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Comparative Activity of N ‐Formimidoyl Thienamycin with Third Generation Cephalosporins and Ureido Penicillins against Multiple Resistant Serratia marcescens
Author(s) -
Miller Marcia A.,
Lefrock Jack L.,
Vercler Mary J.
Publication year - 1981
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.1981.tb00120.x
Subject(s) - thienamycin , moxalactam , cefoperazone , cefotaxime , microbiology and biotechnology , azlocillin , cephalosporin , latamoxef , chemistry , piperacillin , mezlocillin , minimum inhibitory concentration , carbenicillin , imipenem , antibiotics , biology , ampicillin , antibiotic resistance , bacteria , genetics , pseudomonas aeruginosa
Twenty multiple resistant clinical isolates were tested with N ‐formimidoyl thienamycin, moxalactam, cefotaxime, cefoperazone, and the three ureidopenicillins: azlocillin, mezlocillin, and piperacillin. A concentration of < 0.97 μ g/ml inhibited 100% of organisms for N‐f ‐thienamycin and cefotaxime, 90% for moxalactam, and 60% for cefoperazone. An increase in inoculum from 10 3 to 10 6 cells reduced activity fourfold for 95% of isolates with cefoperazone, 70% with N ‐formimidoyl thienamycin, 65% for cefotaxime, but only 15% for moxalactam. For ureidopenicillins, 85% of strains tested had MIC's ≤ 15.6 μ g/ml. An inoculum effect was observed in only 35–50%. At 10 3 , the cidal concentration was the same or twofold greater than the inhibitory level for N‐f ‐thienamycin and cephalosporins in 70% of strains tested and 65% for penicillins. With 10 6 , the 70% value remained for N‐f ‐thienamycin but was reduced to 45% for cefotaxime and 25% for moxalactam; 85% demonstrated > eightfold differences with cefoperazone. Single step high‐level resistance was observed to moxalactam (20%). Carbenicillin resistant strains were cross‐resistant to the ureidopenicillins. N‐f‐ thienamycin and cefotaxime appeared comparable, although important differences between morphological alteration and metabolism may influence their therapeutic effectiveness.