In vitro activity of spectinomycin against recent urinary tract isolates.

The susceptibilities to spectinomycin of 303 recent urinary tract isolates were determined and compared to the susceptibilities of those strains to ampicillin, tetracycline, and gentamicin. Based on minimal inhibitory concentrations, 84% of Escherichia coli, Klebsiella, and Enterobacter, 31% of other Enterobacteriaceae, 7% of Staphylococcus aureus and Streptococcus (including enterococci), and 0% of Pseudomonas aeruginosa were susceptible to concentrations of spectinomycin that are easily surpassed in serum (</=32 mug/ml); 90% of all organisms tested other than P. aeruginosa were susceptible to concentrations that are easily surpassed in urine (</=128 mug/ml). Spectinomycin was active against more isolates than either ampicillin or tetracycline but against fewer isolates than gentamicin. Disk diffusion susceptibility tests did not reliably distinguish susceptible from resistant isolates with any of the four antibiotics studied.