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Questions and Answers
What is a significant feature that differentiates fungi from bacteria?
What is a significant feature that differentiates fungi from bacteria?
Which of the following agents typically requires careful handling due to its toxicity to humans?
Which of the following agents typically requires careful handling due to its toxicity to humans?
What determines the pathogenicity of a fungus?
What determines the pathogenicity of a fungus?
Which of these methods is primarily used to detect the presence of viral proteins?
Which of these methods is primarily used to detect the presence of viral proteins?
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What is a common property of most fungi in relation to antibacterial drugs?
What is a common property of most fungi in relation to antibacterial drugs?
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What is the main structural component of bacterial cell walls?
What is the main structural component of bacterial cell walls?
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Which of the following describes Gram negative bacteria?
Which of the following describes Gram negative bacteria?
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What type of bacterial arrangement is referred to as 'diplo'?
What type of bacterial arrangement is referred to as 'diplo'?
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Which of the following describes the function of antibiotics that target the bacterial cell wall?
Which of the following describes the function of antibiotics that target the bacterial cell wall?
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What is a common virulence factor found in bacteria?
What is a common virulence factor found in bacteria?
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What distinguishes acid-fast bacteria from other bacterial types?
What distinguishes acid-fast bacteria from other bacterial types?
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How do bacteria primarily replicate?
How do bacteria primarily replicate?
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What is the role of lysozyme in relation to peptidoglycan?
What is the role of lysozyme in relation to peptidoglycan?
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What type of bacterial arrangement is indicated by the term 'strepto'?
What type of bacterial arrangement is indicated by the term 'strepto'?
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Which substance within the cell wall of Gram negative bacteria is known for its toxicity?
Which substance within the cell wall of Gram negative bacteria is known for its toxicity?
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What enzyme do RNA viruses use for replication?
What enzyme do RNA viruses use for replication?
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Which statement about DNA and RNA replication errors is correct?
Which statement about DNA and RNA replication errors is correct?
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Which of the following is true about prions?
Which of the following is true about prions?
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What is the primary determinant of viral virulence?
What is the primary determinant of viral virulence?
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Which condition requires sterilization or high-level disinfection?
Which condition requires sterilization or high-level disinfection?
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What is the role of valacyclovir in treating herpes viruses?
What is the role of valacyclovir in treating herpes viruses?
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Which of the following is NOT a method of infection control?
Which of the following is NOT a method of infection control?
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What is the correct definition of sterilization?
What is the correct definition of sterilization?
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What is the characteristic feature of the Lag phase in bacterial growth?
What is the characteristic feature of the Lag phase in bacterial growth?
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Which type of media is formulated with a known composition of nutrients?
Which type of media is formulated with a known composition of nutrients?
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What distinguishing feature do capnophiles require to thrive?
What distinguishing feature do capnophiles require to thrive?
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In which stage of disease does the body begin to show specific signs and symptoms after the incubation period?
In which stage of disease does the body begin to show specific signs and symptoms after the incubation period?
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Which of the following bacteria prefers a neutral pH for optimal growth?
Which of the following bacteria prefers a neutral pH for optimal growth?
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What is the main purpose of differential media like MacConkey agar?
What is the main purpose of differential media like MacConkey agar?
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Which of the following is not a mechanism of bacterial virulence?
Which of the following is not a mechanism of bacterial virulence?
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Which type of infection is likely to occur when the immune system is compromised?
Which type of infection is likely to occur when the immune system is compromised?
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What is the purpose of using agar in solid media?
What is the purpose of using agar in solid media?
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In the context of bacterial growth, what does the Death/decline phase indicate?
In the context of bacterial growth, what does the Death/decline phase indicate?
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Study Notes
Bacterial Taxonomy
- Three interrelated areas of bacterial taxonomy are phenotypic, genotypic, and phylogenetic
- Phenotypic characteristics include morphology, staining, and metabolic capabilities.
- Genotypic characteristics include DNA sequence analysis.
