Ch 12 - Microbial control Chemotherapy (Study guide)

Antibiotics

naturally-occurring substances from a microbe that cause death/inhibit another microbe

Semisynthetic antibiotics

antibiotics that are then modified in a lab

Synthetic antibiotics

antibiotics that are entirely made in a lab; human-made antibiotics

Penicillin, Bacitractin and Vanomycin

• Microbe Type: Bacteria

• Effect of drug:Cell wall damage and lysis

Erthyromycin

• Microbe Type: Bacteria

• Effect of drug:Inhibits ribosomal protein synthesis

Tetracycline and Chloramphenicol

• Microbe Type: Bacteria

• Effect of drug:Inhibits protein synthesis on ribosomes

Sulfa drugs and Trimethoprim

• Microbe Type: Bacteria

• Effect of drug:Inhibits folic acid metabolism

Isoniazid

• Microbe Type: bacteria

• Effect of drug: Completely synthetic antibiotic 

  Used against mycobaterium tuberculosis

  
  

Streptomycin

• Microbe Type: bacteria

• Effect of drug: inhibits bacterial protein synthesis

Metranidazole

• Microbe Type: Protozoa

• Effect of drug: build up toxic free radicals

Quinine

• Microbe Type: Protozoa

• Effect of drug: build up of toxic wastes in the parasite cells

Piperazine

• Microbe Type: Helminths

• Effect of drug: paralyzes muscular system

Cyclovirs

• Microbe Type: virus

• Effect of drug: stop viral replication

Azidothymine

• Microbe Type: stop viral replication

• Effect of drug:blocks formation of DNA from RNA strand

Competitive inhibition

metabolic analogs bind to active sites of enzymes, slowing down/stopping metabolic reactions of bacteria

Metabolic analogs

 drugs that force an enzyme to not produce its target reactants

synergistic compounds

The effects of a combination of drugs > summing each drugs’ effects

• ie: Augmentin= ampicillin + clavonic acid

Augmentin (synergistic compound)

• ampicillin + clavonic acid

• Ampicillin by itself is made of beta-lactam rings; however, its structure is susceptible to beta-lactamase created by bacteria that have adapted

• Clavonic acid kills beta-lactamase

  • So if we put them together, they’re more powerful than if they worked separately!

Beta-lactams

class of antibiotics that have a beta-lactam ring helping with antibacterial activity (Work by inhibiting bacterial wall synthesis, targets penicillin binding proteins which is required for cell wall formation)

Beta-Lactamase

broad term for penicillinase, use beta-lactamase word

Beta lactam summary

Enzyme bacteria produced, 💀beta-lactam rings in antibiotics (makes ineffective) →targets beta-lactam drugs

Common Beta-lactam Drugs

• Penicillin

• Cephalosporins

Synergy

Carbolic acid + other substances (enhanced antimicrobial effect) → effective bacterial killing

Augmentin

Bacterial infection (Augmentin used to treat, Augmentin = amoxicillin + clavulanic acid) - Synergy between clavulanic acid + amoxicillin overcomes bacterial resistance. Makes amoxicillin 💪(parent compound is penicillin)

beta-lactam antibiotics

• Contains a Beta-lactam ring

• Major target: bacterial cell wall (peptidoglycan synthesis)

  • EX. penicillin blocks PPG synthesis

semi-synthetic penicillins

• Penicillin derivatives modified in a lab to improve effectiveness

  • Ex:

    • Methicillin

    • Ampicillin

    • Amoxicillin

    • Carbenicillin

  • Designed to resist beta-lactamase

Tetracycline (ribosome)

• Binds 30S

• Blocks tRNA from attaching

Streptomycin (ribosome)

• Binds 30S

• Causes misreading of mRNA

Erythromycin (ribosome)

• Binds 50S

• Blocks ribosome translocation

Chloramphenicol (ribosome)

• Binds 50S via the A & P sites 

• Inhibits peptide bond formation

sulfa drugs function

• Acts as competitive inhibitors

• Mimic PABA and block folic acid synthesis

Drug resistance in bacteria

•  adaptation to a dosage of a drug that should’ve inhibited them

  • RESULTS FROM:

    • Is innate OR acquired

    • Genetic versatility (→ favorable mutations) & microbes adapting

Tetracycline (side effects)

Constricts melanocytes → increased skin cancer risk

Chloramphenicol (anti biotics)

Increases bone cancer risk, commonly used in veterinary clinics because no effect on animals

Antimalarial

• Drug:

  • Quinine

  • Mefloquine

  • Doxycycline

• Action:

  • Toxic heme buildup kills parasite

  • Synthetic quinine derivatives

  • Used prophylactically to prevent malaria

Antiprotozoal

• Drug:

  • Metranidazole

  • Tetracycline

  • Quinacrine

• Action:

  • Breaks DNA

  • Used for some protozoa

  • Used for Giardia

Anthelminthic

• Drug:

  • Piperazine

• Action:

  • Paralyzes worm muscles

NRTIs

analogs of nucleosides (nitrogenous base + sugar); reverse transcriptase incorporates them into the virus's DNA chain during replication → stops DNA elongation

NtRTIs

similar mode of action but are nucleoside + 1 phosphate

NRTIs and NtRTIs

• Used against HIV

• Fake nucleotides → stop viral DNA

antimalarial drug

• against Malaria

• Quinine: [Protozoa] → Effect: Build up of toxic waste in the parasite’s cells 

Mefloquine, Chloroquine → synthetic derivatives of quinine

antiprotozoal drugs

• Metronidazole

• Tetracycline

• Quinacrine

what is Metronidazole

• Damages DNA

• Causes lethal breaks

• Used for Giardia, Trichomonas, C. Difficile

• Targets protozoa

Tetracycline

• Inhibits protein synthesis (binds 30S ribosomes)

• Used for some protozoa

Quinacrine

• Interferes with DNA and RNA synthesis

• Used mainly for Giardia

Protease inhibitors

• Prevents virus from assembling mature viral proteins; stops viral proteins from being clipped into multiples

• Used against HIVIntegrase inhibitors

Integrase inhibitors

• Prevents viral DNA from integrating into host genome

• Used against HIV

IProtease inhibitors and integrase inhibitors summary

 protease and integrase inhibitors stop viruses from creating proteins & integrating their viral DNA into the host’s; used against HIV

Superinfection

 infection due to antibiotics killing off normal, good human flora, allowing resistant bad bacteria to cause a secondary & more severe infection; caused by stopping medications prematurely

Kirby-Bauer Test

• Tests drug susceptibility

• Larger “zone of inhibition” = more effective drug

MIC test

• ”Minimum Inhibitory Concentration”

• Lowest concentration of drug that prevents growth

• determines exact dosage needed

therapeutic index (TI

• Ratio of toxic dose / effective dose

• Higher TI = safer :)

• Lower TI = YOU WILL DIE

efflux pumps

• Pumps antibiotics out of bacterial cell

• Major mechanism of drug resistance

• Efflux = Exit