Module 2A & 2B Flashcards
1
Q
What are the 2 etiologies agents of infectious disease?
A
Cellular and A-cellular
2
Q
What 2 categories are in the cellular group? What are those subgroups?
A-cellular group?
A
Cellular
Eukaryotes
- Helminths
- Fungi
- Protozoa
Prokaryotes
- Bacteria
A-cellular
- Viruses
- Prions
3
Q
What are the key components about Prokaryotes?
A
Single-cell organisms, no real nucleus, no membrane-bound organelles, unique cell wall
- Bacteria
4
Q
What are the key components about Eukaryotes?
A
Real nucleus, membrane-bound organelles; some have cell walls (plants, fungi), some don’t (animals)
- Protozoa: single-cell organisms similar to animal cells, belong to ‘parasites’
- Fungi: can be single- or multicellular, unique cell wall
- Helminths: multicellular, belong to animals, cells have no cell wall, most closely related to humans, belong to ‘parasites’
5
Q
What are the key components about Prions?
A
Misfolded protein
6
Q
What are the key components about Viroids?
A
RNA molecule (so far only know to cause diseases in plants)
7
Q
What are the key components about Viruses?
A
RNA or DNA surrounded by a structural protein layer, many with additional structural features; no metabolic capability
8
Q
What are the difference between Prokaryotic cells and Eukaryotic cells?
A
Prokaryotic cell
• Small, simple(0.1-5 mm)
• Unicellular
• No nucleus
• Circular DNA
• No membrane-bound organelles
Eukaryotic cell
• Large, complex(10-100) mm)
• Uni- or multicellular
• Nucleus present
• Linear DNA
• Membrane-bound organelles present
Both
Cell membrane
Cytoplasm
DNA and RNA
Ribosomes
9
Q
What are within the cellular membrane and cytoplasm in the Prokaryotic cells?
A
CM:
Lipid bilayer: No cholesterol
Proteins: Higher protein content
Cytoplasm:
Ribosomes - 70S (vs 80S eukaryotic cells)
- Target of certain antibiotics
10
Q
What are the major component of the external structures of prokaryotic cells?
A
- Peptidoglycan
- Protection from osmotic pressure
- Several types of antibiotics inhibit peptidoglycan synthesis
— E.g. penicillin
11
Q
What is the external structures of gram-positive bacteria and gram-negative bacteria? What do both structures have in common?
A
Gram-positive bacteria - Peptidoglycan cell and teichoic acid
Gram-negative bacteria - lipopolysaccharide (LPS)
Both - Peptidoglycan cell
12
Q
What is the process of Gram-positive and Gram-negative stain?
A
- Primary Stain - All bacteria will be stained bluish
- Mordant - Enhance the crystal violet staining by forming crystal violet - iodine complex
- Decolorizer - washes away primary stain from gram-negative bacteria
- Counter Stain - Counterstain stains the colorless gram-negative bacteria
13
Q
What type of Prokaryotic cells is highly susceptible to penicillin?
A
Gram-positive
14
Q
What type of Prokaryotic cells is highly susceptible to lysozyme?
A
Gram-positive
15
Q
What type of Prokaryotic cells is highly susceptible to lysis by complement?
A
Gram-negative
16
Q
What type of Prokaryotic cells is highly sensitive to heat and disinfectants?
A
Gram-negative
17
Q
What type of Prokaryotic cells is has endotoxins?
A
Gram-negative
18
Q
What type of Prokaryotic cells is has exotoxins?
A
Gram-positive: some species
Gram-negative: a few species
19
Q
What type of prokaryotic cells are covered in a wax-like substance called mycolic acid?
A
Gram-positive
20
Q
What are the external structures on the prokaryotic cells that is considered the ‘sticky coat?’ What is the function?
A
Glycocalyx = sugar coat (sticky coat)
- Capsule
- Slime layer
Function:
- Retention of water
- Biofilm formation
21
Q
What are the external structures on the prokaryotic cells that are like projections on the cell? (3 Types)
A
Flagella:
- Visibility through ‘flagella stain’
- Presence and arrangement is species-specific
Fimbriae:
- Sticky, bristle-like appendages
- Usually many
- Purpose: biofilm formation
Pili:
- Hollow tubes
- Longer than fimbriae, shorter than flagella
- Make a connection between two cells
- Only 1-2 per cell
- Purpose: Transfer of DNA between two cells
22
Q
What are Endospores? Why are they important?
