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Questions and Answers
Which type of pathogen is primarily responsible for causing diseases in healthy individuals without predisposing conditions?
Which type of pathogen is primarily responsible for causing diseases in healthy individuals without predisposing conditions?
Which component is characteristic of Gram-negative bacteria as opposed to Gram-positive bacteria?
Which component is characteristic of Gram-negative bacteria as opposed to Gram-positive bacteria?
What is a key characteristic of virulence factors exhibited by pathogenic bacteria?
What is a key characteristic of virulence factors exhibited by pathogenic bacteria?
Which of the following roles do microbes play in human health?
Which of the following roles do microbes play in human health?
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Which attribute is NOT typically associated with the pathogenicity of a microorganism?
Which attribute is NOT typically associated with the pathogenicity of a microorganism?
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Which of the following describes a characteristic of endotoxins?
Which of the following describes a characteristic of endotoxins?
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What is a defining feature of virulence factors?
What is a defining feature of virulence factors?
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Which mechanism of bacterial virulence involves avoiding removal by the immune system?
Which mechanism of bacterial virulence involves avoiding removal by the immune system?
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Which of the following structures is associated with bacterial adhesion?
Which of the following structures is associated with bacterial adhesion?
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What is the function of the lipid envelope in some viruses?
What is the function of the lipid envelope in some viruses?
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Which type of viral symmetry is characterized by a lipid bilayer and glycoprotein spikes?
Which type of viral symmetry is characterized by a lipid bilayer and glycoprotein spikes?
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Which of the following classifications does not include DNA viruses?
Which of the following classifications does not include DNA viruses?
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What is the primary structural component of fungal cell walls?
What is the primary structural component of fungal cell walls?
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Which of these viruses is classified as a double-stranded DNA virus?
Which of these viruses is classified as a double-stranded DNA virus?
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Which type of virus does not have a lipid envelope?
Which type of virus does not have a lipid envelope?
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In which structure do fungi grow as branching, interlacing filaments?
In which structure do fungi grow as branching, interlacing filaments?
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What type of hyphae has perforated cross-walls?
What type of hyphae has perforated cross-walls?
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Which of the following viruses is classified as an enveloped virus?
Which of the following viruses is classified as an enveloped virus?
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Which type of RNA virus is characterized by having a positive-sense single-stranded RNA?
Which type of RNA virus is characterized by having a positive-sense single-stranded RNA?
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Which of the following best describes a non-septate hypha?
Which of the following best describes a non-septate hypha?
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Study Notes
Introduction to Microbiology
- Microbiology is the study of microorganisms, which includes bacteria, viruses, fungi, and parasites.
- Microorganisms can cause disease, but many are beneficial.
- Microorganisms are used to create vaccines and in gene therapy.
- They are also important in normal flora and nutritional processes.
Outline
- Role of microbes in humans
- Pathogenicity and routes of infection
- Mechanisms of bacterial virulence
- Bacterial morphology
- Gram staining properties
- Virulence factors
- Viruses as disease-causing agents
- Fungi as disease-causing agents
Role of Microbes in Humans
- Beneficial: Helpful functions
- Nutritional: Provide nutrients
- Normal flora (especially bacteria): Living in the body
- Vaccine development: Manufacturing vaccines
- Gene therapy: Tool for gene therapy
- Investigative tools: Helpful in investigation
- Disease-causing agents: Causing diseases
Pathogenicity
- Attributes of pathogenicity: Characteristics of a disease-inducing pathogen
- Transmissible: Ability to spread/transfer
- Infectivity: Ability to enter and multiply in host
- Virulence: Ability to cause widespread damage
- Exogenous & endogenous infection: Infections coming from external & internal sources respectively
Sites and routes of microbial infection
- Respiratory tract
- Mouth
- Conjunctiva
- Anus
- Urogenital tract
- Alimentary tract
- Skin
- Scratches/injury
- Arthropod
- Capillary
Pathogen (disease)
- Pathogen: microorganism that causes disease
- Two types of pathogens:
- True pathogens: Always cause disease
- Opportunistic pathogens: Cause disease only under certain conditions
Role of Bacteria in Disease
- Prokaryote: Single-celled organism lacking a nucleus and membrane-bound organelles
- Cell wall: Rigid layer surrounding the cell
- Peptidoglycan: Principal component of bacterial cell wall
- Flagellum: Whip-like structure that enables movement
Bacterial Morphology
- Shapes of bacteria:
- Coccus: spherical
- Bacillus: rod-shaped
- Coccobacillus: short rod-shaped
- Spirillum: spiral-shaped
- Vibrio: comma-shaped
- Spirochete: long, spiral-shaped
Gram Stain
- Gram-positive: Bacteria retain crystal violet stain, appear purple
- Gram-negative: Bacteria lose crystal violet stain, appear pink
Bacterial Membrane Structures
- Cell wall Gram-positive bacteria
- Peptidoglycan: Glycan chain of GlcNAc & MurNAc
- Teichoic acid: polymer of ribitol or glycerol
- Lipoteichoic acid: Lipid-linked teichoic acid
- Cell wall Gram-negative bacteria
- Peptidoglycan: Thinner than gram-positive
- Outer membrane: Contains phospholipids and proteins
- Periplasmic space: Space between the inner and outer membranes
- LPS: Lipid A, core polysaccharide, O antigen
Classification of Gram stainable pathogens
- Bacteria are classified based on various factors including Gram stain properties, genus, and species-examples are listed based on these factors.
