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Path. Microbio > Exam One > Flashcards

Exam One Flashcards

(90 cards)

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1
Q

Sequence the Ames Test. What does it test for?

A

Tests for mutagenic substances.

rat liver extract, histidine-auxotroph salmonella, suspected mutagen cultured on a disk that does not contain histidine

mutation rate measured by the number of salmonella that survive without histidine

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2
Q

List some examples of bacteria that are virulent because of the introduction of toxin-encoding genes by phages

A

Vibrio cholerae – cholera toxin

E coli – shigalike toxin, causing hemorrhagic diarrhea

Clostridium botulinum – botulinum toxin

Corneybacterium diptherine – diptheria toxin

Streptococcus pyogenes – erythrogenic toxin – scarlet fever

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3
Q

What are aponenzymes and holoenzyme?

A

Aponenzyme – enzyme that needs a cofactor

Holoenzyme – enzyme coupled with cofactor

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4
Q

What is the rate of division in E coli, mycobacterium tuberculosis, M. leprae?

A

E coli - 20 min
Mycobacterium tuberculosis - 15-20h
M. leprae - 14 days

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5
Q

What are the four phases of bacterial growth called?

A

Lag, log, stationary, death

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6
Q

What % salt can halotolerant bacteria tolerate?

What % salt do halophilic bacteria prefer?

A

Halotolerant - 10%

Halophilic marine bacteria - 3%
Extreme halophiles - 9% +

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7
Q

What are microaerophiles?

A

Need some oxygen but not a whole load

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8
Q

What are the four temperature preference bacterial classes?

A

Psychrophiles - 0-20 celsius
Mesophiles - 15-40 celsius
Thermophiles - 40-80 celsius
Hyperthermophiles - 60+ celsius

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9
Q

Discuss the relationshiop of helicobacter pylori and vibrio cholerae to PH

A

H. Pylori - not acidophile but acid tolerant, and produces urease

V. Cholerae - survives up to PH 9!

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10
Q

Describe the structure of peptidoglycan

A

Two layers of glycan, made of alternating NAG / NAM subunits

Linked by 2x tetrapeptide chains and a peptide interbridge, built with transpeptidase

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11
Q

How do penicillin, cephalosoprin, lysozomes mess with peptidoglycan?

A

Cephalosporin, penicillin – inhibit transpeptidase

Lysozomes - cleave glycan backbone

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12
Q

Why are cephalosporin and penicillin less effective in gram negative bacteria?

A

Gram negative have less peptidoglycan

Also peptidoglycan hidden behind lipid bilayer outer membrane – inhibits access!

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13
Q

Discuss the cell wall of a gram +ve bacterium, outside in

A
  • Peptidoglycan and telchoic acid trees, in gel-like material (rigid)
  • Cytoplasmic membrane
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14
Q

Discuss the cell wall of a gram -ve bacterium, outside in

A
  • LPS
  • Outer membrane – lipid bilayer, with porins for small molecules
  • Thin layer of peptidoglycan in periplasm
  • Cytoplasm
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15
Q

How does LPS affect the body?

A

Presence triggers immune response

Lipid A = endotoxin – large release causes fever, sepsis

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16
Q

Discuss the structure of LPS, top down

A

O antigen – used to identify spp/strain
Core
Lipid A at bottom

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17
Q

What are the two classes of glycocalces? What are they composed of?

A

Capsule – distinct, gelatinous
Slime layer – diffuse, irregular

Both composed of glycolax and some proteins

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18
Q

What are the functions of glycocalces?

A
  • Protective against phagocytosis [unless opsonized]

- Allows adhesion and formation of biofilm on intert surfaces, e.g. rocks, dental plaque

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19
Q

What are the three classes of flagella?

A

Monotrichous - one flagellum
Lophotrichous – multiple flagella from one place
Petritrichous – many flagella from many places

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20
Q

What are axial filaments?

A

Flagella in periplasmic space. Found in spirochetes - causes corkscrew

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21
Q

Discuss different endospore locations

A

Central, swollen sporangium, terminal, subterminal

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22
Q

What are fimbriae?

A

hairlike bristles extending from surface, help in adhestion

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23
Q

What is an inclusion/granule?

A

Stored nutrients, deposited as crustals

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24
Q

Which bacterium does not have a cell wall?

