Lecture 6 - Antibacterial Agents Flashcards by Raegan Chambers

What was the compound that Paul Ehrlich came up with?

Compound 606 aka Salvarsan

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What was the first real antibiotic?

Penicillin (1928)

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What is the definition of an antibiotic?

Chemical that is able to kill or inhibit the growth of bacterial cells

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What is the definition of antimicrobial?

All agents that kill all types of microorganisms

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What are the two very basic actions carried out by antibiotics?

Bacteriostatic + Bacteriocidal

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What is bacteriostatic?

Inhibits the growth of bacteria

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What is bacteriocidal?

Kills bacteria

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What are the three categories in regards to spectrum of activity?

Narrow - Broad - Moderate

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What is the major goal of antibiotic development (what should be one of the most important?

Selective toxicity

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What is selective toxicity?

AB is more toxic to the bacterial cells than it is the host cells

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What are some basic targets for antibiotics to ensure that they have selective toxicity?

Cell wall + Ribosomes + Bacterial enzymes

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What does it mean to use antibiotics in a non-therapeutic manner?

Commonly seen in food animal medicine. This is the practice of using AB to prevent an infection from occurring before it is even present in the animal.

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What is bad about the non-therapeutic use of AB’s?

This helps increase the rate in which bacterias become resistant to various antibiotics

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What are the five classes of antibiotics?

Inhibition of cell wall synthesis 
Disruption of cell membrane function 
Inhibition of protein synthesis 
Inhibition of nucleic acid synthesis 
Action as antimetabolite

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What are the three AB’s that are inhibitors of cell wall synthesis?

Beta-Lactam
Glycopeptides
Bacitracin

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What is the spectrum of activity of beta-lactam?

Varies

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Is beta-lactam a -cidal or a -static?

Bactericidal

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What is the mechanism of beta-lactam?

Binds/blocks transpeptidase
Prevents peptidoglycan cross-linking
Cell lysis

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What is another name for transpeptidase?

Penicillin binding protein

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What is the spectrum of activity for glycopeptides?

Narrow - Gram(+) only

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Is glycopeptide -cidal or -static?

Bactericidal

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What is the mechanism of glycopeptides?

Binds to the pentapeptide chains of NAM
Blocks transglycosylation + transpeptidation of peptidoglycan syn.
Cell lysis

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What is the spectrum of activity for Bacitracin?

Broad

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What is crucial to know clinically about Bacitracin?

Topical use only, too toxic for systemic use

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Is Bacitracin -cidal or -static?

Bactericidal

What is the mechanism for Bacitracin?

Prevents dephosphorylation of bactoprenol Prevents transport of NAG-NAM monomers Cell lysis

What antibiotic works through disruption of the cell membrane?

Polymyxins

What is the spectrum for Polymyxins?

Moderate

What does polymyxin work on?

Gram-negative bacteria

What is clinically important to know about polymyxin?

Poor selective toxicity therefore topical use only

What is the mechanism for polymyxin?

Works as a cationic detergent Increase water uptake into the cell Cell lysis

What ribosome type is found in bacteria?

70s

What are the subunits of the bacterial ribosome?

30s + 50s

What antibiotics target the 30s subunit of the bacterial ribosome?

Aminoglycosides + Tetracyclines

What antibiotics target the 50s subunit of the bacterial ribosome?

Chloramphenicol Macrolides Lincosamides

What is the spectrum of activity for aminoglycosides?

Broad

What should the use of aminoglycosides be limited to?

Enteric infections and sometimes sepsis

Are aminoglycosides -cidal or -static?

Bactericidal

What is the mechanism for aminoglycosides?

Irreversible binding to 30s Block initiation complex + misreading/premature release of mRNA Stops protein synthesis h

What is the spectrum of activity for tetracyclines?

Broad

What is clinically important to know about tetracyclines?

Have non-antibacterial uses | Can be used as an anti-inflammatory

Are tetracyclines -cidal or -static?

Bacteriostatic

What is the mechanism of action for tetracylines?

Reversibly bind to ribosome Prevent attachment of aminoacyl-tRNA to complex Prevent AA addition to peptide chain Halt protein syntheiss

What is the spectrum of activity for chloramphenicol?

Broad

What is clinically important to know about the use of chloramphenicol?

Can be toxic; causes aplastic anemia in humans

Is chloramphenicol -cidal or -static?

Bacteriostatic

What is the mechanism of chloramphenicol?

Reversibly binds to ribosome Inhibits peptidyl transferase Prevents elongation of peptide chain Halts protein synthesis

What is the spectrum of macrolides?

Narrow

Are macrolides -cidal or -static?

Bacteriostatic

What is the mechanism for macrolides?

Reversibly binds to ribosome Inhibits transpeptidation + translocation Prevention of chain elongation + premature detachment of peptide Halt protein synthesis

What is the spectrum of activity for lincosamides?

Moderate

What microbes do lincosamides target?

Gram-postive Anaerobes Some mycoplasmas

Are lincosamides -cidal or -static?

Bacteriostatic

What is the mechanism of action for lincosamides?

Reversible binds to ribosome Inhibit transpeptidation + translocation Similar to macrolides Halt protein synthesis

What antibiotics target nucleic acid synthesis?

Quinolones + Fluoroquinolones Rifamycins Metronidazole

Are quinolones -cidal or -static?

Bactericidal

What is the spectrum of quinolones?

Varies - normally broad

What is the mechanism for quinolones?

Bind to DNA gyrase + topoisomerase IV Inhibit bacterial replication via interference with DNA supercoiling Stop DNA/RNA synthesis

What is the spectrum of activity for rifamycin?

Broad

Are rifamycins -cidal or -static?

Bactericidal

What is the mechanism of action for rifamycins?

Inhibits DNA-dependent RNA polymerase | Stops transcription of mRNA

What is the spectrum of activity for metronidazole?

Narrow

What microbes does metronidazole target?

Anaerobes + Protozoans

Is metronidazole -cidal or -static?

Bactericidal

What is the mechanism for metronidazole?

Reduction into active form Covalently binds to DNA = breakage Inhibits NA synthesis

What antibiotics are antimetabolites?

Sulfonamides + Diaminopyrimidines

Are the antimetabolite AB's -cidal or -static?

If used alone they are bacteriostatic | If used together (common) bacteriocidal

What is the mechanism of the antimetabolites?

Interfere with folic acid synthesis

What is the specific mechanism of sulfonamides?

Analog of PABA - compete for the enzyme dihydropteroate synthetase

What is the specific mechanism for diaminopyrimidines?

Analogs of pteridine portion of dihydrofolic acid - inhibit dihyro reductase

Who was the first person to begin to find a compound that would kill infectious microbes?

Paul Ehrlich