Biology G210 – Lecture 7: Antimicrobial Drugs

85 question-and-answer flashcards covering key terms, mechanisms, drug examples, advantages, disadvantages, resistance, and antiviral agents from Lecture 7 on Antimicrobial Drugs.

What is an antibiotic?

An antimicrobial substance produced naturally by microorganisms.

Which fungal genus beginning with “P” is a major source of antibiotics?

Penicillium.

Which fungal genus beginning with “C” produces many antibiotics?

Cephalosporium.

Which actinomycete genus yields streptomycin and many other antibiotics?

Streptomyces.

Name an actinomycete genus other than Streptomyces that produces antibiotics.

Micromonospora.

Which Gram-positive rod genus is known for producing bacitracin?

Bacillus.

What does the term “narrow-spectrum antibiotic” mean?

It affects only a specific, limited group of microorganisms.

What does “broad-spectrum antibiotic” mean?

It acts against multiple groups, typically both Gram-positive and Gram-negative bacteria.

Isoniazid is primarily effective against which bacterial group?

Mycobacteria.

Which antibiotic is effective against Gram-positive, Gram-negative, Chlamydias, and Rickettsias?

Tetracycline.

List the five major modes of antibiotic action.

(1) Inhibit cell-wall synthesis, (2) inhibit protein synthesis, (3) injure plasma membrane, (4) inhibit nucleic-acid synthesis, (5) inhibit synthesis of essential metabolites.

Give four examples of antibiotics that inhibit cell-wall synthesis.

Penicillins, cephalosporins, bacitracin, vancomycin.

Which antibiotic binds the 50S ribosomal subunit and blocks peptide-bond formation?

Chloramphenicol.

Which antibiotic changes the 30S ribosomal shape so mRNA is read incorrectly?

Streptomycin (an aminoglycoside).

Which antibiotic family interferes with tRNA attachment to the ribosome-mRNA complex?

Tetracyclines.

Which antibiotic injures the plasma membrane of Gram-negative bacteria?

Polymyxin B.

Quinolones and fluoroquinolones inhibit what enzyme needed for DNA replication?

DNA gyrase (topoisomerase II).

Rifampin inhibits the synthesis of which nucleic acid molecule?

Messenger RNA (mRNA).

Sulfonamides are structural analogs of which folic-acid precursor?

Para-aminobenzoic acid (PABA).

Give one example of a natural penicillin.

Penicillin G (or Penicillin V).

What key structural ring allows penicillin to block cell-wall cross-linking?

The β-lactam ring.

What is a major advantage of natural penicillins?

Very low toxicity to the host.

Give one disadvantage of natural penicillins.

They are narrow spectrum and susceptible to penicillinases (also can cause allergies).

Which natural penicillin must be injected because stomach acid destroys it?

Penicillin G.

Which natural penicillin can be taken orally?

Penicillin V.

How do semi-synthetic penicillins differ structurally from natural ones?

Extra side-chains are added to the β-lactam core.

Name one advantage of semi-synthetic penicillins.

They may be broader spectrum, more stable, and/or penicillinase resistant.

Which semi-synthetic penicillin is penicillinase resistant?

Oxacillin.

Which broad-spectrum semi-synthetic penicillin is often combined with penicillinase inhibitors?

Amoxicillin.

Which antibiotic class contains a β-lactam ring but differs slightly from penicillins?

Cephalosporins.

What is one advantage of cephalosporins?

They are generally broad spectrum.

Name a first-generation cephalosporin that requires injection.

Cephalothin.

Which cephalosporin mentioned in the lecture can be taken orally?

Cefixime.

Bacitracin is mainly used against bacteria with which Gram reaction?

Gram-positive bacteria.

Why is bacitracin restricted to topical use?

Systemic toxicity makes internal use unsafe.

Which antibiotic is considered the last line of defense against MRSA?

Vancomycin.

Isoniazid inhibits the synthesis of what cell-wall component?

Mycolic acid.

Ethambutol blocks the integration of what molecule into the Mycobacterial wall?

Mycolic acid.

What human adverse effect limits chloramphenicol’s systemic use?

Suppression of bone-marrow activity (risk of aplastic anemia).

Aminoglycosides can damage which human organs?

They can harm the auditory nerve (hearing) and the kidneys.

Name a topical aminoglycoside found in Neosporin.

