Micro. Chapter #8

What is antimicrobial chemotherapy?

The use of chemicals to treat a disease.

Who is considered the founder of chemotherapy?

Paul Ehrlich.

What was Paul Ehrlich's contribution to chemotherapy?

In 1910, he developed a treatment for syphilis and introduced selective toxicity.

What is selective toxicity?

A drug is toxic to the microbe but does not harm the host's cells.

Who developed sulfa drugs?

Gerhard Domagk in 1935.

What are antibiotics?

Antibacterial compounds produced by fungi and bacteria.

Who discovered penicillin and when?

Alexander Fleming in 1928.

Where does penicillin come from?

Penicillium mold.

Who discovered streptomycin and when?

Selman Waksman in 1943.

Where does streptomycin come from?

Streptomyces griseus, a filamentous soil bacterium.

What is an antimicrobic?

A general term for all types of antimicrobial drugs, regardless of origin.

What are synthetic antimicrobials?

Antimicrobial chemicals produced artificially.

What is an example of a synthetic antimicrobial?

Sulfa drugs.

What are semisynthetic antimicrobials?

Natural antibiotics that have been chemically modified.

What is an example of a semisynthetic antibiotic?

Methicillin.

What is the therapeutic index (TI)?

The lowest toxic dose divided by the normal therapeutic dose.

What does a high therapeutic index mean?

The drug is generally less toxic to the host.

What does a low therapeutic index mean?

The drug has greater potential to harm the host.

What is considered a good therapeutic index?

Approximately 10:1.

What is the minimum inhibitory concentration (MIC)?

The lowest concentration of a drug that prevents microbial growth.

How is therapeutic index calculated using MIC?

Lowest toxic dose divided by MIC.

What is a broad-spectrum antibiotic?

An antibiotic that affects a wide range of bacteria.

What is a disadvantage of broad-spectrum antibiotics?

They can affect many bacteria, including beneficial bacteria, and often have a lower TI.

What is a narrow-spectrum antibiotic?

An antibiotic that affects a limited range of bacteria.

What is an advantage of narrow-spectrum antibiotics?

They target fewer types of bacteria and usually have a higher TI.

What is a drug's half-life?

The time it takes for the amount of drug in the body to decrease by 50%.

What two processes determine a drug's elimination?

Metabolism and excretion.

Why is half-life important?

It helps determine how much medication and how frequently it should be given.

Why is Penicillin G given by injection instead of orally?

It is not stable in the low pH of the stomach.

What is tissue distribution?

How a drug is administered and how it reaches different tissues in the body.

What is the blood-brain barrier important for when treating meningitis?

Drugs must be able to cross it to reach the infection.

What is intrinsic resistance?

Natural resistance based on a bacterium's characteristics.

What is an example of intrinsic resistance?

Mycoplasma resists antibiotics targeting peptidoglycan because it lacks a cell wall.

What is acquired resistance?

Resistance gained through mutation or genetic exchange.

What are common adverse effects of antimicrobial drugs?

Allergic reactions and toxic effects.

Which antibiotics commonly cause allergic reactions?

Penicillins, cephalosporins, and sulfonamides.

What are possible symptoms of antibiotic allergies?

Fever, rash, and anaphylactic shock.

What are toxic effects of antimicrobial drugs?

Damage to the host caused by high drug concentrations.

What are two toxic effects of streptomycin?

Kidney damage and deafness.

What is an antagonistic drug interaction?

Two drugs become less effective when used together.

What is an example of an antagonistic interaction?

Bacteriostatic drugs interfering with penicillin.

What is a synergistic drug interaction?

Two drugs become more effective when used together.

What is an example of a synergistic interaction?

Penicillin allows streptomycin to enter bacterial cells more easily.

What is an additive drug interaction?

Two drugs have no significant interaction.

Why must existing patient conditions be considered when choosing antibiotics?

Some drugs can worsen existing health problems.

Why should streptomycin be avoided in patients with kidney damage?

It can cause additional kidney damage.

Which microorganisms are easiest to treat with antimicrobial drugs?

Prokaryotes because they have more cellular differences from human eukaryotic cells.

Why are bacteria easier to target than fungi and protists?

Bacteria have more unique cellular structures and processes.

Why are fungi and protists harder to treat?

Their eukaryotic cells have more similarities to human cells.

How do antiviral drugs affect productive viruses?

