Synergism at clinically attainable concentrations of aminoglycoside and β-lactam antibiotics

T. M. Hooton, A. D. Blair, M. Turck, G. W. Counts

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


We evaluated the in vitro synergistic activity at clinically attainable concentrations of combinations of aminoglycoside and β-lactam antibiotics against 30 gentamicin-resistant clinical isolates of gram-negative bacilli. All 56 pairs of 4 aminoglycosides and 14 β-lactams were evaluated. Combinations with amikacin demonstrated inhibitory synergistic activity in 29% of the assays, as compared with 22% for netilmicin (P = 0.018), 17% for gentamicin (P < 0.001), and 13% for tobramycin (P < 0.001). Among the β-lactams, combinations with cefoperazone, ceftriaxone, or cefpiramide (SM-1652) demonstrated inhibitory synergistic activity most often (39, 38, and 35% of the assays, respectively) and with ceforanide, cefsulodin, and imipenem least often (≤8% each). The most active combination was amikacin and ceftriaxone, with which 67% of the assays demonstrated inhibitory synergism. Isolates with high-level resistance to either antibiotic in a combination were unlikely to be inhibited synergistically by the combination. Further, combinations generally demonstrated little synergistic activity against isolates highly susceptible to β-lactams.

Original languageEnglish (US)
Pages (from-to)535-538
Number of pages4
JournalAntimicrobial agents and chemotherapy
Issue number4
StatePublished - 1984
Externally publishedYes

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


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