Comparative bactericidal activities were determined utilizing a relatively large number of test strains, in both agar and broth media, with special reference to the time of exposure of the bacteria to certain /3-lactatn antibiotics. it was apparent that the activities increase with time. The concentrations producing a99.9% kill with cephalothin for Escherichia coli, Klebsiella sp., and carbenicillin for Pseudontonas aerugino.sa were higher in broth than in agar. In contrast, those of benzylpenicillin for a-streptococcus (non-enterococcal) were higher in agar than in broth. If the bactericidal concentrations with 3-hour or 6-hour exposure to antibiotics were used as the criterion, these concentrations of carbenicillin for P. aeruginosa, and benzylpenicillin for a-streptococcus were, in particular, unusually high compared with the conventionally determined bacteriostatic concentrations (MICs).Determination of bactericidal activity is widely accepted to be more important than that of bacteriostatic activity in the treatment of patients with infective endocarditis and presumably in patients with seriously impaired host defence mechanisms. The present paper describes minimal lethal concentrations (MLCs), defined as the concentrations producing a 99.9% kill'1-2, together with bacteriostatic concentrations of /3-lactam antibiotics for a-streptococcus which is the major blood isolate from infective endocarditis',", and also Escherichia coli, Klebsiella sp. and Pseudomonas aeruginosa which are the most frequently encountered infective pathogens in debilitated patients5--8). In many of the studies already reported, bactericidal activity is expressed in terms of the results obtained after overnight exposure of bacteria to antimicrobial agents2'9,10'. Such a long period of continuous exposure of microorganisms to the antimicrobic does not generally occur in clinical practice. Most drugs are administered orally or parenterally, achieving in serum or at the focus of infection antimicrobic concentrations which are higher than the in vitro bactericidal concentrations for a few hours at the most. Based on this reason, we now report on in vitro bactericidal activities after varying periods of exposure of bacteria to /-lactams in agar and broth media.
Materials and MethodsBacterial strains Recent clinical isolates of E. coli, Klebsiella sp., P. aeruginosa, and a.-and /1-streptococcus (nonenterococcal) were used. Media Heart infusion broth (Difco Laboratories) and heart infusion agar (Difco) were used. Defibrinated horse blood (5°0) was supplemented to the agar for the study of a-and /-streptococcus.
The clinical usefulness of Enoxacin (ENX, AT-2266), a new oral antibacterial agent, was compared with that of pipemidic acid (PPA) in the treatment of acute infectious diarrhea (bacillary dysentery, Campylobacter enteritis and enteropathogenic and enterotoxigenic E. coli enteritis) by a double-blind method.Daily dosage of ENX and PPA was 600 mg and 2000 mg, respectively. The duration of the treatment was 5 days. Of 242 cases treated, various statistical analyses were carried out in 146 cases,and 96 cases were excluded.Of 146 cases, 73 cases were treated with ENX or PPA respectively. There was no statistical significance between ENX group and PPA group in terms of the background characteristics and MIC distribution against each drug.The results obtained were as follows.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.