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Micriobiology > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

Moist Heat

A
  • Destroys viruses, fungi, and bacteria but NOT spores

- Degrades nucleic acids, denatures proteins, and disrupts membranes

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2
Q

Steam Sterilization

A

Effective against all types `of microorganisms (including spores!)

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3
Q

Pasteurization

A
  • Controlled heating at temperatures well below boiling
  • Process does not sterilize but does kill pathogens present and slow spoilage by reducing the total load of organisms present
  • Ultra High Temperature Method can sterilize
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4
Q

Dry Heat Sterilization

A
  • Less effective than moist heat sterilization, requiring higher temperatures and often longer exposure times
  • Oxidizes cell constituents and denatures proteins
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5
Q

Ultraviolet (UV) Radiation

A
  • Causes thymine dimers preventing replication and transcription
  • UV limited to surface sterilization because it does not penetrate glass, dirt films, water, and other substances
  • Has been used for water treatment
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6
Q

Ionizing Radiation

A
  • Gamma radiation penetrates objects

- Not always effective against viruses but can kill bacterial endospores

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7
Q

Phenolics

A
  • Denatures proteins and disrupts cell membranes
  • Tuberculocidal, effective in presence of organic material, and long lasting
  • Disagreeable odor and can cause skin irritation
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8
Q

Alcohols

A

-Bactericidal, fungicidal, but not sporicidal
-Inactivates some viruses
-Denatures proteins and possibly dissolves membrane lipids
Among the most widely used antisepsis and disinfectants

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9
Q

Halogens

A
  • Iodine, for example, is an antiseptic
  • Oxidizes cell constituents and iodinates proteins
  • At high concentrations can kill spores
  • Chlorine also oxidizes cell constituents and destroys vegetable bacteria and fungi
  • Chlorine has is sporicidal
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10
Q

Heavy Metals

A
  • Examples are mercury, zinc, copper, silver, and arsenic

- Combine with and inactivate proteins, may also precipitate proteins

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11
Q

Quaternary Ammonium Compounds

A
  • Detergents that have antimicrobial activity and are effective disinfectants
  • Cationic detergents are effective disinfectants
  • Kill most bacteria, but not M. tuberculosis or endospores
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12
Q

Aldehydes

A
  • Sporicidal and can be used as chemical sterilants

- Combine with and inactivate nucleic acids and proteins

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13
Q

Sterilizing Gases

A
  • Used to sterilize heat sensitive material
  • Microbicidal and sporicidal
  • Combine with and inactivate DNA and proteins
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14
Q

Antimicrobial Drugs - Modes of Action

A
  • Inhibition of cell wall synthesis
  • Inhibition of protein synthesis
  • Inhibition of essential metabolite synthesis
  • Inhibition of nucleic acid synthesis
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15
Q

Pencillins

A
  • Most crucial feature is the beta-lactam ring
  • Blocks the enzyme that catalyzes transpeptidation (formation of cross-links in peptidoglycan)
  • Prevents synthesis of complete cells walls leading to lysis of cell
  • Acts only on growing bacteria that are synthesizing new peptidoglycan
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16
Q

Cephalosporins

A
  • Similar to penicillins
  • Broad-spectrum antibiotics that can be used by most patients who are allergic to penicillin
  • Inhibits cell wall synthesis
17
Q

Vancomycin

A
  • Glycopeptide antibiotic
  • Inhibits cell wall synthesis
  • Important for treatment of antibiotic resistant staphylococci and enterococci
18
Q

Aminoglycoside Antibiotics

A

-Bind to 30S ribosomal subunit, interferes with protein synthesis by directly inhibiting the process and by causing misreading of the mRNA

19
Q

Tetracycline

A
  • Four-ring structure
  • Broad spectrum, bacteriostatic
  • Combine with 30S ribosomal subunit, inhibits binding of aminoacyl-tRNA molecules
20
Q

Macrolides

A
  • Contain 12-to 22-carbon lactone rings linked to one or more sugars
  • For example, Erythromycin – broad spectrum, usually
  • binds to 23S rRNA of 50S ribosomal subunit
  • inhibits peptide chain elongation during protein synthesis
  • Used for patients allergic to penicillin
21
Q

Chloramphenicol

A
  • Now is chemically synthesized
  • Binds to 23S rRNA on 50S ribosomal subunit and inhibits peptidyl transferase reaction
  • Toxic with numerous side effects so only used in life-threatening situations
22
Q

Sulfonamides or Sulfa Drugs

A

• Structurally related to sulfanilamide, a p-aminobenzoic acid (PABA) analog
• PABA used for the synthesis of folic acid and is made by many pathogens
– sulfa drugs are selectively toxic due to competitive inhibition of folic acid synthesis enzymes

23
Q

Trimethoprim

A

• Synthetic antibiotic that also interferes with folic acid production
• Broad spectrum
• Can be combined with sulfa drugs to increase efficacy of treatment
– combination blocks two steps in folic acid pathway

24
Q

Quinolones

A
  • Synthetic drugs containing the 4-quinolone ring
  • Nalidixic acid was the first quinolone synthesized
  • Acts by inhibiting bacterial DNA gyrase and topoisomerase II
  • Broad spectrum, bactericidal, wide range of infections
25
Q

Antifungal Drugs

A

Superficial mycoses
– Candida albicans
• causes “yeast infections” of the vagina, skin, etc.
• Nystatin – binds to sterols and damages the membrane
– Griseofulvin – disrupts the mitotic spindle and inhibits cell division
• Used to treat other superficial fungal infections – skin and nails

Treating Systemic Mycoses
• Difficult to control and can be fatal
• Three common drugs
– Amphotericin B - binds
sterols in membranes
– 5-flucytosine – disrupts RNA function
– fluconazole
• low side effects, used prophylactically
26
Q

Antiviral Drugs

A
  • Drug development has been slow because it is difficult to specifically target viral replication
  • Drugs currently used inhibit virus-specific enzymes and life cycle processes

Amantidine
– used to prevent influenza
infections
– blocks penetration and uncoating of influenza virus

Tamiflu
• anti-influenza agent
• a neuraminidase inhibitor
– an enzyme that is essential for the release of virus particles from the host cells
• though not a cure for influenza, has been shown to shorten course of illness

27
Q

Anti-HIV Drugs

A 
• Reverse transcriptase (RT) inhibitors
– nucleoside RT inhibitors
– non-nucleoside RT inhibitors
• Protease inhibitors
– mimic peptide bond that is normally attacked by the protease
• Fusion inhibitors
– prevent HIV entry into cells
• Most successful are drug cocktails to curtail resistance
28
Q

Antiprotozoal Drugs

A
  • Mechanism for drug action not known
  • Some antibiotics that inhibit bacterial protein synthesis are used against protozoa
  • Example are chloroquine and mefloquine for malaria
29
Q

Mechanisms of Bacterial Resistance to Antimicrobial Drugs

A

– an enzyme is produced that destroys or deactivates the drug
• example: β-lactamase
– the drug is inhibited or prevented from entering the cell
• example: alteration in cell wall porin
– the antimicrobial drug is pumped out of the cell before it can act
• example: efflux pumps
– there is an alteration of the target for the drug, so that the drug can no longer bind or attach to the target
• example: mutation in ribosome
– a metabolic pathway is shut down or an alternative pathway is used

30
Q

Electron Carriers

A
  • NAD
  • NADP
  • FAD
  • FMN
  • Coenzyme Q
  • Cytochromes
  • Nonheme iron-sulfur proteins

Micriobiology (1 decks)

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