- Phylogenetic characteristics include evolutionary relationships.
### Bacterial Morphology
- Bacteria are small and rely on diffusion for nutrient uptake and waste removal.
- Most common shapes are cocci (spherical) and bacilli (rod-shaped).
- Other common shapes are vibrios (comma-shaped), spirilla (spiral-shaped), and spirochetes (corkscrew-shaped).
- Arrangements of bacteria include diplococci (pairs), streptococci (chains), staphylococci (clusters), and tetrads (packets of four).
- Some bacteria have no defined shape and are called pleomorphic.
Cell Membrane
- Bacterial cell membranes have a fluid mosaic model, but do not contain sterols.
Cell wall
- The bacterial cell wall is a rigid structure that surrounds the cell membrane.
- Unlike the cell membrane, it maintains cell shape, prevents osmotic lysis, and contributes to bacterial pathogenicity.
- Virtually all bacterial cell walls contain peptidoglycan, a complex polymer composed of sugars and amino acids.
- Peptidoglycan is the target of several antibiotics, such as penicillin and vancomycin.
- Lysozyme, found in tears, saliva, and mucus, degrades the glycine backbone of peptidoglycan.
Gram Stain
- The Gram stain is a differential stain that differentiates bacteria based on the thickness of their peptidoglycan layer.
- Gram-negative bacteria have a thin peptidoglycan layer and are stained pink.
- Gram-positive bacteria have a thick peptidoglycan layer and are stained purple.
- Knowing whether a bacterium is gram-positive or gram-negative helps with initial identification and informs the choice of antibiotic therapy.
- Not all bacteria fit into a single gram-classification. Some bacteria possess different cell wall structures that affect their gram-staining properties (e.g., Mycobacteria with their waxy mycolic acid layer).
Gram-Negative Cell Walls
- Gram-negative bacteria have an outer membrane composed of lipopolysaccharide (LPS), a potent immunostimulant.
- The LPS molecule has three main components: O antigen, core polysaccharide, and lipid A.
- O antigen serves as a protective barrier against host defenses and contributes to bacterial virulence.
- Core polysaccharide provides structural integrity to the outer membrane.
- Lipid A is embedded in the outer membrane and possesses toxin activity.
Effects of Lipopolysaccaride (LPS)
- LPS can bind to receptors on various cells, causing the release of cytokines and pro-inflammatory mediators, which can result in symptoms of septic shock.
Outer Membrane of Gram-Negative
- The outer membrane of gram-negative bacteria contains porins, proteins that allow the passage of small molecules.
- Lipoproteins help anchor the outer membrane to the peptidoglycan layer.
Periplasmic Space
- The periplasmic space is a region between the inner and outer membranes of gram-negative bacteria.
- It contains enzymes involved in nutrient uptake and degradation.
Gram-Positive Cell Walls
- Gram-positive bacteria have a thick peptidoglycan layer that is linked to teichoic acids, polymers of glycerol or ribitol linked by phosphate molecules.
- Teichoic acids are antigenic and contribute to bacterial virulence.
Acid-Fast Cell Walls
- Acid-fast bacteria, such as Mycobacterium tuberculosis, have unique cell walls containing two main components: mycolic acid and tetrameric porins.
- Mycolic acid is a complex lipid that forms a waxy layer that makes the bacteria resistant to antibiotics and other antimicrobial agents.
- Tetrameric porins are protein channels that allow the passage of nutrients and other molecules.
Acid-Fast Organisms
- Acid-fast bacteria are resistant to decolorization with acid-alcohol in the Ziehl-Neelsen staining procedure.
- Organisms include Mycobacterium tuberculosis, Mycobacterium leprae, and Nocardia species.
Bacterial Internal and External Structures
- Many bacterial structures contribute to bacterial virulence.
- External structures include flagella, pili (fimbriae), capsules, and biofilms.
Flagella
- Flagella are long, whip-like appendages that help bacteria move.
- They are composed of a protein called flagellin.
- Bacterial movement is influenced by the number and arrangement of flagella.
