In vitro and in vivo antimicrobial activities of sporaricin A, a new aminoglycoside.

The in vitro and in vivo antimicrobial activity of sporaricin A, a new aminoglycoside, was compared with that of amikacin, dibekacin, and gentamicin. Sporaricin A showed a broad spectrum of activity against various gram-positive and -negative bacteria, including amikacin-, dibekacin-, or gentamicin-resistant strains. Sporaricin A inhibited more than 90% of clinical isolates of staphylococci, Klebsiella, Enterobacter, Citrobacter, Serratia, and Proteus, except for P. morganii and P. inconstans, at the concentration of 3.13 microgram/ml. This activity, except for that against Serratia, was similar to that of amikacin. Against P. inconstans and S. marcescens, sporaricin A was more effective than amikacin, dibekacin, and gentamicin. However, its activity against Pseudomonas aeruginosa was relatively weak in comparison with three other aminoglycosides. Sporaricin A was highly effective against bacteria that had various aminoglycoside-inactivating enzymes and that were resistant to the other drugs tested, but it was not active against those with aminoglycoside 3-acetyltransferase-I. The activity of sporaricin A tended to be greater with a reduction in inoculum size of bacteria and an increase in medium pH and decreased slightly in the presence of 10 to 50% horse serum. The in vitro activity was confirmed by in vivo tests in experimental infections with various bacteria. Its protective effect seemed to be equal to or greater than that of amikacin or dibekacin.