A NEW PENICILLIN WITH ANTI-KLEBSIELLA ACTIVITY: 3-(5-TETRAZOLYL) PENAM

The in vitroactivity of a new semi-synthetic penicillin, CP-35, 587, 3-(5-tetrazolyl) penam, was investigated against 496 clinical isolates of gram-negative bacilli and 113 clinical isolates of gram-positive cocci. All of the gram-positive cocci were sensitive to CP-35, 587 except penicillin G resistant isolates of Staphylococcus aureus. This antibiotic inhibited a majority of isolates of Escherichia coli, Klebsiellaspp. and Proteus mirabilisat a concentration of 6.25 μg/ml. Also, approximately half of the isolates of Serratia marcescensand Enterobacterspp. were inhibited at a concentration of 12.5μg/ml. CP-35, 587 was inactive when high concentrations of organisms were used as inocula. CP-35, 587 was more active than mezlocillin, azlocillin, amoxicillin, ticarcillin and carbenicillin against isolates of K. pneumoniae, but otherpenicillins were more active than CP-35, 587 against other species of gram-negative bacilli.