Antibiotics - classes Flashcards
2 major beta lactams (and thus cell wall synthesis inhibitors)
Penicillin and cephalosporins
What does a beta lactam do to a bacteria (MOA)
Cell wall inhibitor. Prevents the cell wall from forming properly. But the bacteria must be actively dividing and growing in order for this group to work
How do beta lactams differ from each other
The R group (functional group) on the 6-aminopenicillanic acid - garage of the house:)
What is the MOA for penicillin
Interferes with transpeptidation cross-linkage (cell wall cannot connect properly). Which eventually will lead to cell lysis
What other ways to penicillins target bacteria
- Penicillin binding proteins
- Inhibition of transpeptidase
- Production of autolysins
How do penicillin binding proteins work
Penicillin inactivates proteins on the bacteria cell membrane that are involved with cell wall synthesis (these proteins can cause resistance if the bacteria starts to alter them)
How do the autolysins play a role in bacterial cell destruction
Penicillins prevent transpeptidase from linking, but the bacteria still produces enzymes that normal break down and rebuild the cell wall (autolysis). Thus the autolysins continue to produce even after the penicillin as interfered with the cell wall link which leads to faster cell lysis.
What type of bacteria do beta lactams work well on
Gram + streptococcus
What is the biggest clinical application of beta lactams
Pneumonia (streptococcus pneumonia)
What other types of bacteria can penicillin be used against
- Limited gram (-). Neisseria group
- Syphilis - spirochetes
- Anaerobes: oral only!!
What are the natural penicillins
Penicillin V
What are the extended spectrum penicillins
- Ampicillin
2. Amoxicillin
What factors contribute to the antibacterial spectrum of a penicillin
- Ability to cross the peptidoglycan cell wall to reach PBP
2. Size, charge, and lipophilic nature of ABX
What is meant by extended spectrum penicillins
Means that some ABX that are in the penicillin group are more effective against gram (-) bacteria. Ampicillin/amoxicillin
What is the clinical use of the extended spectrum penicillins (amox/amp)
Respiratory infections and prophylactically by dentists for patients with abnormal heart valves.
Types of penicillins (full spectrum)
- Natural
- antistaphylococcal
- Extended-spectrum
- Antipseudomonal
What drugs does penicillin have a synergistic effect with
- clauvonic acid - inhibitor of beta lactamase, which means the penicillin can still do its job
- aminoglycosides - penicillin helps facilitate the entry of other drugs
How do you determine the route of administration with penicillins
Stability of the drug in stomach acid and the severity of the infection
Routes of administration of beta lactams
IM/IV/Oral. Penicillin can only be given orally
Absorption characteristics of penicillins
Incompletely absorbed, which means they will reach the intestines. However, amoxicillin is almost completely absorbed which is not effective in treating bugs that affect the lower GI tract
Distribution of penicillins
- Distribute well
- Penicillins cross the placental barrier
- Poor bone and CSF penetration
How are penicillins excreted
Tubular secretion in the kidneys
Adverse reactions of penicillins
- hypersensitivity - metabolite penicilloic acid, creates an immune reaction
- Diarrhea
- Nephritis
- Neurotoxicity - seizures
- Hematologic toxicities
- High Na+/K+ levels
Which beta lactam is more resistant to Beta lactamases
Cephalosporins
How are cephalosporins classified
1,2,3,4 generation based on their bacterial susceptibility patterns and resistance to beta lactamases
First generation
Best for gram +: Staph, strep, and a few gram (-): e-coli, proteus
Second generation
Mostly gram +. Greater activity against gram (-) and some neisseria
Third generation
Increased activity against gram (-). Very good against meningitis. Very prone to bacterial resistance
Fourth generation
Wide spectrum across both gram +/-. Cefepime is the only one approved in the US. Very good against Staphaureus
What is the MOA for cephalosporins
Same as penicillins. Inhibits cell wall synthesis