Antimicrobial Activity of Isepamicin (SCH21420, 1-N-HAPA Gentamicin B) Combinations with Cefotaxime, Ceftazidime, Ceftriaxone, Ciprofloxacin, Imipenem, Mezlocillin and Piperacillin Tested Against Gentamicin-Resistant and Susceptible Gram-Negative Bacilli and Enterococci

Summary

Isepamicin, formerly SCH21420 or 1-N-HAPA gentamicin B, is an aminoglycoside that was tested alone or in combination with one of seven broad spectrum drugs against 80 clinical isolates. Half of the strains were gentamicin-resistant but only one isolate (1.396) was resistant to isepamicin. The broadest spectrum comparison drugs tested alone (ciprofloxacin at 3.8% resistance and imipenem at 5.096 resistance) were associated with the lowest synergy rates when combined with isepamicin. The rank order of synergy (complete or partial) was; cefotaxime = ceftazidime = ceftriaxone = mezlocillin = piperacillin (7596 to 8096) > imipenem (66%) > ciprofloxacin (38%). Isepamicin/ampicillin combinations produced synergistic killing of those enterococci not having high-grade resistance to gentamicin or kanamycin. Enterococcus faecium strains were also refractory to isepamicin/ampicillin synergy. Isepamicin appears to be widely useable against gentamicin-resistant gram-negative bacilli cither alone or combined with most commonly used broad spectrum bcta-lactams.

Key Words:

• isepamicin
• aminoglycosides
• gentamicin-resistance
• isepamicin/ampicillin.