The sensitivity of urinary isolates to cefuroxime, a new β-lactamase stable cephalosporin

Abstract

The sensitivities to cefuroxime and cephaloridine were compared in 500 bacterial isolates from consecutive cases of urinary tract infection. In the first 200 organisms there was generally good correlation between the diameters of the zone of inhibition around a 30 microgram cefuroxime disc and the MICs. Correlation was poorest with streptococci. From the preliminary observations, criteria were derived to relate the disc sensitivities to MICs for all 500 strains. Neither cephalosporin had significant activity against Pseudomonas spp. but, apart from one strain of Klebsiella and one methicillin-resistant staphylococcus, the only bacteria sensitive to cephaloridine but resistant to cefuroxime were Str. faecalis. Of the 500 organisms, 45% were beta-lactamase-producing Gram-negative bacilli and, overall, cefuroxime was more active than cephaloridine against them. The greater stability of cefuroxime to the beta-lactamases from these bacilli were also supported by a smaller increase in MIC when the inoculum size was increased. On the basis of these results, cefuroxime should prove an effective choice for the treatment of most urinary tract infections.