BETA-LACTAMS Antibiotics

14 Questions

What is the primary mechanism of action of beta-lactam antibiotics?

Binding to penicillin-binding proteins and inhibiting cell wall crosslinking

What is a common side effect of beta-lactam antibiotics?

Hypersensitivity reactions

Which of the following beta-lactam antibiotics has activity against MRSA?

Ceftaroline

Why are oral beta-lactams often poor choices for serious or deep-seated infections?

They have poor bioavailability and achieve low serum concentrations

What is the characteristic of beta-lactam antibiotics in terms of their killing mechanism?

Time-dependent killing

What is the name of the group of organisms that have inducible, chromosomal beta-lactamases and may lead to resistance to beta-lactams?

SPICE-A

Which of the following beta-lactam antibiotics is not affected by the inducible, chromosomal beta-lactamases of the SPICE-A organisms?

Carbapenems

Why are beta-lactam antibiotics preferred in many situations?

They have high efficacy and are bactericidal

What is the main reason why beta-lactams are not effective against atypical intracellular organisms?

They are not able to inhibit cell wall synthesis because atypical intracellular organisms lack a cell wall

What type of infections is Penicillin G or V commonly used to treat?

Strep throat and Syphilis

Which of the following bacteria is universally sensitive to Penicillin?

Group A Strep

What is the primary indication for using Penicillin G or V in pregnant women?

Syphilis treatment

Which of the following is NOT a typical spectrum of activity for Penicillin G or V?

Most strains of Gram-negative bacteria

What type of infections may require desensitization to Penicillin in some cases?

Neurosyphilis or pregnant women

Study Notes

Beta-Lactams

Beta-lactams include PCNs, Cephalosporins, Carbapenems, and Monobactam (Aztreonam)
They inhibit cell wall crosslinking by binding to Penicillin-binding proteins (PBPs) in the cell membrane, making them bactericidal

Side Effects

Hypersensitivity reactions, including anaphylaxis
Rashes
Bone marrow suppression
Interstitial Nephritis
GI symptoms: nausea, diarrhea, and C. diff
Seizures (mainly with high doses in renal failure)

Preferred Use

Beta-lactams are the preferred drug choice for most situations due to high efficacy and cidal nature, as long as the pathogen is susceptible and the patient is not allergic

Pharmacokinetics

Most oral beta-lactams have poor bioavailability and achieve low serum concentrations, making them poor choices for serious or deep-seated infections
Amoxicillin has the best bioavailability among oral beta-lactams

Limitations

No beta-lactam has activity against MRSA, except Ceftaroline
No beta-lactam has activity against atypical intracellular organisms (e.g., Legionella, Mycoplasma, Chlamydia)

Pharmacodynamics

Beta-lactams exhibit time-dependent killing, meaning efficacy depends on the amount of time the drug concentration is above the MIC

Inducible Resistance

SPICE-A organisms (Serratia, Pseudomonas/Providencia, Indole-positive Proteus, Citrobacter, Enterobacter, and Acinetobacter) have inducible, chromosomal beta-lactamases (AmpC) that may not be detected on initial susceptibility testing
These beta-lactamases can lead to resistance while on therapy to all beta-lactams except carbapenems
Cefepime and Piperacillin/Tazobactam can be used with caution as well

Penicillins

Penicillin G is administered intravenously (IV), while Penicillin V is administered orally (PO)

Spectrum of Activity

Effective against many strains of Streptococci, including Group A Strep (universally PCN sensitive)
Effective against a minority of Staphylococci (most are resistant)
Effective against some Enterococcus and most oral anaerobes
Effective against Syphilis (universally PCN sensitive)

Indications

Treats Strep throat and other infections caused by Group A Strep
Treats Syphilis (must desensitize to PCN for neurosyphilis or pregnant women)
Treats bacteremia and endocarditis caused by PCN sensitive Streptococcus, Enterococcus, or Staph aureus