In vitro antibacterial activity of E-3604, a new 6-fluoroquinolone, on clinical isolates

From a series of pyrrol-containing antibacterial agents, E-3604 was selected for development and compared with nalidixic acid, norfloxacin and ciprofloxacin against strains of clinical isolates. The in vitro activity of E-3604 was greater than that of nalidixic acid, similar to that of norfloxacin and lower than that of ciprofloxacin, except in the case of Staphylococcus where E-3604 showed the best in vitro activity of all the studied compounds, with a MIC range of 0.25-0.03 mg/ml. E-3604, like the other quinolones, presented a pH-dependent variation of activity, greater activity being observed in slightly acidic pH values.     

In vitro antibacterial activity of irloxacin (E-3432) on clinical isolates

Irloxacin (E-3432) is a new quinolone derivative. In this study, the activity of irloxacin was compared with that of nalidixic acid, norfloxacin and ciprofloxacin against strains of clinical isolates. Irloxacin showed greater in vitro activity than nalidixic acid, similar activity to norfloxacin and lower activity than ciprofloxacin. Against Staphylococcus, the MIC range of E-3432 was 0.06-1 mg/l, better than the other compounds studied.     

The sensitivity of gram-negative and gram-positive bacteria to ofloxacin

The in vitro antimicrobial activity of ofloxacin, a new fluorinated quinolone, was evaluated against 165 Gram-negative rods, both fermentative and non-fermentative, and against 57 Gram-positive strains (coagulase-positive and -negative staphylococci both methicillin-resistant and -susceptible, and Streptococcus faecalis). Minimal inhibitory concentrations were determined by using the macrodilution test and the activity was compared with nalidixic acid, norfloxacin, ampicillin, piperacillin, ceftazidime and gentamicin for Gram-negative rods; norfloxacin and gentamicin for Staphylococcus strains; and norfloxacin, ampicillin, piperacillin and gentamicin for enterococci. Ofloxacin inhibited all fermentative Gram-negative bacteria tested, in a range of 0.05-3.12 mcg/ml, and had good antimicrobial activity against non-fermentative Gram-negative strains: it inhibited 90% of Acinetobacter and 80% of P. aeruginosa tested, at 3.12 mcg/ml. Ofloxacin had a high antimicrobial activity against Staphylococcus and Enterococcus strains tested.     

Influence of pH and human urine on the antibacterial activity of ciprofloxacin, norfloxacin and ofloxacin

The influence of pH on the antibacterial activity of ciprofloxacin, norfloxacin and ofloxacin was studied in broth and pooled human urine by microdilution susceptibility tests. Selected strains of E. coli, Staphylococcus aureus and Pseudomonas aeruginosa were used as test organisms. The results show that cultivation at pH 5.7 in urine increased the MIC values for all three quinolones 8, 16 and 32-fold compared with broth at pH 7.1. Killing curves show that in urine with 10 mcg/ml ciprofloxacin, rapid killing of E. coli and Pseudomonas aeruginosa occurred, whereas ofloxacin and especially norfloxacin were less effective.     

Screening of some medicinal plants used in south-west Nigerian traditional medicine for anti-Salmonella typhi activity

Ten Nigerian medicinal plants used traditionally for the treatment of several ailments of both microbial and non-microbial origins were tested on multi-drug resistant S. typhi (MDR) strains of which six of them were active. The results revealed that both the aqueous and ethanol extracts of Terminalia avicennioides, Momordica balsamina, Combretum paniculatum and Trema guineensis were effective on the MDR-S. typhi strains with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values ranging from 9.60 to 14 mcg/ml and 24 to 33 mcg/ml, respectively. Whereas, only the aqueous extracts of Morinda lucida and Ocimum gratissimum were found to be active against this pathogen with MIC and MBC values of 9.60 and 24 mcg/ml for M. lucida, 40 and 55 mcg/ml for O. gratissimum, respectively. There was no statistical significant difference (P > 0.05) between the activity of each plant extract and the decoctions prepared from them. All the six active plants showed positive reactions to alkaloids, tannins, flavonoids and anthraquinones but in variable degrees. All but M. balsamina, indicated the presence of saponin.     

