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Cephalosporins are a class of beta-lactam antibiotics that share structural similarities with penicillins and are used to treat a wide range of bacterial infections. These drugs are categorized into five generations, each with their own distinct characteristics and treatment coverage. They span from primarily treating gram-positive infections in the first generation to having broad-spectrum coverage in later generations.

1st generation cephalosporins, which include cephalexin and cefazolin, are effective against gram-positive cocci such as staphylococcus and streptococcus. They treat infections like cellulitis, soft tissue abscesses, and strep throat, and they also cover gram-negative bacteria in the treatment of urinary tract infections.

2nd generation cephalosporins (such as cefuroxime, cefotetan, and cefoxitin) maintains the gram-positive coverage of the first generation, but have extended gram-negative coverage to treat sinusitis, otitis, and lower respiratory infections.

3rd generation cephalosporins (like ceftriaxone and cefotaxime) have extended gram-negative coverage beyond the second generation, and are key in treating serious infections caused by drug-resistant bacteria. They are also able to cross the blood-brain barrier, making them ideal for meningitis treatment.

4th generation cephalosporins (such as cefepime) are broad spectrum antibiotics that can penetrate the CNS and are active against pseudomonas infections.

Lastly, 5th generation cephalosporins (which includes ceftaroline) are also broad spectrum antibiotics that are notably effective against MRSA.

Lesson Outline

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1. What are the key characteristics of cephalosporins, and how do they function as antibiotics?

Cephalosporins are a type of beta-lactam antibiotic because they contain a beta-lactam ring. Their primary mode of action involves binding to penicillin-binding proteins (PBPs), thereby halting the synthesis of the peptidoglycan wall, an integral component of bacterial cell walls. This results in the death of the bacterial cells due to instability of the cell walls.

2. What are 1st generation cephalosporins and what infections do they treat?

1st generation cephalosporins, such as cephalexin and cefazolin, are primarily active against gram-positive organisms like staphylococcus and streptococcus. They are therefore effective in treating skin and soft tissue infections, including cellulitis and abscesses, streptococcal pharyngitis, and urinary tract infections caused by gram negative bacteria (e.g. Proteus, E.coli, and Klebsiella). Cefazolin is often used for surgical prophylaxis as well.

3. What distinguishes 2nd generation cephalosporins from the 1st generation?

While 2nd generation cephalosporins, like cefuroxime, cefotetan, and cefoxitin, are still effective against many gram-positive bacteria, they have extended coverage against gram-negative bacteria. They can target pathogens such as Haemophilus influenzae, Neisseria, and Serratia.

4. How do 3rd generation cephalosporins improve upon earlier generations?

3rd generation cephalosporins, including ceftriaxone, cefotaxime, and ceftazidime, have even further extended gram-negative coverage compared to 2nd generation. They are the first-line empiric treatment for meningitis. They are also effective against organisms that cause community and hospital-acquired pneumonia, and furthermore, ceftazidime can be used to treat Pseudomonas infections.

5. Are there any cephalosporins that are effective against methicillin-resistant Staph aureus (MRSA)?

Yes, 5th generation cephalosporins such as ceftaroline are broad spectrum antibiotics that are effective against MRSA. This generation of cephalosporins has the broadest coverage among all cephalosporins and is the latest addition to the cephalosporin group.