A

Mycoplasma

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25
CC peptidoglycan in gram+, gram-, acid fast bacteria cell walls
Gram+ = thick Gram- = thin Acid fast = small amount
26
CC teichoic acid in gram+, gram-, acid fast bacteria cell walls
gram+ = often gram- = none acid fast = none
27
CC lipids in gram+, gram-, acid fast bacteria cell walls
gram+ = v. little gram- = LPS acid fast = mycolic acid, waxes, glycolipids
28
CC outer membrane presence in gram+, gram-, acid fast bacteria cell walls
Only present in gram- bacteria
29
CC periplasmic space presence in gram+, gram-, acid fast bacteria cell walls
Only present in gram- bacteria
30
CC cell shape in gram+, gram-, acid fast bacteria cell walls
Gram+ is always rigid, others rigid or flexible
31
CC result of digestion in gram+, gram-, acid fast bacteria cell walls
gram+ = protoplast gram- = spheroplast acid fast = hard to digest
32
CC antibiotic sensitivity in gram+, gram-, acid fast bacteria cell walls
gram+ = most gram- = some acid fast = least
33
List six key bacterial shapes
``` Coccus - sphere Bacillus = rod coccobacillus = oval Vibria = bean Spirillum = rigid spiral Spirochete = non rigid spiral ```
34
What do strepto- and staphylo-
``` Strepto- = strip Staphylo- = cluster ```
35
What does the cholera toxin do?
Activates adenallyl cyclase in intestinal cells - > increased cAMP, fluid, electrolyte secretion - > diarrhea
36
What does the tetanus toxin do?
Inhibits release of inhibatory neurotransmitters in CNS => spastic paralysis
37
What does the botulism toxin do?
Inhibits release of acetylcholine from neurons => flaccid paralysis
38
What does the diptheria toxin do?
Inhibition of protein synthesis => cell death
39
What does streptolysin toxin from streptococcus pyogenes do?
Creates protein that blocks cell membrane pores -> cell death
40
What does the pneumolysin txin from streptococcus pneumoniae do?
Creates protein that blocks cell membrane pores -> cell death
41
What does alpha toxin from staphylococcus aureus do?
Creates protein that blocks cell membrane pores -> cell death
42
What does beta toxin from staphylococcus aureus do?
Phospholipase - degrades cell membranes
43
What does phospholipase C from pseudomonas aeruginosa do?
Phospholipase - degrades cell membranes
44
What does alpha toxin from clostridium perfringens do?
Phospholipase - degrades cell membranes
45
Which bacterium causes toxic shock syndrome?
Staphylococcus aureus
46
Which bacterial toxins cause excessive cytokine stimulation?
Streptococcal mitogenic exotoxin and streptococcal pyrogenic exotoxin, both from streptococcus pyogenes
47
What virulence factors aid adhesion?
Adhesins on pili/fibrae, e.g. in neisseria gonorrhaeae Glycocalyx layers
48
What virulence factors aid invasion?
Degrading extracellular matric, through hyaluronidase / collagenase Modulating blood clotting in host - coagulase accelerates clotting, streptokinase dissolves clots
49
What virulence factors aid bacterial defense?
Capsules Proteases to degrade IgA, IgG Antigenic variation
50
What adaptations enable intracellular bacterial growth?
Inhibition of fusion with lysosome; inhibition of acidification of phagosome [mycobacterium legionella] Escape from phagosome into cytoplasm [listeria]
51
What is toxemia?
Presence of toxins in blood
52
What are the differences between endotoxins and exotoxins?
Endotoxins -- heat stable, systemic effect, high LD50 Exotoxins -- not heat stable, specific and receptor mediated, low LD50
53
What are the fie stages of infection?
``` Incubation Prodromal Illness Decline Convalescence ```
54
What are the most common healthcare associated infection sites?
Urinary tract - 40% Surgical wounds - 20% Respiratory - 15%
55
What is the difference between bacteremia, septicaemia, septic shock?
Bacteraemia - bacteria in blood Septicaemia - in blood and multiplying Septic shock -- systolic pressure <90mmHg
56
What is the difference between ID50 and LD50
``` ID50 = median infectious dose LD50 = median lethal dose ```
57
What are Koch's postulates, 1884?
Agent present in diseased organism but not in healthy Must be isolatable When inoculated into healthy individual, must cause same disease Must then be reisolatable
58
What are nosocomial infections?
Healthcare related infections
59
SEQ gram staining
1) Crystal violet added, stains +/- purple 2) Iodine added, makes stain adhere to cell walls 3) Alcohol added, stain washes off -ve 4) Safranin applied, -ve stained pink
60
SEQ acid staining
1) Basic fuschin added, all stained pink | 2) Acid-alcohol added, non-acid fast stained blue
61
What types of staining other than gram / acid staining exist?
Endospore, capsule, flagella
62
