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Chapter 16: Penicillin-Family Antibiotics


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What does penicillin do biologically?
Beta-lactam ring inhibits the transpeptidase enzyme, arresting cell wall synthesis --> bacteriacidal.
How can bacteria defend themselves from the penicillin family - 3 ways?
1. Gram (-) bugs can alter their porins preventing penicillin penetration
2. Bacteria can have beta-lactamase enzymes
3. Bacteria can alter the molecular structure of the transpeptidase so the beta-lactam can't bind
Describe the possible manifestations of an anaphylactic reaction to penicillin?
Bronchospasm, urticaria, anaphylactic shock. Delayed rash is most common.
List the 5 types of penicillins?
Penicillin G, aminopenicillins, penicillinase-resistant penicillins, anti-pseudomonal penicillins, and cephalosporins.
When is Penicillin G currently used?
Pneumonia caused by Strep pneumo.
Strep pharyngitis.
Describe the coverage of aminopenicillins?
Broader than Penicillin G, hitting more gram (-)'s. In particular, E coli and the other enterics. Also effective against the gram (+) enterococcus.
Which penicillin-family antibiotic is taken orally and used in the outpatient treatment of bronchitis, UTIs, and sinusitis?
What is the ampicillin-gentamicin combo used for?
Broad gram (-) coverage.
Which penicillin-family antibiotics is taken orally and used in the outpatient treatment of bronchitis, UTIs, and sinusitis?
What are methicillin, nafcillin, and oxacillin?
Penicillinase-resistant drugs that can kill Staph aureus.
What type of drugs are cloxacillin and dicloxacillin?
Penicillinase-resistant penicillins.
Describe the coverage of anti-pseudomonal penicillins?
Expanded gram-negative rod coverage, especially against pseudomonas. Also active against anaerobes (Bacteroides) and many gram (+)s.
What are the "pip and gent" and "ticar and gent" antibx combos used against?
Clavulanic acid and sulbactam are what type of antibxs? What's their coverage?
Beta-Lactamase inhibitors - provide broad coverage against the beta-lactamase producing gram (+)s, gram (-)s, and anaerobes.
The newer cephalasporins are less effective against...?
Gram (+)s.
Which bugs are resistant to all cephalosporins?
MRSA and the enterococci.
Cephalothin, cefazolin, cephalexin - what type of antibxs?
1st generation cephalosporins.
Cefamandole, cefuroxime, and cefoxitin - what type of antibxs?
2nd generation cephalosporins.
Ceftriaxone, ceftazidime, ceftibuten - what type of antibxs?
3rd generation cephalosporins.
Name the 4th generation cephalosporin?
When are 1st generation cephalosporins used?
Alternatives to penicillin for staph and strep infections. Prophylaxis against skin infections before surgery.
What is a good class of agents for community-acquired bacterial pneumonia with negative sputum? Why?
2nd generation cephalosporins (cefuroxime), with good coverage of Strep pneumo and H flu.
Which antibxs are used for the multi-drug resistant aerobic gram (-) organisms that cause nosocomial pneumonia, meningitis, sepsis, and urinary tract infections?
3rd generation cephalosporins
Which antibx has the best CSF penetration?
Imipenem - what is it?
A new class of beta-lactam antibx that has the broadest antibacterial activity of them all.
Which bugs are resistant to Imipenem?
MRSA, some Pseudomonas, ajd mycoplasma (no cell walls)
What agent must be given alongside imipenem? why?
Cilastin - inhibits the digydropeptidase that the normal kidney produces that breaks down imipenem.
What is Aztreonam? It is a magic bullet for which bugs?
Monobactam. Effective against gram (-) aerobic bacteria.

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