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MBIO 345 > Module 6 > Flashcards

Module 6 Flashcards

1
Q

What are most antimicrobial agents?

A

Antibiotics or chemically reproduced agents

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2
Q

What are the criteria for clinical use of antimicrobials?

A

Selective toxicity

Shouldn’t cause allergic reactions

Soluble in body fluids and capable of penetrating infected tissue

Microorganisms shouldn’t readily develop resistance

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3
Q

How can antimicrobials be described?

A

In terms of activity (broad or narrow)

In terms of effect (bactericidal or bacteriostatic)

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4
Q

What are the modes of action of antimicrobials?

A 
Cell wall synthesis
Protein synthesis 
DNA/RNA synthesis
Cell membrane function
Other metabolic processes
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5
Q

What are the two major groups of beta lactam antibiotics?

A

Penicillins and cephalosporins

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6
Q

What is the mode of action of beta lactam antibiotics?

A

Ring structure combined with cell wall enzymes (PBPs) so no cross linking occurs, the cell wall weakens and the cell dies.

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7
Q

What are the different types of penicillins and their characteristics?

A

Natural- narrow G+ spectrum, sensitive to B-lactamase, penicillin G and V, class concept applies

B-lactamase resistant- bulky side chain protects from B-lactamase, narrow G+ spectrum, resistant bacteria can alter PBPs, eg) cloxacillin, class concept applies

Extended spectrum- amine group added to side chain, broad spectrum (better for G-), sensitive to B-lactamase, amoxicillin and ampicillin, class concept applies

Anti-pseudomonal- increased activity against amp-resistant, carboxypenicillins and ureidopenicillins, broad spectrum (better for G-), sensitive to B-lactam are, class concept doesn’t apply

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8
Q

How do cephalosporins differ in action from penicillins?

A

B-lactam ring is fused to a different structure

More resistant to B-lactamase

Easier to manipulate

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9
Q

What are the different generations of cephalosporins and their characteristics?

A

1st- broad spectrum (more G+), class concept applies, cephalothin and cefazolin

2nd- broad spectrum (increased G-), no class concept, cefador, cefonicid, cefotiam

3rd- broad (less G+), no class concept, crosses BBB easier, cefixime, cefotaxime, ceftizoxime, cefoperazone

4th- broader spectrum, cefipime (less likely to induce resistance), cepirome

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10
Q

What is the “other” B-lactam antibiotic and what are its characteristics?

A

Aztreonam

B-lactam core with no ring structure

Attaches to PBPs

Narrow G- spectrum (ineffective against anaerobes)

Effective against enteriobacteriaceae and pseudomonas

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11
Q

What are B-lactamase inhibitors?

A

Weak antibiotics, inhibit some B-lactamases

Given in combination with B-lactam antibiotics

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12
Q

What are the two types of B-lactamase inhibitors and what are they given with?

A

Clavulanic acid- given with amoxicillin or ticarcillin

Sulbactan- given with ampicillin

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13
Q

What are extended spectrum B-lactamases?

A

Enzymes that mediate resistance to extended spectrum (gen 3) cephalosporins.

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14
Q

What bacteria produce ESBLs?

A

G-

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15
Q

What if a microorganism is positive for ESBLs?

A

All penicillins, cephalosporins and aztreonam should be reported as resistant.

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16
Q

What other antimicrobials act against the cell wall? What are their characteristics?

A

Imipenem- carbapenum class, resistant to most B-lactamases, binds PBPs, broadest spectrum, not effective against MRSA or VRE

Vancomycin- glycopeptide class, binds cell wall precursors, not affected by B-lactamase, narrow G+, reserved for MRSA, C. diff and resistant enterococcus

Teicoplanin- similar to vancomycin

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17
Q

What are antimicrobial agents?

A

Chemotherapeutic agents used for the treatment of infectious diseases.

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18
Q

How do antimicrobials that inhibit protein synthesis work?

A

They function where tRNA brings amino acids into place in the ribosomes.

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19
Q

Why aren’t antimicrobials that target protein synthesis excessively toxic?

A

Bacterial ribosomes differ from human.

20
Q

What antimicrobials inhibit protein synthesis?

A

Erythromycin

Clindamycin

Chloramphenicol

Tetracyclines

Aminoglycosides

21
Q

Describe the characteristics of erythromycin.

A

Macrolides group

Binds 50S subunit to stop amino acid addition and halt protein synthesis.

