Laboratory and Clinical Evaluation of a New Antibiotic—Cephalothin

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Abstract
A new antibiotic, cephalothin, a semi-synthetic derivative of Cephalosporin-C, possesses a broad-spectrum of antibacterial activity when tested in-vitro against approximately 1,500 pathogenic microorganisms. Staphylococci, including penicillinase-producing strains, were inhibited by 1 mcg/ml or less cephalothin. The gram-negative spectrum of the new antibiotic is more variable; cephalothin is very active against many strains of Proteus mirabilis but less active against Klebsiella-Aerobacter, Escherichia coli and paracolon species. Pseudomonas and indole-producing strains of Proteus were generally highly resistant. The results of single-disc and tube-dilution sensitivities if a minimum inhibitory concentration (MIC) of 25 mcg/ml was used as the criterion for susceptibility usually agreed. Treatment of 103 hospitalized patients with infections due to Diplococcus pneumoniae, penicillinase and non-penicillinase-producing staphylococci, streptococci, E. coli, Klebsiella-Aerobacter, P. mirabilis and other gram-negative organisms with cephalothin resulted in clinical and bacteriologic improvement in 78 of 103 (76%) patients. Relapse following cessation of treatment was common in patients with chronic infection of the urinary tract. This antibiotic must be administered parenterally at frequent intervals. It was usually accompanied by pain at the injection site. There were no other untoward reactions except for the development of rash in 3 patients; 9 additional patients with a previous history of penicillin allergy received cephalothin without incident.