Cephalexin, a derivative of cephalosporin C, produces high serum and urine concentrations after oral administration. In addition, it shows good activity in vitro against most gram-positive and some gram-negative organisms. This study reports the in vitro susceptibility to cephalexin of a series of clinical isolates, the serum levels and urine concentrations in human volunteers and the results of its use in infections due to susceptible organisms. Results of in vitro susceptibility testing reveal that cephalexin was effective against most strains of the gram-positive organisms tested — group A streptococci, pneumococci, and staphylococci — although the MIC's are higher than those found for cephaloridine and ampicillin, with the one exception being penicillinase producing staphylococcus against which ampicillin is ineffective. Cephalexin is effective against most strains of indole-negative proteus, Klebsiella and E. coli, but all strains of enterobacter show resistance. Forty-seven patients with a variety of clinical illnesses were treated with cephalexin. Five of 14 patients with urinary tract infections were cured and nine had a remission followed by a bacteriologic relapse. All patients with soft tissue infection were cured as were nine of 12 patients with pneumonia. Of the three patients with pneumonia who were not cured, one improved, while two were classified as treatment failures. Similarly, 11 of 12 patients with streptococcal pharyngitis had a clinical remission, although in three, the organism was isolated after therapy. One patient with an associated coagulase-positive staphylococci cultured from the pharynx failed to respond to treatment.
Cox, Frank Jr.; Quinn, Edward L.; Gatmaitan, Bienvenido G.; and Peterson, Nancy
"Cephalexin: In Vitro and in Vivo Studies,"
Henry Ford Hospital Medical Journal
: Vol. 18
Available at: https://scholarlycommons.henryford.com/hfhmedjournal/vol18/iss2/3