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MICRB 265 > Week 5 > Flashcards

Week 5 Flashcards

1
Q

OD is representative of ____

A

total cell count (# of intact cells) not the viable cell count

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2
Q

Microorganisms are not killed instantly, rather population death usually occurs _______

A

exponentially

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3
Q

A measures of agent’s killing efficiency of bacteria

A

-decimal reduction time- time to kill 90%

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4
Q

Killing efficiency of bacteria agent is affected by ____ cells. They are _____. We need to be sure that they are ____

A

-persister cells
-viable but nonculturable (VBNC) cells
-dead because once they recover they may regain the ability to reproduce and cause infection

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5
Q

Controls of bacterial populations are ____

A

reversible and irreversible

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6
Q

Types of controls of bacterial populations

A

-bacteriostatic
-bactericidal
-bacteriolytic

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7
Q

bacteriostatic (def.) + graph

A

-prevents growth but doesn’t kill bacteria
-viable cell count = total cell count but cell number is static until agent is removed
-reversible

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8
Q

bactericidal (def.) + graph

A

-kills cells but not lyse them
-total cell count (OD) stays stable but viable cell count reduces
-somewhat reversible

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9
Q

bacteriolytic (def.) + graph

A

-kills cells and lyse them when they die
-viable cell count = total cell count
-generally irreversible

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10
Q

cell number is ____ on normal graph; cell number is _____ on log graph

A

-exponential
-linear

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11
Q

5 methods of killing microbial cells

A

-sterilization
-disinfection
-sanitization
-antisepsis
-chemotherapy

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12
Q

sterilization (def.)

A

-destruction or removal of all viable organisms (no bacteria or endospores)

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13
Q

disinfection (def.)

A

-killing, inhibition or removal of pathogenic organisms but not endospores (ex. disinfectants), usually used on inanimate objects

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14
Q

sanitization (def.)

A

-reduction of microbial pop’n to levels deemed safe by public health standards (more bacteria survive than disinfection)

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15
Q

antisepsis (def.)

A

-prevention of infection of living tissue by micro-organisms
-chemical agents that kill or inhibit growth of microorganisms when applied to surface of tissue

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16
Q

chemotherapy aka ____ (def.)

A

-antibiotics
-kill or inhibit internal microorganisms

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17
Q

4 methods to control bacterial growth + main types of each method

A

-physical methods (heat + radiation)
-chemical methods (gas + liquids)
-mechanical methods (filtration)
-biological methods (antimicrobials)

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18
Q

high moist heat: type of bacterial growth control method? function? example?

A

-physical
-destroys viruses, fungi, bacteria, endospores
-autoclaving (used in lab, dentists); form of sterilization

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19
Q

low moist heat aka _____: type of bacterial growth control method? function? example?

A

-pasteurization
-physical
-controlled heating at temp below boiling (73 C)
-does not sterilize but kills most pathogens present and slow spoilage by reducing total load of organisms present
-used for milk, beer, other beverages

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20
Q

UV radiation: type of bacterial growth control method? function? example?

A

-physical
-260 nm is the most bactericidal; absorbed by DNA -> doesn’t kill endospores well & doesn’t lyse cells
-cause thymine/cytosine dimers which prevent replication and transcription
-only surface sterilization because it does not penetrate glass, films, water etc.
-used for water treatment (need to move water to surface)

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21
Q

Gamma radiation: type of bacterial growth control method? function? example?

A

-physical
-penetrates deep into objects & make DSB in DNA, ROS, membrane damage
-kills living organisms/ bacterial endospores but not viruses
-used for sterilization, pasteurization of antibiotics, hormones, sutures, plastic supplies, food

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22
Q

mechanical methods to kill microbes involve ____

A

movement of microbes with filters

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23
Q

mechanical methods to kill microbes with liquid samples

A

-membrane filtration pass through 0.2 um filter (bacteria can’t pass)

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24
Q

mechanical methods to kill microbes with gaseous samples (air)

A

-membrane filtration containing high efficiency particulate air (HEPA0 filter

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25
Q

Chemical methods to kill microbes (6)

A
  1. phenolics
  2. alcohols
  3. halogens
  4. aldehydes
  5. quaternary ammonium compounds
  6. hydrogen peroxide
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26
Q

phenolics are commonly used as ______; they act by _______; they kill _____ but do not kill ______; effective in the presence of _____; ____-lasting; problem: _____; structure based on ______; example: _____

A

-lab and hospital disinfectants
-denaturing proteins and disrupting cell membranes
-bacteria, including mycobacterium tuberculosis, fungi and enveloped viruses
-spores
-organic material
-long
-bad odor & can cause skin irritation
-phenol (benzene ring + OH)
-triclosan

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27
Q

alcohols are the most widely used ______; effect on bacteria, fungi, endospores; kills _____; denatures _______; structure based on ____; example: ______

