Cephalosporins: Structure and Classification

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Questions and Answers

What is the main difference between cephalosporins and penicillins?

  • Cephalosporins are more resistant to beta lactamase inactivation (correct)
  • Cephalosporins have a six-membered dihydrothiazine ring
  • Cephalosporins are more prone to hydrolytic degradation
  • Cephalosporins have a narrower spectrum of activity

Which generation of cephalosporins is active against E. coli, Klebsiella, and Proteus?

  • 1st Generation
  • 2nd Generation (correct)
  • 3rd Generation
  • All of the above

What is the primary use of 1st Generation cephalosporins?

  • Treat URTI, LRTI, sinusitis, and otitis media
  • Treat gram-negative infections
  • Treat skin and soft-tissue infections, as well as streptococcal pharyngitis (correct)
  • Treat anaerobic infections

What is the main advantage of 3rd Generation cephalosporins?

<p>Better activity against gram-negative organisms (D)</p> Signup and view all the answers

Which of the following is a characteristic of cephalosporins?

<p>They consist of a six-membered dihydrothiazine ring fused to a beta lactam ring (C)</p> Signup and view all the answers

What is the primary limitation of cephalosporins?

<p>They are prone to hydrolytic degradation (A)</p> Signup and view all the answers

What is the mechanism of action of Aminoglycosides?

<p>They inhibit bacterial protein synthesis by binding to the 30s subunit and blocking tRNA binding to the A site. (B)</p> Signup and view all the answers

Which of the following is NOT a use of Streptomycin?

<p>Urinary tract infections (B)</p> Signup and view all the answers

What is a unique property of Meropenem?

<p>It is resistant to dehydropeptidase enzyme. (A)</p> Signup and view all the answers

Which Aminoglycoside is most active among the Nebramycins?

<p>Tobramycin (C)</p> Signup and view all the answers

What is a characteristic of Macrolides?

<p>They contain a many-membered lactone ring. (C)</p> Signup and view all the answers

What is the mechanism of action of Ertapenem?

<p>It inhibits bacterial cell wall formation. (D)</p> Signup and view all the answers

What happens when Azithromycin is administered with food?

<p>Food has no significant effect on absorption (C)</p> Signup and view all the answers

Which antibiotic is a derivative of dichloroacetic acid?

<p>Chloramphenicol (D)</p> Signup and view all the answers

Which antibiotic is a reversible inhibitor of CYP3A4 enzyme?

<p>Telithromycin (A)</p> Signup and view all the answers

What is the mechanism of action of Clindamycin?

<p>Binds exclusively to the 50S subunit of bacterial cell (B)</p> Signup and view all the answers

Which antibiotic is effective against macrolide-resistant G(+)?

<p>Telithromycin (B)</p> Signup and view all the answers

What is the spectrum of activity of Clindamycin?

<p>Bacteriostatic against S.epidermidis, S.aureus, M.pneumonia, and bactericidal against H.influenzae, N.meningitides, B (C)</p> Signup and view all the answers

What is the primary mechanism of action of Cephalosporins against bacteria?

<p>Inhibition of cell wall formation (C)</p> Signup and view all the answers

What is the main adverse effect of Cephalosporins due to inhibition of Vitamin K?

<p>Hypoprothrombinemia (A)</p> Signup and view all the answers

Which of the following bacteria is NOT typically treated with Aztreonam?

<p>Staphylococcus aureus (A)</p> Signup and view all the answers

What is the main characteristic of Carbapenems?

<p>Broad spectrum of activity (B)</p> Signup and view all the answers

What is the primary mechanism of action of Olivanic acids?

<p>Inhibition of beta-lactamases (C)</p> Signup and view all the answers

What is the main characteristic of Imipenem?

<p>High beta-lactamase resistance (A)</p> Signup and view all the answers

What is the mechanism of action of quinolones?

<p>Inhibition of Topoisomerase IV and DNA gyrase enzymes (A)</p> Signup and view all the answers

Which of the following quinolones is NOT mentioned in the text?

<p>Cinafloxacin (A)</p> Signup and view all the answers

What is the adverse effect of quinolones that is associated with Hepatotoxicity?

