Comparative in vitro activity of a semisynthetic derivative of gentamicin B (SCH 21420) and five other aminoglycosides.

With the increasing prevalence of Gramnegative bacilli resistant to existing aminoglycosides, new semisynthetic aminoglycosides with more potent in vitro activity or with effectiveness against resistant bacteria are continually being developed. Sch 21420 is 1-N-[(S)-3-amino-2hydroxypropionyl]-gentamicin B, a new semisynthetic compound developed in the research laboratories of Schering Corporation (T.L. NAGABHUSHAN, A. B. COOPER, H. TSAI and P. J. L. DANIELS. Programs & Abstracts, 17th Interscience Conference on Antimicrobial Agents and Chemotherapy, New York, abstr. no. 249, 1977). There have been two preliminary studies of the in vitro activity of this compound1) (K. P. Fu and H. C. NEU. Programs & Abstracts, 17th Interscience Conference on Antimicrobial Agents and Chemotherapy, New York, abstr. no. 250, 1977). In this study, the in vitro activity of Sch 21420 against both gentamicin-resistant and gentamicin-susceptible Gram-negative bacilli was compared with that of gentamicin, tobramycin, sisomicin, netilmicin and amikacin. All Gram-negative bacilli used in this study were isolated from clinical materials. The gentamicin-resistant (MIC> 4 ug/ml) strains consisted of Pseudomonas aeruginosa (17 strains), Pseudomonas species (10 strains), Klebsiella species (7 strains), Serratia species (6 strains), Enterobacter species (6 strains), Proteus species (9 strains), Providencia species (14 strains) and Escherichia coli (6 strains). Also tested were 41 strains of gentamicin-susceptible (MIC<4,ug/ml) Enterobacteriaceae which included Klebsiella species (8 strains), Serratia species (9 strains), Enterobacter species (9 strains), Proteus species (5 strains), Providencia species (1 strain) and E. coli (9 strains). The MIC of Sch 21420, gentamicin, tobramycin, sisomicin, netilmicin, and amikacin was determined simultaneously by the WHO-ICS agar dilution method". MUELLER-HINTON agar