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The cephalosporins, are a class of -lactam antibiotics. Together with cephamycins they belong to a sub-group called cephems.


Cephalosporin was first isolated from cultures of Cephalosporium acremoniumfrom a sewer in Sardinia in 1948 by an italian scientist Guiseppe Brotzu. He noticed that these cultures produced a substance that was effective against salmonella typhi, the cause of typhoid. In 1960s, Eli Lilly launched the first cephalosporins on the market.

Mode of action

Cephalosporins work the same way as penicillins, they interfere with the peptidoglycan synthesis of the bacterial wall by inhibiting the final transpeptidation needed for the cross-links. This effect is bactericidal.

The generations

The cephalosporin nucleus can be modified to gain different properties.

First generation cephalosporins have a spectrum that includes penicillinase-producing, methicillin-susceptible staphylococci and streptococci, though they are not the drugs of choice for such infections. They also have activity against some E. coli, Klebsiella pneumoniae and Proteus mirabilis, but have no activity against Bacteroides fragilis, enterococci, methicilllin-resistant staphylococci, Pseudomonas, Acinetobacter, Enterobacter, indole-positive Proteus or Serratia''.

First generation cephalosporins:

The second generation cephalosporins have a greater gram-negative spectrum while retaining some activity against gram-positive cocci. They are also more resistant to

Second generation cephalosporins:

Third generation cephalsporins have a broad spectrum of activity against enteric gram-negative rods and thus are particularly useful in treating hospital-acquired infections.

Third generation cephalosporins: