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RUSVM Principles Of Infectious Diseases > Week 4 + 5 > Flashcards

Week 4 + 5 Flashcards

1
Q

What is the difference between spontaneous generation and biogenesis?

A
  • spontaneous generation - the idea that living organisms could arise from non-living things
  • biogenesis - the idea that all living things come from other living things
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2
Q

T/F: Bacteria are visible to the naked eye

A

False

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3
Q

What is the difference between eukaryotic and prokaryotic cells?

A
  • eukaryotic: plant + animal cells with a nucleus and membrane-bound organelles
  • prokaryotic: unicellular organism without a nucleus or membrane-bound organelles
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4
Q

What are the features of a bacterial cells structure?

A
  • cytoplasm
  • ribosomes
  • nucleoid
  • plasma membrane
  • complex and rigid cell wall
  • capsule
  • flagella
  • pili/fimbriae
  • endospores
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5
Q

What are some features of bacterial cytoplasm?

A
  • jelly-like aqueous solution
  • 3 main groups of molecules:
    • macromolecules: proteins (enzymes), mRNA, tRNA
    • small molecules: energy sources, precursors of macromolecules, metabolites, or vitamins
    • inorganic ions: requires for enzymatic activity (co-factors)
  • contains the nucleoid (DNA) and ribosomes (protein synthesis)
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6
Q

What are the function of bacterial cytoplasm?

A
  • facilitate chemical reactions
  • dissolve solutes (eg. carbohydrates + proteins)
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7
Q

What is a nucleoid? What are some features?

A
  • location in prokaryotic cell where primary genetic material is found
    • bacterial genome: single haploid circular chromosome w/ DNA
    • proteins: involved in DNA compaction and transcription factors that regulate expression of bacterial genome
    • RNA: mRNA (for coding) and ncRNA (non-coding RNA), involved in DNA organization and expression of the bacterial genome
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8
Q

What is a plasmid?

A
  • circular molecule of DNA that replicates separately from the genome
  • NOT part of the nucleoid
  • plasmid genes are not essential under “normal” conditions
  • several different plasmids may be present in individual bacterial cells
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9
Q

What is the function of the plasmid?

A
  • contain genes associated with disease (virulence factors)
  • survive in presence of antibiotics and other oxidative compounds (resistance genes)
  • conjugation plasmids: cell-to-cell transfer by conjugation
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10
Q

What are ribosomes?

A
  • ribonucleoproteins with large 50S subunit and small 30S subunit
  • all protein synthesis takes place on ribosomes
  • bacterial ribosomes are structurally DIFFERENT from those in eukaryotic cells
  • applications:
    • ribosomes as a target for antibiotics
    • 16S rRNA gene encoding for component of 30S subunit is used in reconstructing phylogenies
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11
Q

Describe the bacterial envelope

A
  • cytoplasmic or plasma membrane
  • cell wall (peptidoglycan layer)
  • periplasmic space
  • outer membrane (gram-negative bacteria)
  • capsule (some bacteria)
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12
Q

T/F: bacteria do not have a plasma membrane

A
  • False; innermost layer next to cytoplasm, composed of a phospholipid bilayer and proteins
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13
Q

What proteins are in the phospholipid bilayer?

A
  • transport proteins: enable specific transport of molecules in and out of the cell
  • energy generation components: used for synthesis of adenosine 5’-phosphate (ATP)
  • proteins that function as anchors or help in the assembly of external structures
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14
Q

What are the main functions of the plasma membrane?

A
  • selectively permeable barrier
  • bacterial respiration and energy generation
  • anchor for external structures
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15
Q

What are some features of the peptidoglycan layer?

A
  • peptidoglycan: polymer unique to prokaryotic cells
  • mesh-like structure consisting of chains of alternating subunits of N-acetylglucosamine (NAG) and N-acetylmuranic acid (NAM) cross-linked with peptides by trans peptides each enzymes called penicillin-binding proteins (PBPs)
    • allows enlargement
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16
Q

What are the functions of the peptidoglycan layer?

A
  • protection against mechanical damage and osmotic lysis
  • transport: non-selective permeability
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17
Q

What are features of the outer membrane?

A
  • common to gram-NEGATIVE bacteria
  • protein-containing asymmetrical lipid bilayer
    -lipopolysaccharide (LPS or endotoxin)
    -porin proteins that allows small hydrophilic molecules to passively enter the cell
    -transport proteins that enable transport of larger nutrients into the cell
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18
Q

What are functions of the outer membrane?

