Comparative in vitro activity of ciprofloxacin and five other quinoline derivatives against gram-negative isolates

A total of 375 Gram-negative bacterial strains were isolated from midstream urine specimens of the same number of patients affected by urinary tract infections. All bacteria were identified by standard bacteriological methods and their susceptibility to six quinoline derivatives (ciprofloxacin, cinoxacin, norfloxacin, oxolinic acid, pipemidic acid, nalidixic acid) was studied by determining the MICs and MBCs for each compound using a miniaturized dilution broth method in microtitre plates and twofold dilutions of each drug from 256 to 0.12 mcg/ml. Ciprofloxacin, a new quinoline carboxylic acid compound structurally related to nalidixic acid, showed a much higher antibacterial activity against all bacterial strains under examination, including Pseudomonas, than the other compounds, except for norfloxacin. The MIC90 and MBC90 of ciprofloxacin never exceeded 1 mcg/ml with any of the bacterial species; and MBC/MIC ratios were very low, which represents an important clinical advantage. Only norfloxacin showed comparable effectiveness. No bacterial strain showed resistance to the drug and the MIC90 and MBC90 never exceeded 8 mcg/ml.     

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 clinafloxacin against fluoroquinolone resistant Spanish clinical isolates.

The in vitro activity of clinafloxacin against 162 ciprofloxacin-resistant clinical isolates was determined. Isolates were selected when their MIC to ciprofloxacin was 2 mg/l (intermediate) or > 2 mg/l (resistant). The following strains were tested: 61 Escherichia coli, 12 Klebsiella pneumoniae, 7 Proteus mirabilis, 21 Serratia marcescens, 4 Enterobacter cloacae, 21 Pseudomonas aeruginosa, 21 Staphylococcus. aureus (resistant to methicillin) and 15 Enterococcus spp. Clinafloxacin, ciprofloxacin, ofloxacin and norfloxacin activities were evaluated by agar dilution using Müeller-Hinton agar according to NCCLS recommendations. Of the 162 isolates, 16 (9.8%) were intermediate and 146 (90.1%) resistant to ciprofloxacin. 95 of the 162 strains (58.6%) were susceptible, 27 (16.7%) intermediately susceptible, and 40 strains (24.7%) were resistant to clinafloxacin. The percentage susceptible to clinafloxacin was 65.6% for E. coli, 75% for K. pneumoniae, 71.4% for P. mirabilis, 28.6% for S. marcescens, 75% for E. cloacae, 33.3% for P. aeruginosa, 90.5% for S. aureus and 40% for Enterococcus spp. Clinafloxacin was active against 58.6% of the ciprofloxacin-resistant clinical isolates tested. It was particularly active against S. aureus strains resistant to both ciprofloxacin and methicillin.     

In-vitro antibacterial activity of noxythiolin and taurolidine

The minimum inhibitory concentrations (MIC) of noxythiolin and taurolidine were determined for strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Tests were performed in broth alone and in broth plus 25% v/v serum or 25% v/v urine. Inoculum density was either 10(3), 10(5) or 10(7) colony forming units per mL-1. Slight inoculum-dependent variation in the activity of both agents was observed for some, but not all, strains of P. aeruginosa and S. aureus. A more pronounced medium-dependent increase in activity was observed with both drugs, with up to 8-fold reduction of values for MIC when tested in the presence of serum or urine. These observations may help to clarify the disparity between the observed clinical efficacy of these agents and relatively poor in-vitro activity when tested using conventional methods in synthetic media.     

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.     

荧光分光光度法测定制剂和人尿样中的诺氟沙星含量

目的建立用于制剂和人体尿样中诺氟沙星含量测定的荧光分光光度法。方法研究不同pH条件下诺氟沙星的光谱行为,对样品测定条件进行优化,并对胶囊和人体尿液中诺氟沙星进行定量分析。结果用于制剂分析时,λex和λem分别为333nm和448nm,其线性范围为0．01μg·mL^-1～1．0μg·mL^-1;用于人尿样分析时,为了避免尿液中杂质的干扰,选定λex和λem分别为290nm和448nm,其线性范围为0：01μg·mL^-1～2．0μg·mL^-1;最低检出限均为0．01μg·mL^-1。结论该方法简便、快速、灵敏、无干扰,可作为尿样或制剂的含量直接分析方法。     

In vitro effect of pH and glucose concentration on the antibacterial activity of norfloxacin in urine

The in vitro effect of pH and glucose concentration on the antibacterial activity of norfloxacin in urine was studied. Norfloxacin effectively inhibited the growth of four gram-negative pathogens in urine in vitro at pH values of 6.0, 7.0, and 8.0. The antibacterial activity of norfloxacin in urine was reduced severalfold at pH 6, but minimum inhibitory concentrations (MICs) at this pH remained clinically significant. Glucose at concentrations of 200 mg/dl and 400 mg/dl (simulating glucosuria of diabetes) did not significantly affect the antibacterial activity of norfloxacin when tested against clinical isolates of Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, or Pseudomonas aeruginosa. Norfloxacin appears to be a highly effective antibiotic in vitro under conditions which simulate normal and diabetic states.     

