Pharmacology: Antibiotics Flashcards by Brett Gillespie

Why are synthetic antibiotics not “true” antibiotics?

By definition, ABX are naturally occurring substances produced by a microorganism to target another microorganism

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What is the ideal trait of antibiotics to effectively treat a patient? What microbes present an issue for this?

Selective toxicity

Viruses, cause they use our cell’s machinery
Fungi and Parasites: they’re euks and have similar functions

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What is the minimum inhibitory concentration?

The concentration of an antibiotic where the colony cannot grow its numbers

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What is the minimum bacteriocidal concentration?

The concentration that kills 99.9% of microorganisms in a colony

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Why is MIC or MBC unreliable for clinical dosing?

Pharmacokinetic functions, such as first pass metabolism, protein binding, and metabolism, may decrease the effective dose of ABX in a patient

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What areas are difficult to reach and may require a larger dose of antibiotics?

CNS, bone, adipose tissue

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What is the reason some people have allergic responses to ABX?

ABX are antigenic, so they can react with the host immune system

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What are bacteriostatic and bactericidal ABX?

Static: halt growth of bacterium

Cidal: kill and decrease concentration of ABX

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Knowing the action of bacteriostatic ABX, how does a infection clear? What is a contraindication for this type?

Via host immune system

Compromised immunity

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What are the chemotherapeutic spectrum types?

Broad, narrow, and extended

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What are the three general areas that ABX target in a bacterial cell?

Nucleic acid synthesis, ribosomal protein synth, and the cell wall

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Describe a few ways bacterium can defend and adapt against ABX?

Reduced entry or drug, efflux pumps (MDR protein), alteration of target proteins, alteration of metabolism

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What kind of antibiotic destabilizes the cell wall of a bacterium?

Bactericidal

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What enzyme links the layers of sugars in the peptidoglycan walls? What residues are used in this linkage?

Transpepditases

D-alanine

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What do beta-lactam drugs target in a cell?

Transpeptidase in the cell wall

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What is another name for transpeptidase?

Penicillin binding protein

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What does penicillin target? What types of bacterium does this work against? What are its extended-spectrum agents? What do they work against?

1&2)Transpeptidases; & Gram positive bacterii and syphilis

3&4) amoxicillin, ampicillin, amniopenicillin; gram + and -

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How effective is Penicillin against today’s bacterium?

Not good due to resistance; only acts well with syphilis

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What class are cephalosporins? How can they be recognized via nomenclature?

Beta-lactams; largest B-lac class; have ceph- or cef- in name

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What class is carbapenem ABX? What is its spectrum? Potency? What are common clinical uses?

B-lactam; broad spectrum and potent; usually used as a combination therapy drug; NEEDS INHIBITORS WITH ITS MOST UNSTABLE FORM

Are monobactams considered true B-lactams? What does it target? What is its spectrum?

No; Gram -; narrow-spectrum

What are common allergic responses to B-lactams?

Anaphylaxis/cytolytic anemia

How are B-lactams allergenic? What if a patient is allergic to penicillin, what B-lactams can be prescribed?

Bind to human proteins;

NO B-lactams can be prescribed, it is a classwide (monobactams are safe since it does not have extra ring structure)

What enzyme gives bacteria resistance to B-lactams?

B-lactamase

What are some ways around B-lactamases? How does this work?

Combination therapy: strong B-lact with weak B-lact- weak B-Lac binds to enzyme, strong kills the bacteria Chemical modifications to drugs (ie Methicillin from penicillin)

How do glycopeptides work to be an ABX?

Bind to D-alanine and prevent crosslinking from transpeptidase

What antibiotic is historically effective against MRSA? What class is this ABX? What is this drug not effective against? How has MRSA adapted to this drug?

- Vancomycin - Glycopeptide - gram - bacteria - changed transpeptidases to not use D-alanine links in cell wall

What type of antibacterial inserts into the plasmalemma and disrupts the cell wall? What are these effective against?

Lipopeptides (like Daptomycin) -vancomycin resistant strains

How do lipopeptides kill bacteria?

Create pores in the cell mem to disrupt osmolarity

What does bacitracin do?

Prevents peptidoglycan subunits from reaching cell surface

Are bacitracin and lipopeptides bacteriostatic or bactericidal? What are their draw backs? How are they typically administered?

- cidal - very toxic to humans (nephrotoxic due to lipid mems in the kidney) - topical administration

What are polymixins? What are they effective against? What are its drawbacks?

Positively charged peptides that disrupt cell membrane structure - gram - - cannot be taken orally due to charge

Are direct nucleotide synthesis inhibitors cidal or static? Broad or narrow spectrum?

Cidal and broad

How can bacteria become resistant to nucleotide synthesis disrupting ABX?

Changing the antibiotic, altered protein targets, expression of protective proteins

What do quinolones do?

Inhibit topoisomerases on bacterial DNA during replication

What does rifampin target?

RNA polymerase to prevent mRNA synth

What does metronidazole do?

Cleaves daughter strand of DNA to prevent replication

Are indirect DNA/RNA synth inhibs bacteriostatc or cidal? Broad or narrow?

Static; broad spectrum (even protozoa)

How do sulfonamides function on bacteria?

Targets dihydropteroate synthase (in folic acid synthesis)

How does trimethoprim target bacteria?

Inhibits dihydofolate reductase (in folic acid synthesis)

How are indirect RNA/DNA synth inhibs resisted?

Increased substrates for their target proteins to overpower them

Are protein synth inhibs bacteriocidal or static? Where do they function? Broad or narrow? Gram + or -?

Mostly static, but can be cidal Mostly on the ribosome Can be broad or narrow Can be Gram - or +

Why shouldnt protein synth inhibs be used as first line against infections?

Toxicity is abundant in this class

Where does tetracycline bind? What does it do?

Binds to 30s subunit/ disrupts tRNA interaction

Where does erythromycin bind? What does it do?

Binds to ribosome/ prevents translocation of peptide chain

Where does chloramphenicol bind? What does it do?

Mimics/binds to amino group attached to tRNA; prevents formation of peptide chain

What are some reasons to do combination therapy?

Multiple microbes, very ill patients, prevent spread of drug resistant pathogens, reduce chances of toxicity Cons: drug-drug interactions

What are addative and synergistic combinations?

Addative is the addition of each drug’s potency Synergy is 1+1=4 (more than sum of parts)

What is a good example of antagonistic combinations?

Tetracyclines and penicillins- tet reduce efficacy of penicillin (Penicillin better on growing bacterial colonies)