In vitro activity of sisomicin, an aminoglycoside antibiotic, against clinical isolates.

Sisomicin, a new aminoglycoside antibiotic which is produced by Micromonospora myoensis, was studied against 565 clinical isolates of gram-negative bacilli and gram-positive cocci. With the exception of Serratia marcescens, over 90% of isolates of gram-negative bacilli were inhibited by 1.56 mug/ml or less of sisomicin. Sisomicin was slightly more active than gentamicin and tobramycin aganist isolates of Escherichia coli, Proteus mirabilis and Klebsiella spp. It was substantially more active than butirosin and kanamycin against all gram-negative bacilli. Isolates of gram-negative bacilli which were resistant to gentamicin and tobramycin were also resistant to sisomicin. Most of these isolates were sensitive to amikacin.