Molecular Postulates
- Virulence factors: Attributes associated with causing disease (only in pathogenic strains)
- Mutation: Organisms can become less virulent
- Transfer to a non-pathogenic organism: It can become pathogenic
- Immune response: A protective reaction from the host organism
Mechanisms of Bacterial Virulence
- Adherence (sticking)
- Invasion: (entering and multiplying)
- By-products of growth (e.g., gas, acid)
- Toxins (harmful substances)
- Degradative enzymes (breaking down tissues)
- Cytotoxic proteins (killing cells)
- Endotoxin
- Superantigen
- Induction of excess inflammation Evasion of phagocytic and immune clearance
- Capsule (protective barrier)
- Resistance to antibiotics
- Intracellular growth
Tissue Injury
- Toxins: Damage to tissues
- Exotoxins: Specific immunity (antigen)-based damaging substances
- Endotoxins: Non-specific damaging substances.
What Are Viruses?
- Viruses: Organized associations of macro-molecules
- Nucleic acid: Blueprint for replication
- Progeny virions: New virus particles
- Protective shell: Protein units
What Are Viruses? (continued)
- Nucleic acid genome: DNA or RNA
- Protein coat: Protection and entry
- Lipid envelope: Present in some viruses
- Small: 20-400nm
- Obligate intracellular parasites: Depend on host cells for replication
Virus particle (virion)
- DNA Viruses: Examples are listed.
- RNA Viruses: Examples are listed.
Host Range
- Cell surface receptor: Allows viruses to attach and enter cells
- Ability to get out of cell and spread
- Host anti-viral response: Defense mechanisms of the host
Viral Symmetry
- Icosahedral, enveloped icosahedral, helical, enveloped helical, complex
DNA Viruses/RNA viruses
- Classification based on strandedness, enveloped/non-enveloped, and shape.
Viruses: Images
- Various viruses are shown in images
Fungi
- Fungi: Non-photosynthetic protists
- Grow as single-celled yeasts or mass of branching, interlacing filaments (hyphae)/mycelium
- Hyphae have perforated cross-walls (septate) or no cross-walls (coenocyte)
- Cell wall of the tube is made of chitin
Fungi: Images
- Illustrations of septate hyphae and yeasts.
Mycotic Diseases
- Hypersensitivity (allergy)
- Mycotoxicosis (toxin production)
- Mycetismus (mushroom poisoning)
- Infection (invasion of tissues)
Laboratory methods in fungal identification
- Wet mount (Lactophenol cotton blue, KOH)
- Staining (Giemsa, mucicarmine, Calcoflour white stain, Gram, PAS)
- Fluorescent monoclonal antibody
- Skin test
- Biopsy & histopathology (GMS, H&E)
- Serology
- Culture
- DNA probes
Human mycotic infections
- Superficial mycoses
- Cutaneous mycoses
- Subcutaneous mycoses
- Deep or systemic mycoses: Examples shown
Molds: Penicillium species
- Images illustrating molds.
Candida
- Images illustrating Candida.
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Description
Explore the fascinating world of microbiology, focusing on the diverse roles of microorganisms in human health and disease. This quiz delves into beneficial microbes, pathogenicity, and the mechanisms that enable bacteria and viruses to cause illness. Test your knowledge on the impacts of these tiny organisms on vaccines, gene therapy, and nutritional processes.
