Antimicrobial agents Flashcards
Bactericidal means
killing bacteria
Bacteriostatic means
inhibition of bacterial growth
Minimal inhibitory concentration means
the lowest concentration that inhibits visible growth
Minimum bactericidal concentration means
the concentration that results in 99.9% death of bacteria
Name the antibiotic classes that effect Cell Wall Biosynthesis
B-lactams
Glycopeptides
Cycloserine
Fosomycin
Name the B-lactams that inhibit cell wall biosynthesis
Penicillins
Cephalosporins
Monobactams
Cephamycins
Name the glycopeptide that effects cell wall biosynthesis
vancomycin
Name the antibiotic class that effects DNA replication
Quinolones
Name the antibiotic that effects DNA dependent RNA polimerase
Rifamicin
Name the antibiotics that effect bacterial growth by inhibiting the 30s subunit of ribosomes
Aminoglycosides
Tetracyclines
Name the antibiotics that effect bacterial growth by inhibiting the 50s subunit of ribosomes
Macrolides (erthromycin)
Lincosamides (clindamycin)
Chloramphenicol
Name the antibiotic class that disrupts the bacterial membrane
Polymixins
Name a common polymixin
daptomycin
Name the two antibiotics that effect folic acid metabolism in bacteria
sulfonamides
trimetheprim
What is the difference between gram - and gram + bacteria
gram + bacteria lack outer membrane
gram - contains outer membrane
Name similarities between gram-/gram+ bacteria
Both contain plasma membrane and peptidoglycan
How does B-Lactam antibiotics work
Inhibits a set of enzymes called transpeptidases and carboxypeptidases (AKA- Penicillin Binding Proteins) that make cell wall.
The B-lactam antibiotic becomes covalently bound to the PBP inactivating it and blocking cell wall biosynthesis
Are B-lactam static or cidal to bacteria
cidal- the blockage of the cell wall leads to cell lysis
Imipenem is a broad spectrum cell wall biosynthesis inhibitor that works against g-/g+ bacteria except which two
MRSA
VRE
Aztreonam is a cell wall biosynthesis inhibitor that works against —– —— bacteria only
gram -
What are the four mechanisms that bacteria use to resist antibiotic activity
Decreases cell wall permeability
Alters their target site
Inactivates target enzyme
Bybasses their own metabolic pathway
Gram negative bacteria confer resistance by what intrinsic or acquired method
Membrane permeability
*most important resistanct factor for gram - bacteria
Beta Lactamase works by
breaking the β-lactam ring open, deactivating the molecule’s antibacterial properties.
Name three Beta lactamase inhibitors
Sulbactam
Augmentin
Tazobactam
Augmentin is made from
Amoxicillin + Clavulanic acid
What drug is designed to decrease excretion of other drugs (i.e. PCN)
Probenecid
Strep. Pneumoniae confers resistance to Beta Lactams by what mechanism
altering target site (i.e. Penicillin binding proteins)
MRSA confers resistance by what mechanism
Bypassing the normal metabolic pathway of S. aureus by adding an additional gene that Beta lactams cannot bind to
Name the Glycopeptide antimicrobial involved in inhibition of cell wall biosynthesis
Vancomycin via binding to D-Ala-D-Ala aa during peptidoglycan synthesis and inhibiting cell wall growth
Vancomycin is used to treat gm - or gm + bacteria
gram positive Staph enterococcus
*vancomycin is structurally too big to go through gram - bacteria
Vancomycin resistance is based on the presences of Transposons which are effective due to
their inherent ability to move DNA sequences and thus inhibiting vancomycin’s ability to bind to D-Ala-D-Ala
Cycloserine is a cell wall biosynthesis inhibitor used to treat what conditon
TB
Fosfomycin is a cell wall biosynthesis inhibitor used to inhibit enolpyruvyl transferase which is an enzyme used during which step in the synthesis of peptidoglycans
first step
Fosfomycin is a broad spectrum antibiotic used to treat
UTIs
Name the two Protein synthesis inhibitors of the 30s subunit of ribosomes
Aminoglycosides
Tetracyclines
Name two common aminoglycoside antibiotics
gentAMicin
AMikacin
Aminoglycosides must be incorporated into the bacterial cell to work. True or False
TRUE
*they work on 30s unit of ribosomes
Aminoglycosides are mainly used to treat gram positive bacteria
False
- they are MAINLY used to tx gram negative bacteria
- BACTERIOCIDAL
Are aminoglycosides effective against anaerobic bacteria
No
- energy is needed for drug uptake into bacterial cell. Energy is obtained through the electron transport chain which requires oxygen
Aminoglycoside resistances is conferred by what mechanism
enzymes that inactivate the drug by reacting via three mechanisms
- phosphorylation
- acetylation
- adenylation
Tetracycline is a protein synthesis inhibitor that works via
attaching to 30S subunit to prevent binding of incoming aa-tRNA
Macrolides/Lincosamides work by
binding to 50S subunit and blocking translocation
Name a Macrolide
erthyromycin
Name a Lincosamide
clindamycin
True/False- resistance to erthromycin=resistance to clindamycin
TRUE
Chloramphenicol is a protein synthesis inhibitor that works how
works on the 50S subunit by inhibiting the enzyme need to form a peptide bond.
Oxazolidinones are newer antibiotics that work how
by binding to 50s subunit and preventing association with 30s subunits
Name a oxazolidinone
Linezolid
Linezolid is active against
gram positive bacteria
MRSA
VRE
Bacteria use PABA and Folic acid to produce what
purines
pyrimidines
*bases needed for DNA/RNA
Name two antibiotics that work by altering the production of folic acid and therefore, purines/pyrimidines
Sulfonamides
Trimethoprim
Bacteria utilize what mechanism to confer resistance
Bypasses the enzymes that sulfonamide and trimethoprim use to block folic acid production.
Name the nucleic acid synthesis inhibitor class
Quinolones
Name two quinolones
ciprofloxacin
norfloxacin
How do quinolones work
by blocking DNA gyrase (Topoisomerase) activity
Ciprofloxacin/Norfloxacin is used to treat what type of bacteria + or -
gram negative
*bactericidal
Rifampicin is classified as a
DNA dependent RNA polymerize inhibitor
Polymixins work by
disrupting the bacterial cell membrane
- detergent-like activity
Name a polymixin
Colistin
Colistin treats what type of infections
High drug resistant gram negative infections
Daptomycin works by
disrupting the bacterial cell membrane
*depolorizes bacteria causing death d/t release of intracelluar ions
Daptomycin works against
gram positive bacteria
*MRSA/ VRE
What two antibiotics have an ANTAGONISTIC effect on each other
Tetracycline (bacteriostatic) antagonizes beta-lactam (bacteriocidal)
What two antibiotics have a SNYERGISTIC effect on each other
PCN and Aminoglycosides