Sporaricin A

Two new aminoglycoside antibiotics, sporaricins C and D have been isolated from the culture broth of Saccharopolyspora hirsuta subsp. kobensis, which produced sporaricins A and B. The structures of sporaricins C and D have been determined to be 4-N-carbamoyl-glycylsporaricin B and 4-N-formylglycylsporaricin B, respectively. Sporaricins C and D are active against Gram-negative and Gram-negative bacteria including aminoglycoside-resistant strains.

The antibacterial activities of K-4619 (3-de-O-methylsporaricin A sulfate) were compared with those of sporaricin A, amikacin, dibekacin, and gentamicin. K-4619 exhibited a high order of activity against gram-positive and gram-negative bacteria, including Pseudomonas aeruginosa. Its activity against Providencia species and Serratia marcescens was the highest of all drugs tested. K-4619 was highly effective against bacteria that produce various aminoglycoside-inactivating enzymes, except for 3-acetyltransferase I. The bactericidal activity of K-4619 was somewhat greater than that of amikacin. The activity of K-4619 against gram-negative bacteria increased at alkaline pH and was hardly affected by inoculum size, addition of horse serum, and composition of the medium. The in vivo protective effect of K-4619 against infections with Klebsiella pneumoniae, S. marcescens, and P. aeruginosa in mice was greater than that of sporaricin A. K-4619 was also active in mice infected with gentamicin- or amikacin-resistant strains bearing some of the aminoglycoside-inactivating enzymes.

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.