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. 1972 Sep;2(3):236–241. doi: 10.1128/aac.2.3.236

In Vitro Activity of Tobramycin and Gentamicin

Michael R Britt 1, Richard A Garibaldi 1, James N Wilfert 1, Charles B Smith 1
PMCID: PMC444298  PMID: 4790564

Abstract

The in vitro antimicrobial activity of tobramycin and gentamicin was compared against 362 bacterial isolates. The minimal inhibitory concentration (MIC) of tobramycin was fourfold less than the MIC of gentamicin against most of 119 Pseudomonas organisms. Gentamicin and tobramycin had similar in vitro activity against Enterobacteriaceae and Staphylococcus aureus. Proteus rettgeri were commonly resistant to both tobramycin and gentamicin. The 10-μg tobramycin disc separated resistant (MIC ≥5 μg/ml) and susceptible (MIC <5 μg/ml) organisms in 359 of 362 tested. In disc diffusion testing, the tobramycin and gentamicin zone diameters were found to vary significantly with concentrations of magnesium ions in the media employed. The MIC of tobramycin varied with the size of the inoculum, and tobramycin was most effective at a neutral pH.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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