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Bacteriology > Antibiotics - Cell Wall Inhibitors > Flashcards

Antibiotics - Cell Wall Inhibitors Flashcards

1
Q

How do beta-lactams work?

A

Inhibit transpeptidation in cell wall formation and activate autolysins in cell walls.

They bind to PBPs (penicillin binding proteins), which are responsible for building the cell walls.

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2
Q

How can bacteria be resistant to beta-lactams?

A
  • Beta-lactamases
  • Lack of PBPs (penicillin binding proteins)
  • Autolysin mutations
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3
Q

List some (broad category) classes of beta-lactams.

A

Penicillins, Cephalosporins, Monobactams, Carbapenems

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4
Q

The two natural penicillins are _______ and they are best again _____ bacteria.

A

penicillin G (IV) and penicillin V (oral); G+

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5
Q

Some examples of beta-lactamase resistant penicillins are (3) __________, but they have lower activity.

A

Nafcillin, oxacillin, cloxacillin

NOT effective against MRSA (methicillin-resistant Staph aureus)

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6
Q

Expanded/broad spectrum penicillins (effective against G+ and G-) are:

A
  • Ampicillin
  • Piperacillin
  • Mezlocillin
  • Ticarcillin (vs. Pseudomonas)
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7
Q

Acid resistant (oral) penicillins include:

A

Amoxycillin, Penicillin V, Oxacillin

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8
Q

Sometimes, penicillins are used together with beta-lactamase inhibitors. Some examples are (3):

A
  • Augmentin (amoxicillin + clavulanic acid)
  • ampicillin + sulbactam
  • Zosyn, Taxomed (piperacillin + tazobactam)
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9
Q

Cephalosporins are _____ sensitive to beta-lactamases than penicillins.

A

Less!

Great work, guys.

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10
Q

1st Generation Cephalosporins:

List the types of bacteria they are effective against and some examples of 1st generation.

A

G+ action, for prophylaxis only

Cephalexin, cephalothin, cefazolin

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11
Q

2nd Generation Cephalosporins:

List the types of bacteria they are effective against and some examples of 2nd generation.

A

G+ and G- action (including Bacteroides, NOT Pseudomonas)

Cefaclor, cefuroxime, cefoxitin

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12
Q

3rd Generation Cephalosporins:

List the types of bacteria they are effective against and some examples of 3rd generation.

A

G+ and G-, including Pseudomonas. Used mostly for G- to avoid overuse; can penetrate CNS (meningitis treatment).

Ceftazidime, cephotaxime, cephtriaxone, cefdinir

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13
Q

Why are the 3rd generation cephalosporins special?

A

Because their mother said so.

Broad spectra!, G+/G-, Pseudomonas treatment, MRSA/VRE, can cross BBB

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14
Q

4th Generation Cephalosporins:

List the types of bacteria they are effective against and some examples of 4th generation.

A

Slightly expanded spectrum from 4th gen (broadest of all!)

Cefepime

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15
Q

5th Generation Cephalosporins:

List the types of bacteria they are effective against and some examples of 5th generation.

A

Still has a broad spectrum… Activity vs. MRSA, drug-resistant Staph pneumoniae (but not Pseudomonas)

Ceftaroline

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16
Q

Describe the structure of monobactams and why it is important.

A

Monocyclic beta-lactam ring; resistant to beta-lactamases.

17
Q

What type of bacteria are monobactams effective against?

What is an example?

A

G- ONLY (not G+ or anaerobes)

Aztreonam

18
Q

What type of bacteria are carbapenems effective against?

A

Broad spectrum (G+ and G-)

19
Q

What is a potential problem with carbapenems? List some examples of carbapenems.

A

Can be toxic!

Imipenem, ertapenem, meropenem (reduced toxicity)

20
Q

Beta-lactams have side effects. Sad, but true! Rank the severity of allergic reactions among a few beta-lactam drugs.

A

Penicillin > cephalosporins > monobactams

21
Q

Beta-lactams have side effects. Sad, but true! Rank the severity of toxicity among a few beta-lactam drugs.

A

Carbapenems (seizures) > cephalosporins (thrombophlebitis) > penicillin > monobactams

22
Q

How does Bacitracin work?

A

Blocks dephosphorylation of bactoprenol (a lipid important in synthesis of peptidoglycan for the cell wall).

23
Q

What are uses of bacitracin?

A

Mainly topical vs. G+ (way too large in size for G-)

Often used in conjunction with others (triple antibiotic ointment: BAC, NEO, PMB)

24
Q

What are some side effects of bacitracin?

A

Poorly absorbed, renal toxicity

25
Q

How do glycopeptides work?

A

Bind to end of amino acid side chain in developing cell wall; block transglycosylation as well as transpeptidation

(in addition, telavancin inserts in membrane and collapses pH gradient…which sounds epic)

26
Q

What are some examples of glycopeptides? (2)

A

Vancomycin, telavancin

27
Q

How can bacteria develop resistance to glycopeptides?

A

Use -ala-lactate (rather than -ala-ala) to end pentapeptide side chain

Chromosomal (vanB) and plasmid (vanA) genes

28
Q

What are uses of glyocpeptides?

A

Treatment of only G+ (Staphylococci, Enterococci)…NOT G- (can’t get through pores)

Drugs must be injected.

29
Q

Other Drugs:

Cycloserine is a D-ala analong, so inhibits _______.

A

Alanine racemase

Neurotoxic - use carefully
Sometimes used for UTI
2nd line drug against TB

30
Q

Other Drugs:

Fosfomycin inhibits synthesis of ________ from ________.

A

UDP-MurNAc; UDP-GlcNAc

Good against UTI
Resistance by loss of transporter
Resistance develops quickly; use in short-term in one large dose

31
Q

What are some special drugs used to treat Mycobacterium?

A

INH, EMB, PZA, RMP, BDQ

Isoniazid/ethionamide
Ethambutol
Pyrazinamide
Rifampicin
Bedquiline
32
Q

Mode of action for isoniazid, ethionamide:

A

Inhibit pyridoxine step in mycolic acid synthesis (often taken with pyridoxine)

33
Q

Mode of action for ethambutol:

A

Inhibits arabinogalactan (mycolic acids in outer membrane) synthesis (rapid resistance, so use with other antibiotics)

34
Q

Mode of action for pyrazinamide:

A

Activated by Mycobacteria enzyme; inhibits trans-translation (pathway necessary to restart stalled ribosomes during stress response)

35
Q

Mode of action for rifampicin:

A

…he didn’t cover in this lecture. Sorry, team.

36
Q

Mode of action for bedaquiline:

A

Blocks mycobacterial ATP synthase (c subunit) - used to treat mulit-drug-resistant TB

Bacteriology (18 decks)

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