Norfloxacin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Norfloxacin is one of the new 4-quinolone antibacterial agents. A fluorinated piperazinyl-substituted congener of nalidixic acid, it demonstrates a much wider in vitro antibacterial spectrum and greater potency than the parent compound. Its antibacterial activity against most Gram-negative pathogens is enhanced in comparison to nalidixic acid, but is similar to that of some of the other new 4-quinolones like enoxacin, and slightly less than that of ciprofloxacin. Unlike nalidixic acid, norfloxacin is also active against Pseudomonas aeruginosa and some Gram-positive organisms. In acute or uncomplicated urinary tract infections, norfloxacin has repeatedly been shown to be as effective as co-trimoxazole. Single studies have demonstrated a significantly better bacteriological cure rate with norfloxacin than with pipemidic acid, and similar cure rates with norfloxacin and both a nalidixic acid/sodium citrate mixture and amoxycillin. Similar results were found in a few studies comparing norfloxacin to pipemidic acid or amoxycillin in patients with chronic and/or complicated urinary tract infections. Norfloxacin is as effective as spectinomycin in gonorrhoea due to penicillin-resistant N. gonorrhoeae, and cures bacterial gastroenteritis caused by several gastrointestinal pathogens. Norfloxacin appears to be well tolerated and may have a low propensity to select for bacterial resistance during clinical use, although the latter needs further confirmation.     

In vitro antibacterial activity of prulifloxacin, a new oral quinolone, and comparative susceptibility rate at clinical breakpoint MIC

In vitro drug sensitivity of clinically isolated bacteria against prulifloxacin (PUFX), which is a new quinolone, was investigated, and the antibacterial activity and susceptibility rate at clinical breakpoint were compared with those of norfloxacin, ofloxacin (OFLX), ciprofloxacin, tosufloxacin, fleroxacin, sparfloxacin and levofloxacin (LVFX). The following results were obtained. 1) PUFX showed a broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. 2) MIC80 of PUFX was 0.25 and 1 microgram/ml, against methicillin susceptible Staphylococcus aureus and Streptococcus pneumoniae, respectively and below 0.125 microgram/ml against Gram-negative Enterobacteriaceae. MIC90 of PUFX against Pseudomonas aeruginosa, which has MIC not exceeding 4 micrograms/ml to OFLX, was 0.5 microgram/ml. 3) PUFX was judged as active against the bacteria under the criteria proposed presented by "the Sensitivity Determination Committee for Antibiotics, Japan Society of Chemotherapy: Break Point for Respiratory Infectious Diseases and Sepsis". It is suggested that the sensitivity of each bacterial species to PUFX was high. 4) From the correlation analysis of MIC, PUFX was shown to have two to eight times higher antibacterial acitivity than LVFX for Citrobacter freundii, Serratia marcescens and Pseudomonas aeruginosa. 5) PUFX showed potent short-time bactericidal activity against S. aureus and P. aeruginosa.     

Diclofenac in the management of E. coli urinary tract infections

E. coli is the main agent of uncomplicated urinary tract infections (UTIs) and accounts for more than 85% of recurrent cystitis and at least 35% of recurrent pyelonephritis. Despite the widespread availability of antibiotics, UTIs remain the most common bacterial infection in the human population. It is currently advised that the clinical administration of antibiotics against the pathogenic bacteria should be prohibitted due to the emergence of multidrug resistant (MDR) bacterial strains. Therefore, newer and more effective antimicrobials are in demand to treat such cases. One hundred and thirty six urine samples were collected from UTI patients. E. coli was isolated from 85 samples, out of which 33% were resistant to common antibiotics. The isolates were decreasingly resistant to ampicillin, tobramycin, augmentin, nalidixic acid, cefuroxime, nitrofurantoin, kanamycin, pipemidic acid, chloramphenicol, cefotaxime, cefamendol, ofloxacin, ceftizoxime, norfloxacin and amikacin. The anti-inflammatory drug diclofenac exhibited significant antibacterial activity against common bacterial strains both in vitro and in vivo. The present work was conducted to evaluate the in vitro inhibitory effect of this drug on the clinically isolated strains of E. coli in hospitals. All the isolates were sensitive to diclofenac, with MIC values ranging from 5-50 microg/mL. The MIC90 value of the drug was 25 microg/mL. Therefore, it may be suggested that diclofenac has the capacity to treat UTI caused by E. coli.     