A

-disinfectants and antiseptics (used on skin)
-bactericidal, fungicidal but not sporadical
-enveloped viruses
-proteins and possibly dissolve membrane lipids (conc. dependent)
-alcohol (OH)
-ethanol (50-70%), isopropanol

28
Q

halogens are ____; oxidizes _____ and iodinates ______; kills _____; at high conc. may kill _____; problem: _____; structure based on _____; examples: _____

A

-skin antiseptic
-cell constituents
-proteins
-bacteria, fungi, viruses
-spores
-skin damage, staining, and allergies can be a problem
-halogens (F, Cl, I, Br)
-halazone, triiodide

29
Q

aldehydes do what; stop _____; kills _______; structure based on _______; examples: _______

A

-crosslink proteins; used to preserve tissue
-metabolic activity
-most bacteria and fungi including spores
-aldehyde (O=CH)
-formaldehyde, gluteraldehyde

30
Q

Quaternary ammonium compounds are detergents that have ______; effective _______; kills ______; safe and easy to use; inactivated by ______; structure based on _____; examples: _____

A

-antimicrobial activity
-disinfectants
-most bacteria but not M. tuberculosis or endospores (mild); kills enveloped viruses and some fungi
-hard water and soap
-4o amine (ammonium : N+)
-cetylpyridinium chloride, benzalkonium chloride

31
Q

hydrogen peroxide (funfact: ROS) kills _____; oxidized ________; can put on ______; structure: ____

A

-most viruses, bacteria, and fungi
-proteins, lipids, and sugars
-skin + solid surfaces
-H2O2

32
Q

Chemotherapeutic agents (def.) + examples; where do they come from?

A

-chemical agents used to treat disease
-antibacterials, antifungals, antivirals
-nature (plants, bacteria, fungi-> they are ancient)

33
Q

Alexander Fleming accidentally discovered _______ . He called the secreted material mould juice until finally deciding on _____.

A

-Penicillium (a fungi that commonly causes food spoilage)
-penicillin

34
Q

Selective toxicity (def.)

A

ability of drug to kill or inhibit pathogen while damaging host as little as possible

35
Q

Therapeutic dose (def.)

A

drug level required for clinical treatment

36
Q

Toxic dose (def.)

A

drug level at which drug becomes too toxic for patient (i.e., produces side effects)

37
Q

Therapeutic index (def.)

A

ratio of toxic dose to therapeutic dose

38
Q

Side effects (def.)

A

Undesirable effects of drug on host cells

39
Q

Narrow spectrum drugs (def.)

A

Attack a few specific organisms

40
Q

Broad spectrum drugs (def.)

A

Attack a wide range of organisms

41
Q

Minimal inhibitory concentration (MIC) (def.)

A

lowest concentration of drug that inhibits growth of pathogen

42
Q

Minimal lethal concentration (MLC) (def.)

A

lowest concentration of drug that kills pathogen

43
Q

Two ways to determine effectiveness of antimicrobials

A

-dilution susceptibility tests for MIC
-disk diffusion tests (Kirby Bauer)

44
Q

Dilution susceptibility test (descr.)

A

-take inoculating media containing different conc of drug
-broth/agar with lowest concentration showing no growth = MIC
-for broth, tubes showing no growth can be subcultured into drugfree medium; broth from which no microbe can be recovered is MLC

45
Q

Disk diffusion tests (Kirby Bauer) (descr.)

A
  1. inoculate nutrient agar plate with liquid culture
  2. place disk containing antimicrobial agent on surface
  3. Incubate for 24-48 h
  4. Measure zones of inhibition (ZOI) = no growth around disks
46
Q

antibiotic targets

A

-inhibitors of cell wall synthesis
-protein synthesis inhibitors (rna poly, ribosomes, mRNA)
-metabolic antagonists
-nucleic acid synthesis inhibition (DNA gyrase etc)

47
Q

8 Things to consider about antibiotics

A
  1. ability of drug to reach site of infection
  2. susceptibility of pathogen to drug
  3. ability of drug to reach conc in body > MIC of pathogen
  4. amount given
  5. route of administration (topical, oral intravenous)
  6. speed of uptake
  7. rate of clearance (elimination from body)
  8. toxicity
48
Q

There are many classes of _____ but only 1 news class has been discovered in the last ____

A

-antibiotics
-60 years

49
Q

Classes of antibiotics

A
50
Q

Penicillins (B-lactam) ate ________ antibacterial effective against mainly _____; mode of action: _____. acts only on _____. structure allows it to _____. antibiotic resistance?

A

-narrow spectrum
-gram-positive bacteria
-blocks enzyme that catalyzes transpeptidation (cross links in peptidoglycan), prevents synthesis of complete cell walls leading to lysis of cell
-growing bacteria that are synthesizing new peptidoglycan
-bind to active site of enzyme because it looks like peptide bond
-easy to develop resistance

51
Q

penicillin G? penicillin V? ampicillin? carbenicllin? methicillin? ticarcillin?

