Pharmacology 3: Antibacterial agents for systemic therapy Flashcards
Minimum inhibitory concentration (MIC)
lowest concentration of drug that INHIBITS visible bacterial growth
ex. MIC90 = concen for INHIBITING 90% of the bacteria
Minimum Bactericidal Concentration (MBC)
KILLS
lowest concentration of a drug that KILLS 99.9% of bacteria
LARGER
Mutant Prevention Concentration (MPC)
LEAST susceptible single-step mutant
-theory, kills them all so mutants (resistant bacteria) can NOT form
What requires host immune response?
hint* something to do with infection
Elimination of infection
Bacteriostatic bacteria
STOP bacteria from multiplying; don’t kill them
MBC much LARGER that the MIC
Bacteriostatic NEED what to eliminate infection?
Requires host immune response
Bactericidal is preferred for what kin of patients?
Immunosuppressed
Severely ill patients
-sepsis
-neonates
-on glucocorticoids
-on cancer chemotherapy
Bactericidal
kill bacteria if concentration reach MBC for a certain period of time
- MBC at or near the MIC
A drug can be both Bacteriostatic and Bactericidal?
True
Bactericidal antimicrobials are or are NOT always bactericidal?
NOT
static at concentration below MBC
- dose dependent
- bacteria dependent
Bacteria must be dividing or multiplying for bactericidal to work
bacteria must be MULTIPLYING
Postantibiotic effect (PAE)
Persistent drug effect
- After plasma concentration decline below the MIC/MBC
What are mechanisms for Postantibiotic effect
decreased virulence of the bacteria
development of abnormal cell wall or septum
increased susceptibility to host defenses
Persistence at sites of infection
When does PAE occur?
Only with SOME drugs and is BACTERIA-dependent
What do we use pharmacokinetic and pharmacodynamic interactions for?
How we determine dosing
Drug bug interactions
PREDICT SUCCESS OF ANTIMICROBIAL THERAPIES
- Relate concentrations of drug to MIC of the pathogen
- vary by class of drug
- vary with each pathogen
PK refresher
Cmax: maximum plasma
AUC: area under the plasma concentration time curve
Pharmacodynamic targets
Time dependent antibiotics
- T>MIC: duration plasma concentration is above the MIC over 24h
Concentration-dependent antibiotics
- Cmax: MIC ratio of the maximum plasma concentration (C max) to the MIC
Concentration/Time dependent antibiotics
- AUC:MIC: ratio of the AUC0-24 to the MIC
Antibiotic mechanism of action
Cell wall: inhibit synthesis and function
NA: inhibit synthesis and function
Protein synthesis: inhibits 50s ribsomal, subunits
inhibt 30s ribosomal, subunits
Spectrum activity
describing general activity of antimicrobial
- narrow=limited subsets of bacteria
- broad=treats a lot (not always well)
–> may include mycoplasma, rickettsia, and chlamydia
Individual isolates of bacteria may be resistant to an antibacterial even though they are part of the SPECTRUM?
true
Antibacteral spectrum 4 quadrants
Aerobic
+ and -
Anaerobic
+ and -
Broad spectrum
- all four quadrants
- other categories
Intermediate spectrum (NOT *)
- 2-3/4 quadrants
Narrow spectrum
- 1-2/4 quadrants
Davis 6 quadrants antibacterial spectrum
Aerobic bacteria
- gram +
(step and staph) ococci
- gram -
respiratory pathogens
enteric pathogens
Anaerobic bacteria
- gram +
- gram -
PENICILLINS
- activate against streptococci, NOT most staphylococci
- NOT active against gram -
- active against most gram + and gram - anaerobes
AMINOGLYCOSIDES
- active against staphylococci, NOT most streptococci
- active against respiratory and enteric gram -
- NO activity against anaerobes
MACROLIDES
- active against gram - aerobes
- active against respiratory gram - but NOT enteric
- active against most gram + anaerobes
Facts about Facultative anaerobes
are AEROBES
-CAN grow in anaerobic conditions
-culture as aerobes
-test susceptibility in aerobic conditions
-In vitro susceptibility may NOT equal in vivo susceptibility
- when anaerobic conditions are present in the patient
antimicrobial drug interactions
additive/indifferent
- used to extend the spectrum
- does NOT enhance activity of either
