Penicillin: Natural and Semisynthetic Overview

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Questions and Answers

Which penicillin is known for its biliary excretion?

Methicillin

Dicloxacillin

Cloxacillin

Nafcillin (correct)

What type of infections is Ampicillin commonly used for in combination with aminoglycosides?

Enterococcal infections (correct)

Staphylococcal infections

Klebsiella infections

Pseudomonal infections

Which of the following penicillins is not stable in acid and not penicillinase resistant?

Carbenicillin (correct)

Nafcillin

Oxacillin

Amoxicillin

Which penicillin is rarely used due to nephrotoxicity?

Methicillin Signup and view all the answers

Which bacterial infection is specifically noted to be less active against by Carbenicillin?

Klebsiella Signup and view all the answers

Which of the following bacteria are identified as having resistance through B lactamase production?

Staphylococcus aureus Signup and view all the answers

What is the primary use of aminoglycosides in the context of resistance management?

To treat syphilis Signup and view all the answers

Which of the following is a characteristic of semisynthetic penicillin?

Acid-stable and useful for oral administration Signup and view all the answers

Which category of bacteria is treated by PBP-altered penicillin?

Narrow spectrum gram-positive bacteria Signup and view all the answers

What is one of the known applications of expanded activity penicillin?

Managing infections caused by penicillinase-susceptible organisms Signup and view all the answers

Which of the following organisms is NOT included in the prophylactic use of penicillin?

Tetanus Signup and view all the answers

Which type of penicillin is primarily effective against Streptococcus and other gram-positive organisms?

Penicillin G Signup and view all the answers

Among the following, which condition can be treated with the use of aminoglycosides?

Enterococcal infections Signup and view all the answers

What is the primary mechanism by which B lactams exert their antibacterial effect?

Inhibit cross-linking of the cell wall Signup and view all the answers

Which of the following adverse effects is associated with the use of Methicillin?

Neutropenia Signup and view all the answers

What is the spectrum of activity of natural penicillin?

Narrow spectrum Signup and view all the answers

Which of the following is a characteristic of B lactamase susceptibility?

Sensitivity to degradation by specific enzymes Signup and view all the answers

What severe allergic reaction is associated with penicillin use?

Anaphylaxis Signup and view all the answers

Which bacterial feature affects the access of PBPs in certain strains?

Alterations in porin structures Signup and view all the answers

Which natural source was penicillin first discovered from?

Fungi Signup and view all the answers

What type of adverse effect can result from the use of ampicillin?

Maculopapular rash Signup and view all the answers

What is the primary mechanism of action for the drugs discussed?

Bind PBPs to inhibit cell wall synthesis Signup and view all the answers

Which of the following statements about resistance is correct?

MRSA is resistant to cephalosporins. Signup and view all the answers

Which generation of cephalosporins would you likely use for surgical prophylaxis?

First generation Signup and view all the answers

Ceftriaxone is primarily indicated for which condition?

Gonorrhea Signup and view all the answers

Which of these organisms is less active against by the drugs discussed?

MRSA Signup and view all the answers

Cefepime is noted for its resistance against which of the following?

Beta-lactamases producing Enterobacter Signup and view all the answers

Which drug can be used for treating acute otitis media?

Ceftriaxone Signup and view all the answers

Which drug is primarily effective against Pseudomonas infections?

Cefepime Signup and view all the answers

Which carbapenem is not degraded by renal dehydropeptidase I?

Ertapenem Signup and view all the answers

What is a significant risk associated with the use of drugs containing methylthiotetrazole groups?

Hypoprothrombinemia Signup and view all the answers

Which antibiotic shows wide activity against Gram-positive cocci and is effective against MRSA?

Teicoplanin Signup and view all the answers

Which of these is a characteristic feature of Aztreonam?

Resistance to beta-lactamases Signup and view all the answers

What mechanism does vancomycin resistance in bacteria involve?

Replacement of D-Alanine by D-lactate Signup and view all the answers

Which organism is commonly resistant to Carbapenems?

Klebsiella pneumoniae Signup and view all the answers

Which antibiotics are typically considered narrow spectrum?

Vancomycin and Teicoplanin Signup and view all the answers

What side effect is commonly associated with intravenous injection of certain antibiotics?

Local irritation and pain Signup and view all the answers

What effect do aminoglycosides have when used in combination with carbapenems?

Increased nephrotoxicity Signup and view all the answers

Which of the following antibiotics is effective against Pseudomonas aeruginosa?

Aztreonam Signup and view all the answers

Study Notes

Penicillin

First antibiotic discovered by Alexander Fleming.
Derived from Penicillium notatum and Penicillium chrysogenum.
Classified into natural and semisynthetic forms.