A

-high activity against gram +, low against gram -; destroyed by acid and penicillinase
-same spectrum; more acid-resistant than penicillin G
-broader spectrum, active against gram +/-, acid stable (consume orally)
-active against gram - (pseudomonas and proteus), acid stable, not well absorbed by small intestine
-penicillinase-resistant but less activate than penicillin G; acid-labile (destroyed by acid)
-similar to carbenicillin, but more active against pseudomona

52
Q

Cephalosporins are structurally and functionally similar to _____; ____ antibiotics that can be used by most patients allergic to _____; 1st gen targeted ____ but later gen also target _____

A

-pencillins
-broad spectrum
-penicillin
-gram +
-gram -

53
Q

Vancomycin + Teicoplanin are _____; inhibit _____; vancomycin is important for _____

A

-gram + glycopeptide antibiotic
-cell wall synthesis (binds to N-acyl-D-Ala-D-Ala motif)
-treatment of antibiotic-resistant MRSA and enterococcal infections

54
Q

Aminoglycosides is a large group all with _____; example: ____; antibacterial with activity against _____; binds to _____, interfere with ______

A

-cyclohexane ring, amino sugars
-streptomycin
-gram - aerobic and facultative anaerobic bacteria
-30S ribosomal subunit
-protein synthesis by directly inhibiting the process and by causing misreading of mRNA

55
Q

tetracyclines all have ____; are ____spectrum, _____; combine with _____; inhibits binding of _____; sometimes used to treat ____

A

-four-ring structure to which a variety of side chains are attached
-broad
-bacteriostatic
-30S ribosomal subunit
-aminoacyl-tRNA molecules to the A site of ribosome
-acne

56
Q

macrolides contain ______; eg _______, ______ spectrum, usually ______; binds to ______, inhibits ______, used for patients allergic to ______

A

-12- to 22-C lactone rings to one or more sugars
-erythromycin
-broad
-bacteriostatic
-23S rRNA of 50S ribosomal subunit
-peptide chain elongation
-penicillin

57
Q

sulfa drugs are _____; ____; have ____. ex. _____, sulfa drugs are selectively toxic due to ______

A

-metabolic drugs
-bacteriostatic
-sulfur
-sulfanilamide, furosemide
-competitive inhibition of folic acid synthesis enzymes

58
Q

Folic acid is _____, necessary for _____, cofactor in ______; structurally related to _____. PABA is used for the synthesis of ______ and is made by many pathogens

A

-Vitamin B9
-DNA synthesis
-many biological rxns
-sulfanilamide, a PABA (p-aminobenzoic acid) analog
-folic acid

59
Q

Trimethoprim is a synthetic antibiotic that also interferes with ______; _____ spectrum. Can be combined with ______. Combination blocks _______, has a variety of side effects including ______, Used to treat ____; binds to different enzyme than _____

A

-folic acid production
-Broad
-sulfa drugs to increase efficacy of treatment
-two steps in folic acid pathway (harder to develop resistance)
-abdominal pain and photosensitivity reactions
-UTIs
-sulfa drugs

60
Q

Quinolones are ____-spectrum synthetic drugs containing the
______, act by inhibiting _____, ______, Excellent ______, ex. _____

A

-Broad
-4-quinolone ring
- bacterial DNA gyrase and topoisomerase II (needed for replication)
-Bactericidal
-tissue penetration
-ciprofloxacin

61
Q

Lipopeptides: Only effective against _____ organisms but very effective. Used against ______. Inserts into membrane near ______
ex.______

A

-Gram positive
-S. aureus but can be toxic
-phosphatidylglycerol, then aggregates, changing membrane curvature and allowing little holes to form (depolarizes membrane)
-daptomycin

62
Q

mechanisms of antimicrobial resistance (7)

A

-efflux pumps
-decreased uptake
-target alternations
-alternative enzyme
-inactivating enzyme
-sporulation
-shutting down cell growth

63
Q

antimicrobial resistance comes from ____ (3)

A

-microbial warfare
-horizontal gene transfer (ex. plasmid)
-evolutionary pressure from widespread antibiotic use

64
Q

antimicrobial resistance can exist in a pop’n because ____

A

eventhough on average there is one mutation per cell, in a typical infection, you can have billions or trillions of cells meaning more opportunity to have advantageous mutations

65
Q

antimicrobial resistance is a huge problem because _____

A

-once resistance is developed, it can be transmitted
-a specific resistance mechanism can give resistance to many classes of drugs
-microbes in abscesses or biofilms growing slowly and may not be susceptible
-resistance mutants arise spontaneously and are then selected for

MICRB 265 (12 decks)

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