In vitro activity of seven gyrase inhibitors of a group of heterocyclic carbonic acids against nonfermenting gram negative rods (nonfermenters)

MIC (minimal inhibitory concentration) determinations for nalidixic acid, cinoxacin, pipemidic acid, norfloxacin, enoxacin, and ciprofloxacin were done by agar dilution on isosensitest agar (oxoid). Bacterial strains investigated were 189 Pseudomonas aeruginosa, 164 Acinetobacter lwoffii, 4 Ps. maltophilia, 3 Ps. putrefaciens and 3 Ps. odorans. The results in summary are: Ciprofloxacin is the most active gyrase inhibitor against Ps. aeruginosa as well as against other nonfermentative gram-negative rods, versus Ps. aeruginosa norfloxacin is a little more active than ofloxacin, against nonfermentative gram-negative rods other than Ps. aeruginosa norfloxacin is markedly less active than ofloxacin. Problems concerning cross-resistance of new gyrase inhibitors are discussed.     

In vitro susceptibility of new generation of antibacterial antibiotics against pathogenic bacteria

Antibiotic susceptibility of ten bacteria i.e. Neisseria catarrhalis, Salmonella typhi, S. enteritidis, Haemophilus influenzae, Bacillus subtilis, Pseudomonas fluorescence, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus and E. coli to twenty antibiotics i.e. cefpirom (30 mcg), ceftriaxone (30 mcg), erythromycin (15 mcg), doxycycline (30 mcg) lomefloxacin (10 mcg), sisomicin (30 mcg), vancomycin (30 mcg), augmentin (30 mcg), ampicillin (30 mcg), cotrimoxazole (25 mcg), cefotaxime (30 mcg), Chloramphenicol (30 mcg), cephalexin (30 mcg), tetracycline (30 mcg), ciprofloxacin (5 mcg), nitrofurantoin (300 mcg), nalidixic acid (30 mcg), pefloxacin (10 mcg), norfloxacin and ofloxacin (5 mcg) was studied to evaluate the antimicrobial efficacy of recently introduced second and third generation antibiotics. All the test strains were sensitive to pefloxacin, erythromycin, augmentin and chloramphenicol. Maximum resistance to cefpirom excluding E. coli and S. typhi and co-trimoxazole except S. typhi, Pseudomonas aeruginosa was observed, occasional resistance was seen against ceftriaxone, vancomycin and cefotaxime.     

MICs and MBCs of cefotaxime, desacetylcefotaxime and ceftriaxone against four principal bacteria causing meningitis

The MICs and MBCs of cefotaxime (CTX), desacetylcefotaxime (Des-CTX) and ceftriaxone (CTRX) were determined in relation to 4 of the principal bacterial species which cause meningitis, i.e., S. pneumoniae, S. agalactiae, H. influenzae and E. coli. These tests were performed using final inocula of 10(8) cells/ml and 10(6) cells/ml. Comparison was made with the MIC and MBC values of benzylpenicillin (PCG) and ampicillin (ABPC). 1. Against 25 strains of S. pneumoniae, the MIC 90 values with inocula levels of 10(8) and 10(6) cells/ml were as follows: CTX, 0.05 and 0.024 micrograms/ml; Des-CTX, 0.39 and 0.20 micrograms/ml; CTRX, 0.10 and 0.05 micrograms/ml, respectively; and PCG, less than 0.012 micrograms/ml at both size. Similarly, the MBC 90 values were: CTX, 0.01 and 0.05 micrograms/ml; Des-CTX, 0.78 and 0.39 micrograms/ml; CTRX, 0.20 and 0.10 micrograms/ml; and PCG, 0.024 and 0.012 micrograms/ml, respectively. It is thus apparent that PCG showed the lowest values for both the MIC and MBC, followed by CTX, CTRX and then Des-CTX. Against 25 strains of S. agalactiae, the MIC 90 values with inocula of 10(8) and 10(6) cells/ml were as follows: CTX, 0.05 and 0.05 micrograms/ml; Des-CTX, 0.39 and 0.20 micrograms/ml; CTRX, 0.10 and 0.05 micrograms/ml; and PCG, 0.39 and 0.20 micrograms/ml, respectively. Similarly, the MBC 90 values of Des-CTX were 0.78 and 0.39 micrograms/ml, while the other 3 antibiotics showed the same values with both the 10(8) and 10(6) cells/ml inocula: 0.10 micrograms/ml for CTX, 0.20 micrograms/ml for CTRX and 0.39 micrograms/ml for PCG. Accordingly, CTX showed the lowest values, followed by CTRX and then PCG being about the same as Des-CTX. Against 25 strains of H. influenzae, the MIC 90 values with inocula levels of 10(8) and 10(6) cells/ml were as follows: CTX, 0.10 and 0.05 micrograms/ml; Des-CTX, 0.39 and 0.39 micrograms/ml; CTRX, 0.10 and 0.05 micrograms/ml; and ABPC, 50 and 6.25 micrograms/ml, respectively. Similarly, the MBC 90 values were: CTX, 0.20 and 0.10 micrograms/ml; Des-CTX, 1.56 and 1.56 micrograms/ml; CTRX, 0.39 and 0.20 micrograms/ml; and ABPC, greater than 100 and 50 micrograms/ml, respectively. Accordingly, in terms of the MIC 90, CTX and CTRX showed the same values, but in terms of the MBC 90 CTX was superior. (ABSTRACT TRUNCATED AT 400 WORDS)     

