In vitro activity against aerobes and anaerobes of Trospectomycin versus Spectinomycin

The general antibacterial properties of trospectomycin (TRO) were compared with those of spectinomycin (SPEC) in an in vitro study using a collection of recent clinical isolates: 50 Gram-positive and 25 Gram-negative aerobes and 30 Gram-positive and 15 Gram-negative anaerobes. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined for all strains by microtitre using serial dilutions in Mueller-Hinton broth for aerobes and Brucella broth for anaerobes. The final inoculum in each well was 10(5) cfu/ml. This study shows that none of the Gram-negative organisms was sensitive to TRO; the most sensitive were streptococci aerobic strains; TRO exhibited antibiotic activity against all anaerobes tested, which was not seen with SPEC, and also exhibited bactericidal activity. The MICs of Staphylococcus epidermidis and Bacteroides fragilis tested with TRO and SPEC were not significantly affected by the size of bacterial inoculum tested, and the nature of the growth medium did not alter the susceptibility tests.