Bact cell wall synth inhibitor Flashcards by Joy S

Name 2 classes of bacterial cell wall synthesis inhibitors.

Beta-lactams, Glycopeptide

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Beta lactams bind to the active site of which enzyme?

Transpeptidase (penicillin binding protein)

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Effect of beta lactams

Bacteriocidal on actively growing cells

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Name 4 types of beta lactams

Penicillins, cephalosporins, carbapenems, monobactam

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Name the 4 classes of penicillins

natural penicillins (Pen G and Pen V),
penicillinase resistant penicillins (cloxacillin, flucloxacillin),
aminopenicillins (amoxicillin, ampicillin),
antipseudomonal penicillins (piperacillin)

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Which natural penicillin is administered parenterally?

Penicillin G

vs V (phenoxymethylpenicilin) oral - more acid stable

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3 types of Penicillin G

Potassium

Procaine
Benzathine
- slow release

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Syphilis caused by Treponema pallidum can be treated with which penicillin?

Penicillin G

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Natural penicillin indications

gram +ve except staph
gram -ve (meningococcus, gonorrhea)
Treponema pallidum (syphilis)–G

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What’s IV aq pencilin G used for?

Inflamed meninges– greater CSF penetration

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Are natural penicillins commonly used against Staphylococcus aureus?

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How does methicillin sensitive Staphylococcus aureus acquire resistance against the natural penicillins?

They produce penicillinases

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Which class of penicillin is commonly used against methicillin sensitive Staphylococcus aureus?

Penicillinase resistant penicillin

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Penicillinase resistant penicillin – 3 drugs

Cloxacillin
Flucloxacillin
Oxacillin

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Indications of Penicillinase resistant penicillin

Staph
Ineffective against gram -ve
if strain susceptible to penicillin G, shld use (as PRP will be less effective in this case)

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Why Penicillinase resistant penicillin ineffective against gram -ve

Bulky side group
which limits pencillinase access to catalytic site
limits entry to gram -ve bact

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Which bacteria is cloxacillin effective against?

Methicillin Sensitive Staphylococcus Aureus (MSSA)

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So since PRP cannot target gram -ve, what is used?

Aminopenicillin (broad spectrum penicillins)

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List 2 drugs under this class

Ampicillin

Amoxicillin

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Which of the aminopenicillins (amoxicillin or ampicillin) has better oral absorption?

Amoxicillin

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Why aminopenicillins can target gram -ve?

Addnal Hydrophilic group– allow penetration

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Indications of aminopenicillins

Non beta-lactamase producing strains of gram -ve/+ve bacteria

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Aminopenicillins does not cover…

Pseudomonas & klebsiella

nosocomial infections

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So you need…

Extended spectrum penicillins (antipseudomonals penicillins)

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Drug under this class

Piperacillin

How is piperacillin administered?

Indications of piperacillin

1. Pseudomonas, proteus, klebsiella 2. Anaerobes 3. Non beta-lactamase gram +ve : S pyogenes + Enterococcus

Which 2 types of penicillins are used w beta-lactamase inhibitors?

Broad spectrum- aminopenicillins (ampicillin/amoxicillin) | Extended spectrum- antipseudom p (piperacillin)

MOA of beta-lactamase inhibitors (BLI)

Clavulanic acid -- suicide inhibitor covalent bonds w beta-lactamase & restructures it Sulbactam & tazobactam- irrev bind to active site

Name 3 beta lactams- beta-lactamase inhibitor combination drugs.

1. Augmentin (Amoxicillin + clavulanic acid) 2. Unasyn (ampicillin + sulbactam) 3. Zosyn (piperacillin + tazobactam)

How are all penicillins cleared by?

Renal clearance

Name a microbe that commonly causes nosocomial infections and is resistant to all penicillins.

MRSA (methicillin resistant Staphylococcus aureus)

Mechanism of resistance to penicillin

1. PBP2a (altered transpeptidase reduced affinity for penicillins)-- MRSA 2. beta-lactamase (hydrolysis of b-l rings) 3. Increased efflux pumps 4. Decreased porins (for penicillin influx)

Name at least 2 penicillins related life-threatening allergic reactions.

1. Hypersensitivity (Anaphylaxis, SJS, TEN) 2. CDAD (clostridium difficile associated diarrhea)- BSP amox (augm)/amp 3. Neurotoxicity (esp in renal imp--> high doses seizures) 4. Hepatic toxicity (PRP ox/fluclox/cloxacillin) 5. Anosmia

Str of cephalosporin

1. modification at position 7 of BL ring associated w alteration in antibacterial activity 2. Sub at position 3 of dht ring alters metab & pk

Which generation of cephalosporins does cefazolin and cephalexin belong to?

