Antimicrobial agents Flashcards by hassan gonzales

Bactericidal means

killing bacteria

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Bacteriostatic means

inhibition of bacterial growth

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Minimal inhibitory concentration means

the lowest concentration that inhibits visible growth

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Minimum bactericidal concentration means

the concentration that results in 99.9% death of bacteria

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Name the antibiotic classes that effect Cell Wall Biosynthesis

B-lactams
Glycopeptides
Cycloserine
Fosomycin

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Name the B-lactams that inhibit cell wall biosynthesis

Penicillins
Cephalosporins
Monobactams
Cephamycins

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Name the glycopeptide that effects cell wall biosynthesis

vancomycin

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Name the antibiotic class that effects DNA replication

Quinolones

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Name the antibiotic that effects DNA dependent RNA polimerase

Rifamicin

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Name the antibiotics that effect bacterial growth by inhibiting the 30s subunit of ribosomes

Aminoglycosides

Tetracyclines

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Name the antibiotics that effect bacterial growth by inhibiting the 50s subunit of ribosomes

Macrolides (erthromycin)
Lincosamides (clindamycin)
Chloramphenicol

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Name the antibiotic class that disrupts the bacterial membrane

Polymixins

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Name a common polymixin

daptomycin

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Name the two antibiotics that effect folic acid metabolism in bacteria

sulfonamides

trimetheprim

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What is the difference between gram - and gram + bacteria

gram + bacteria lack outer membrane

gram - contains outer membrane

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Name similarities between gram-/gram+ bacteria

Both contain plasma membrane and peptidoglycan

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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

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Are B-lactam static or cidal to bacteria

cidal- the blockage of the cell wall leads to cell lysis

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Imipenem is a broad spectrum cell wall biosynthesis inhibitor that works against g-/g+ bacteria except which two

MRSA

VRE

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Aztreonam is a cell wall biosynthesis inhibitor that works against —– —— bacteria only

gram -

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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

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Gram negative bacteria confer resistance by what intrinsic or acquired method

Membrane permeability

*most important resistanct factor for gram - bacteria

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Beta Lactamase works by

breaking the β-lactam ring open, deactivating the molecule’s antibacterial properties.

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Name three Beta lactamase inhibitors

Sulbactam
Augmentin
Tazobactam

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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

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 1. phosphorylation 2. acetylation 3. 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