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Questions and Answers
Which type of antibiotics acts by inhibiting bacterial multiplication?
Which type of antibiotics acts by inhibiting bacterial multiplication?
- Narrow-spectrum
- Bacteriostatic (correct)
- Broad spectrum
- Bactericidal
Which pharmacological feature is characteristic of antibiotics?
Which pharmacological feature is characteristic of antibiotics?
- Broad spectrum effect
- Not toxic for host
- Selective toxicity
- Pass through into tissues and body fluids (correct)
Which enzyme is responsible for making chains and cross-links in the peptidoglycan structure of the bacterial cell wall?
Which enzyme is responsible for making chains and cross-links in the peptidoglycan structure of the bacterial cell wall?
- Transglycosylase
- Penicillin binding proteins
- Carboxypeptidase
- Transpeptidase (correct)
What is the main content of the bacterial cell wall?
What is the main content of the bacterial cell wall?
Which type of antibiotics can act on only a few different pathogens?
Which type of antibiotics can act on only a few different pathogens?
Which antibiotic feature refers to its ability to target specific pathogens without harming the host.
Which antibiotic feature refers to its ability to target specific pathogens without harming the host.
Which type of antibiotics can act on many different pathogens?
Which type of antibiotics can act on many different pathogens?
What is the main feature of antibiotics that allows them to target bacteria without harming the host?
What is the main feature of antibiotics that allows them to target bacteria without harming the host?
Which pharmacological feature ensures that antibiotics do not harm the host?
Which pharmacological feature ensures that antibiotics do not harm the host?
Which enzyme is a member of serine proteases and referred to as penicillin binding proteins (PBPs)?
Which enzyme is a member of serine proteases and referred to as penicillin binding proteins (PBPs)?
Which antibiotic binds irreversibly to the 30S ribosomal subunit and causes misreading of mRNA?
Which antibiotic binds irreversibly to the 30S ribosomal subunit and causes misreading of mRNA?
What is the mechanism of action of polymyxins like Polymyxin B and Polymyxin E (colistin)?
What is the mechanism of action of polymyxins like Polymyxin B and Polymyxin E (colistin)?
Which antibiotic is primarily used for Gram-negative bacteria and has a severe nephrotoxicity effect if used systemically?
Which antibiotic is primarily used for Gram-negative bacteria and has a severe nephrotoxicity effect if used systemically?
What is the primary mode of action of Aminoglycosides like Gentamicin and Tobramycin?
What is the primary mode of action of Aminoglycosides like Gentamicin and Tobramycin?
Which antibiotic binds to the D-Ala-D-Ala chain and prevents the bridging between peptidoglycan chains?
Which antibiotic binds to the D-Ala-D-Ala chain and prevents the bridging between peptidoglycan chains?
What is the primary mechanism of action of beta-lactam antibiotics combined with clavulanic acid, sulbactam, or tazobactam?
What is the primary mechanism of action of beta-lactam antibiotics combined with clavulanic acid, sulbactam, or tazobactam?
Which antibiotic is highly effective against staphylococci and is commonly resistant in both hospital and community-acquired isolates?
Which antibiotic is highly effective against staphylococci and is commonly resistant in both hospital and community-acquired isolates?
What is the primary target of cephalosporins like Cefotaxime, Ceftazidime, and Ceftriaxone?
What is the primary target of cephalosporins like Cefotaxime, Ceftazidime, and Ceftriaxone?
$Imipenem$, $Doripenem$, $Ertapenem$, and $Meropenem$ have broad-spectrum activity. Which antibiotic class do they belong to?
$Imipenem$, $Doripenem$, $Ertapenem$, and $Meropenem$ have broad-spectrum activity. Which antibiotic class do they belong to?
What is the primary function of Bacitracin when used in the treatment of skin infections caused by Gram-positive bacteria?
What is the primary function of Bacitracin when used in the treatment of skin infections caused by Gram-positive bacteria?
Which antibiotic is replaced by cipro, levo, and moxifloxacin (fluoroquinolones)?
Which antibiotic is replaced by cipro, levo, and moxifloxacin (fluoroquinolones)?
What is the mechanism of action of fluoroquinolones like cipro, levo, and moxifloxacin?
What is the mechanism of action of fluoroquinolones like cipro, levo, and moxifloxacin?
In which condition is cipro, levo, and moxifloxacin used orally for treatment?
In which condition is cipro, levo, and moxifloxacin used orally for treatment?
What is the mechanism of action of Sulfonamids?
What is the mechanism of action of Sulfonamids?
How do Sulfonamids inhibit the first step of folic acid synthesis?
How do Sulfonamids inhibit the first step of folic acid synthesis?
What is the mechanism of action of Trimethoprim?
What is the mechanism of action of Trimethoprim?
Fluoroquinolones like cipro, levo, and moxifloxacin are ineffective against aerobic and facultative anaerobic bacteria.
Fluoroquinolones like cipro, levo, and moxifloxacin are ineffective against aerobic and facultative anaerobic bacteria.
Sulfonamids work by breaking down bacterial DNA.
Sulfonamids work by breaking down bacterial DNA.
Trimethoprim prevents the formation of tetrahydrofolic acid from dihydrofolic acid by inhibiting the dihydrofolate reductase enzyme.
Trimethoprim prevents the formation of tetrahydrofolic acid from dihydrofolic acid by inhibiting the dihydrofolate reductase enzyme.
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Study Notes
Inhibitors of Bacterial Cell Wall
- Inhibit the last step of peptidoglycan synthesis (transpeptidation reaction)
- Examples:
- Clavulanic acid
- Sulbactam
- Tazobactam
- They act by inhibiting the β-lactamase enzyme, which breaks the β-lactam ring
Beta-Lactam Antibiotics
- Combined use with β-lactamase inhibitors
- Examples:
- Penicillins
- Cephalosporins
- Cephamycins
Penicillins
- Natural penicillins:
- Penicillin G: inactivated by stomach acid, IV use possible for limited susceptible bacteria
- Penicillin V: acid-resistant, oral form can be used
- Penicillinase-resistant penicillins:
- Methicillin
- Oxacillin
- Cloxacillin
- Dicloxacillin
- Similar to natural penicillins, highly effective against staphylococci
- Methicillin-resistant isolates are common in both hospital and community-acquired (MRSA)
Aminopenicillins
- Broad-spectrum penicillins
- Examples:
- Ampicillin
- Amoxicillin
Other Penicillins
- Carbenicillin
- Ticarcillin
- Piperacillin
- Broader spectrum of action, including Gram-negative bacteria (Klebsiella, Enterobacter, and Pseudomonas species)
Cephalosporins and Cephamycins
- First isolated from Cephalosporium mold
- Cephamycins are similar to cephalosporins but more resistant to β-lactamase hydrolysis
- Examples:
- 1st Generation Cephalosporins:
- Cephalexin
- Cephalothin
- Cefazolin
- Cefapirin
- Cefradin
- 2nd Generation Cephalosporins:
- Increased Gram-negative activity
- Cefochlor
- Cefuroxime
- 3rd Generation Cephalosporins:
- More resistant to β-lactamases
- Cefoxitin
- Cefotetan
- 4th Generation Cephalosporins:
- Pass through the outer membrane of Gram-negative bacteria easier and faster
- Cefotaxime
- Ceftazidime
- Ceftriaxone
- Cefixime
- 5th Generation Cephalosporins:
- Increased Gram-negative activity
- Cefepime
- Cefpirom
- 1st Generation Cephalosporins:
Carbapenems
- Examples:
- Imipenem
- Doripenem
- Ertapenem
- Meropenem
- Frequently prescribed, broad-spectrum
Monobactams
- Narrow-spectrum drugs, only aerobic Gram-negative activity
- Example:
- Aztreonam
Inhibitors of Bacterial Cell Wall
- Vancomycin
- Teicoplanin
- Ineffective against Gram-negative bacteria
- Bind to D-Ala-D-Ala chain, preventing bridging between peptidoglycan chains
- Bactericidal effect
Polypeptides
- Bacitracin
- Isoniazid
- Ethionamide
- Ethambutol
- Cycloserine
- Cell wall-effective antibiotics used in the treatment of Mycobacteria sp.
Inhibitors of Cytoplasmic Membrane Function
- Polymyxins (A, B, C, D, E)
- Obtained from Bacillus polymyxa
- Act as a detergent, binding to the outer membrane, increasing cell permeability, and causing cell death
- Polymyxin B and E (colistin) have severe nephrotoxicity, used systemically in isolates sensitive to only colistin (e.g., Acinetobacter and Pseudomonas)
Daptomycin
- Effective against Gram-positive bacteria
- Cannot pass through the Gram-negative cell wall and reach the cytoplasmic membrane
- Binds irreversibly to the cytoplasmic membrane, causing disruption in depolarization and ion exchange, leading to cell death
- Used against Staphylococci, Streptococci, and Vancomycin-resistant Enterococci (VRE)
Protein Synthesis Inhibition
- Aminoglycosides (bactericidal)
- Tetracyclines (bacteriostatic)
- Glycylcyclines (bacteriostatic)
- Aminoglycosides:
- Streptomycin
- Neomycin
- Kanamycin
- Tobramycin
- Gentamicin
- Sisomycin
- All bind irreversibly to the 30S ribosomal subunit, causing misreading of mRNA and early separation of mRNA from the ribosome
Tetracyclines
- Bacteriostatic
- Reversible attachment to 30S, inhibiting aminoacyl-tRNA binding to the 30S ribosome-mRNA complex
- Examples:
- Tetracycline
- Doxycycline
- Minocycline
Macrolides
- Erythromycin
- Modifications:
- Azithromycin
- Clarithromycin
- Roxithromycin
- Binds reversibly to the 50S ribosomal subunit, blocking polypeptide elongation
Quinolones
- Examples:
- Nalidixic acid
- Ciprofloxacin
- Levofloxacin
- Moxifloxacin
- Inhibit DNA topoisomerase type II (DNA gyrase) or type IV enzymes necessary for DNA replication, recombination, and DNA repair
Antimicrobic Features
- Selective toxicity
- Broad-spectrum effect
- Bacteriosidal effect
- Pharmacological features:
- Not toxic to the host
- Pass through into tissues and body fluids
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