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Microbiology > E2L17: Chemical Methods - Disrupt Phospholipoprotein Membrane > Flashcards

E2L17: Chemical Methods - Disrupt Phospholipoprotein Membrane Flashcards

1
Q

What part of the phospholipid is hydrophilic? Hydrophobic?

A
  • hydrophilic head

- hydrophobic tail

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2
Q

Talk to me about things that disrupt phospholipoprotein membranes in general.

A
  • disrupts cell/plasma membrane and its phospholipids
  • are SURFACTANTS, which mimic phospholipids –> poke holes + dissolve membrane
  • are CIDAL agents b/c membrane damaged
  • toxic to us if used systemically b/c we have cell membranes!!!
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3
Q

What are some broad categories whose MOA is disrupt phospholipoprotein membranes? (disrupt cell wall synthesis)

A

Detergents (cationic, anionic, non-ionic), Polymyxins, Polyenes, Azoles

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4
Q

What are Cationic Detergents? MOA? Examples? Efficacy against TB, Hep B, spores? Disinfectant/Sterilant?

A
  • detergents w/ + charge, most effective of detergents
  • MOA: disrupt phospholipoprotein membranes
  • ex: benzalkonium chloride (benzyl ammonium chloride), cetylpyridium chloride
  • NOT v effective against TB, Hep B, nor spores
  • -> disinfectant (not effective towards spores)
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5
Q

Why do hospitals and food industries use cationic detergents?

A
  • low toxicity
  • G+ org (ex: staph + strep) still problem in hospitals
  • -> cationic detergents better for G+ bacteria
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6
Q

What are Quaternary Ammonium Cmpds?

A
  • nitrogen w/ 4 alkyl groups attached
  • 1 alkyl is long+non-polar = tail
  • in most Lysol brands
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7
Q

Are cationic detergents more effective towards G+ or G- bacteria and why?

A

More effective towards G+ b/c G+ have murein and NO OUTER MEMBRANE. G-‘s outer membrane blocks cationic detergents. G-‘s cell wall still damaged (outer membrane portion), but not as vital as if the cell membrane itself was damaged.

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8
Q

What are Anionic Detergents? MOA? Examples? Typ. used for what org?

A
  • detergents w/ - charge, not as effective as cationic
  • MOA: disrupt phospholipoprotein membrane
  • typ. used for weak org (ex: gonococcus [Neisseria gonorrhea], meningococcus [Neisseria meningitidis], pneumococcus [Strep. pneumo], syphilis [Treponema pallidum])
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9
Q

What is Benzalkonium Chloride?

A
  • MOA: disrupt phospholipoprotein membrane
  • quaternary ammonium cmpd
  • cationic detergent
  • -> good against G+ org (staph/strep)
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10
Q

What’s Cetylpyridium Chloride?

A
  • MOA: disrupt phospholipoprotein membrane
  • quaternary ammonium cmpd
  • cationic detergent
  • -> good against G+ org (staph/strep)
  • preservative in mouthwashes, cosmetics, ophthalmic soln
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11
Q

What’s Sodium Lauryl Sulfate?

A
  • MOA: disrupt phospholipoprotein membrane
  • anionic detergent
  • preservative in some mouthwashes
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12
Q

What are Bile Salts?

A
  • MOA: disrupt phospholipoprotein membrane
  • anionic detergent
  • helps emulsify lipids in intestines
  • found in MacConkey’s agar, which is selective for G- due to bile working against G+ org
  • Taxo P discs have bile salts
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13
Q

What are the organisms that Anionic detergents normally treat against?

A
  • gonococcus –> Neisseria gonorrhea
  • meningococcus –> Neisseria meningitidis
  • pneumococcus - Strep. pneumo.
  • syphilis –> Treponema pallidum
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14
Q

What are Taxo P discs?

A
  • have bile salts - MOA: detergent -> disrupt phospholipoprotein membrane
  • “P” = strep. “P”neumo
  • used for ID, there’d be zone of inhibition around disc
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15
Q

What are non-ionic detergents? MOA?

A
  • only surfactants (mimic phospholipids)
  • ex: “bland” soaps –> MOA: mechanical - scrubbing
  • NO antimicrobial action
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16
Q

Talk about Polymyxins as a whole.

A
  • they’re series of amino acids connected by polypeptides (peptide bonds)
  • have polar, cyclic head + non-polar tail
  • Bacillus species (ex: subtilis) make polymyxins for protection
  • B and E (colistin) used clinically
  • NOT DOC!!! b/c neurotoxic + nephrotoxic (kidney)
  • narrow spectrum for G-
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17
Q

Okay, talk about Kirby-Bauer Technique.