Quinolones in vitro

The first quinolone compound, nalidixic acid, showed activity against a limited number of Gram-negative micro-organisms. ‘One step’ resistance developed hiin vitro and during treatment. Resistance was not mediated by transfer of R-plasmids, which is a characteristic of all quinolones. Newer quinolones like oxolinic acid, piromidic acid, cinoxacin and pipemidic acid exhibit an extended spectrum of activity against Gram-negative bacteria at lower MIC values. In recent years fluorinated quinolones were introduced like ciprofloxacin, norfloxacin, pefloxacin, ofloxacin, enoxacin and amifloxacin. These compounds exhibitin vitro a broad spectrum of activity against Gram-negative and Gram-positive bacteria at MIC values seventy to four hundred times less than those for nalidixic acid. Thein vitro activity of these compounds has been investigated in a large study of uncomplicated urinary tract infections in general practice (PINISU). No resistance was found. The fluorinated quinolones are very promising antimicrobial agents for a limited number of indications.     

In vitro susceptibility of four serotypes of enterohaemorrhagic Escherichia coli to antimicrobial agents

We evaluated the in vitro susceptibility of four serotypes of enterohaemorrhagic Escherichia coli (E. coli 026, E. coli O111, E. coli O157, and E. coli O165) with diverse DNA patterns to antimicrobial agents. The minimum inhibitory concentrations (MIC) determined in a total of 83 strains using Mueller-Hinton agar under aerobic and anaerobic conditions were 0.015-0.12 microg/ml for ciprofloxacin, 0.06-1 microg/ml for norfloxacin, 2-64 microg/ml for fosfomycin without glucose-6-phosphate (G-6-P), 0.25-32 microg/ml for fosfomycin with G-6-P, 2- > or = 256 microg/ml for kanamycin, 0.125-2 microg/ml for cefoperazone, and 0.06-1 microg/ml for ceftazidime. The MIC of ciprofloxacin, norfloxacin, cefoperazone, and ceftazidime were low in all strains examined.     

复方奥硝唑栓的体外抗菌活性研究

目的:研究复方奥硝唑栓的体外抗菌活性。方法:采用试管二倍稀释法测定复方奥硝唑栓对金黄色葡萄球菌、大肠杆菌、粪肠球菌及脆弱拟杆菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC),并以氧氟沙星栓和替硝唑栓进行对照。结果:复方奥硝唑栓对金黄色葡萄球菌、大肠杆菌、粪肠球菌及脆弱拟杆菌显示很强的抗菌活性,其MIC值分别为0.061、0.015、0.49、0.031μg/ml,MBC值分别为0.12、0.031、0.98、0.031μg/ml。无论是对标准菌株还是临床分离菌株,复方奥硝唑栓MIC、MBC值均明显低于氧氟沙星栓及替硝唑栓,其组方中2组分具有良好的协同作用。结论:复方奥硝唑栓对妇科炎症具有广谱、高效、低毒的特点。     

Toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals

A toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals was undertaken using nalidixic acid as a standard drug. Norfloxacin and nalidixic acid were subcutaneously administered to rats and rabbits, orally administered to dogs, and norfloxacin was orally dosed to monkeys once a day for 7 consecutive days. Of the dose levels tested, the minimum arthropathic doses of norfloxacin were 100, 25, and 50 mg/kg/day in rats, rabbits, and dogs, respectively. At these doses, the peak serum concentrations (Cmax) on Day 6 were 16.1, 9.73, and 5.11 micrograms/ml, and the areas under the serum concentration/time curve (AUC0----infinity) were 31.9, 22.9, and 26.2 micrograms.hr/ml, in respective animals. Monkeys showed no arthropathy with norfloxacin at doses of less than 500 mg/kg/day, at which the Cmax and AUC0----infinity were 15.6 micrograms/ml and 103 micrograms.hr/ml, respectively. The minimum arthropathic doses of nalidixic acid were 50, 100, and 25 mg/kg/day in rats, rabbits, and dogs, respectively. The Cmax and AUC0----infinity of nalidixic acid were higher than those of norfloxacin in all animals. Joint tissues took up more norfloxacin than nalidixic acid, but when arthropathy was present the articular cartilage concentrations of the two drugs were in the same range. The penetration of norfloxacin into the articular cartilage was the same regardless of the joint's anatomical locations, but differed among species, being highest in rats and lowest in monkeys. The Cmax and AUC0----infinity of norfloxacin in animals at their arthropathic doses were far higher than those measured clinically in children, whereas those of nalidixic acid in animals did not differ much from its clinical parameters.     

Antimicrobial activity of norfloxacin in enteric and urinary tract infections: combined effect of norfloxacin with aminoglycosides, tetracycline and chloramphenicol

A comparative study of the in vitro activity of norfloxacin was performed versus that of aminoglycosides, pipemidic acid, tetracycline and chloramphenicol. These antibiotics are the most commonly used antimicrobial agents in the treatment of enteric and urinary tract infections. Results obtained with norfloxacin against Gram-negative isolates tested were very encouraging. MIC values for the Enterobacteriaceae were less than or equal to 0.47 mcg/ml, and for Pseudomonas and Acinetobacter less than or equal to 32.5 mcg/ml. The activity of norfloxacin against Pseudomonas was inferior to that of amikacin, but superior to that of gentamicin. In association with aminoglycosides, norfloxacin proved to be most useful in the treatment of urinary tract infections, while norfloxacin associated with tetracycline and chloramphenicol did not give satisfactory results in the treatment of enteric infections.     

In vitro activity of norfloxacin in synthetic media and human urine compared to that of cinnoxacin, nalidixic acid and pipemidic acid

Activity of norfloxacin was compared to that of cinnoxacin, nalidixic acid and pipemidi acid in DST-agar and human urine solidified by adding 1.2% agar. Norfloxacin was the most active compound when tested on DST-agar but the MIC values increased from 64 to 128 fold when tested in urine. Other compounds also showed an increase in MIC in urine-agar, but the increase was less marked. MICs for norfloxacin in DST-agar and Müller-Hinton-Agar were similar. Higher concentrations were required in Müller-Hinton-Broth than in Müller-Hinton-Agar.     

Antibacterial activity of the metabolites of ciprofloxacin and its significance in the bioassay

The antibacterial activity of the metabolites of ciprofloxacin (1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3- quinolinecarboxylic acid, Bay o 9867; designated tradename: Ciprobay) M1, M2, M3 and M4 was tested with the agar dilution method against various Gram-positive and Gram-negative bacteria in comparison to ciprofloxacin, norfloxacin and nalidixic acid. The results show that M1 had only a weak antibacterial activity comparable to nalidixic acid, whereas M2 was significantly less active. M3, which is one of the main metabolites in urine has a broad antibacterial activity but was less active than ciprofloxacin or norfloxacin. M4 which is a very minor metabolite of ciprofloxacin was the most active compound with minimal inhibitory concentrations for strains of Escherichia coli or Klebsiella pneumoniae in the range of norfloxacin, whereas with staphylococci the antibacterial activity was comparable to ciprofloxacin. Possible interactions between ciprofloxacin and the metabolites in the bioassay system, using Escherichia coli (ICB 4004) were studied, to explain discrepancies between the microbiological assay and the HPLC-method reported in the literature. It could be demonstrated that under conditions where the concentration of ciprofloxacin exceeds or equals the concentration of the metabolites or mixtures of them no increase in the inhibition zones for ciprofloxacin could be observed, which would have led to false high values for ciprofloxacin in the bioassay system. From these data we conclude that the antibacterial activity of the metabolites in biological specimens, e.g. urine, does not influence the bioassay results.     

