41 Questions
What was the cause of John McCrae's death?
Streptococcal pneumonia/meningitis
In which war did Norman Bethune serve and get wounded?
World War I
What led to the miraculous revolution in medicine and the curing of infectious diseases?
Treatment with a new experimental drug
Which enzyme is inhibited by trimethoprim in the folic acid biosynthesis pathway?
Enzyme #3
What is the synergistic effect observed when trimethoprim and sulfonamide are used in combination?
Enhanced antimicrobial activity
What is the substrate of the enzyme involved in folic acid biosynthesis that is structurally similar to sulfa drugs?
PABA
What type of inhibition is exemplified by the action of sulfa drugs on the enzyme involved in folic acid biosynthesis?
Competitive inhibition
Which antibiotic irreversibly binds to the 30S ribosomal subunit, causing it to malfunction and blocking initiation of translation?
Aminoglycosides
Which antibiotic class is often the drug of choice for patients allergic to penicillin?
Macrolides
Which antibiotic class interferes with protein synthesis at various steps?
Macrolides
Which antibiotic is crucial for treating Gram-positive bacteria resistant to β-lactam drugs?
Vancomycin
Which antibiotic class has low affinity for Gram-positive bacteria?
Cephalosporins
Which antibiotic class is effective against a wide range of bacteria and resists β-lactamases?
Carbapenems
Which antibiotic class has greater activity against Pseudomonas species?
Extended-spectrum penicillins
Which antibiotic class is bacteriostatic and reversibly binds to the 30S subunit, blocking tRNA attachment?
Tetracyclines
Which antibiotic inhibits topoisomerases and is bactericidal against a wide variety of bacteria?
Fluoroquinolones
Which antibiotic blocks prokaryotic RNA polymerase from initiating transcription and is used to treat tuberculosis, Hansen’s disease, and meningitis?
Rifamycins
Which type of antimicrobial drug can be 'static' or 'cidal'?
Antibiotics
Who isolated Streptomycin from S. griseus?
Selman Waksman
What test is commonly used to determine the susceptibility of bacterial strains to drugs?
The Kirby-Bauer disc diffusion test
What is the main concern in the industry regarding antimicrobial drugs?
Few new antibiotics being developed
'Antimicrobial drugs exhibit selective toxicity' - how is relative toxicity expressed?
$Therapeutic hinspace index$
'Determining susceptibility of bacterial strains involves minimum inhibitory and bactericidal concentrations' - what does MIC stand for?
$Minimum hinspace inhibitory hinspace concentration$
'Antimicrobials differ in behavior in the body, with some requiring multiple doses per day' - what term describes this behavior?
Pharmacokinetics
Which antimicrobial drug was identified as most suitable for treating humans post-1960?
Penicillin G
What term describes combinations of antimicrobial drugs that can be antagonistic, synergistic, or additive?
Interactions
'Adverse effects of antimicrobial drugs include toxicity, allergic reactions, and suppression of normal microbiota' - what are normal microbiota also known as?
Normal flora
'Antimicrobials differ in behavior in the body' - what term describes the study of the action of drugs within the body?
Pharmacodynamics
'Antimicrobial drugs are classified as antibiotics, antifungals, antiparasitics, and antivirals' - what term describes their ability to affect only microbial cells while causing little or no harm to host cells?
Selective toxicity
Who discovered the first successful antimicrobial chemical in 1910?
Paul Ehrlich
Which discovery marked the finding of the first 'sulfa' drug?
Prontosil
Who discovered the effectiveness of penicillin against bacterial species in 1928?
Alexander Fleming
Who led the efforts in 1941 to purify and test penicillin?
Howard Florey
'Sulfa' drugs are derivatives of which antimicrobial chemical?
\text{Prontosil}
'Ampicillin' and 'Methicillin' are chemical derivatives of which antimicrobial drug?
\text{Penicillin}
Which method uses a strip with a gradient of drug to determine MIC?
E test
What is the primary target of β-lactam drugs in bacteria?
Cell wall synthesis
Which antibiotic interferes with the transport of peptidoglycan precursors across the cytoplasmic membrane?
Bacitracin
Which type of cells are weakened by penicillins, cephalosporins, and other β-lactam drugs?
Actively growing cells
What is the mode of action of vancomycin in bacteria?
Inhibition of peptidoglycan synthesis
Diffusion bioassay is used for comparing known concentrations with patient samples to yield drug concentration through:
Diffusion rates
Study Notes
Antimicrobial Drugs: Features and Susceptibility Testing
- Penicillin, initially difficult to purify, was proven effective in humans by a police officer
- Penicillin G identified as most suitable for treating humans post-1960
- Streptomycin isolated by Selman Waksman from S. griseus, prompting further antibiotic screening
- Few new antibiotics being developed, leading to a concern in the industry
- Antimicrobial drugs exhibit selective toxicity, with relative toxicity expressed as therapeutic index
- Antimicrobial drugs are classified as antibiotics, antifungals, antiparasitics, and antivirals
- Antimicrobial drugs can be "static" (inhibit growth) or "cidal" (kill microbes), with varying spectra of activity
- Combinations of antimicrobial drugs can be antagonistic, synergistic, or additive
- Antimicrobials differ in behavior in the body, with some requiring multiple doses per day
- Adverse effects of antimicrobial drugs include toxicity, allergic reactions, and suppression of normal microbiota
- Determining susceptibility of bacterial strains involves minimum inhibitory and bactericidal concentrations
- The Kirby-Bauer disc diffusion test is commonly used to determine the susceptibility of bacterial strains to drugs
Commercial Modifications of Susceptibility Testing
- Commercial modifications of susceptibility testing aim to be less labor-intensive and provide faster results.
- One automated system uses turbidity in cards to determine growth rate and interprets results to determine minimum inhibitory concentrations (MICs) in 6–15 hours.
- E test, a modification of the disc diffusion test, uses a strip with a gradient of drug to determine MIC. The intersection of the zone of inhibition indicates MIC.
- Measuring concentration of antimicrobial drugs in blood or other body fluids is important to determine blood toxicity and achievable levels for new drugs.
- Diffusion bioassay compares known concentrations with patient samples and produces a standard curve to yield drug concentration.
- Drug targets of bacteria include cell wall synthesis, nucleic acid synthesis, cell membrane integrity, metabolic pathways, and protein synthesis.
- β-lactam drugs competitively inhibit enzymes that help form peptide bridges between adjacent glycan chains in cell walls.
- Vancomycin binds to the amino acid side chain of NAM molecules, blocking peptidoglycan synthesis.
- Bacitracin interferes with the transport of peptidoglycan precursors across the cytoplasmic membrane.
- Penicillins, cephalosporins, and other β-lactam drugs competitively inhibit enzymes that catalyze formation of peptide bridges between adjacent glycan strands, disrupting peptidoglycan synthesis.
- These drugs weaken cell walls, leading to cell lysis and are only effective against actively growing cells.
- Penicillins have a basic structure and side chain and are grouped into narrow-spectrum, penicillinase-resistant, and broad-spectrum categories based on their activity against Gram-positive and Gram-negative bacteria.
Learn about less labor-intensive, faster susceptibility testing methods such as automated systems and E test modifications for determining minimum inhibitory concentrations (MICs) in a shorter time frame. Understand the intersection of zone of inhibition to indicate MIC.
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