A
  • a disc diffusion technique
  • antibiotic discs on streaked agar plate
  • measure zones of inhibition
  • qualitative
  • break points: R (resistant), I (intermediate), S (sensitive)
  • -> R/I/S measurement depends on antibiotic
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18
Q

What are some advantages of Kirby-Bauer? Disadvantages?

A
  • adv: can test multiple antibiotics simul. + can possible approx. MIC
  • dis: not good for anaerobes or slow-growing bacteria (ex: mycobacterium - takes 2-4 weeks to grow)
  • -> b/c disc diffuses quick, if slow-grow, only small [] over long period of time –> ineffective
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19
Q

Okay, talk about Tube Dilution Technique.

A
  • dis: test only 1 at a time
  • serial dilution, take certain dilution (ex: 128 micrograms/ml), 1/2 that dilution each time until 0 (- control)
  • can determine MIC (quantitative)
  • break points: S/I/R defined in micrograms/ml
  • can also test for MBC (minimum bactericidal [])
20
Q

What do the S/I/R break points relate to?

A
  • relates to breakpoints in blood, [able to be achieved in blood] must be higher than MIC
  • [] in blood relates to optimal therapy
  • optimal therapy (method): topically, oral, intramuscular (IM), intravenous (IV)
21
Q

How would you find an MBC? (minimum bactericidal []) What are the benefits to finding an MBC?

A
  • perform MIC 1st
  • inoculate all clear tubes onto fresh plates w/o antibiotics
  • MIC should grow out b/c only inhibitory
  • MBC typ 1-2 dilutions higher than MIC
  • good to know for immunocompromised patients, adv b/c related to [blood] + measured in micrograms/ml
22
Q

Talk about E-Tests.

A
  • strip w/ gradient of [antibiotic]’s placed on culture plate lawn
  • easier, more fool-proof way of finding MIC than serial tube dilution – more $$$ tho, lmao
23
Q

Talk about Polymyxin B.

A
  • ex: polymyxin - disrupts phospholipoprotein membrane
  • narrow spectrum for G-
  • LAST CHOICE for Acinetobacter + Pseudomonas systemic infections
  • EXTERNAL use for:
  • -> otic (ear) infections - otitis externa (outer ear), swimmer’s ear
  • -> ophthlamic (eye)
  • -> triple ointment (polymyxin b + bacitracin + neomycin)
24
Q

How and where would you get Acetinobacter baumannii + Pseudomonas aeruginosa infections?

A
  • affects immuno compro. patients in hospitals (nosocomial infections)
  • these develop resistance easily, so polymyxins might required
25
Q

Talk about Polymyxin E.

A
  • AKA colistin
  • ex: polymyxin - disrupts phospholipoprotein membrane
  • narrow spectrum for G-
  • very toxic
  • EXTERNAL use - otitis externa
  • for LAST CHOICE systemic infections Acetinobacter + Pseudomonas
  • used in Thayer Martin Selective Agar
26
Q

What’s in Thayer Martin Selective Agar? What’s it used for?

A
  • used to ID gonorrhea in patients, by selecting for it
  • includes: vancomycin (inhibits G+) + colistin (polymyxin E, for G- rods) + nystatin (inhibits yeasts)
  • -> selects for G- cocci like gonorrhea
27
Q

Talk about Polyenes as a whole.

A
  • cyclic, multiple 2x bonds
  • bind to sterols in cell membrane (ex: cholesterol in humans, ergosterol in fungi)
  • antifungal –> binds to sterol in membrane –> CIDAL
  • most bacteria lack sterols, but fungi have ‘em
  • can be toxic to us b/c we have cholesterol (ex: of sterol)
28
Q

Name some Polyenes.

A

nystatin and amphotericin B

29
Q

Talk about Nystatin.

A
  • ex: polyene - binds to sterols - disrupt membrane
  • NOT a DOC nor an alternate, but still commonly used
  • used for dermatophytes + superficial fungal infections by Candida albicans
  • kinds of superficial fungal infections (vulvovaginal candidiasis - yeast infection; oropharyngeal candidiasis - thrush)
30
Q

When can Candida albicans be a threat to us? (Threat to whom?)

A
  • immuno compro.
  • extreme youth
  • pregnant women
  • ppl w/ nutritional disorders (ex: diabetes)
31
Q

Is Nystatin absorbed in the stomach? What uses come out of this?