First generation

What's the second generation cephalosporin?

Cefuroxime

Which generation of cephalosporins are primarily administered orally?

First & second generation EXCEPT cefazolin can IV

How are the 3rd, 4th and 5th generation cephalosporins administered?

Parenterally

1st to 4th generation are ineffective against?

1. Listeria monocytogenes, 2. Atypicals (Mycoplasma, Chlamydia, Legionella spp.), 3. MRSA, and 4. Enterococcus species

What are the drugs under 3rd, 4th and 5th generation cephalosporins?

3rd- ceftriaxone, ceftazidime 4th- cefepime 5th- ceftobiprole, ceftaroline

Which cephalosporins could be used for pseudomonas?

Third generation – Ceftazidime Fourth generation - Cefepime & 5th gen

Which generation of cephalosporins has coverage against MRSA?

Fifth generation (ceftobiprole, ceftaroline)

Indications for cephalosporin

First gen- Gram +ve: staph & strep **(except pencillinase producing strep + MRSA) Second gen- 1st&2nd g Cannot be used for enterococcus/pseudomonas Third gen- Enteroc, Pseud, N. gonorrhea & gram +ve ** (except Bacteroides spp.

How are most cephalosporins cleared?

Renal clearance

How is ceftriaxone cleared?

Hepatic clearance (40% bile)

What should ceftriaxone not be mixed with?

Ca2+ containing soln (eg. Hartmann's / Ringer's)

Name 3 advantages the third generation and fourth generation cephalosporins have over the first and second generations.

1. Higher activity against Gram-negative bacteria 2. Greater resistance against the beta-lactamase producing strains 3. Greater CSF penetration

What are the adverse reactions to cephalosphorins?

1. hypersensitivity 2. GIT - diarrhea (esp oral ceph) + CDAD 3. Thrombophlebitis

What are the adverse reactions to carbapenems?

1. GIT-related (N/V, diarrhea) 2. Neurotoxicity (at high blood [ ]) 3. Rashes 4. Cross hypersensitivity w pencillin

What are carbapenems prescribed for?

Commonly used against extended spectrum beta-lactamase (ESBL) producing bacteria Gram -ve & anaerobes spp.

Name 3 carbapenems.

1. Imipenem, 2. meropenem, 3. ertapenem

Carbapenems are resistant to?

MRSA

Imipenem is combined with __________, which works by __________.

Cilastatin inhibiting dehydropeptidase 1 (DHP1) found in the brush border of the proximal renal tubule. (DHP1 is necessary for the hydrolysis of imipenem. It is not a beta lactamase inhibitor.)

Which carbapenem has good CSF penetration?

Meropenem

Which of the following carbapenems is not effective against Pseudomonas aeruginosa (&enterococcus)?

Ertapenem

How are carbapenems administered?

Parenterally (as poor absorption)

If pt is allergic (anaphylaxis) to penicillin, what drugs can you not give her?// Which drug classes of beta lactams have cross reactivity with penicillins?

Cephalosporins, carbapenems (cross hypersensitivity)

Which drug class does aztreonam belong to?

Monobactam

Aztreonam is effective against Gram-

negative bacteria (no activity against Gram positive and anaerobic microbes)

Does aztreonam have cross-sensitivity to penicillin?

How is aztreonam administered?

Parenterally IM/IV

Which drug class does vancomycin belong to?

Glycopeptide- bact cell wall inhibitor

Vancomycin is useful against Gram ___________

positives

How is vancomycin commonly administered?

Intravenously

When is oral vancomycin preferred?

Clostridium difficile-associated diarrhea (CDAD) or the more severe antibiotic-associated pseudo-membranous colitis (AAPMC).

What is the first line of antibiotics for CDAD?

Vancomycin

Vancomycin interferes with cell wall synthesis by inhibiting ___________

transglycosylation | b/n Ala-Ala of NAM & NAG

Name 3 antibiotics that work by inhibiting bacterial cell wall synthesis, and are effective against MRSA?

1. ceftobiprole (Fifth generation cephalosporins) 2. ceftaroline (Fifth generation cephalosporins) 3. Vancomycin

How is vancomycin cleared?

Renal clearance

Name 3 adverse effects related to vancomycin

1. Nephrotoxicity, 2. Ototoxicity, 3. Red man syndrome (rash above nipple line due to histamine release w rapid infusion) 4. rare thrombph

How to resolve red man syndrome?

1. Antihistamine | 2. Prolong infusion vancomycin to 1-2 hrs

Vancomycin resistance due to?

substituting terminal D-alanine for D-lactate/serine reducing vancomycin binding affinity --> VREnterococcus

Vancomycin ineffective against?

all Gram -ve & mycobacteria

Bact cell wall synth inhibitor Flashcards

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