[In vitro examination on antibacterial activities of broad-spectrum antibiotics against gram-negative clinical isolates (author's transl)].

In vitro studies were undertaken on clinically isolated strains of various bacteria to examine the antibacterial activity of ampicillin (AB-PC), carbenicillin (CB-PC), sulbenicillin (SB-PC) cephalothin (CET), cefazolin (CEZ) and gentamicin (GM). Fifty three % of Escherichia coli strains 53.3% of Citrobacter sp., 80% of Proteus mirabilis, 42.9% of Morganella and 80% of Bacteroides sp. were susceptible (MIC being not higher than 12.5 mug/ml) to AB-PC. The eight other species were not so susceptible to this penicillin. CB-PC and SB-PC were almost as effective as AB-PC against Escherichia coli and Citrobacter sp. They were less active against Klebsiella sp., but more active against Enterobacter sp., Serratia sp., indole-positive Proteus group and Pseudomonas sp. than AB-PC, SB-PC was more effective than CB-PC against Pseudomonas sp. The strains of Pseudomonas sp. which were resistant to higher concentrations of CB-PC and SB-PC were pyocyanine-negative strains. All strains (100%) of Escherichia coli, Klebsiella sp. and Citrobacter sp. were susceptible to CET and CEZ, while none of Enterobacter sp. , Serratia sp., Proteus vulgaris. Morganella, Rettgerella, Providencia and Pseudomonas sp. were susceptible to these cephalosporins. The MICs of CET and CEZ against Bacteroides sp. were moderately low. Some strains of Providencia and Alkaligenes sp. were resistant of GM but the other 10 species were not resistant to this antibiotic, though it showed comparatively high MICs against Bacteroides sp. When seen from the MIC distribution of each antibiotic, there was a tendency that the strains isolated from the pus were more resistant than those isolated from the other sources (urine, sputum and bile).