Pili (Fimbriae)
- Pili (fimbriae) are short, hair-like appendages that help bacteria adhere to surfaces.
- They are composed of a protein called pilin.
- They are involved in attachment to host tissues, which promotes colonization and infection.
Capsules
- Capsules are a layer of polysaccharides that surround some bacteria.
- They have several functions:
- They protect bacteria from phagocytosis by host immune cells.
- They help bacteria adhere to surfaces.
- They contribute to bacterial virulence.
- They can be used for diagnostic testing (e.g., encapsulated pneumococci).
Biofilms
- Biofilms are complex communities of bacteria that adhere to surfaces.
- These are embedded in a matrix of extracellular polymeric substances (EPS), which is composed of polysaccharides, proteins, and other molecules.
- Biofilms offer protection from antibiotics and host defenses.
Internal Structures
- Internal structures include the cytoplasm, ribosomes, nucleoid, plasmids, and endospores.
Cytoplasm
- The bacterial cytoplasm is the gel-like substance that fills the space between the cell membrane and the nucleoid.
- It contains the bacterial DNA and all the enzymes and other molecules necessary for bacterial life.
Ribosomes
- Ribosomes are the sites of protein synthesis in bacteria.
- They are composed of ribosomal RNA (rRNA) and proteins.
Nucleoid
- The bacterial nucleoid is a region of the cytoplasm where the bacterial DNA is located.
- The DNA is not enclosed within a membrane.
- Bacterial DNA consists of a single, circular chromosome.
Plasmids
- Plasmids are small, circular DNA molecules that are separate from the bacterial chromosome.
- They can carry genes that provide bacteria with resistance to antibiotics or toxins.
- They can be transferred between bacteria by conjugation.
Endospores
- Some bacteria form endospores in response to unfavorable environmental conditions.
- Endospores are highly resistant to heat, radiation, and chemicals.
- They are dormant structures that can survive for long periods of time.
- Endospores can germinate under favorable conditions, giving rise to new, vegetative bacteria.
Binary Fission
- Bacteria replicate by binary fission, a process that involves the following:
- The bacterial cell grows in size.
- The DNA replicates.
- The cell divides into two daughter cells.
Measuring Bacterial Growth
- Bacterial growth can be measured using optical density, colony-forming units, biomass, and bacterial growth curves.
- Optical density (OD) measures the turbidity (cloudiness) of a bacterial culture using a spectrophotometer.
- Colony-forming units (CFUs) measure the number of viable bacteria in a sample using a plating technique.
- Biomass measures the total mass of bacterial cells in a sample.
Bacterial Growth Curve
- The bacterial growth curve describes the stages of bacterial growth.
- LAG phase: period of adjustment and preparation for growth, with zero population growth. Includes time for cells to synthesize enzymes and proteins.
- LOG (Exponential) phase: phase of rapid growth, with exponential population growth. During this phase, cells are actively dividing and growing.
- Late LOG phase: transition to stationary growth, includes slowing down of cell division due to nutrient depletion and accumulation of waste products.
- Stationary phase: period of equilibrium where cell division rate and death rate are equal. Overall bacterial population remains relatively stable. Contributes to competition for resources and potential toxin release.
- Death/Decline phase: more bacteria are dying than growing, and the population declines.
Bacterial Cultivation
- Media: Bacterial cultivation requires the use of a suitable growth medium to provide the necessary nutrients for bacterial growth.
- Media can be liquid (broth) or semi-solid (gel).
- Solid media contains agar, which immobilizes the bacteria to provide isolated colonies.
Types of Media
- Defined media: All components are known and in specific concentrations. Used in research and diagnostic testing.
- Complex (undefined) media: Contain extracts, digests, or other undefined components. Used for general bacterial cultivation and often used in clinical settings.
- Enriched media: Contains additional nutrients or growth factors to support the growth of fastidious organisms. Important to identify specific organisms like Haemophilus influenzae or Neisseria gonorrhoeae.
