Antibacterial activity of cefixime against Salmonella typhi and applicability of Etest.

Recent clinical studies have shown the excellent efficacy of cefixime for the treatment of typhoid fever. In this study, the in vitro antibacterial activity of various antibiotics including cefixime against 73 clinical isolates of Salmonella typhi from a variety of sources was evaluated by the conventional agar-dilution method and Etest. Eighteen strains of these 73 isolates were chloramphenicol- and cotrimoxazole- (sulfamethoxazole-trimethoprim) resistant, and 12 of these 18 strains were also resistant to amoxicillin because of beta-lactamase production. Cefixime showed excellent activity against all 73 strains with an MIC90 value of 0.25 &mgr;g/ml. Reflecting its high beta-lactamase stability, cefixime also had excellent activity against beta-lactamase-producing amoxicillin-resistant strains. Antibacterial activity of cefixime was comparable to ceftriaxone, ofloxacin, and ciprofloxacin, which are often used for the treatment of typhoid fever. The MIC values obtained from the Etest correlated well with the results of the conventional agar-dilution method, suggesting the usefulness of the Etest as a new easy MIC determination method. The microbiological results supplement the previous clinical data, which showed that oral cefixime provides a safe and effective alternative for the treatment of typhoid fever, even in cases of multidrug-resistant S. typhi.