacteria in blood, can lead to sepsis. - Sepsis: Active multiplication in blood, high mortality.
Endocarditis
- Vegetations: Bacterial colonization on heart valves, can cause blockages and ongoing bacteremia. 
Nervous System Infections
- Bacterial Meningitis: More severe than viral, often caused by Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae. - Tetanus: Caused by Clostridium tetani, produces tetanospasmin toxin. - Botulism: Caused by Clostridium botulinum, produces botulinum toxin.
Skin Infections
- Impetigo: Caused by Staphylococcus aureus or Streptococcus pyogenes. - Scalded Skin Syndrome: Toxin-mediated by S. aureus. - Necrotizing Fasciitis: Rapid tissue destruction, often S. pyogenes. - Gas Gangrene: Clostridium perfringens, produces toxins and gas.
Urogenital Infections
- UTIs: Often caused by Escherichia coli. - Bacterial Vaginosis: Loss of normal flora, overgrowth of anaerobes. - Gonorrhea: Neisseria gonorrhoeae. - Chlamydia: Chlamydia trachomatis. - Syphilis: Treponema pallidum.
Respiratory Infections
- Upper Respiratory: Often viral, but can be caused by S. pyogenes, S. pneumoniae. - Pertussis: Bordetella pertussis, toxin-mediated. - Tuberculosis: Mycobacterium tuberculosis, chronic, drug-resistant forms exist. - Pneumonia: S. pneumoniae (classical), Mycoplasma pneumoniae (atypical), Legionella pneumophila (environmental).
Summary Table: Adhesive Properties of Microbes
Microbe | Disease | Adhesion Mechanism |
|---|---|---|
Neisseria gonorrhoeae | Gonorrhea | Fimbriae attach to genital epithelial cells |
Escherichia coli | Diarrhea | Fimbrial adhesin |
Shigella | Dysentery | Fimbriae attach to intestinal epithelium |
Mycoplasma | Pneumonia | Specialized tip attaches to lung epithelium |
Pseudomonas aeruginosa | Burn, lung infections | Fimbriae and slime layer |
Streptococcus pyogenes | Pharyngitis, impetigo | Lipoteichoic acid and capsule anchor cocci to epithelium |
Streptococcus mutans, S. sobrinus | Dental caries | Dextran slime layer glues cocci to tooth surface |
Summary Table: Microbial Control Methods
Summary Table: Qualities of Chemical Agents
Summary Table: Disk Diffusion Susceptibility Test
Summary Table: Mechanisms of Antibacterial Drug Action
Summary Table: Healthy vs Infected Heart Valve
Summary Table: Exiting Host
Summary Table: Hemolysis Types
Summary Table: A-B Toxin Subunits
Summary Table: Pore Forming Toxins
Summary Table: Phospholipase Action
Summary Table: Biofilm Formation
Summary Table: Adhesive Properties of Microbes
Summary Table: Categories of Virulence Factors
Summary Table: Exoenzymes Breaking Down Cell Cement
Summary Table: Hyaluronidase and Collagenase Action
Summary Table: Coagulase and Streptokinase Action
Summary Table: Microbial Control Methods Flowchart
Summary Table: Table of Chemical Agents Used in Health Care
Summary Table: Kirby-Bauer Disk Diffusion Test
Summary Table: Mechanisms of Antibacterial Drug Action
Summary Table: Healthy vs Infected Heart Valve
Summary Table: Portals of Exit for Pathogens
Summary Table: Alpha and Beta Hemolysis on Blood Agar
Summary Table: A-B Toxin Subunits
Summary Table: Pore Forming Toxins Mechanism
Summary Table: Phospholipase Action on Cell Membrane
Summary Table: Stages of Biofilm Formation
Summary Table: Adhesive Properties of Microbes Table
