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Cephalosporins: Structure and Classification

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What is the main difference between cephalosporins and penicillins?

Cephalosporins are more resistant to beta lactamase inactivation

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

2nd Generation

What is the primary use of 1st Generation cephalosporins?

Treat skin and soft-tissue infections, as well as streptococcal pharyngitis

What is the main advantage of 3rd Generation cephalosporins?

Better activity against gram-negative organisms

Which of the following is a characteristic of cephalosporins?

They consist of a six-membered dihydrothiazine ring fused to a beta lactam ring

What is the primary limitation of cephalosporins?

They are prone to hydrolytic degradation

What is the mechanism of action of Aminoglycosides?

They inhibit bacterial protein synthesis by binding to the 30s subunit and blocking tRNA binding to the A site.

Which of the following is NOT a use of Streptomycin?

Urinary tract infections

What is a unique property of Meropenem?

It is resistant to dehydropeptidase enzyme.

Which Aminoglycoside is most active among the Nebramycins?

Tobramycin

What is a characteristic of Macrolides?

They contain a many-membered lactone ring.

What is the mechanism of action of Ertapenem?

It inhibits bacterial cell wall formation.

What happens when Azithromycin is administered with food?

Food has no significant effect on absorption

Which antibiotic is a derivative of dichloroacetic acid?

Chloramphenicol

Which antibiotic is a reversible inhibitor of CYP3A4 enzyme?

Telithromycin

What is the mechanism of action of Clindamycin?

Binds exclusively to the 50S subunit of bacterial cell

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

Telithromycin

What is the spectrum of activity of Clindamycin?

Bacteriostatic against S.epidermidis, S.aureus, M.pneumonia, and bactericidal against H.influenzae, N.meningitides, B

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

Inhibition of cell wall formation

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

Hypoprothrombinemia

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

Staphylococcus aureus

What is the main characteristic of Carbapenems?

Broad spectrum of activity

What is the primary mechanism of action of Olivanic acids?

Inhibition of beta-lactamases

What is the main characteristic of Imipenem?

High beta-lactamase resistance

What is the mechanism of action of quinolones?

Inhibition of Topoisomerase IV and DNA gyrase enzymes

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

Cinafloxacin

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

Trovafloxacin

What type of organisms are Polypeptides effective against?

Bacteria

What is the source of Polypeptides?

Bacillus and Streptomyces spp.

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

All of the above

What is the unique property of 4th generation cephalosporins?

Increased stability to hydrolysis by inducible chromosomal β-lactamases

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

Hypoprothrombinemia, leading to an increased tendency to bleed

What is the mechanism of action of Aztreonam?

Inhibition of cell wall formation by binding to PBP3 in Gram-negative bacteria

What is the characteristic of Carbapenems?

Fused β-lactam rings with a broad antimicrobial spectrum

What is the source of Olivanic acids?

Streptomyces olivaceus

What is the characteristic of Thienamycins?

Broad-spectrum antibiotic activity with high β-lactamase resistance

What is the primary use of Aztreonam?

Treatment of Gram-negative bacterial infections, including UTI, LRTI, intra-abdominal infection, gynecological infection, and septicemia

What is the primary characteristic of Monobactams?

Binding to PBP3 in Gram-negative bacteria

Which type of organisms is Lledo effective against?

G(+) and nonspore forming anaerobes

What is the mechanism of action of Quinolones?

Inhibition of Topoisomerase IV and DNA gyrase enzymes

What is a common adverse effect of Quinolones?

GI disturbances

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

Clinafloxacin

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

UTI

What is the source of Polypeptides?

Bacillus and Streptomyces spp.

What is a characteristic of Polypeptides?

Most powerful antibiotics

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

Tendon Rupture

What is the primary site of action of Bacitracin?

Cell wall

Which type of leprosy is associated with a malignant course?

Lepromatous leprosy

What is the primary mechanism of action of Amphotericin B?

Interfering with cell membrane function

What is the characteristic shape of Mycoplasma pneumoniae?

Pleomorphic

What is the primary treatment for leprosy?

Dapsone

What is the unique feature of Mycoplasma pneumoniae?

It lacks a peptidoglycan cell wall

What is the primary source of Bacitracin?

Bacillus

What is the term for the treatment of tuberculosis?

TB-DOTS

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

Clindamycin

What is the main advantage of Clindamycin over Lincomycin?

Improved absorption and distribution

Which of the following antibiotics is a CYP3A4 inhibitor?

Telithromycin

Which antibiotic is produced from Streptomyces venezuelae?

Chloramphenicol

What is the primary use of Clindamycin?

Staph infections, cellulitis, and osteomyelitis

Which antibiotic is not administered with food?

Clindamycin

What is the spectrum of activity of Clindamycin?

Anaerobes, S.epidermidis, S.aureus, and others

What is a unique chemical feature of Chloramphenicol?

Contains a nitrobenzene moiety

What is the mechanism of action of Vancomycin?

Interferes with bacterial cell wall synthesis

What is the primary route of administration for Vancomycin?

Intravenous

Which of the following antibiotics is derived from Streptomyces orientalis?

Vancomycin

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

G(-) bacteria

What is the mechanism of action of Mupirocin?

Reversibly binds to isoleucyl transfer-RNA synthetase

What is the primary use of Mupirocin?

Topical use

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

Decreased auditory acuity

Which of the following antibiotics is derived from Pseudomonas fluorescens?

Mupirocin

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

This quiz covers the structure and classification of cephalosporins, a type of broad-spectrum antibiotic. Learn about their characteristics, generations, and uses in treating various infections.

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