Quinolones in vitro

The first quinolone compound, nalidixic acid, showed activity against a limited number of Gram-negative micro-organisms. One step resistance developed hiin vitro and during treatment. Resistance was not mediated by transfer of R-plasmids, which is a characteristic of all quinolones. Newer quinolones like oxolinic acid, piromidic acid, cinoxacin and pipemidic acid exhibit an extended spectrum of activity against Gram-negative bacteria at lower MIC values. In recent years fluorinated quinolones were introduced like ciprofloxacin, norfloxacin, pefloxacin, ofloxacin, enoxacin and amifloxacin. These compounds exhibitin vitro a broad spectrum of activity against Gram-negative and Gram-positive bacteria at MIC values seventy to four hundred times less than those for nalidixic acid. Thein vitro activity of these compounds has been investigated in a large study of uncomplicated urinary tract infections in general practice (PINISU). No resistance was found. The fluorinated quinolones are very promising antimicrobial agents for a limited number of indications.     

Comparative studies on activities of antimicrobial agents against causative organisms isolated from urinary tract infections (1985). I. Susceptibility distribution

The results of determinations of sensitivities of bacterial strains to various antibiotics are summarized as follows: 1. Against Escherichia coli, ofloxacin (OFLX) showed the strongest activity among oral antibacterial and antibiotic agents. Its MIC90 was below 0.10 micrograms/ml. The next strongest activity was found in mecillinam (MPC), cefaclor (CCL) and pipemidic acid (PPA); MIC90's of these agents 3.13 micrograms/ml. Cefotiam (CTM), cefotaxime (CTX), ceftizoxime (CZX), cefmenoxime (CMX) and latamoxef (LMOX) had MIC90 below 0.39 micrograms/ml. MIC90's of cefmetazole (CMZ) and cefoperazone (CPZ) were 1.56 micrograms/ml. Aztreonam (AZT) and carumonam (CRMN) in the monobactam group showed strong activities with MIC90's at 0.20 micrograms/ml. 2. Although Klebsiella pneumoniae had a strong resistance to ampicillin (ABPC) and showed relatively low sensitivities to other oral antibacterial and antibiotic agents, OFLX maintained high activity against this species and showed MIC90 of 0.39 micrograms/ml. Among injectable antibiotics, third generation cephems showed the strongest activity to this species with MIC90 of CZX below 0.10 micrograms/ml, of CTX and CMX 0.20 micrograms/ml, and of LMOX 0.78 micrograms/ml. MIC90 of CPZ was 6.25 micrograms/ml, which was the same as those of cefazolin (CEZ) and cefoxitin (CFX). CTM had similar MIC90 to LMOX, namely, 1.56 micrograms/ml. MIC90 of CMZ was 3.13 micrograms/ml. Monobactams AZT and CRMN showed strong activities to this species; their MIC90's were below 0.10 micrograms/ml and 0.20 micrograms/ml. 3. Although Citrobacter freundii generally exhibited low sensitivities to antibacterial and antibiotic agents examined, it showed high sensitivity to OFLX, at MIC80 of 0.78 micrograms/ml. This species showed low sensitivities to MPC, nalidixic acid (NA), PPA, and sulfamethoxazole-trimethoprim (ST). Among injectable antibiotics, LMOX and CMX had activities against this species; namely, MIC80's were 6.25 and 3.13 micrograms/ml, respectively. Among monobactams, AZT showed MIC80 of 12.5 micrograms/ml, and CRMN had that of 6.25 micrograms/ml. 4. Against Enterobacter cloacae, the strongest antibacterial activity was found with OFLX which had MIC90 of 0.39 micrograms/ml. A relatively strong activity was seen with MPC. MIC80 of MPC was 1.56 micrograms/ml. Except to CTM, this species had poor sensitivities to injectable first and second generation cephems, and their MIC80's were over 200 micrograms/ml. MIC80 of CTM was 25 micrograms/ml.(ABSTRACT TRUNCATED AT 400 WORDS)