- Selective media: Contains inhibitors that allow the growth of certain microorganisms while inhibiting the growth of others. Used in selective isolation of specific microbes.
- Differential media: Allows for the visual differentiation of different bacterial colonies based on their characteristics (e.g., color change). For example, MacConkey agar differentiates lactose-fermenting bacteria from non-lactose fermenting bacteria.
Fastidious Organisms
- Fastidious organisms have complex nutritional requirements and may require specialized media. Include organisms like:
- Haemophilus influenzae
- Neisseria gonorrhoeae
- Streptococcus pneumoniae
Nutritional Requirements
- Understanding the nutritional requirements of a bacterial organism is crucial for proper cultivation and identification.
Obligate vs Facultative
- Obligate: Bacteria that require the presence of a specific nutrient (e.g., oxygen). Obligate aerobes require oxygen, and obligate anaerobes cannot tolerate oxygen.
- Facultative: Bacteria that can grow in the presence or absence of a specific nutrient. For example, facultative anaerobes can grow in the presence or absence of oxygen.
Environmental Factors Influencing Growth
-
Temperature:
- Mesophiles: Bacteria that grow best at moderate temperatures between 20-45°C. Most human pathogens are mesophiles.
- Psychrophiles: Bacteria that grow best at low temperatures (0-20°C).
- Thermophiles: Bacteria that grow best at high temperatures (50-80°C).
-
pH:
- Neutrophiles: Bacteria that grow best at a neutral pH of 7.0.
- Acidophiles: Bacteria that grow best at low pH (e.g., Lactobacillus spp. & Coxiella burnetii)
- Alkalophiles: Bacteria that grow best at high pH (e.g., Bacillus spp., Vibrio cholerae)
-
Oxygen:
- Aerobes: Require oxygen for growth.
- Anaerobes: Cannot grow in the presence of oxygen.
- Facultative anaerobes: Can grow in the presence or absence of oxygen.
- Microaerophiles: Require low oxygen levels.
- Capnophiles: Require high carbon dioxide levels.
CO2
- Capnophiles require high CO2 levels for growth.
- Many human pathogens are capnophiles.
Water Availability and Osmotic Pressure
- Bacteria require water for growth and metabolism.
- Osmotic pressure refers to the pressure that is exerted by water as it moves across a semi-permeable membrane.
- Halophiles: are bacteria that thrive in high salt environments. Bacteria require specific osmotic pressure to survive.
Microbial Pathogenicity
- Pathogenicity refers to the ability of a microorganism to cause disease.
- Virulence is the degree of pathogenicity.
Colonization
- Colonization refers to the establishment of a microorganism in a host without causing disease. Most of the bacteria in our bodies are commensal and are associated with colonization.
Infection
- Infection is the invasion and multiplication of a microorganism in a host. Infections are classified based on the site of infection (e.g., respiratory, urinary tract, etc).
- Infectious agents are the specific microbes that cause infection.
Disease
- Disease is any departure from the healthy state. Disease is caused by infection and other factors.
- The presence of disease can be determined by the appearance of signs and symptoms.
Signs & Symptoms
- Symptoms are subjective experiences of the disease felt by the patient (e.g., headache).
- Signs are objective evidence of the diseases that can be observed by a healthcare professional (e.g., fever).
Stages of Disease
- Incubation stage: period between exposure to the pathogen and the onset of symptoms, during which the pathogen multiplies. The duration varies depending on the pathogen and the host.
- Prodromal stage: a short period with mild, non-specific symptoms such as fatigue, headache, fever or loss of appetite. Indicates the early stage of an infection.
- Acute stage: period of peak of the infection, where the disease is most severe, with specific signs and symptoms becoming apparent.
- Decline stage: period when the symptoms begin to subside due to the host's immune response or therapy.
- Convalescent stage: period of recovery as the body returns to its normal state. It may take weeks or months to completely recover.
Opportunistic Pathogens
- Opportunistic pathogens are microorganisms that typically do not cause disease in healthy individuals. These can cause infection when the host's immune system is weakened.
