Flashcards in Infectious Dz - Antibiotic Review Deck (103)
What do bacteriostatic antibiotics do?
They stop bacterial growth by interfering with protein synthesis and metabolism
What do bactericidal antibiotics do?
The kill bacteria by interfering with cell wall or nucleic acid synthesis
What antibiotics are bacteriostatic?
Chloramphenicol, sulfanomides, trimethoprim, clindamycin, doxycycline, and macrolides
What antibiotics are bactericidal?
Beta-lactams, fluoroquinolones, aminoglycosides, Timethoprim sulfas (which is the combo of sulfanomides and trimethoprim), vancomycin, and metronidazole
When will the classification of an antibiotic (static or cidal) influence your choice of antibiotic?
If there are life-threatening infections or an immunocompromised individual
What is the minimum inhibitory concentration (MIC)?
The lowest concentration of an antimicrobial that will inhibit bacterial growth
What factors does the in vitro value not take into account?
In vivo factors - Antibody in the serum, urine, and bile, pH of the infected environment, and presence of biofilms
What is efficacy of an antibiotic related to?
the amount of time that the antibiotic concentration is above the MIC
What maximizes efficacy of antibiotics?
Multiple daily doses, continuous administration, OR giving a single daily (high) dose
What antibiotics are time-dependent?
Penicillins, cephalosporins, carbapenems, macrolides, lincosamides, and tetracyclines
What antibiotics are concentration dependent?
Fluoroquinolones, aminoglycosides, and metronidazole
What four antibiotics/groups are part of the beta lactam structural group?
Penicillins, cephalosporins, carbapenems, and monobactams
Are the beta lactams cidal or static? Time or concentration dependent?
Cidal and time-dependent
How do beta lactams work?
They block cell wall synthesis by inhibiting penicillin-binding proteins
How are beta lactams metabolized?
They are renally excreted - high concentrations in the urine
What forms of penicillin do we use in small animals?
Amoxicillin/ampicillin and Ticarcillin
What is the spectrum of activity of penicillins?
Excellent activity against Gram + and anaerobes
Some gram - efficacy
Not effective against Pseudomonas
What enzyme do gram - bacteria produce that inactivates beta-lactam antibiotics?
What can extend the efficacy of penicillins against beta lactamase inhibitors?
Clavulanic acid (Clavamox) and Sulbactam (Unasyn)
What generation of cephalosporins has the most activity against gram negative organisms?
4th generation - activity increases with the generation
What is the spectrum of cephalosporins?
Effective against Gram positives
Resistant to all Gram + beta-lactamases
What carbapenems are used in small animal medicine?
Imipenem and Meropenem
What 'effect' do carbapenems have that other beta-lactams don't have?
a post-antibiotic effect
What are Carbapenems effective against?
Gram negative and positive bacteria - there is little resistance as of now because these drugs are reserved for serious infections (the big guns)
How are Carbapenems formulated?
In IV and SQ routes because there is poor oral absorption
Uses of Carbapenems should be limited to what?
Serious multi-drug resistant gram - infections and in immunocompromised individuals
What glycopeptide do we use in small animal medicine?
Is Vancomycin static or cidal? Time or concentration dependent?
Cidal and time-dependent
How do glycopeptides work?
They inhibit cell wall synthesis by binding amino acids used in its synthesis