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.
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 (1.3%) was resistant to isepamicin. The broadest spectrum comparison drugs tested alone (ciprofloxacin at 3.8% resistance and imipenem at 5.0% 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 (75% to 80%) greater than imipenem (66%) greater than 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 either alone or combined with most commonly used broad spectrum beta-lactams.
Jones
R N
RN
Department of Pathology, University of Iowa College of Medicine, Iowa City.
Johnson
D M
DM
Barrett
M S
MS
Erwin
M E
ME
D002439:Cefotaxime / Q000494:pharmacology; D002442:Ceftazidime / Q000494:pharmacology; D003470:Culture Media; D004347:Drug Interactions; D004352:Drug Resistance, Microbial; D004357:Drug Synergism; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000187:drug effects; D016983:Enterococcus / Q000187:drug effects*; D005839:Gentamicins / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D015378:Imipenem / Q000494:pharmacology; D008802:Mezlocillin / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D011549:Pseudomonas / Q000187:drug effects
D003470:Culture Media; D005839:Gentamicins; D015378:Imipenem; D002442:Ceftazidime; C016927:isepamicin; D002439:Cefotaxime; D008802:Mezlocillin; D010878:Piperacillin