A
  • selective permeability barrier
  • resistance to large or hydrophobic toxic compounds
  • tolerance to detergents and bile salts
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19
Q

What are lipopolysaccharides (LPS)?

A
  • virulence factor
  • lipid A component is molecule with endotoxin ability
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20
Q

What are exceptions to the two main classes of bacteria?

A
  • mycobacteria
    • bacterial envelope: gram-positive but contains mycolic acid
    • acid-fast staining for identification
  • mollicutes (mycoplasma)
    • plasma membrane with sterols
    • no cell wall - no peptidoglycan layer
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21
Q

What are some features of the capsule? Functions?

A
  • glycocalyx = polysaccharide layer
  • only in some bacterial species
  • clear: hard to stain
  • functions:
    • protection: from adverse environmental conditions (desiccation)
    • virulence factor: facilitate adherence to surfaces and interfere with phagocytosis
    • nutrient reserve
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22
Q

What are some features of endospores? Functions?

A
  • cryptobiotic state of dormancy and most durable type of cell found in nature
  • produced by genera Bacillus and Clostridium
  • function:
    • ensure survival during adverse environmental conditions
    • dormant highly resistant bodies (BURN THEM)
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23
Q

What are some features of flagella?

A
  • present on bacterial surface
  • flagellar arrangement:
    • # of flagella
    • position at which flagella insert into bacterial cell wall
      *can be temp dependent
  • function: locomotion/bacterial motility
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24
Q

What are some features of pili/fimbriae?

A
  • fine, straight, hair-like appendages attached to cell wall
  • most common on gram-negative bacteria
  • function:
    • adhesion to host tissues
    • contribute to antigenicity
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25
Q

What are some important bacterial shapes and arrangements?

A
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26
Q

What is the shape and arrangement of this bacteria?

A
  • diplobacilli

(Bacillus cereus)

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27
Q

What is the shape and arrangement of this bacteria?

A
  • staphylococci + bacillus

(Staphylococcus aureus + Escherichia coli)

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28
Q

What is the shape and arrangement of this bacteria?

A
  • streptococcus

(Streptococcus agalactiae)

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29
Q

What is the shape and arrangement of this bacteria?

A
  • coccobacillus

(Macrophages w/ Neisseria gonorrhoeae)

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30
Q

What is the shape and arrangement of this bacteria?

A
  • tetrad cocci

(Micrococcus luteus)

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31
Q

What is the shape and arrangement of this bacteria?

A
  • spirochete
32
Q

What are some features of bacterial colony appearance?

A
  • a single bacterium multiplies on solid growth media
  • this produces a bacterial colony visible without a microscope
  • some bacteria need to be cultured in broths in which turbidity (cloudiness) indicates growth
33
Q

T/F: the same bacterial species looks the same no matter how or where it is grown

A
  • false; morphology is dependent on culture medium, incubation time, temperature, oxygen, and genetic differences
34
Q

What are some factors required for bacterial growth?

A
  • source of metabolic energy: fermentation, respiration, photosynthesis
  • environmental factors:
    • nutrients
    • pH (most pathogenic bacteria grow best at 7.2-7.4)
    • ionic strength and osmotic pesssure
    • light
    • temperature (most are mesophilic w/ growth at 30-37C)
    • gaseous requirement (O2 + CO2)
35
Q

What are methods of classification of bacteria for growth?

A
36
Q

How do bacteria multiply?

A
  • bacteria replicate by binary fission
  • generation time = length of time required for a singe bacterial cell to yield two daughter cells (30m-2hr)
37
Q

What is the bacterial growth curve?

A
  • 4 phases:
    • lag phase: increase in cell size, active metabolism but no division
    • exponential phase or logarithmic phase: cells multiply at maximum rate
    • maximal stationary phase: due to exhaustion of nutrients or accumulation of toxic products, growth is ceased, balance between slow multiplication and death rate
    • decline phase or death phase: progressive death of cells
38
Q

What are characteristics of fungi?