A
- Found in some gram-positive genera of bacteria
- Clinically important: certain species of Bacilius and Clostridium
- Dormant stage
- Resistant to commonly used methods of sterilization
- Not to be confused with reproductive spores of fungi!
23
Q
What are the commonly used stains?
A
Gram stain
Acid-fast stain
Endospore stains
Flagella stain
Capsule stain - aka ‘Negative stain’
24
Q
What is metabolism?
A
Metabolism = catabolism + anabolism
Ultimate function: growth and reproduction
25
In fermentation, what are the reasons for not completely oxidizing glucose and/or other nutrients?
Lack of O2
Lack os genes for some enzymes of the cellular respiration process
26
For Aerobic Respiration:
Is O2 required?
What kind of phosphorylation?
What is the final e- acceptor?
How many ATP/Glucose created?
Yes
Mostly oxidative phophorylation
O2
Lots (30-32)
27
For Fermentation:
Is O2 required?
What kind of phosphorylation?
What is the final e- acceptor?
How many ATP/Glucose created?
No
Substrate-level phosphorylation
Organic metabolite (pyruvate)
Few (2)
28
What are some of the fermentation products? What are those commercial products? (NOT TO MEMORIZE; just a good reference)
- Acetone, butanol, ethanol, CO2 = gasoline alternative
- Ethanol, CO2 = Beer, bread
- Formic and lactic acid, ethanol, acetoin, 2, 3, buanediol; CO2, H2 = Chardonnay wine
- Butyrin acid, CO2, H2 = Butter
- Lactic acid = Sauerkraut, yogurt, cheese
- Acetic, formic, lactic, and succinic acids; ethanol, CO2, H2 = Vinegar, cosmetics, pharmaceutical
- Acetic acid, propionic acid, CO2 = Swiss cheese
29
What is microbial ‘growth’ referring to?
- Does NOT refer to size of cells, but to size of the bacterial culture or the number of cells
- Under good circumstances, growth is exponential with a generational time as short as 20 minutes
30
What are optimal conditions for microbial growth? Chemical and Physical
Chemical: Macro- and micronutrients, oxygen, water
Physical: Temperature, pH, osmolarity
31
What are the phases on the microbial growth curve?
1. Lag phase
2. Log phase
3. Stationary phase
4. Death or decline phase
32
What are Plasmids?
- Small circular DNA molecules
- Replicate independently
- Do not contain essential genes for metabolism
- Some plasmids are called ‘factors’
— R factor = ‘resistance factor’; encodes for a capability to survive antibiotics and/or heavy metals
— F factor = ‘fertility factor’ (see process of conjugation)
— ‘Virulence factor’; encodes for a capability of a strain or species to cause disease (e.g., capsule formation, see process of transformation)
— ‘Bacteriocin factor’; kill bacterial cells that are competitors
33
What is genetic recombination?
Exchange of segments, typically genes, between two DNA molecules
34
What is recombinants?
Cells with DNA molecules that contain one or more
new nucleotide sequence
35
What is vertical gene transfer?
An organism replicates its genome and provides copies to descendants, including permanent mutations; transfer from one generation to the next generation
36
What is horizontal gene transfer?
Donor cell contributes part of its genome to a recipient cell; transfer within generation important for genetic variability in species that have no sexual reproduction
37
What are the steps to horizontal gene transfer in prokaryotic?
1. Transformation
2. Transduction
3. Conjunction
38
Describe PCR. What are the areas of application? What is the 3 step process?
PCR = polymerase chain reaction
- Groundbreaking technology to amplify DNA (or RNA) in vitro
- Areas of application:
— Sensitive diagnostic tests (in the early stage of infectious diseases)
— Forensic science
— Biomedical research
— Repetitive process consisting of three steps:
1. Denaturing
2. Priming
3. Extension
39
Describe CRISPR. What are the areas of application?
- CRISPR = clustered, regularly interspaced, short palindromic repeats
- CRISPR-Cas = CRISPR-associated enzymes
- CRISPR-Cas9 applied in gene editing (adding or removing of nucleotides)
- Areas of application:
— Medicine: Treatment of genetic disorders (first successful application in a patient with sickle cell anemia in 2023); treatment of viral infections (e.g., HIV)
— Biotechnology: Creation of medicines
— Agriculture: Development of disease resistant crops
— Epidemiology: Disease of RNA virus disease outbreaks (Ebola, Zika,…)
40
How do Eukaryotes reproduce?
