Phenelfamycins, a novel complex of elfamycin-type antibiotics. III. Activity in vitro and in a hamster colitis model.

Phenelfamycins A, B, C, E, F and unphenelfamycin make up a recently isolated group of elfamycin-type antibiotics. All of the phenelfamycins were active against Gram-positive anaerobes, including Clostridium difficile. Phenelfamycin A was also active in vitro against Neisseria gonorrhoeae and Streptococci. Phenelfamycin A was found to be effective in prolonging the survival of hamsters in an animal model of C. difficile enterocolitis. After oral administration of phenelfamycin A to hamsters, antibiotic was detected in the caecal contents but not in the blood.

A-61827 (A-60969), a new fluoronaphthyridine with activity against both aerobic and anaerobic bacteria.

A-61827 (A-60969 is the hydrochloric salt of A-61827) is a new aryl-fluoronaphthyridine which is active against aerobic and anaerobic bacteria. The MICs of A-61827 for 90% of strains (MIC90) of staphylococci and streptococci were less than or equal to 1 microgram/ml and were generally 1 to 4 twofold dilutions less than those of ciprofloxacin for these bacteria. The MIC90S of A-61827 for members of the family Enterobacteriaceae and Pseudomonas aeruginosa were also less than or equal to 1 microgram/ml. Ciprofloxacin was 1 to 3 twofold dilutions more active than A-61827 against these gram-negative bacteria. Neisseria gonorrhoeae, Campylobacter jejuni, and Haemophilus influenzae were susceptible to less than 0.06 microgram of A-61827 per ml. The MIC90 of A-61827 for Legionella pneumophila was 0.25 microgram/ml. A-61827 was as potent or 1 to 2 twofold dilutions more potent than ciprofloxacin against these organisms. The MIC90 of A-61827 for all anaerobic bacteria was less than or equal to 4 micrograms/ml compared with less than or equal to 32 micrograms/ml for ciprofloxacin. In mouse protection tests, A-61827 was as active as ciprofloxacin against Escherichia coli, P. aeruginosa, and Salmonella typhimurium and 5 to 10 times more active than ciprofloxacin against Staphylococcus aureus and Streptococcus pyogenes. A-61827 was as active as ciprofloxacin against P. aeruginosa in a mouse pyelonephritis model and more active than ciprofloxacin and metronidazole in a mouse Bacteroides fragilis abscess model. After oral administration of 100 mg/kg to mice, the peak concentrations of A-61827 and ciprofloxacin in serum were 2.3 and 2.4 micrograms/ml and the half-lives in serum were 3.9 and 1.2 h, respectively.

Comparative antibacterial activities of temafloxacin hydrochloride (A-62254) and two reference fluoroquinolones.

The in vitro and in vivo properties of a new 1-difluorophenyl-6-fluoroquinolone, temafloxacin hydrochloride (A-62254), were compared with those of difloxacin and ciprofloxacin. Temafloxacin hydrochloride was as active as ciprofloxacin and difloxacin against staphylococci and as active as ciprofloxacin and 2 twofold dilutions more active than difloxacin against streptococci. Against gram-negative enteric bacteria and Pseudomonas aeruginosa, temafloxacin hydrochloride was 2 twofold dilutions more active than difloxacin but 2 to 4 twofold dilutions less active than ciprofloxacin. The MICs of temafloxacin hydrochloride and difloxacin were increased by 2 to 5 twofold dilutions in urine at pH 6.5 compared with 4 to 5 twofold-dilution increases in the MICs of ciprofloxacin. The MICs of temafloxacin hydrochloride, difloxacin, and ciprofloxacin were increased by 1 to 3 twofold dilutions in serum. The MICs of temafloxacin hydrochloride, difloxacin, and ciprofloxacin were the same or within 1 to 2 twofold dilutions at pHs 6.5, 7.2, and 8.0. When administered orally in mouse protection tests, temafloxacin hydrochloride was as active as difloxacin and 5 to 10 times more active than ciprofloxacin against infections with Staphylococcus aureus and streptococci. Against infections with gram-negative enteric bacteria and P. aeruginosa, temafloxacin hydrochloride was as active as difloxacin and ciprofloxacin. Temafloxacin hydrochloride was three times less active than difloxacin but was five times more active than ciprofloxacin against infections with Salmonella typhimurium. Temafloxacin hydrochloride was as active as difloxacin and ciprofloxacin against P. aeruginosa and Proteus mirabilis pyelonephritis in mice. The peak serum concentration and serum half-life of temafloxacin hydrochloride in mice were approximately one-half and one-sixth, respectively, that of difloxacin after oral administration. The peak serum concentration of temafloxacin hydrochloride in mice after oral administration was six times higher than that of ciprofloxacin, and the serum half-life was equal to that of ciprofloxacin.

In vivo evaluation of A-56619 (difloxacin) and A-56620: new aryl-fluoroquinolones.

A-56619 and A-56620 are two new aryl-fluoroquinolones which are as potent as or more potent than norfloxacin when administered orally and subcutaneously in mouse protection tests against Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus pneumoniae. A-56619 and A-56620 were more potent than norfloxacin when administered orally against Escherichia coli, Proteus mirabilis, Serratia marcescens, and Pseudomonas aeruginosa. A-56620 was as potent or two- to threefold more potent than norfloxacin when administered subcutaneously against members of the family Enterobacteriaceae and Pseudomonas aeruginosa. Infection with Salmonella typhimurium was more effectively treated with A-56619 (50% effective dose [ED50], 1.4 mg/kg per day) than with norfloxacin (ED50, 62.8 mg/kg per day). E. coli or Pseudomonas pyelonephritis in mice was more effectively treated with A-56619 or A-56620 than with norfloxacin. After oral treatment, the ED50s of A-56619 and A-56620 were less than 12.5 mg/kg per day against E. coli and 62.9 and 38 mg/kg per day against P. aeruginosa pyelonephritis, respectively. Norfloxacin was ineffective at 200 mg/kg per day against E. coli or P. aeruginosa pyelonephritis. A-56619 and A-56620 were also more potent than norfloxacin in treatment of mixed bacterial pyelonephritis caused by E. coli and Streptococcus faecalis. A-56619 was at least 30 times more potent than norfloxacin and A-56620 was 4 to 11 times more potent than norfloxacin when administered against Klebsiella pneumonia in mice. A-56619 and A-56620 were at least 2 to 10 times more potent than norfloxacin against Staphylococcus aureus infections in immunosuppressed mice. A-56619 was equally potent in all in vivo tests when administered orally or subcutaneously, whereas A-56620 was similar to norfloxacin in being more potent when administered subcutaneously. The peak serum levels after subcutaneous and oral administration of A-56619 and A-56620 were higher than that of norfloxacin. The serum hal-lives of A-56619 and A-56620 after subcutaneous and oral administration were longer than the serum half-life of norfloxacin.