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PID > Bacteriology & Mycology > Flashcards

Bacteriology & Mycology Flashcards

1
Q

Spontaneous generation

A

Aristotles and others believed that living organisms could develop from non-living materials (because flies flew out of meat)

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2
Q

Biogenesis

A

All living things come from other living things

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3
Q

Scale of bacterial life

A

One cell in body= 10 bacterial cells
Wrap earth 2.5 times laid end to end
Large in number, small in size and invisible to the naked eye

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4
Q

Eukaryotic cells

A

Plant and snimal cells with a nucleus and membrane-enclosed organelles

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5
Q

Prokaryotic cells

A

Unicellular organisms without a nucleus or membrane-enclosed organelles

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6
Q

Bacterial cell structure

A 
Cytoplasm
Ribosomes
Nucleoid
Plasma membrane
Complex and rigid cell wall
Capsule
Flagella
Pili/fimbriae
Endospores
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7
Q

Cytoplasm

A

Cytosol= jelly-like aqueous solution
Contains three main groups of molecules
-macromolecules such as proteins (enzymes), mRNA, tRNA
-small molecules that are energy sources, precursors of macromolecules, metabolites or vitamins
-inorganic ions required for enzymatic activity (co-factors)

Contains the nucleoid (DNA) and ribosomes (protein synthesis)

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8
Q

Cytoplasm function

A 
Facilitate chemical reactions
Dissolve solutes (carbohydrates and proteins)
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9
Q

Nucleoid

A

Location in prokaryotic cell where primary genetic material is found
Bacterial genome
Proteins
-proteins involved in DNA compaction
-transcription factors that regulate the expression of the bacterial genome
RNA
-mRNA coding for proteins
-ncRNA involved in DNA organization and expression of the bacterial genome

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10
Q

Bacterial genome

A

Single haploid circular chromosome containing double-stranded DNA

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11
Q

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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12
Q

Plasmid function

A

Contain genes associated with disease (virulence factors) or to survive in presence of antibiotics and other toxic compounds (resistance genes)
Conjugative plasmids: cell-to-cell transfer by conjugation

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13
Q

Conjugative plasmids

A
  1. Donor cell attaches to a recipient cell with its pilus. The pilus draws the cells together
  2. The cells contact one another
  3. On strand of plasmid DNA transfers to the recipient
  4. The recipient synthesizes a complementary strand to become an F+ cell; the donor synthesizes a complementary strand, restoring its complete plasmid
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14
Q

Ribosomes

A

Ribonucleoproteins with large 50S subunit + 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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15
Q

Bacterial envelope

A 
Cytoplasmic or plasma membrane
Cell wall (peptidoglycan layer)
Periplasmic space
Outer membrane (Gram - bacteria)
Capsule (some bacteria)
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16
Q

Plasma membrane

A

Innermost membrane, next to cytoplasm

Composed of a phospholipid bilayer and proteins

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17
Q

Phospholipid bilayer

A

Layer of phospholipid molecules with a head that loves water (hydrophilic) and two tails that fear water (hydrophobic). Only hydrophobic (lipid soluble) compounds can enter the cell by passive diffusion through the lipids in the bilayer

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18
Q

Membrane Proteins

A

Transport proteins enable specific transport of molecules into and out of the cell
Energy generation components used for the synthesis of adenosine 5’-triphosphate (ATP)
Proteins that function as anchors or help in the assembly of external structures

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19
Q

Plasma membrane functions

A

Selective permeability barrier: transport proteins mediate passage of hydrophilic substances into and out of the cell
Bacterial respiration and energy generation
Serve as an anchor for external structures

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20
Q

Cell wall: peptidoglycan layer

A

Peptidoglycan: polymer unique to prokaryotic cells
Mech-like structure consisting of chains of alternating subunits of NAG and NAM cross-linked with peptides by transpeptidase enzymes called penicillin-binding proteins (PBPs)

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21
Q

Peptidoglycan layer function

A

Protection against mechanical damage and osmotic lysis
Transport: non-selective permeability
Composition of bacterial envelope determines the two main structural classes

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22
Q

Outer membrane

A

Common to gram negative bacteria
Protein-containing asymmetrical lipid bilayer
-lipopolysaccharide (LPS or endotoxin)
-porin proteins that allow small hydrophilic molecules to passively enter the cell
Transporter proteins that enable transport of larger nutrients into the cell

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23
Q

Outer membrane function

A

Selective permeability barrier
Resistance to larger or hydrophobic toxic compounds
Tolerance to detergents and bile salts