– More complex and variable than in prokaryotes
– Many fungi and some protozoa reproduce sexually and asexually
– Asexual reproduction in eukaryotes through mitosis:
– Binary fission (similar to bacteria)
– Budding
- Schizogony
41
How do eukaryotes sexually reproduce?
Requires the formation of gametes through the process of meiosis:
One diploid nucleus (two sets of chromosomes) ———> Four haploid nuclei (one set of chromosomes each)
For genetic variability, during meiosis
– the ‘maternal’ and ‘paternal’ chromosomes get randomly reassorted into new sets
– Recombination of genes through ‘cross-over’ process
42
What is the significance of fungi?
– Decompose dead organisms and recycle their nutrients
– Help plants absorb water and minerals
– 30% cause diseases of plants, animals, and humans
– Can spoil fruit, pickles, jams, and jellies
– Used for food and in manufacture of foods and beverages
– Produce antibiotics
– Serve as important research tools
43
How does the growth of fungi happen?
– Cell wall made of chitin (polysaccharide)
– Acquire nutrients by absorption, after releasing lytic enzymes
– Most are saprobes feeding on dead organisms
– Some can derive nutrients from living plants and animals
– Some trap and kill microscopic soil-dwelling nematodes
– Most fungi are aerobic
– Many yeasts are facultative anaerobes (fermentation)
– May use ionizing radiation as energy source
44
What is the morphology of fungi?
– Filamentous growth (hypha = fungal filament;
plural is hyphae); many hyphae create a
mycelium (typical for molds)
– Yeast cells are single cells, which may form
chains called ‘pseudo- hyphae’
– Dimorphic species of fungi can grow as hyphae or yeast cells (depends on growth
conditions)
45
What are the ways fungi can reproduce?
All use forms of asexual reproduction
- Budding
- Asexual spore formation (typical mold spores)
Most fungi also reproduce sexually
– Fungal mating types are designated as + and –
(morphologically indistinguishable)
– In essence also go through meiosis and formation of ‘zyogote’ through fusion of haploid cells
– Not relevant in pathogenic fungi
46
What are Protozoa? (3 characteristics)
Diverse group defined by three characteristics
– Eukaryotic (animal-like ‘-zoa’)
– Unicellular
– Lack a cell wall
47
What are some types of Protozoa?
Entamoeba
Giardia
Balantidium
Trypanosoma
48
What are the typical life cycle of many Protozoa?
1. Trophozite (active, feeding stage)
2. Cyst formation
3. Cyst (dormant, resting stage)
4. Release of active cellular form
5. Repeat
49
What are Helminths?
Parasitic worms have microscopic infective and diagnostic stages
– Each species has a unique life cycle
— Some require an intermediate host
– Grouping:
— Platyhelminths (flatworms)
— Nematodes (roundworms)
50
What are examples of Platyhelminths?
- Beef Tapeworms
- Liver Flukes
51
What are examples of Nematodes?
Hookworms
Pinworms
52
What 2 groups of arthropods are disease vectors?
- Arachnida
- Insecta
53
What are 2 arachnid vectors?
Ticks
Mites (chiggers)
54
What are 5 insect vectors?
Lice
Fleas
Flies
Mosquitoes
Bugs
55
What are the basic structural features of viruses?
All viruses contain:
- Genetic information: DNA or RNA (never both!)
- A capsid: Made of multi-subunit proteins (capsomer)
— Surrounds nucleic acid
— Shape of capsid varies (grouped into helical, polyhedral, or complex)
- Glyproteins: called spikes at the surface - attachment to host cells
Many animal/human viruses are surrounded by a lipid bilayer, called ‘envelope’
Grouping of viruses into:
- Non-enveloped or naked and enveloped viruses
- Lipids from the host cells Many animal
- Proteins and glycoproteins based on viral genes
56
What are bacteriophages?
- Infected bacteria
- Built to ‘inject’ DNA into host cells
- Involved in the process of transduction
57
What are the classification and taxonomy of viruses?
– Type of nucleic acid (viral genomes size: 10’000-50’000 bp)
— DNA – RNA
— double-stranded – single-stranded
— 1 or multiple nucleic acid fragments
– Type of organism/tissue targeted
– Capsid morphology (helical, polyhedral, complex)
– Enveloped – Non-enveloped (naked)
– For most viruses, Family is the highest level of taxonomic order
— No Latin species names
– ‘Arboviruses’ = viruses that are transmitted by arthropod vectors
58
What are the key characteristics of growth and reproduction in viruses?
