The in vitro activity of ciprofloxacin, a quinolone-carboxylic acid derivative, was compared with those of norfloxacin, cefotaxime, cephalexin, ceftazidime, moxalactam, amoxicillin, and methicillin and other agents, as appropriate. The MICs of ciprofloxacin for 90% of members of the family Enterobacteriaceae and for Pseudomonas aeruginosa, Neisseria spp., and Bacteroides fragilis were between 0.005 and 0.8 ,ug/ml, whereas streptococci and staphylococci were all inhibited by c6.3 p,g/ml. Ciprofloxacin was 4-to 32-fold more active than norfloxacin and inhibited gentamicin-, ameikacin-, cefotaxime-, and moxalactam-resistant members of the family Enterobacteriaceae and P. aeruginosa and methicillin-resistant Staphylococcus aureus. The activity of ciprofloxacin wkas not affected by serum but decreased in the presence of acid urine.The frequency of resistance to ciprofloxacin was between 10-7 and 10-9.Nalidixic acid, a pyridone-carboxylic acid compound, was introduced into medical use in 1963. It was not used clinically to any great extent because of the rapid development of resistance to the compound (5). In the 1970s, pipemidic acid was synthesized in Japan (6). This compoqnd, which provided reasonable concentrations in tissue, was used to treat infections other than urinary tract infections, as was nalidixic acid and other compounds of this class, such as oxolinic acid and cinoxacin.The development of norfloxacin, a pyridone-carboxylic acid derivative, showed that it was possible to develop compounds of this class which, by virtue of their broad spectrum of activity and the low incidence of resistance to them, would be clinically useful (2, 4). Although the expanded-spectrum cephalosporins inhibit many clinically important bacteria, resistance has already been encountered among Enterobacter and Pseudomonas spp. (3). For this reason, we sought to study cirprofloxacin, a novel quinolone compound, and to compare its activity with those of other agents currently in use. MATERIALS AND METHODSCompounds. All compounds were obtained from their respective manufacturers. Ciprofloxacin was a gift of Bayer; norfloxacin was obtained from Merck Sharp & Dohme.Fresh dilutions of each compound were prepared daily in sterile medium. Bacterial isolates were obtained from patients treated at The Columbia-Presbyterian Medical Center, New York. Both recent isolates and isolates that are multiply resistant to antibiotics had been saved over the past 5 years and were tested. Only one isolate from a patients was tested to avoid multiple copies of the same strain.Susceptibility testing. Antimicrobial susceptibility tests were performed by an agar dilution method with MuellerHinton agar, except where otherwise specified. A final inoculum of 105 CFUs, prepared by dilution of a fresh overnight broth culture, was applied to agar with a replicating spot device. Broth dilutions were performed with 105 CFU in tubes each having a volume of 1 ml. Agar plates and tubes were incubated at 35°C for 18 h. RESULTSCiprofloxacin had an extremely broad rang...

A multicenter study was conducted to expand the generation and analysis of data that supports the proposal of a reference method for the antifungal susceptibility testing of filamentous fungi. Broth microdilution MICs of amphotericin B and itraconazole were determined in 11 centers against 30 coded duplicate pairs of Aspergillus spp., Fusarium spp., Pseudallescheria boydii, and Rhizopus arrhizus. The effect of inoculum density (approximately 10 3 and 10 4 CFU/ml), incubation time (24, 48, and 72 h), and procedure of MIC determination (conventional and colorimetric [Alamar Blue] evaluation of growth inhibition) on intra-and interlaboratory agreement was analyzed. Based on intra-(97 to 100%) and interlaboratory (94 to 95%) agreement for both drugs, the overall optimal testing conditions identified were determination of colorimetric MICs after 48 to 72 h of incubation with an inoculum density of approximately 10 4 CFU/ml. These testing conditions are proposed as guidelines for a reference broth microdilution method.

The in vitro activity of Ro 23-6240 (AM833), 6,8-difluoro-l-(2-fluoroethyl)-1,4-dihydro-4-oxo-7(4-methyl-lpiperazinyl) quinolone-3-carboxylic acid, was compared with those of norfloxacin, enoxacin, ofloxacin, and ciprofloxacin. Ro 23-6240 inhibited the majority of Enterobacteriaceae isolates at a concentration of c0.5 ,ug/ml. It was especially active against Shigella sp., SalmoneUla sp., Escherichia coli, and Yersinia enterocolitica, with an MIC for 90% of the strains of

Enoxacin is a new quinolone carboxylic acid compound. Its activity against 740 bacterial isolates was determined. It inhibited 90% Escherichia coli, Klebsiella sp., Aeromonas sp., Enterobacter spp., Serratia spp., Proteus mirabilis, and Morganella morganii at -0.8 ,ug/ml. The majority of Pseudomonas aeruginosa was inhibited by <3.1 p.g/ml. Haemophilus spp. and Neisseria spp. were inhibited by <0.1 jig/ml. Although most Staphylococcus aureus were inhibited by 3.1 ,ug/ml, some streptococcal species had minimal inhibitory concentrations of 6.3 to 12.5 ,ug/ml and Bacteroides sp. had minimal inhibitory concentrations -25 ,ug/ml. Activity of enoxacin and norfloxacin was similar. Enoxacin inhibited organisms resistant to cefotaxime, moxalactam, gentamicin, and piperacillin. Enoxacin was less active in urine at an acid pH than in broth, but serum did not decrease minimal inhibitory concentrations or minimal bactericidal concentrations. There was no major difference between minimal inhibitory concentrations and minimal bactericidal concentrations. Resistance frequency development was <10-9 for most bacterial species.Quinolone antimicrobial agents such as nalidixic acid and related compounds have been used primarily to treat urinary tract infections. Agents of this class have various ring structures affixed to y-pyridone-p-carboxylic acid which appears to be essential for the activity of these synthetic compounds. Recently, compounds have been synthesized which do not appear to suffer from the defects of nalidixic acid, namely restricted antibacterial activity and poor oral absorption. These agents are active against bacteria resistant to nalidixic acid, and they inhibit gram-positive species and Pseudomonas aeruginosa (4, 7). Enoxacin, formerly called AT-2266 or CI 919, is a 1-ethyl-6-fluro-1,4-dihydro-4-oxa-7-(1-piperazinyl)-

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