Neomycin.

Besides broad spectrum activity, streptomycin is particularly effective against which pathogen group?

Mycobacteria.

Which aminoglycoside is often used against Pseudomonas aeruginosa?

Gentamicin.

Tetracyclines are especially useful against which two intracellular bacteria?

Chlamydias and Rickettsias.

What cosmetic side effect can tetracycline cause in children?

Permanent discoloration of teeth.

Which tetracycline derivative stays in the body longer?

Doxycycline.

Macrolide antibiotics are characterized by what structural feature?

A large macrocyclic lactone ring.

Which macrolide is an oral alternative to penicillin for Gram-positive infections?

Erythromycin.

Which macrolide has broader spectrum and treats Chlamydia infections?

Azithromycin.

Polymyxin B is usually administered in what form?

Topically (e.g., ointments).

What unusual body-fluid discoloration can rifampin cause?

Orange-red urine, sweat, tears, and feces.

Fluoroquinolones are valued for what pharmacokinetic property?

Excellent penetration into tissues.

Give one fluoroquinolone used in human medicine.

Ciprofloxacin.

What is the mechanism of action of sulfonamides?

They competitively inhibit folic-acid synthesis enzymes.

Which paired drug combination is a common sulfonamide therapy?

Sulfamethoxazole–Trimethoprim.

List the four main bacterial resistance mechanisms.

(1) Prevent drug entry, (2) enzymatic destruction/inactivation, (3) alteration of target site, (4) efflux pumping.

Resistance genes are often located on what mobile elements?

Plasmids or transposons.

Why should patients complete the full prescribed antibiotic course?

Stopping early allows resistant survivors to multiply and spread.

What is the goal of combination drug therapy regarding resistance?

To reduce the chance that bacteria evolve resistance to all agents.

Name the three major categories of antiviral drugs discussed.

Nucleoside/nucleotide analogs, enzyme inhibitors, and interferons.

How does acyclovir halt viral DNA replication?

It is converted to a false nucleotide that stops DNA polymerase.

Acyclovir is primarily used against which family of viruses?

Herpesviruses.

Which viral enzyme activates acyclovir inside infected cells?

Virus-encoded thymidine kinase.

Amantadine blocks which step in the influenza life cycle?

Uncoating of the virus after entry.

Indinavir inhibits which HIV enzyme?

The viral protease.

Oseltamivir inhibits which influenza surface enzyme?

Neuraminidase.

Interferon-α is used clinically to treat infections by which virus type?

Hepatitis viruses.

Gentamicin is combined with other drugs to treat infections by which opportunistic pathogen?

Pseudomonas aeruginosa.

Which capsule component helps Pseudomonas aeruginosa evade phagocytosis?

Alginate capsule.

Mycobacterium leprae causes which chronic disease?

Leprosy (Hansen’s disease).

What property makes rifampin especially useful against tuberculosis and leprosy lesions?

It penetrates tissues and cells very well.

Varicella-zoster virus remains latent in which part of the nervous system?

Dorsal root ganglia.

Which antiviral drug is commonly given to manage shingles outbreaks?

Acyclovir.

Which two surface proteins of influenza A are crucial for entry and exit?

Hemagglutinin (HA) and neuraminidase (NA).

Oseltamivir specifically targets which influenza protein?

Neuraminidase.

What is the general antiviral role of interferons?

They are cytokines that prevent the spread of viruses to new cells.

Which antibiotic in Neosporin ointment increases membrane permeability of Gram-negative bacteria?

Polymyxin B.

Vancomycin belongs to which antibiotic class?

Polypeptide antibiotics.

β-lactam antibiotics mimic what dipeptide in transpeptidase active sites?

D-Ala–D-Ala.

Blocking transpeptidase prevents cross-linking of which cell-wall polymer?

Peptidoglycan.

Name the three antibiotics typically found in over-the-counter Neosporin.

Bacitracin, neomycin, and polymyxin B.

What life-threatening blood disorder can chloramphenicol cause?

Aplastic anemia.

Which antibiotic group works by changing the shape of the 30S ribosomal subunit?

Aminoglycosides.

How do efflux pumps confer antibiotic resistance?

They actively expel the antibiotic from the bacterial cell.

What improper medical practice, aside from incomplete dosing, accelerates resistance development?

Indiscriminate or inappropriate use of antibiotics.