– Cannot carry out any metabolic pathway
– Neither grow nor respond to the environment
– Cannot reproduce independently
– Recruit the host cell’s metabolic pathways to increase their numbers
– Have extracellular and intracellular state
59
What is the lytic cycle of a life cycle of a prokaryotic host?
1. Attachment: The phage attaches to the surface of the host
2. Penetration (Entry): The viral DNA enters the host cell
3. Biosynthesis: Phage DNA replicates and phage proteins are made
4. Maturation (Assembly): New phage particles are assembled
5. Lysis (Release): The cell lyses , releasing the newly made phage.
60
What is the lysogenic cycle of a life cycle of a prokaryotic host?
1. The phage infects a cell
2. The phage DNA becomes incorporated into the host genome
3. The cell divides, and pro phage DNA is passed on to daughter cells
4. Under stressful conditions the prophage DNA is excised from the bacterial chromosome and enters the lytic cycle.
5. Phage DNA replicates and phage proteins are made.
6. New phage particles are assembled
7. The cell lyses, releasing the newly made phages.
61
What are the 5 stage in life cycle of viruses in animal host?
1. Attachment
2. Entry: 3 processes (depends on virus)
3. Synthesis (or biosynthesis) (depending on the type of genome variation in location in the host cell and process
4. Assembly (DNA = nucleus; RNA = cytoplasm)
5. Release (naked viruses released by exocytosis by or lysis of the host cell)
62
What is the latency of animal viruses?
– Similar to lysogeny
– Only possible for ds DNA viruses
– Virus dormant in cells
— Some latent viruses do not get incorporated into host chromosomes
— Some latent viruses get incorporated into host DNA
63
What percentage of human cancers are caused by viruses?
20-25%
64
What are the characteristics of prions? Cellular vs Rogue?
Cellular prion proteins: PrPc
- Found in all mammals
- Structures: All alpha helices
Rogue prion protein: PrPsc
- Structure: Misfolded, containing some beta-sheet
65
What are some of the human prion diseases?
Creutzfeldt-Jakob disease
Gerstmann-Straussler-Scheinker syndrome
fatal animal insomnia
Kuru
66
What are some of the animal prion diseases?
Scrapie
Transmissible mink encephalopathy
Chronic wasting disease
Bovine spongiform encephalopathy (“mad cow disease”)
67
How do we control microbial growth?
- Medicine
- Everyday life:
— Food and water safety
— Food preservation
— Healthy crops and life stock
68
What are the factors affecting the efficacy of antimicrobial methods?
Site to be treated
- Some effective methods not suited for fragile objects
- Type of medical procedure
Relative susceptibility of microbes
69
What do antimicrobial target?
- Cell wall
- Cell membrane/ viral envelope (lipid bilayer)
- Proteins
- Nucleic acids
70
What is fomite?
Inanimate objects that may harbor microbes and aid in their transmission
71
What is disinfection?
Removal of potential pathogens from fomites (reduction of microbial load, not removal of all microorganisms)
72
What is antisepsis?
Removal of potential pathogens from living tissue (reduction of microbial load, not removal of all microorganisms)
73
What is sanitization?
Removal of pathogens from objects to meet public health standards
74
What is Pasteurization?
Use of heat to destroy pathogens and reduce the number of spoilage microorganisms in foods and beverages
75
What is sterilization?
Destruction of all microorganisms and viruses in or on an object
76
What are the types of physical methods of disease?
Temperature
pH
Osmolarity
Radiation
Filtration
77
How is temperature a way to control diseases?
Moist heat: after molecules are good conduits of energy
- Boiling
- Autoclaving: 121 degrees C at 1 atm pressure
- Pasteurization: important food safety protocol
Dry heat:
- Incineration: ultimate means of sterilization
- Flaming of tools in microbiology labs
Low Temp:
- Refrigeration (0-7 degrees C)
- Freezing (< -2 degrees C)
- Ultralow temperature (<-70 degrees C)
— Lyophilization (=freezedrying; flash-freezing under vacuum)
78
What are ways osmotic pressure helps control diseases?
Low or no water:
- High osmotic pressure used by adding salt or sugar for food preservation
- Desiccation (drying): Commonly used for food preservation
- Lyophilization: Flash-freezing under vacuum removes water - less harmful for biomolecules; long-term storage
79
What are ways radiation helps control diseases?
Damages DNA = MO cannot multiply
Ionizing radiation (x-ray, gamma ray)
- High energy
- Penetrates packaging and tissues
- Sterilization of items that cannot be autoclaved
UV
- Lower energy than ionizing - useful to disinfect surfaces
- Low key method of water sterilization: Expose clear closed water containers to sunlight for multiple hours
80
What are ways filtration helps control diseases?