<p>Trovafloxacin (B)</p> Signup and view all the answers

What type of organisms are Polypeptides effective against?

<p>Bacteria (B)</p> Signup and view all the answers

What is the source of Polypeptides?

<p>Bacillus and Streptomyces spp. (D)</p> Signup and view all the answers

What is the therapeutic use of quinolones mentioned in the text?

<p>All of the above (D)</p> Signup and view all the answers

What is the unique property of 4th generation cephalosporins?

<p>Increased stability to hydrolysis by inducible chromosomal β-lactamases (A)</p> Signup and view all the answers

What is the primary adverse effect of cephalosporins due to inhibition of Vitamin K?

<p>Hypoprothrombinemia, leading to an increased tendency to bleed (C)</p> Signup and view all the answers

What is the mechanism of action of Aztreonam?

<p>Inhibition of cell wall formation by binding to PBP3 in Gram-negative bacteria (A)</p> Signup and view all the answers

What is the characteristic of Carbapenems?

<p>Fused β-lactam rings with a broad antimicrobial spectrum (A)</p> Signup and view all the answers

What is the source of Olivanic acids?

<p>Streptomyces olivaceus (A)</p> Signup and view all the answers

What is the characteristic of Thienamycins?

<p>Broad-spectrum antibiotic activity with high β-lactamase resistance (A)</p> Signup and view all the answers

What is the primary use of Aztreonam?

<p>Treatment of Gram-negative bacterial infections, including UTI, LRTI, intra-abdominal infection, gynecological infection, and septicemia (C)</p> Signup and view all the answers

What is the primary characteristic of Monobactams?

<p>Binding to PBP3 in Gram-negative bacteria (A)</p> Signup and view all the answers

Which type of organisms is Lledo effective against?

<p>G(+) and nonspore forming anaerobes (C)</p> Signup and view all the answers

What is the mechanism of action of Quinolones?

<p>Inhibition of Topoisomerase IV and DNA gyrase enzymes (C)</p> Signup and view all the answers

What is a common adverse effect of Quinolones?

<p>GI disturbances (C)</p> Signup and view all the answers

Which of the following Quinolones is NOT mentioned in the text?

<p>Clinafloxacin (D)</p> Signup and view all the answers

What is a therapeutic use of Quinolones mentioned in the text?

<p>UTI (D)</p> Signup and view all the answers

What is the source of Polypeptides?

<p>Bacillus and Streptomyces spp. (B)</p> Signup and view all the answers

What is a characteristic of Polypeptides?

<p>Most powerful antibiotics (B)</p> Signup and view all the answers

What is an adverse effect of Quinolones associated with Tendon Rupture?

<p>Tendon Rupture (B)</p> Signup and view all the answers

What is the primary site of action of Bacitracin?

<p>Cell wall (C)</p> Signup and view all the answers

Which type of leprosy is associated with a malignant course?

<p>Lepromatous leprosy (D)</p> Signup and view all the answers

What is the primary mechanism of action of Amphotericin B?

<p>Interfering with cell membrane function (B)</p> Signup and view all the answers

What is the characteristic shape of Mycoplasma pneumoniae?

<p>Pleomorphic (C)</p> Signup and view all the answers

What is the primary treatment for leprosy?

<p>Dapsone (B)</p> Signup and view all the answers

What is the unique feature of Mycoplasma pneumoniae?

<p>It lacks a peptidoglycan cell wall (D)</p> Signup and view all the answers

What is the primary source of Bacitracin?

<p>Bacillus (C)</p> Signup and view all the answers

What is the term for the treatment of tuberculosis?

<p>TB-DOTS (D)</p> Signup and view all the answers

Which antibiotic binds exclusively to the 50S subunit of bacterial cell?

<p>Clindamycin (A)</p> Signup and view all the answers

What is the main advantage of Clindamycin over Lincomycin?

<p>Improved absorption and distribution (A)</p> Signup and view all the answers

Which of the following antibiotics is a CYP3A4 inhibitor?

<p>Telithromycin (A)</p> Signup and view all the answers

Which antibiotic is produced from Streptomyces venezuelae?

<p>Chloramphenicol (C)</p> Signup and view all the answers

What is the primary use of Clindamycin?