Bacteriostatic

Narrow G+ spectrum

Absorbed into tissues except CNS

Destroyed by gastric acid, vomiting

22
Q

Describe the characteristics of clindamycin.

A

Lincosamide group

Better absorption and penetration than erythromycin

Effective against anaerobics

Diarrhea in 20% of patients, may develop pseudomembranous colitis

23
Q

Describe the characteristics of chloramphenicol.

A

Small molecule with nitrobenzene ring and small side chain.

Competes with erythromycin to bind 50S subunit

Broad spectrum, G+ and some enteriobacteriaceae

Penetrates most tissues

Very toxic, reserved for when other antimicrobials can’t be used

24
Q

What are some side effects of using chloramphenicol?

A

Gray syndrome- toxic levels of the antimicrobial accumulate

Aplastic anemia- marrow asplasia

Dose-related marrow depression

25
Q

Describe the characteristics of tetracyclines.

A

Core of four fused ring structures

Bind 30S subunit to prevent tRNA-mRNA binding and inhibits protein synthesis

Bacteriostatic

Broad spectrum

May be taken orally

Ex) terramycin, doxycycline, minocycline

26
Q

What are some cons of tetracyclines?

A

Milk prevents absorption

Shouldn’t be given to children

Interferes with birth control action

27
Q

Describe the characteristics of aminoglycosides.

A

Amino sugars linked by glycosidic bonds

Bind 30S unit, interrupts protein synthesis

Bactericidal

Unable to penetrate cells in a reduced oxygen state, ineffective against anaerobes

No CNS penetration

Uptake facilitated by B-lactam antibiotics (synergists)

Broad spectrum

28
Q

What tissues are aminoglycosides toxic to?

A

Kidney tissues

8th cranial nerve

29
Q

What are some examples of aminoglycosides?

A

Kanamycin

Gentamycin

Tobramycin

Amikacin

Spectinomycin

30
Q

Does class concept apply to aminoglycosides?

A

Nope

31
Q

What antimicrobials inhibit DNA and RNA synthesis?

A

Fluoroquinolones

Nalidixic acid

Metronidazole

Polymixins

32
Q

Describe the characteristics of fluoroquinolones.

A

Quinolone class

Two rings modified with different side chains and substitutions including a fluoride

Binds and interferes with DNA gyrase preventing normal unwinding and replication

Bactericidal

Broad spectrum

33
Q

What are some examples of fluoroquinolones?

A

Ciprofloxacin

Norfloxacin

34
Q

What are the draw backs to fluoroquinolones?

A

Irreversible cartilage and skeletal damage.

35
Q

Describe the characteristics of nalidixic acid.

A

Quinolone antibiotics

Broad spectrum (G- and enterococci)

Concentrations in blood too low to be effective

Treats UTI

36
Q

Describe the characteristics of metronidazole (flagyl).

A

Anaerobic infections

Breaks up DNA

Bactericidal

Used for protozoan infections too

37
Q

Describe the characteristics of polymixins.

A

Polypeptide group

Binds cell membrane, causes cell lysis

Bactericidal

Narrow spectrum (G-)

38
Q

What are polymixins used for?

A

Inhibiting G- growth in media

Gram reaction

39
Q

What tissues are polymixins toxic to?

A

Neutrons and kidneys

40
Q

What are some examples of polymixins?

A

Polymixin B

Polymixin E (colistin)

41
Q

What antimicrobials inhibit other metabolic processes?

A

Sulfonamides

Trimethoprim

Nitrofurantoin

42
Q

What are the characteristics of sulfonamides?

A

Derivative of para-aminobenzene sulfonamide (similar to PABA)

Prevents folic acid synthesis from PABA

Competition inhibition

Bacteriostatic

Broad spectrum

43
Q

What antimicrobial do sulfonamides act synergistically?

A

Trimethoprim

44
Q

What infections do sulfonamides treat?

A

UTIs

45
Q

What are the characteristics of trimethoprim?

A

Interferes with folic acid production from PABA by competitive inhibition

Broad spectrum

Combines with sulfamethoxazole to form cotrimoxazole

Treats UTIs

46
Q

What are the characteristics of nitrofurantoin?

A

Nitrofuran group

May damage DNA or interfere with protein translation enzyme

Broad spectrum

Levels in blood are low but effective against UTIs

MBIO 345 (11 decks)

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