- Ex: Pseudomonas aeruginosa in burn victims and Candida albicans in immunocompromised patients.
Virulent Pathogens
- Virulent pathogens are microorganisms that are more likely to cause disease. They have traits that make them more pathogenic like toxins and capsules.
- Ex: Streptococcus pneumoniae.
Mechanisms of Bacterial Virulence
-
Tissue damaging metabolites: Some bacteria produce toxic compounds that damage host tissues.
- Streptococcus pyogenes produces hemolysins that destroy red blood cells.
- Clostridium perfringens produces toxins that cause gas gangrene.
Invasins or Spreading Factors
- Invasins are bacterial products that help bacteria spread through host tissues.
-
Examples:
- Hyaluronidase: degrades hyaluronic acid, a component of connective tissue.
- Collagenase: degrades collagen, a major protein found in connective tissue.
Adhesins
- Adhesins are bacterial proteins that allow bacteria to bind to host cells.
- They play a crucial role in colonization and infection.
-
Examples:
- Fimbriae: help bacteria adhere to host cells and can trigger immune responses.
- Capsules: protect bacteria from phagocytosis and help them adhere to surfaces.
Toxins
- Toxins are poisonous substances produced by bacteria.
- Classified as exotoxins and endotoxins.
Exotoxins
- Exotoxins are protein toxins released by living bacteria into their surroundings. They can cause various harmful effects, such as:
- Cytotoxins: kill cells.
- Neurotoxins: damage nerve cells.
- Enterotoxins: act on intestinal cells, causing diarrhea and vomiting.
Enterotoxins
-
Examples:
- Staphylococcal enterotoxin: causes food poisoning.
- Vibrio cholerae toxin: causes cholera.
E-B Exotoxins
- Examples:
- Diphtheria toxin: inhibits protein synthesis in host cells, leading to cell death.
- Botulinum toxin: blocks the release of acetylcholine at neuromuscular junctions, leading to flaccid paralysis.
- Tetanus toxin: blocks the release of inhibitory neurotransmitters, leading to spastic paralysis.
- Pertussis toxin: damages respiratory epithelial cells, leading to whooping cough.
- Cholera toxin: increases cAMP levels in intestinal cells, leading to severe diarrhea.
Superantigens
- Superantigens are exotoxins that stimulate a massive immune response.
-
Examples:
- Staphylococcal enterotoxins: cause food poisoning and toxic shock syndrome.
- Streptococcal pyrogenic exotoxins: cause scarlet fever and toxic shock syndrome.
Membrane Active Exotoxins
- Affect cell membranes by:
- Forming pores in the membrane, leading to cell lysis.
- Disrupting membrane phospholipid bilayers, causing cell damage.
-
Examples:
- Hemolysins: lyse red blood cells.
- Leukocidins: kill white blood cells.
Virulence Mechanisms
- Antigenic variation: some bacteria can change their surface antigens.
- Antigenic drift: gradual accumulation of mutations in viral genes that code for surface antigens.
- Antigenic shift: the mixing of genetic material from two different viruses is most common in influenza viruses (e.g., avian influenza).
- Antigenic switching: change in expression of a gene that encodes a surface protein, like the flagella.
Fungal Agents
- Fungi are eukaryotic organisms that can be unicellular (e.g., yeasts) or multicellular (e.g., molds).
- They are heterotrophic, meaning that they obtain nutrients from other organisms.
- Many fungal infections are opportunistic infections.
Fungal Structures
- Cell wall: composed of chitin, a structural polysaccharide that provides rigidity.
- Cell membrane: contains ergosterol, a sterol that is a target for antifungal drugs.
Fungal Pathogenicity
- Dimorphism: some fungi exhibit dimorphism, meaning they can exist in both yeast and mold forms.
- Capsules: some fungi have capsules, which help them evade the host's immune system.
- Toxins: some fungi produce toxins that can cause disease.
