Packet 2 Flashcards
What are some drugs in the beta-lactam group?
Penicillins (large group)
Cephalosporins
Carbapenems
Monobactams
What are some other cell wall synthesis inhibitors that are not beta-lactams?
Vancomycin Bacitracin Cycloserine Polymyxins Fosfomycin Daptomycin Telavancin
What are some beta-lactamase inhibitors?
Clavulanic acid
Sulbactam
Tazobactam
What do cell wall synthesis inhibitors do?
Kill bacteria (bactericidal) that are dividing and growing
What are the 3 classes of Penicillins?
- Natural penicillins (Penicillin G)
- Antistaphylococcal penicillins (Nafcillin)
- Extended spectrum penicillins (Ampicillin and the antipseudomonal penicillins)
What is the MOA of penicillins?
They inhibit the cross-linking step in the synthesis of bacterial cell walls. They inactivate a transpeptidase which is normally responsible for cross-linking the linear glycopeptide strands of bacterial cell walls. They are bactericidal causing cell lysis and death.
What type of organisms are needed in order for penicillins to work the best?
Rapidly growing organisms with a peptidoglycan cell wall.
-These organisms do NOT have these structures and therefore are inactive against these: Mycobacteria, fungi, protozoa, and viruses.
What are the 3 steps that are taken in the process of cell wall disruption by penicillins?
- Penicillins bind to enzymes involved in cell wall synthesis called Penicillin binding proteins (PBPs).
- Some PBPs are transpeptidases which help in the cross-linking of cell wall chains. When the penicillin binds to the transpeptidase it causes blocking of the cross-linking.
- Gram-positive cocci also produce degradative enzymes called autolysins that help in the remodeling of the cell wall if something goes wrong. Penicillins have also been found to bind to these autolysins, causing self-destruction.
Gram __(+/-)__ bacterial cell walls are easily transversed by penicillins.
Gram+
Why don’t penicillins affect gram negative bacteria?
Gram negative bacteria have an extra outer wall known as the LPS. This LPS layer blocks the penicillin from entering on its own. The lipid filled channels (porins) on the outer membrane are needed in order for penicillin to enter. This is why penicillins differ in their capability for entry between gram+ and gram- bacteria.
What are the natural penicillins?
Penicillin G and Penicillin V
What type of infections is penicillin G used for?
Treponemal and clostridium infections
What bacteria is penicillin G good to treat against (more general groups not specific names per say)?
Gram + cocci and gram+ bacilli, Gram- cocci and spirochetes. Also, many oral anaerobes are susceptible
T/F - Penicillin G is NOT susceptible to beta lactamases.
FALSE - Penicillin G IS susceptible to beta lactamases. They are also unstable at acidic pH and gastric environment inactivates it.
What is the drug of choice for gas gangrene usually due to Clostridium perfringens?
Penicillin G (in combination with Clindamycin)
What drug is used in diphtheria for acute and chronic carrier states?
Penicillin G
It is also used in anthrax, actinomycosis, and listeria infections.
What drug is highly active against Treponema palladium (syphilis) with no resistance?
Penicillin
If a patient was to have syphilis and was penicillin allergic, what would be the drug of choice (hint: more than one drug)?
Benzathine penicillin and doxycycline
Penicillin G is used in conjunction with __________ in order to achieve a bactericidal effect when treating enterococcal endocarditis.
Aminoglycosides
What are two forms of repository penicillin (insoluble salts)?
- Benzathine penicillin (can provide effective blood levels for up to a week)
- Procaine penicillin G
Which natural penicillin is more stable in acidic environment and is the oral form of penicillin?
Penicillin V
It is used for oral infections against anaerobes and in only minor infections because of poor bioavailability (4x/day).
Of the two penicillins that are natural which one has a high minimal lethal concentration, and is therefore not a good choice in bacteremia?
Penicillin V
Penicillin V and G should be administered when (in relation to eating)?
Should be administered at least 1 hour before meals or 2-3 hours after meals since food interferes with absorption.
The simultaneous administration of ____________ prolongs the duration of penicillin in the body due to proximal renal tubule blockage and reduced drug excretion.
probenecid
_____% of penicillin G and pencil V are eliminated via the kidney.
99%
Prophylactic uses of penicillins.
- Streptococcal infections
- Rheumatic fever recurrences
- Gonorrheal ophthalmia in neonates
- Surgical procedures in patients with valvular disease
- Dental extractions, tonsillectomy, and intestinal and genitourinary operations
- Bacteremia is not totally prevented by using prophylactic penicillin.
Antistaphylococcal penicillins are resistant to ___________________________.
Staphylococcal beta lactamases.
_________________ penicillins are active against staphylococci and streptococci but inactive agains enterococci, anaerobic bacteria, and gram-negative cocci and rods.
Antistaphylococcal
Name the anti staphylococcal penicillins.
Methicillin (not in US) Nafcillin Oxacillin Cloxacillin Diclocillin
NAF is on METH and CLOX the OX with his DIC
T/F - Antistaphylococcal drugs are beta-lactamase resistant.
True
-Therefore, they are indicated against staphylococci that are penicillinase producing.
In Staphylococci that are penicillinase positive, what drug should be used instead?
Any of the antistphylococcal drugs
Methicillin Nafecillin Oxacillin Cloxacillin Diclocillin
Which of the anti staphylococcal drugs is nephrotoxic and rarely used? (hint: not available in the US)
Methicillin
Which anti staphylococcal drug is given orally because it is acid stable? It is also 8 times as potent than methicillin.
Oxacillin
-Ox is big and a lot of ppl eat ox
Which anti staphylococcal drug is given via all routes but can cause neutropenia and phlebitis?
Nafcillin
Which anti staphylococcal drug is highly resistant to penicillinases and is very effective orally?
Dicloxacillin
For serious systemic staphylococcal infections which two anti staphylococcal drugs are given by intermittent intravenous infusion?
Oxacillin or Nafcillin
Resistant strains of bacteria that are usually of nosocomial origin are usually susceptible to __________________.
Vancomycin
Why are extended spectrum penicillins called that?
Because while retaining the antibacterial spectrum of penicillins, they are also effective against gram negative bacilli.
Are extended spectrum penicillins resistant to beta-lactams?
NO - they are destroyed by beta-lactams
What are the extended spectrum antibiotics?
Amoxicillin and Ampicillin
What is the drug of choice for Listeria (aerobic/facultative anaerobic gram positive bacilli)?
Ampicillin
What drug is given orally only and achieves higher blood levels and lower incidence of diarrhea than penicillin?
Amoxicillin
What drug is used prophylactically for patients with abnormal heart valves who are to undergo oral surgery?
Amoxicillin
Which of the extended spectrum penicillins is acid stable, but NOT penicillinase resistant?
Ampicillin
-Amoxicillin on the other hand IS penicillinase resistant!
Due to ________ mediated penicillinases, organisms like E. coli and H. influenza usually develop resistance.
Plasmid mediated
What type of things are added to help protect drugs from hydrolysis?
Beta lactamase inhibitors: Clavulanic acid, Sulbactam and Tazobactam
Use of Ampicillin and _________ are commonly used for treating intra-abdominal and gynecological infections.
Sulbactam (Unasyn)
