Antimicrobials Flashcards
Antibiotic definition
Compound prodcued by a living microorganism w/ antimicrobial activity
Selective toxicity
Antimicrobial that targets a specific pathogen only
- easier to use against viruses/ other organisms that are not biologically similar to humans
Minimum inhibitory concentration (MIC)
Lowest concentration of a compound that can inhibit growth of a microorganisms in vitro
Minimum bactericides concentration (MBC)
Lowest concentration of compound needed to kill 99.9% of a Colony in vitro
Difference between bactericidal and bacteriostatic
Bactericidal: kill microorganisms
Bacteriostatic: stop growth of infection
Chemotherapeutic spectrum
Range of organisms that an agent is effective against
- can be broad, extended or narrow
Ways Bacterial resistance to antimicrobials is conducted.
Reduced entry of the drug
Enhanced export of the drug by upregulation of effusion pumps
Increased microbial enzymes that destroy the antimicrobial
Alteration of target proteins
Alteration of targeted metabolic pathways
Cell wall synthesis inhibitors action
Inhibit peptidoglycan wall via prevention of cross linking or peptidoglycan cross linking.
Bactericidal antimicrobial
Peptidoglycan crosslinking mechanisms
Bacteria uses transpeptidase enzymes to cross link D-alanine residues
(B)-lactam class
Cell wall synthesis antimicrobial classthat inhibits transpeptidase activity
(B)-lactam examples
Penicillins
Cephalosporins
Carbapenems
Monobactams
Penicillins
Cell wall synthesis inhibitor that are effective against gram-positive and syphillis
- narrowed spectrum or extended spectrum
- extended spectrum penicillins = aminopenicllins, amoxicillin and ampicillin.
- natural penicillin is very narrowed spectrum due to penicillin resistance.
Aminopenicillins, amoxicillin and ampicillin
(B) lactam penicillins derivatives that have an extended spectrum to gram positive and gram negative bacteria.
Cephalosporins
Type of (b) lactam that has an altered spectra and is resistance of degradation
(Cef)
Carbapenems
Type of (b)-lactam that has a very broad spectrum in gram positive and gram negative bacteria
- is potent
Monobactams
Type of (b)-lactam that has a narrow spectrum to only gram negative organisms
- not technically a true (b)-lactams but uses the same action as true (b)-lactams
- most common form is aztreonam
(B)-lactam allergic response
Adducted (b)-lactam protein on human proteins trigger anaphylaxis and cytolytic anemia
- allergies present contraindication for use of (B)-lactams with the exception of monobactams
Strategies to combat (B)-lactam resistances
Combine weak with strong (b)-lactams to make the lactamases of resistance bacteria preoccupied with the weak versions
Chemically modify the enzyme affinity or access to the (B)-lactam ring
Glycopeptides
Class of wall-inhibiting synthesis antibacterial that binds to D-alanine and inhibits cross-linking
- most common form is vancomycin
Vancomycin
Most common form of Glycopeptides antimicrobial
- used most often against MRSA, however is cannot be used against gram negative bacteria (narrow spectrum)
- bacteria can grow resistance by straight up not using D-alanine in wall synthesis
Lipopeptides
Class of wall synthesis inhibitors that work by inserting into the plasma membrane to increase leakage of membranes
Affective against vancomycin resistant bacteria, but can also not be used against gram negative bacteria (narrow spectrum)
Bacterialcidal
Bacitracin
Class of wall-synthesis inhibitors that prevent peptidoglycan subunits from being available for transpeptidase to use
Bactericidal
DNA and RNA stability and synthesis inhibitors
Class of antimicrobials that inhibit DNA and RNA synthesis
Can be direct(bactericidal) or indirect (bacteriostatic)
Very broad spectrum agents
Indirect inhibitors almost always work synergistically
Trimethoprim
Type of indirect DNA synthesis inhibitor that inhibits DHF reductase
- broad spectrum
- can easily have a resistance developed against them by bacteria increasing a viable subunits.
Sulfonamides
Type of indirect DNA synthesis inhibitor that inhibits DHP synthase
- broad spectrum
- can easily have a resistance developed against them by bacteria increasing a viable subunits.
Protein synthesis inhibitors
Class of antimicrobials that inhibit ribosomal subunits or protein synthesis.
- ultimately produces inhibition of protein translation
- mostly bacterio static
- tend to have high toxicity rates (should be used as last resort)
Erythromycin
Type of protein synthesis inhibitor that prevents translocation of a peptide chain through the ribosome during protein translation
Tetracyclines
Type of protein synthesis inhibitors that disrupt 30S ribosome action
Chloramphenicol
Type of protein synthesis inhibitor that prevents peptide chain formation in the ribosome
Combination therapy
Treatment with multiple drugs, usually not used unless necessary
Reasons to use combination therapy
Need a broader spectrum in severely ill patients
High amounts of microbes to where differentiating is hard
Decrease dose related toxicity
Decrease change of resistance
Enhanced inhibition or killing
Additive combination of therapy
Drugs add to each other’s efficacy in a sum fashion (1+1 =2)
- (B)-lactamase inhibitors w/ (b) lactams
- amoxicillin/clavulanate
Synergistic combination therapy
Drugs enhance each other’s efficacy in a more exponential effect
-Sulfonamides and trimethoprim
Antagonistic combination therapy
One drug impaired the efficacy of the other
-tetracyclines/ penicillin