A
  • NO, not absorbed by stomach –> doesn’t go systemically when taken orally
  • used to reduce yeast #’s in patients before surgery
  • used in mouth rinses, lozengers to clear out Candida
32
Q

Talk about Amphotericin B.

A
  • DOC for systemic/deep mycoses (fungal infection)
  • CIDAL, toxic tho
  • also used for severe candida albicans infections
  • immuno compro @ most risk
  • zygomycosis: rhizopus (black bread mold)
  • aspergillosis: common soil org
  • dimorphic fungi –> grow as yeast (large cocci w/ bud) @ 37C (body temperature), grow as mold @ 25C (RT) + looks like mold (hyphae) –> v pathogenic
33
Q

What do Azoles do? What are some broad categories of Azoles?

A
  • interfere w/ sterol synthesis (ergosterol)
  • inhibitory/static
  • complex, ringed structures
  • broad categories: imidazoles, triazoles
34
Q

What are some examples of Imidazoles? What are imidazoles?

A
  • 2 nitrogens in a ring
  • INSOLUBLE in H2O
  • ex: clorimazole and miconazole, ketoconazole
35
Q

Talk about Clorimazole and Miconazole

A
  • used similarly, both for mild dermatophyte infections (candida), good for vulvovaginal infection
  • used for ringworm and its 3 causes
36
Q

What are the 3 causes of ringworm? What’s a common name for a kind of ringworm? What can you use to treat these ringworm infections? Is there a genetic predisposition for ringworm?

A
  • 3 causes: microsporum, trichophyton, epidermophyton
  • -> microsporum: skin, most common
  • -> trichophyton: skin-nails-hair, NASTIEST
  • -> epidermophyton: skin-nails
  • ringworm on feet = athlete’s foot (tricho. or epidermo.)
  • generally genetic predisposition
37
Q

Talk about Ketoconazole.

A
  • ex: imidazole (H2O insoluble) - azole - disrupt membrane
  • TOPICALLY, alternate for systemic mycoses (zygomycosis, aspergillosis, dimorphic)
  • alt. b/c more toxic
  • if aspergillosis gets to brain, can’t use Ketoconazole b/c can’t pass BBB
38
Q

What are the 3 causes of systemic mycoses?

A
  • zygomycosis
  • aspergillosis
  • dimorphic fungi
39
Q

What are Triazoles? Examples?

A
  • azoles that are more H2O soluble
  • MOA: disrupt membrane
  • ex: fluconazole (diflucan) and voriconazole
40
Q

What’s fluconazole? Other name? Used for…? DOC?

A
  • aka Diflucan
  • ex: triazole - azole - disrupt membrane
  • DOC for systemic mycoses, including those of nervous system (can pass BBB)
41
Q

Which of the following isn’t true about quaternary ammonium cmpds?

a) greater activity against G+
b) outer membrane of G- decreases effectiveness
c) viricidal against Hep
d) ineffective against tubercule bacillus

A

c) viricidal against Hep

42
Q

Which of the following statements is TRUE regarding use of non-germ. soaps over 4 day period?

a) show a persistant reduction of microbes on skin over time
b) reduce bacterial count by 1/2 over 4 days
c) just as effective as germicidal soaps in reducing microbial contamination
d) microbial count actual increases 2x using non-germ
e) no sustained effect of non-germ. on reduction of microbial contam.

A

e) no sustained effect of non-germ. soap on reduction of microbial contamination

43
Q

Which of the following antibiotics are used to treat fungal infections?
1 - penicillins, 2 - cephalosporins, 3 - triazoles, 4 - polyenes, 5 - nystatin
a) 1,2,3
b) 3, 4
c) 3,4,5
d) 4,5
e) all of ‘em

A

c) 3,4,5 (triazoles, polyenes, nystatin)

44
Q

These agents work as microbicidal agents b/c they lower surface tension of cell membranes.

a) penicillin
b) surfactants
c) lysozyme
d) metallic ions
e) dry heat

A

b) surfactants

45
Q

Which of the following statements regarding antifungal agents is incorrect?

a) amphotericin B - systemic fungal infections
b) nystatin - superficial candidiasis
c) ketoconazole - infections of the nervous system
d) fluconazole - yeast infections
e) none of these

A

c) ketonazole - infections of the nervous system

b/c can’t pass the BBB!!! voriconazole can pass BBB tho

46
Q

Treatment of severe superficial candidiasis includes?

a) cetylpyridinium chloride
b) sodium lauryl sulfate
c) amphotericin B
d) polymyxin E
e) miconazole

A

c) amphotericin B

note: it’s a DOC for systemic/deep mycoses!

Microbiology (9 decks)

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