Cephalosporins Overview

Study Notes

Cephalosporins are a class of antibiotics derived from the fungus Cephalosporium acremonium.
They are similar to penicillin, but are more stable to many bacterial beta-lactamases.
Cephalosporins have a broader spectrum of activity against bacteria than penicillin.
Cephalosporins are not active against enterococci, Listeria monocytogenes, Acinetobacter, or MRSA (except for ceftaroline).
Some strains of E.coli and Klebsiella species express extended-spectrum beta-lactamases that can hydrolyze most cephalosporins.
Classified into four generations (1st, 2nd, 3rd, and 4th).
From the 1st to the 3rd generation, there is broader activity against Gram-negative bacteria with a slight decrease in Gram-positive activity.
4th generation cephalosporins have the broadest Gram-negative activity without sacrificing Gram-positive activity.
They inhibit bacterial growth by interfering with bacterial cell wall synthesis.
They are bactericidal and kill bacteria when they are actively growing and synthesizing cell walls.

Drugs include Cefadroxil, cephalexin, cephradine, and Cefazolin.
They are sensitive to beta-lactamases.
They are active against Gram-positive cocci such as most streptococci strains and S.aureus (but not MRSA). They are also active against Gram-negative rods such as E.coli, K.pneumoniae, and Proteus mirabilis.
They are active against anaerobic Gram-positive Peptostreptococci, but not B.fragilis.
They are used for uncomplicated community-acquired infections such as UTIs and upper respiratory tract infections.
Used for cellulitis and other skin infections.
Prophylaxis is considered before surgery (mainly cephazolin).

Drugs include Cefoxitin, cefuroxime axetil, cefprozil, and cefaclor.
More resistant to beta-lactamases than 1st generation cephalosporins.
Active against Gram-positive cocci, Gram-negative rods such as H.influenzae, Moraxella catarrhalis, and K.pneumoniae (including beta-lactamase producing K.pneumoniae).
Cefoxitin is also active against anaerobic bacteria including B.fragilis.
Cefuroxime is highly active against beta-lactamase-producing Moraxella catarrhalis.
Used for URTIs (sinusitis, otitis, pharyngitis), UTIs, and pneumonia (mainly cefuroxime).
Used for intra-abdominal infections, peritonitis, and diverticulitis (mainly cefoxitin).

Drugs include Cefotaxime, ceftazidime, ceftriaxone, cefdinir, and cefixime.
Active against Serratia and beta-lactamase strains of Neisseria and H.influenzae.
Enterobacter species are not reliably sensitive.
Less active against Gram-positive cocci (vs 1st generation) except for S.pneumoniae.
Ceftazidime is the only third generation cephalosporin active against P.aeruginosa.
Anti-pseudomonal drugs (Ceftazidime) as well as the oral drugs (cefdinir and cefixime) have decreased Gram-positive activity compared to the other 3rd generation agents.
Used for sepsis of unknown cause, UTIs, and P.pneumoniae.
Given with meropenem for the treatment of complicated UTIs including pyelonephritis.

Carbapenems have similar antibacterial spectrum to cefepime/cefpirome (4th Gen) plus ESBL produced by Gram-negative bacteria including pseudomonas, anaerobes.
Carbapenems are not suitable for treating penicillin-resistant S.pneumoniae.

Ceftaroline is active against MRSA, penicillin-resistant S.pneumoniae.
It is not active against enterococci, pseudomonas, B.fragilis, or ESBL-producing bacteria.