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24
Q

Lipopolysaccharides

A

Virulence factor

Lipid A component is molecule with endotoxic activity

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25
Q

What will you see from LPS

A 
Fever 
Leukopenia
Anorexia
Diarrhea
Blood coagulation
Hemorrhagic shock
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26
Q

Myobacteria

A

Bacterial envelope- gram positive bacteria but contains mycolic acid
Acid fast staining for identification

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27
Q

Mollicutes (mycoplamsa)

A

Plasma membrane with sterols

No cell wall- no peptidoglycan layer

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28
Q

Capsule

A

Glycocalyx= polysaccharide layer

Only in some bacterial species

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29
Q

Capsule function

A

Protection from adverse environmental conditions (desiccation)
Virulence factor facilitate adherence to surfaces and interfere with phagocytosis
Nutrient reserve

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30
Q

Endospore

A

cryptobiotic state of dormancy and most durable type of cell found in nature
Produced by pathogenic genera Bacillus and clostridium

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31
Q

Endospore function

A

ensure survival during adverse environmental conditions

Dormant highly resistant bodies

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32
Q

Flagella

A

Present on bacterial surface
Flagellar arrangement
-number of flagella
-position at which flagella are inserted into bacterial cell wall

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33
Q

Flagella function

A

Locomotion or bacterial motility

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34
Q

Pili/Fimbriae

A

fine, straight, hair-like appendages attached to cell wall

most common on gram-negative bacteria

35
Q

Pili/Fimbriae function

A

Adhesion to host tissues

Contribute to antigenicity

36
Q

Bacterial shapes and arrangements

A

Cocci
Bacilli
Budding and appendaged bacteria

37
Q

Bacterial colony appearance

A

A single bacterium multiplies on solid growth media. Growth of bacteria produces a bacterial colony that is visible without a microscope
Some bacteria need to be cultured in broths in which tubidity indicates growth

Same bacterial species can have different morphology depending on the culture medium, incubation time/temperature/oxygen or genetic difference

38
Q

Factors required for bacterial growth

A

Sources of metabolic energy: fermentation, respiration and photosynthesis
Environmental factors
-nutrients
-pH (most pathogenic bacteria grow best at 7.2-7.4)
-ionic strength and osmotic pressure
-light
-Temperature (most are mesophilic with growth at 30-37 C)
Gaseous requirement: oxygen and carbon dioxide

39
Q

Classification of bacteria

A 
Based on oxygen requirement
-Obligate aerobes
-obligate anaerobes
-Facultative anaerobes
-Aerotolerant anaerobes
Based on temperature range for optimal growth
40
Q

Bacterial growth curve

A 
Bacteria replicate by binary fission
Generation time 
Four phases
-Lag phase
-Exponential phase or logarithmic phase
Maximal stationary phase
-Decline phase or death phase
41
Q

Generation time

A

length of time required for a single bacterial cell to yield two daughter cells (30 min to 20 hours)

42
Q

Lag phase

A

Increase in cell size, active metabolism of cells but no division

43
Q

Exponential phase or Logarithmic phase

A

cells multiply at maximum rate

44
Q

Maximal stationary phase

A

Due to exhaustion of nutrients or accumulation of toxic products, growth is ceased, balance between slow multiplication and death rate

45
Q

Decline phase or death phase

A

progressive death of cells

46
Q

Fungal Characteristics

A

Eukaryotic
Non-photosynthetic heterotrophs: produce exoenzymes to obtain nutrients by absorption
Widely distributed in the environment
Fungi grow aerobically and many are strict aerobes
Cell membrane contains sterols and plant-like cel wall with chitin, glucan and mannoproteins

47
Q

Branching hyphae multicellular molds

A

Hyphae and fruiting bodies containing spores

Mycelium: filamentous mass of hyphae

48
Q

Unicellular yeast

A

Round single cells characterized by budding
Reproduce both sexually (spores) and asexually (spores, budding or fragmentation)
Resistant to classical antimicrobial drugs

49
Q

Spore cycle

A

Sporangia burst
Spores
Spores grow hyphae
Sporangia appears

50
Q

Cycle of infection

A

An infection starts with exposure to the pathogen from either animate or inanimate reservoir

51
Q

Host pathogen interaction

A 
Pathogen
Reservoir
modes of shedding
modes of transition
portal of entry
Host susceptibility
52
Q

Pathogenicity

A

Ability of a microorganism to cause disease

53
Q

Pathogenesis

A

Biological mechanism(s) that lead to a disease

54
Q

Bacterial pathogenesis

A

Important to know reservoir of bacterial agents

Disease carrier

55
Q

Convalescent carrier

A

Those who recovered but continue to shed the pathogen
Clinical recovery does not coincide with bacteriological recovery&raquo_space;> bacteriological surveillance of carrier state is necessary

56
Q

Healthy carrier (subclinical)

A

Carrier state without clinical symptoms but shedding the pathogen

57
Q

Incubatory carrier

A

Carrier that is incubating the pathogen but not not yet ill (shedding of pathogen during incubation period)

58
Q

Strangles in horses

A

Detection of convalescent carriers
Highly contagious febrile disease involving upper respiratory tract with abscessation of regional lymph nodes in equines
Follow up: 3 negative culture at weekly intervals

59
Q

Virulence

A

Measurement of pathogenicity

60
Q

Virulence factors

A 
Bacterial characteristics that contribute to virulence 
Physical structures (cell wall, capsule)
Chemical substances (toxins, adhesins)
61
Q

Pathogenicity islands

A

Carry genes coding for one or more virulence factors. This group of mobile genetic elements may be located on bacterial chromosome or plasmids and can be transferred through horizontal gene transfer

62
Q

Bacterial transformation

A

Release of DNA

63
Q

Bacterial transduction

A

Release of phage

64
Q

Bacterial conjugation

A

Connected, whole plasma moves over

65
Q

Quorum sensing

A

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

Low density: autoinducers diffuse away from bacteria promoting individual cell behavior (doesn’t cause disease-invisible)
High density: autoinducers bind to receptors and promote group behavior
Talk through autoinducers

66
Q

Group behavior

A 
Symbiosis
Virulence
Competence
Conjugation
Antibiotic production
Motility
Sporulation
Biofilm formation
67
Q

Penetration or evasion of host defenses

A 
Capsules
Cell wall components
Enzymes
Antigenic variation
Invasins
Intracellular growth
68
Q

Damage to host cells

A 
Siderophores
Direct damage
Toxins (exotoxins, endotoxins)
Lysogenic conversion
Cytopathic effects
69
Q

Adherence and colonization

A

Flagella
Pili/Fimbriae
Capsule= glycocalyz, layer of exopolysaccharides
-protection from phagocytosis: inhibition of opsonization
-Protection from antibiotics

70
Q

Invasion

A

The ability of the pathogen to spread to other locations in the host, by invading host cells or tissues

71
Q

Extracellular invasion

A

When bacteria break down barriers of a tissue to disseminate in the host while remaining outside of host cells
-production of extracellular enzymes (collagenase, coagulase)

72
Q

Intracellular invasion

A

When bacteria penetrate cells and survive within this environment

  • facultative intracellular (listeria)
  • obligate intracellular (myobacterium)
73
Q

Exotoxins

A

Exotoxins are generally proteinaceous toxins. The mode of location of toxin delivery affects the clinical symptoms manifested by the infected host
Delivery mode
-secretion into surrounding millieu
-Direct injection into host cell cytoplasm
Three major classes

74
Q

Type I Endotoxin

A

cell surface active
Disturbance of cell metabolism
Clostridium perfringens
Activate second messenger pathways

75
Q

Type II Endotoxin

A

Membrane damaging
Staphylococcus aureus
Damage cellular membranes/matrices

76
Q

Type III Endotoxin

A

Intracellular (A-B toxins)
Clostridium botulinum
Inhibit protein synthesis

77
Q

Endotoxins

A

Endotoxin are 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 and death

78
Q

LPS

A

Heat stable
Lipid A acts as endotoxin
Mediator of septic shock
Only in gram-negative bacteria

79
Q

(Lipo)Teichoic acid

A

Mediator of septic shock

Only in Gram-positive bacteria

80
Q

Exotoxin more info

A

Species: some species of both gram-poitive and gram negative bacteria

Protein location: proteins secreted from cell

Gene location: usually on plasmids

Toxicity: high toxicity

Antigenicity: highly antigenic

Heat stability:heat labile

Vaccine: vaccine available

81
Q

Endotoxin more info

A

Species: Mostly Gram-negative bacteria and listeria

Protein location: part of cell wall

Gene location: usually on bacterial chromosome

Toxicity: low toxicity

Antigenicity: poorly antigenic

Heat stability: heat stable

Vaccine:no vaccine available

82
Q

Biofilms

A

Mass of bacteria cling to surfaces, producing extracellular polymer matrix and exchange nutrients

83
Q

Biofilms Function

A

Bacterial persistence (endocarditis)
Reduction of host immunity
Local damage (catheters, drinking water pipelines)
Reduced susceptibility to antibiotics

84
Q

Iron uptake

A

Vertebrate tissue is virtually devoid of free iron
Iron is needed for bacterial growth
Changing the battlefield
-bacterial cytotoxins damage host cells- release of ferritin, hemoglobin, lactoferrin
-receptor mediated recognition

PID (14 decks)

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