They slow viral replication or penetration but do not kill viruses.

Can latent viruses currently be effectively treated with drugs?

There are no effective drugs for latent viruses according to the lecture.

Why is the bacterial cell wall a good antimicrobial target?

Humans do not have peptidoglycan cell walls, allowing high selective toxicity.

What is the therapeutic index of drugs targeting cell walls?

High.

Why do drugs targeting cell membranes often have a low TI?

Cell membranes are similar in both microbes and host cells.

What is the therapeutic index of drugs targeting proteins and metabolic pathways?

High.

What is the therapeutic index of drugs targeting RNA transcription?

High.

What is the therapeutic index of drugs targeting translation?

Generally high.

What is the therapeutic index of drugs targeting DNA synthesis?

Generally high.

What are the eight major antibacterial drug groups discussed in lecture?

Sulfonamides, beta-lactams, glycopeptides, aminoglycosides, tetracyclines, macrolides, rifamycins, and quinolones.

What is the mode of action of sulfonamides?

They competitively inhibit the metabolic pathway that synthesizes folic acid.

Why is folic acid important to bacteria?

It is needed to produce precursors for proteins and nucleic acids.

Are sulfonamides natural, synthetic, or semisynthetic?

Synthetic.

What is the therapeutic index of sulfonamides?

High; they are nearly harmless to humans.

What is the spectrum of sulfonamides?

Broad spectrum; they affect Gram-positive and Gram-negative bacteria.

What is a major problem with sulfonamides today?

Many bacteria have developed resistance due to extensive use.

What infections can sulfonamides treat?

UTIs, some causes of meningitis, and leprosy.

What are beta-lactams?

Antibiotics containing a beta-lactam ring.

What are two examples of beta-lactams?

Penicillins and cephalosporins.

What are examples of semisynthetic beta-lactams?

Methicillin and ampicillin.

What is the mode of action of beta-lactams?

They interfere with bacterial cell wall synthesis.

How do beta-lactams cause bacterial cells to die?

They prevent cross-linking of peptidoglycan, causing cells to lyse.

Why do beta-lactams only work on actively growing bacteria?

They interfere with new cell wall synthesis.

What is the therapeutic index of beta-lactams?

High.

What is a major adverse effect of penicillin?

Severe allergic reactions.

Which bacteria are beta-lactams usually more effective against?

Gram-positive bacteria.

Why does beta-lactam effectiveness against Gram-negative bacteria vary?

Some drugs cannot penetrate the Gram-negative outer membrane.

Why were semisynthetic penicillins developed?

To help reduce antibiotic resistance problems.

What is vancomycin?

A glycopeptide antibiotic naturally produced by Streptomyces-type bacteria.

What is the mode of action of vancomycin?

It inhibits cell wall synthesis by binding to peptidoglycan.

What is the therapeutic index of vancomycin?

High.

What is the spectrum of vancomycin?

Narrow spectrum; it primarily targets Gram-positive bacteria.

How is vancomycin usually administered?

By injection because it is poorly absorbed through the intestines.

When can vancomycin be given orally?

When treating intestinal pathogens.

What are aminoglycosides?

Antibiotics that include streptomycin, gentamicin, and neomycin.

Where do aminoglycosides originate?

Streptomyces bacteria.

What is the mode of action of aminoglycosides?

They inhibit translation by binding to the small ribosomal subunit.

What is the therapeutic index of aminoglycosides?

Low.

Why are aminoglycosides given in low doses?

They can cause severe toxicity.

What are two possible toxic effects of streptomycin?

Kidney damage and deafness.

What is the spectrum of aminoglycosides?

Broad spectrum.

Why are aminoglycosides not used as frequently today?

Many bacteria have developed resistance.

Which antibiotic works synergistically with streptomycin?

Penicillin.

What are tetracyclines?

Antibiotics that include tetracycline, doxycycline, and oxytetracycline.

Where do tetracyclines originate?

Streptomyces bacteria; some are semisynthetic.

What is the mode of action of tetracyclines?

They inhibit translation by binding to the small ribosomal subunit.

What is the therapeutic index of tetracyclines?

High.

What is the spectrum of tetracyclines?

Very broad spectrum.

What is a major problem with tetracyclines?

Antibiotic resistance is common.

What is a noted use of tetracyclines in lecture?

They can be used for undiagnosed diseases.

What are macrolides?

Antibiotics that include erythromycin and azithromycin.