What are the pros and cons of identifying an organism through culture and visual / metabolic identification?
+ : sensitive, inexpensive | - : can be slow
63
SEQ the streak method for isolating pure colonies
Sterilize wand, make one streak from last sample | x 4 until pure colonies are apparent
64
What are the pros and cons of molecular methods of microbial detection?
+ : no culturing required, good for fastidious or uncultivable bacteria, no need for sample purity, specific, sensitive, rapid, accurate - : needs trained personnel, expensive
65
How is bacterial genomic sequencing undertaken?
Gold standard = sequencing of 16S rRNA subunit.
66
What does MALDI-TOF MS stand for?
Matric-assisted laster desorption ionisation time of mass-spectrometry
67
What are the pros and cons of MALDI-TOF MS
Pros: rapid, fast, sensitive, less expensive than molecular identification methods, does not need trained lab personnel Cons: identification only possible if species/strain present if database has peptide mass fingerprints of specific strains
68
What is the major disadvantage of PCR amplification for diagnostic microbiology?
At least some sequence must be known to synthesize appropriate primers
69
What is precipitin?
An insoluble complex formed when antigens and antibodies are present in appropriate ratio
70
What are the pros and cons of serologic tests?
Pros: fast Cons: less sensitive, accurate than nucleic acid methods; limited by availability of appropriate antibodies/antigens
71
What are the pros and cons of serologic tests?
Pros: fast Cons: less sensitive, accurate than nucleic acid methods; limited by availability of appropriate antibodies/antigens
72
What is selective toxicity?
The ability to harm pathogens but not host
73
What is the measure of toxicity?
Therapeutic index
74
What is the difference between bacteriostatic and bacteriocidal drugs?
``` Bacteriostatic = inhibits growth Bacteriocidal = kills them ```
75
What is a superinfection? Give examples
Large population of drug-resistant bacteria after even normal flora have been killed off by antibiotics E.g. candiasis after UTI treatment; Pseudomembranous colitis caused by C diff
76
What are good selectively toxic bacterial targets?
Cell wall Plasma membrane Ribosomes -- 30S subunit and 50S subunit Metabolic pathways -- esp. folic acid synthesis and mycolic acid synthesis
77
What are good selectively toxic bacterial targets?
``` Cell wall Plasma membrane Ribosomes -- 30S subunit and 50S subunit Metabolic pathways -- esp. folic acid synthesis and mycolic acid synthesis DNA/RNA synthesis Mycobacterial ATP synthesis ```
78
What are some key anti-drug bacterial adaptations?
``` Efflux pump Blocked penetration Enzyme inactivation Target modification Target overproduction Target mimicry Enzymatic bypass ```
79
Describe penicillin
Contains beta-lactam ring -- types differentiated by side chains on ring Prevents crosslinking of peptidoglycans
80
How are cephalosporins different from penicillin?
Different beta-lactam ring | Classed according to generation of development
81
Give an example of intrinsic drug resistance in bacteria
Mycoplasma lack cell wall => do not respond to penicillin or cephalosporins
82
Give an example of intrinsic drug resistance in bacteria
Mycoplasma lack cell wall => do not respond to penicillin or cephalosporins
83
What does the Kirby-Bauer test test?
Sensitivity of particular bacterium to antibiotic
84
SEQ the Kirby-Bauer test
Culture bacteria on plate Add antibiotic drops Measure radius of killed bacteria
85
What are the limitations of the Kirby-Bauer test?
Qualitative not quantitative Does not provide bactericidal v. bacteriostatic info Not good for tricky/slow/anaerobic bacteria Biofilm bacteria may be affected differently
86
In the dilution test what is MBC and what is MIC?
``` MIC = minimum inhibitory concentration MBC = minimum bactericidal concentration ```
87
How is MBC measured in the dilution test?
Take some drops from each clear flask, place on petri dish, see if bacteria grow
88
What is a biofilm?
Complex community of one or more microbe spp Forms slimy coating Attaches to inert or organic substances through secretin of EPS [extrapolymeric substance]
89
What challenges to biofilms present?
Hard to observe -- thick! Resistant to antibiotics and immune system Can form on medical devices Hard to dehydrate b/c hold water like sponge
90
What are the stages of biofilm development?
Initial attachment of planktonic cells to surface Irreversible attachment [become sessile -- attached to surface] Maturation I - growth Maturation II - EPS production Dispersion

Path. Microbio (6 decks)

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