Isolation and Lab Culture
- Fungi can be isolated and cultured on specific media using standard microbiological techniques.
- Direct microscopy and molecular techniques are used for detection.
Mycoses
- Mycoses are diseases caused by fungi.
- They can be classified as superficial, cutaneous, subcutaneous, or systemic.
Primary Pathogens
- Primary pathogens are fungi that can cause disease in healthy individuals.
-
Examples:
- Histoplasma capsulatum
- Blastomyces dermatitidis
- Coccidioides immitis
Opportunistic Pathogens
- Opportunistic pathogens cause diseases in individuals with a weakened immune system.
-
Examples:
- Candida albicans
- Aspergillus fumigatus
Candida Albicans
-
Candida albicans is a common yeast that can cause a variety of infections, including:
- Oral thrush
- Vaginal yeast infections
- Candidiasis
Antifungal Therapy
- Antifungal therapy is used to treat fungal infections.
- Most antifungals target the cell wall or cell membrane.
-
Examples:
- Nystatin: targets ergosterol in the cell membrane.
- Amphotericin B: targets ergosterol in the cell membrane.
- Azoles: inhibit ergosterol biosynthesis.
- Terbinafine: inhibits squalene epoxidase, an enzyme involved in ergosterol synthesis.
- Echinocandins - inhibit the synthesis of glucan, a major component of fungal cell walls.
Viruses
- Viruses are non-living, obligate intracellular parasites. They can only replicate inside host cells.
- They are composed of a nucleic acid genome (DNA or RNA) surrounded by a protein coat called a capsid.
- Some viruses have an envelope, which is a membrane derived from the host cell.
Viral Structure
- Capsid: the protein coat that surrounds the viral genome, can be helical, icosahedral, or complex.
- Envelope: a membrane derived from the host cell that surrounds the capsid of some viruses.
- Genome: the viral genetic material, can be DNA or RNA.
Viral Replication
- Viral replication is host cell dependent, and can lead to disease through:
- Cytopathic Effects (CPE): visible changes in cells due to viral infection.
- Viral culture: a method of growing viruses in cells to identify and amplify the virus.
- PCR: a molecular technique used to detect viral DNA or RNA.
- Reverse transcriptase: a technique used to measure viral RNA.
- Antigen tests: detect viral proteins.
Viral Replication Steps
-
Entry:
- Attachment: the virus attaches to a specific receptor on the host cell.
- Penetration: the virus enters the host cell.
- Uncoating: the viral capsid is removed.
-
Replication:
- Viral genome replication: the viral genome is transcribed and replicated.
- Protein synthesis: viral proteins are synthesized.
- Assembly: new viral particles are assembled.
- Release: new viruses are released from the host cell.
RNA vs DNA viruses
-
DNA viruses:
- Replicate in the host cell nucleus.
- Use host cell DNA polymerase.
-
Examples:
- Herpesviruses
- Adenoviruses
- Poxviruses
-
RNA viruses:
- Replicate in the cytoplasm.
- Use their own RNA-dependent RNA polymerase (RdRp).
-
Examples:
- Influenza viruses
- Coronavirus
- HIV
Reverse Transcriptase
- Retroviruses use reverse transcriptase (RT) to convert RNA into DNA.
-
Examples:
- HIV
- HTLV
- CMV
Viral Architecture Classification
- Baltimore classification classifies viruses based on their genome and how they replicate.
Families of Viruses
- Viruses are grouped into families based on their shared characteristics.
- These families can be used to determine effective treatments, as some antiviral drugs work based on specific virus families.
Viral Virulence
- Virulence: is the degree of pathogenicity, which is determined by the host and the virus.
- Mutations: can change viral properties and lead to changes in virulence.
Principles of Infection Control
- Infection control: is a set of practices designed to prevent the spread of infections.
-
Three most important rules:
- Handwashing: prevents the spread of bacteria.
- Respiratory hygiene: protects the host from respiratory droplet transmission.
- Isolation: separates infected individuals and prevents the spread of pathogens.