A
  • eukaryotic*
  • branching hyphae multicellular molds*
    • hyphae and fruiting bodies contain spores
    • mycelium: filamentous mass of hyphae
  • unicellular yeasts*
  • reproduce both sexually (spores) and asexually (spores, budding, fragmentation)*
  • resistant to classical antimicrobial drugs*
  • non-photosynthetic heterotrophs: produce exoenzymes to obtain nutrients by absorption
  • widely distributed in the environment
  • grow aerobically/strict aerobes
  • cell membrane contains sterols (ergosterol) and a plant-like cell wall with chitin, glucagon,and mannopoteins
39
Q

T/F: vast majority of fungi are saprophytes and pathogenic

A
  • false; non-pathogenic
40
Q

What is the cycle of infection?

A
  • pathogen > reservoir > shedding > transmission > portal of entry > host susceptibility
41
Q

What is pathogenicity? Pathogenesis?

A
  • ability of a microorganism to cause disease
  • biological mechanisms that lead to a disease
42
Q

What are the types of bacterial disease carriers?

A
  • Convalescent carrier: those who recover but continue to shed the pathogen (clinical recovery does not necessitate bacteriological recovery)
    ex: strangles in horses
  • Healthy carrier (subclinical): carrier state without clinical symptoms but shedding the pathogen
  • Incubatory carrier: carrier that is incubating the pathogen but not yet ill (shedding during incubation period)
43
Q

What is virulence? Some factors?

A
  • measurement of pathogenicity
  • factors: characteristics that contribute to virulence
    • physical structures (ex: capsule, cell wall)
    • chemical substances (ex: toxins, adhesions)
44
Q

What are pathogenicity islands?

A
  • group of mobile genetic elements that may be located on bacterial chromosomes or plasmids and can be transferred through horizontal gene transfer. Carry genes coding for one or more virulence factors
45
Q

Describe horizontal gene transfer

A
46
Q

What quorum sensing?

A
  • the regulation in gene expression in response to fluctuations in cell-population density, mediated by chemical signal molecules (autoinducers)
47
Q

What are some bacterial mechanism of pathogenicity?

A
48
Q

What are some features of adherence and colonization?

A
  • flagella
  • pili/fimbriae
  • capsule = glycocalyx, layer of exopolysacchirides
    • protection from phagocytosis, inhibition of opsonization
    • protection from antibiotics
49
Q

What are some features of invasion?

A
  • invasion: ability of pathogen to spread to other locations in the host by invading host cells or tissue
  • extracellular invasion: when bacteria break down barriers of a tissue to disseminate in the host while remaining outside of host cells
    • production of extracellular enzymes
  • intracellular invasion: when bacteria penetrates cells and survive within this environment
    • facultative intracellular (ex: listeria)
    • obligate intracellular (must be inside cell to replicate) (ex: rickettsia, mycobacterium)
50
Q

What are some features of exotoxins?

A
  • generally proteinaceous toxins. Mode + location of toxin delivery effects clinical symptoms manifested by infected host
  • delivery mode:
    • secretion - into surrounding milieu
    • direct injection - into host cytoplasm
  • 3 major classes
51
Q

What are the three classes of exotoxins? Features?

A
  • type i ex: necrotizing haemorrhagic enteritis
52
Q

T/F: Proteolytic toxins are an example of class ii exotoxins

A
  • False; class iii
53
Q

What are some features of endotoxins?

A
  • toxic components of the prokaryotic cell wall that are not released until cell death and lysis of bacteria
  • effect: fever, diarrhea, weakness, blood coagulation, septic shock, death
54
Q

Compare + contrast endo and exotoxins

A
55
Q

What are some features of Lipopolysaccharides (LPS) and Teichoic acid?

A
  • LPS
    • heat-stable
    • lipid A acts as endotoxin
    • mediator of septic shock
    • only in gram-negative bacteria
  • Teichoic acid
    • mediator of septic shock
    • only in gram-positive bacteria
56
Q

What are biofilms? What are some functions?

A
  • mass of bacteria clinging to surfaces, visible, producing extracellular polymer matrix and exchanging nutrients
  • function:
    • bacterial persistence (ex: endocarditis)
    • reduction of host immunity
    • local damage (ex: catheters, drinking water pipelines)
    • reduced susceptibility to antibiotics
  • might have to mechanically break films
57
Q

What are some features of iron uptake in bacteria?

