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Cefixime is a third generation cephalosporin antibiotic.

The cephalosporins, a class of β-lactam antibiotics, are originally derived from the fungus Acremonium.

In vitro: Previous study found that cefixime was more active than cephalexin, cefaclor, and amoxicillin against various gram-negative bacteria. Cefixime was also significantly more active than tested reference drugs against clinical isolates of Klebsiella pneumoniae, Escherichia coli, indole-positive and -negative Proteus species, Providencia species, and Neisseria gonorrhoeae. Moreover, cefixime was active against strains of K. pneumoniae, E. coli, as well as Proteus mirabilis resistant to the reference agents [1].

In vivo: The therapeutic activities of cefixime in mice infected with gram-negative bacilli were found to be far superior to the activities of cephalexin, cefaclor, and amoxicillin, but they were inferior to the activities against infection with Staphylococcus aureus [1].

Clinical trial: Previous study showed that the clinical success was observed in 94% of cefixime-treated patients. At the end of treatment, the overall eradication rate in the cefixime treatment group was 92% and ranged from 76% (cefaclor) to 98% (cefuroxime axetil) in the comparator treatment groups [2].

References:
[1] Kamimura, T.?,Kojo, H.,Matsumoto, Y., et al. In vitro and in vivo antibacterial properties of FK 027, a new orally active cephem antibiotic. Antimicrobial Agents and Chemotherapy 25(1), 98-104 (1984).
[2] Quintiliani R.? Cefixime in the treatment of patients with lower respiratory tract infections: results of US clinical trials. Clin Ther. 1996 May-Jun;18(3):373-90; discussion 372.