<p>Staph infections, cellulitis, and osteomyelitis (B)</p> Signup and view all the answers

Which antibiotic is not administered with food?

<p>Clindamycin (A)</p> Signup and view all the answers

What is the spectrum of activity of Clindamycin?

<p>Anaerobes, S.epidermidis, S.aureus, and others (A)</p> Signup and view all the answers

What is a unique chemical feature of Chloramphenicol?

<p>Contains a nitrobenzene moiety (D)</p> Signup and view all the answers

What is the mechanism of action of Vancomycin?

<p>Interferes with bacterial cell wall synthesis (A)</p> Signup and view all the answers

What is the primary route of administration for Vancomycin?

<p>Intravenous (B)</p> Signup and view all the answers

Which of the following antibiotics is derived from Streptomyces orientalis?

<p>Vancomycin (B)</p> Signup and view all the answers

What is the spectrum of activity of Polymyxin B and Colistin?

<p>G(-) bacteria (A)</p> Signup and view all the answers

What is the mechanism of action of Mupirocin?

<p>Reversibly binds to isoleucyl transfer-RNA synthetase (B)</p> Signup and view all the answers

What is the primary use of Mupirocin?

<p>Topical use (A)</p> Signup and view all the answers

What is the adverse effect associated with Vancomycin's 'Red Man or Red Neck Syndrome'?

<p>Decreased auditory acuity (A)</p> Signup and view all the answers

Which of the following antibiotics is derived from Pseudomonas fluorescens?

<p>Mupirocin (A)</p> Signup and view all the answers

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Study Notes

Cephalosporins

  • Structure: consist of a six-membered dihydrothiazine ring fused to a beta lactam ring
  • Broad spectrum and resistant to beta lactamase inactivation
  • Classified into generations, each with its own spectrum of activity:
    • 1st Generation: excellent gram-positive and modest gram-negative activity, alternatives for skin and soft-tissue infections, and for streptococcal pharyngitis
    • 2nd Generation: better activity against gram-negative organisms with some gram-positive action, treats URTI, LRTI, sinusitis, and otitis media
    • 3rd Generation: activity against gram-positive organisms and much more activity against Enterobacteriaceae
    • 4th Generation: encompasses the antimicrobial spectrum of all the third-generation agents and has increased stability to hydrolysis by inducible chromosomal -lactamases

Carbapenems

  • Comprise a family of fused beta lactam rings
  • Has broadest antimicrobial spectrum of any antibiotic
  • Analogues of penicillins or clavams, the sulfur or oxygen being replaced with carbon
  • Examples: Olivanic acids, Thienamycin, Imipenem, Meropenem, Ertapenem

Aminoglycosides

  • Natural products or semi-synthetic derivatives of compounds produced by a variety of soil actinomycetes
  • Mechanism of Action: binds to 30s ribosomal subunit and interferes with initiation of protein synthesis
  • Examples: Streptomycin, Tobramycin, Neomycin, Spectinomycin, Netilmicin, Amikacin

Macrolides

  • Contain a many-membered lactone ring (14-membered ring: Erythromycin and Clarithromycin, 15-membered ring: Azithromycin)
  • Basic in nature due to the presence of a glycosidically linked amino sugar
  • Spectrum of Activity: resembles that of Penicillin, used as an alternative to PCN
  • Examples: Erythromycin, Clarithromycin, Azithromycin

Chloramphenicol

  • Produced from Streptomyces venezuelae
  • May cause blood dyscrasias
  • Contains a nitrobenzene moiety and is a derivative of dichloroacetic acid
  • Clindamycin: a congener of Lincomycin, improved absorption and distribution than Lincomycin

Monobactams

  • Binds with PBP3 in gram-negative bacteria only
  • Treats UTI, LRTI, intra-abdominal infection, gynecological infection, and septicemia
  • Examples: Aztreonam

Quinolones

  • Mechanism of Action: inhibition of Topoisomerase IV and DNA gyrase enzymes
  • Spectrum of Activity: specific agents with activity against Streptococci, active against Chlamydia, Mycoplasma, Legionella, Brucella, and Mycobacterium
  • Examples: Levofloxacin, Gatifloxacin, Moxifloxacin, Ofloxacin, Ciprofloxacin

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