Effectiveness of Ampicillin Against Gram-Negative Bacteria

Abstract

Gram-negative bacteria consisting of approximately 50 strains each of Escherlchia coli, Proteus mirabilis, Klebsiella-Aerobacter, paracolon sp., indol-fermenting strains of Proteus, and Pseudomonas aeruginosa were tested against a new penicillin, a-amino-benzyl-penicillin (ampicillin) in vitro. The drug was effective against E. coli and P. mirabilis but was less effective against the other organisms than agents already available. There was good correlation between results of sensitivity tests performed by the tube dilution and single disc technics. Patients with urinary tract infections were treated with 2-3 g/day for 2 wks. Infections with E. coli were most amenable to therapy, and patients with acute uncomplicated pyelonephritis responded better than those with chronic bacteriuria. Diarrhea was the only side-effect associated with ampicillin.