A
  • iron is needed for bacterial growth, but vertebrate tissue is virtually devoid of free iron so:
    • bacterial cytotoxins damage host cells which then release ferritin, hemoglobin, lactoferrin
    • receptor-mediated recognition
58
Q

T/F: all bacteria in the body is bad

A
  • False, needed for gut homeostasis
59
Q

What is a symbiosis? Symbionts?

A
  • symbiosis: an association of two organisms who can not exist independently
  • symbionts: organisms that live in close association with each other
60
Q

What are the kinds of symbiosis?

A
  • phoresis: an association in which two organisms are merely traveling together
  • mutualism: “++” association in which both organisms benefit
  • commensalism: “+=“ association in which one organism benefits and the other is unaffected
  • parasitism: “+-“ association in which one organism benefits and the other is harmed
61
Q

What are the kinds of parasitic hosts?

A
  • definitive: harbors adult (sexual) stage of parasite. If there is only one host needed, its definitive
  • intermediate: harbors larval (asexual) stage of parasite
  • paratenic: harbors a parasite that does not undergo required development: ie: transfer host
  • reservoir: a definitive host that serves to maintain the parasites life cycle in nature
  • incidental: a accidental host, unnecessary for maintenance of the parasite in nature, end of one for specific parasite
62
Q

What is a vector? What are the two types?

A
  • an object of organism responsible for transmitting a parasite from one host to another
  • biological: vector in which the parasite multiplies or develops (ex: mosquito w/ malaria)
  • mechanical: vector which transmits the parasite unchanged from host to host (ex: housefly carrying E. histolytica)
63
Q

What are the kinds of parasites?

A
  • obligate: totally physiologically dependent on the host
  • temporary: parasitic for limited periods for other feeding or reproduction
  • facultative: organisms that are not normally parasitic but can survive for limited period when they find themselves in another organism
  • ectoparasite: lives ON host, cause inFESTations
  • endoparasite: lives IN host, cause INFECTions
64
Q

What is a zoonosis?

A
  • any disease of animals that can be transmitted to humans

ex: trichinellosis, giardiasis, toxoplasmosis, Chagas’ disease, schistosomiasis, amebiosis, echinococcosis

65
Q

What are the main differences between protozoa and helminths?

A
  • protozoa multiply in definitive host
  • helminths do not multiply in definitive host, so severity of disease is proportional to initial worm load
66
Q

What are some survival facts and functions?

A
  • parasites adopt to every niche in a host
  • best adapted are the least pathogenic
  • parasite-host relationship is typically long term/chronic/intimate
67
Q

What are the conditions required for endemic parasitism?

A
  • reservoir of infection
  • means of transmission to susceptible hosts
  • ability to invade and establish in new hosts
  • ability to reproduce
68
Q

Why is host specificity important?

A
  • parasite life cycles can often only be completed in a particular host
69
Q

What are kinds of life cycles?

A
  • direct (with no intermediate host)
  • indirect (with a intermediate host)
  • indirect (with a vector)
70
Q

Why are disease outcomes important for hosts? What are they dependent on?

A
  • disease manifestations may be different depending on whether the animal is a definitive, intermediate, of incidental host.
    • ex: intermediate host can have severe consequences, while definitive hosts are generally asymptomatic
  • severity: infection dose + # of organisms
  • chronic: months to years
  • route of exposure
71
Q

What are common routes of parasite entry?

A
  • ingestion
  • skin or mucosal penetration
  • transplacental
  • transmammary
  • arthropod bite (vector)
  • sexual contact
72
Q

What are some features of virulence and pathogenesis?

A
  • ineffective dose + exposure
  • penetration of an anatomic barriers
  • attachment
  • cell + tissue damage
  • loss of nutrients
  • disruption, evasion, and inactivation of host defenses
73
Q

What are methods of attachment?

A
  • mechanical or biting mouthparts
    • oral cavity (capsule)
    • attachment organs
    • suction disk
    • biting mouthparts
    • direct penetration
  • molecular interaction
74
Q

What are kinds of cell/tissue damage?

A
  • mechanical damage
    • blockage of internal organs
    • pressure atrophy
    • migration through tissues
  • toxic products
    • destructive enzymes
    • endotoxins
    • toxic secretions (e: tick paralysis)
  • immunopathologic reactions
75
Q

What are examples of nutrient loss in a host?

A
  • competition with hosts for nutrients
  • interference with nutrient absorption
  • nutrient loss

RUSVM Principles Of Infectious Diseases (6 decks)

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