Natural Penicillin (Penicillin G, Benzylpenicillin)

Narrow spectrum, beta-lactamase susceptible.
Acid labile, requiring injection.
Procaine and benzathine forms allow for slow intramuscular release.
Uses: Syphilis, against enterococci with aminoglycosides, Anthrax, Actinomycosis, Diphtheria, Pneumococcus, Bacilli (gram-positive), prophylaxis for rheumatic fever, endocarditis, and agranulocytosis.
Adverse effects: local irritancy, hypersensitivity reactions (urticaria, pruritus, fever, joint swelling, hemolytic anemia, nephritis, anaphylaxis, Jarisch-Herxheimer reaction).

Semisynthetic Penicillin

Acid-stable (Penicillin V) oral form (Phenoxymethyl penicillin) for oropharyngeal infections.
Beta-lactams inhibit cross-linking in cell walls.
Expanded activity: wider spectrum, penicillinase-susceptible and resistant options available.
Amino-acid stable, penicillinase-susceptible variations work against many gram-negative bacilli ( H. influenzae, E. coli, Proteus, Moraxella, L. monocytogenes, Salmonella, Shigella, Helicobacter pylori).
Ampicillin is a prototype.
Resistance mechanisms include changes in porin structures and PBPs. Pseudomonas aeruginosa is particularly resistant.

Penicillinase-Resistant Penicillins

Very narrow spectrum.
Examples: Cloxacillin, Oxacillin, Nafcillin (biliary excretion), Dicloxacillin, Methicillin (rarely used due to nephrotoxicity).
Methicillin is not resistant to gram-negative bacteria; MRSA and MRSE are resistant to all penicillins.

Carboxyl Penicillins

Not acid-stable, not penicillinase-resistant.
Example: Carbenicillin - active against Pseudomonas and indole-positive Proteus, less active against Salmonella, E. coli, and Enterobacter. Not active against Klebsiella or gram-positive cocci.

Penicillin Mechanism of Action (MOA)

Binds to penicillin-binding proteins (PBPs), inhibiting cell wall synthesis.
Bactericidal.

Cephalosporins

First-generation drugs (Cefazolin, Cephalexin): Primarily active against gram-positive cocci (staphylococci, streptococci), E. coli, and K. pneumoniae. Limited activity against gram-negative cocci, enterococci, MRSA, and most gram-negative rods. Used in surgical prophylaxis.
Second and third-generation drugs have increased gram-negative activity and resistance to some beta-lactamases. Ceftriaxone and Cefotaxime are highly active against penicillin-resistant Streptococcus pneumoniae (PRSP). Pseudomonas coverage is provided by cefoperazone and ceftazidime; B. fragilis coverage by ceftizoxime. Ceftriaxone (parenteral) and Cefixime (oral) are first-line drugs for gonorrhea.
Fourth-generation drugs (Cefepime): Resistant to many beta-lactamases.

Carbapenems (Imipenem, Meropenem, Ertapenem, Doripenem)

Low susceptibility to beta-lactamases.
Broad activity against gram-positive cocci (PRSP), gram-negative rods, and anaerobes.
Used for serious infections caused by antibiotic-resistant organisms, including MRSA.
Often used in combination with aminoglycosides for Pseudomonas infections.
Imipenem is administered with cilastatin to inhibit renal dehydropeptidase I.
Adverse Effects: Phlebitis (IV administration), Increased nephrotoxicity with aminoglycosides, Methylthiotetrazole containing drugs (cefamandole, cefoperazone, cefotetan) may cause hypoprothrombinemia and disulfiram-like reactions with ethanol.

Aztreonam (Monobactam)

Resistant to beta-lactamases.
Active against gram-negative rods (Klebsiella, Pseudomonas, Serratia).
Inactive against gram-positive bacteria and anaerobes.
Synergistic with aminoglycosides. Administered intravenously.

Resistance to Beta-Lactams

Decreased membrane permeability.
Changes in PBPs.
Beta-lactamase production.
MRSA is also resistant to many cephalosporins.
VRE and VRSE result from D-Ala replacement by D-lactate.

Other Important Notes

Partial cross-allergenicity exists between penicillins and cephalosporins.
Clostridium difficile infections can occur as a complication.
Teicoplanin and Teicovalcin are alternative options in cases of VRE and MRSA resistance.

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Description

This quiz explores the discovery and classification of penicillin, the first antibiotic identified by Alexander Fleming. Dive into the details of natural and semisynthetic forms, their uses, adverse effects, and the spectrum of activity they cover.