Typical pore size: 0.3 um (not small enough to catch all viruses!)
Air filtration
- HEPA (‘high-efficiency particulate air’) filters
Liquid filtration (‘membrane’ filtration)
- Typically used for small volumes of solutions that contain substances that are not heat stable (eg vitamins)
- Water filtration systems for camping
81
What is the of effectiveness of antiseptics and disinfectants?
The larger the ‘zone of inhibition,’ the better the substance (the concentration is highest on the disk and gets smaller with distance from the disk)
82
How many microorganisms are antimicrobial drugs effective against?
Most antimicrobial drugs are only effective against one type of microorganism:
– Antibacterial drugs, commonly called antibiotics
– Antiviral drugs
– Antifungal drugs
– Antiprotozoan drugs
– Antihelminthic drugs
83
What are some antibiotics resistant infections?
- Sepsis
- Surgery
- Chronic conditions
- Organ transplants
- Dialysis for advanced kidney disease
- Cancer
84
What are the common mechanisms of drug resistance?
- Efflux pump
- Blocked penetration
- Inactivation by enzymes
- Target modification
85
What are the types of symbiotic relationships? Is that relationship beneficial or harmful to the human?
Mutualism = benefits human
Commensalism = neither benefits nor is harmed
Parasitism = human is harmed
86
What does normal microbiota do?
Organisms that colonize the body’s surface without causing disease
87
What are the many factors influence the composition of normal resident microbiota?
-age
- breast/bottle feeding
- diet
- exposure to animals
- geographical location
- host genetics
- hygiene practice
- medication
88
What are some reasons transient microbiota disappear?
- Competition
- Elimination
- Chemical or physical changes
89
When is the acquisition of normal microbiome important?
- Initiated during the birthing process
- Mostly established during first months of life
90
What is it called when normal microbiota becoming pathogens?
Opportunities Pathogens
91
What are diseases can be caused by opportunistic pathogens in immunocompromised individuals?
- Genetic immunodeficiency disorder
- Acquired immunodeficiency (HIV/AIDS; malnutrition)
- Antibiotic treatment (especially when extended)
- Chemotherapy (targets fast-dividing tissues, including bone marrow, the origin of leukocytes)
- Chronic diseases, eg diabetes
92
What are the reservoirs for pathogens that can linger?
- Animal reservoirs
- Human carriers
- Inanimate reservoir
93
What are zoonoses?
Infectious diseases that can be transmitted from an animal to a human host
94
What are transmission routes for zoonoses diseases?
– Direct contact with the animal, its waste or secretion (ringworm, rabies)
– Consumption of infected animals (e.g., tapeworm, nvCJD)
– Arthropod vector-borne diseases (e.g., malaria, West Nile virus, Lyme disease)
95
What are some nonliving reservoirs?
- Soil
- Water
- Food
- Air
Can be contaminated through feces, urine, or bodily secretions
96
What are four pathways that microbes enter the body?
- Skin
- Mucous membranes
- Placenta: ‘Congenital infections’
- Parenteral route: broken skin or mucous membranes
97
What is pathogenicity?
Ability of a microbe to cause disease (eg normal microbiota have low pathogenicity)
98
What is virulence?
Degree of pathogenicity (the four examples at the bottom are considered opportunistic pathogens)
99
What are the factors of infectious agents that contribute to virulence?
– Adhesion factors
– Biofilms – Extracellular enzymes (typically lysing extracellular structural biomolecules)
– Toxins (exo- and endotoxins)
– Antiphagocytic factors (e.g., capsule formation, antiphagocytic chemicals)
– Intracellular state (all viruses, some bacteria, protozoan Plasmodium)
100
What are the factors of infectious agents?
Enzymes
- Hyaluronidase and collagenase
- Coagulase and kinase
Toxins
- Endotoxins
- Exotoxins
101
What are the 3 modes of transmission?
Contact
- Direct
- Indirect
- Droplets
Vehicle
- Airborne
- Waterborne
- Foodborne
Vector
- Biological
- Mechanical
102
What are the five stages of infectious diseases?
1. Incubation period
2. Prodromal period
3. Illness
4. Decline
5. Convalescence
103
What is another name for hospital-acquired disease?
‘Nosocomial infections’
Healthcare-associated infections (HAI)
- Typically expected to be drug-resistant