Transmission of Respiratory Pathogens
- Respiratory pathogens can be transmitted via:
- Droplets: released from a cough or sneeze.
- Airborne transmission: inhalations of droplet nuclei or aerosols.
Respiratory Precautions
- Standard precautions: used for all patients, regardless of their infection status.
- Droplet precautions: used for patients with infections that are spread through respiratory droplets.
- Airborne precautions: used for patients with infections that are spread through airborne transmissions.
Common Chemical and Standard Precautions
- Critical items: items that penetrate tissues and contact bone, blood, or normally sterile areas.
- Semi-critical items: items that contact but do not penetrate tissues.
- Non-critical items: items that have only casual contact.
Standard Precautions
- Include hand hygiene, use of personal protective equipment, environmental disinfection, and waste disposal.
Ebola Virus
- Ebola virus can enter the eye through mucous membranes, and can cause conjunctivitis (inflammation of the conjunctiva, the thin membrane that lines the inside of your eyelid and covers the white part of your eye).
Prions
- Prions are infectious proteins that cause fatal neurodegenerative diseases.
- They are unique because they lack nucleic acids.
- Prion diseases include:
- Creutzfeldt-Jakob disease (CJD)
- Kuru
- Bovine spongiform encephalopathy (BSE)
Antibiotics
- Antibiotics are antimicrobial drugs that target bacteria specifically.
- The appropriate antibiotic choice is based on:
- Infectious agent: the type of bacterium causing the infection.
- Patient/history: patient’s allergies and susceptibilities.
- Drug resistance: the susceptibility of the bacterium to the antibiotic.
Antimicrobial Resistance
- Antimicrobial resistance is the ability of a microorganism to survive and multiply in the presence of an antimicrobial drug.
- The development of antibiotic resistance is a major concern due to the increased reliance on antibiotics.
Sterilization
- Sterilization is the process of destroying all microorganisms, including spores.
-
Methods:
- Autoclaving: uses high temperatures and pressure.
- Dry heat sterilization: uses high temperatures and dry air.
- Radiation sterilization: uses ionizing radiation.
- Ethylene oxide sterilization: uses ethylene oxide gas.
Disinfection
- Disinfection is the process of killing, inhibiting, or removing microorganisms that cause disease.
-
Methods:
- Chemical disinfectants: various chemicals that are effective against bacteria.
- Physical disinfection: uses heat, UV light, or filtration.
Antisepsis
- Antisepsis is the process of killing, inhibiting, or removing microorganisms on living tissues using specific agents called antiseptics.
-
Examples:
- Alcohol-based hand rubs
- Iodine solutions
- Chlorhexidine
Autoclaves
- Autoclaves use steam under pressure to sterilize.
- Indicators: used to ensure the sterilization process is working, such as chemical indicator strips.
Time to Sterilize
- The time required to sterilize a sample depends on:
- Temperature: the higher the temperature, the faster the process.
- Pressure: higher pressure increases efficiency.
- Nature of the load: dense loads take longer to sterilize.
- Exposure time: how long the load is exposed to the sterilization conditions.
Non-Critical Items
- Includes items that have contact with intact skin, such as stethoscopes, blood pressure cuffs.
Standard Precautions
- Guidelines to protect healthcare workers and patients from infection. Include:
- Hand hygiene
- Use of personal protective equipment (PPE), such as gloves, gowns, masks, and face shields.
- Environmental disinfection.
- Waste disposal.
Septic
- Refers to a condition where the body is infected with bacteria, especially in the bloodstream.
- Sepsis can be a life-threatening condition.
Aseptic
- Refers to the absence of pathogenic microorganisms.
- Aseptic techniques are used to prevent contamination in laboratory settings, surgical procedures, and other medical treatments.
Antiseptic
- Chemicals used to reduce the number of microbes on skin or tissues.
Biocide
- A chemical agent that kills microorganisms.
Bacteriostatic
- An agent that inhibits the growth of bacteria.
Bactericidal
- An agent that kills bacteria.
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