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.     

Characterization of sparfloxacin-resistant mutants of Staphylococcus aureus obtained in vitro

A sparfloxacin-susceptible clinical isolate of Staphylococcus aureus was grown in increased concentrations of sparfoxacin. The presence of mutations in gyrA, gyrB, grlA and grlB genes was analyzed. The primary point mutation was located in the gyrA gene (Glu-88 to Lys). Two further mutation steps appeared in the amino acid change Ser-80 to Tyr in GrlA. No mutations occurred in the gyrB or grlB genes. Efflux pumps involved in the increase of resistance were also found to affect norfloxacin and ciprofloxacin. This effect may be related to NorA. An overexpression of NorA, may be associated with the increase of the MIC of norfloxacin from 32 mg/l to >200 mg/l in the final mutant. The MICs levels of sparfloxacin were affected by unknown mechanism.     

Quantitation of norfloxacin, a new antibacterial agent in human plasma and urine by ion-pair reverse-phase chromatography

A specific and sensitive high-performance liquid chromatographic method for the analysis of norfloxacin in human plasma and urine is described. Norfloxacin was extracted from the sample matrix using dichloromethane under neutral conditions, followed by back extraction into dilute phosphoric acid for chromatographic analysis on a reverse-phase column with a mobile phase consisting of methanol, phosphate buffer, and ion-pairing reagent (pH 3.0) at a flow rate of 2.0 mL/min. The ability of this method to distinguish intact norfloxacin from its metabolites was demonstrated. The method is linear, quantitative, and reproducible for both plasma analysis (0.05-2.5 microgram/mL) and urinalysis (1.0-500 micrograms/mL) using peak area ratios (norfloxacin-internal standard) for quantitation. The stability of norfloxacin and its metabolites in dilute phosphoric acid was studied. To assess the presence of norfloxacin conjugates in the urine of dosed individuals, the effects of urine hydrolysis on drug quantitation were examined. Urine and plasma levels of norfloxacin at selected time points following the administration of single drug doses are presented.     

Synergistic effect of artocarpin on antibacterial activity of some antibiotics against methicillin-resistant Staphylococcus aureus,Pseudomonas aeruginosa,and Escherichia coli

Context: Antibacterial resistance has dramatically increased and resulted in serious health problems worldwide. One appealing strategy to overcome this resistance problem is the use of combinations of antibacterial compounds to increase their potency.

Objective: The objective of this study is to determine the synergistic effects of artocarpin for ampicillin, norfloxacin, and tetracycline against methicillin-resistant Staphylococcus aureus (MRSA) as well as the Gram-negative bacteria Pseudomonas aeruginosa and Escherichia coli.

Materials and methods: A broth microdilution method (1.95–250?µg/mL) was used to determine the minimum inhibitory concentration (MIC) of artocarpin and the antibiotics. Any synergistic effects were evaluated at their own MIC using the checkerboard method and a time-kill assay at 37?°C for 24?h.

Results and discussion: Artocarpin showed antibacterial activity against MRSA and E. coli with an MIC value of 62.5?µg/mL, and against P. aeruginosa with an MIC value of 250?µg/mL. The interaction of artocarpin with all tested antibiotics produced synergistic effects against MRSA with a fractional inhibitory concentration index (FICI) of 0.15–0.37. In addition, a combination of artocarpin and norfloxacin showed a synergistic effect against E. coli with an FICI value of 0.37, while the combinations of artocarpin and tetracycline as well as artocarpin and norfloxacin exhibited synergy interactions against P. aeruginosa with FICI values of 0.24 and 0.37, respectively. Time-kill assays indicated that artocarpin enhanced the antimicrobial activities of tetracycline, ampicillin, and norfloxacin against MRSA as well as Gram-negative bacteria.     

Bacteriological in vitro studies with a new cephalosporin: cefotiam (author's transl)

MIC determinations with the dilution method using DST-agar show that 7 beta-[2-amino-thiazol-4-yl)acet-amido-3-less than ([1-(2-dimethylaminoethyl)-1H-tetrazol-5-yl]thio)methyl greater than-ceph-3-em-4-carboxylic acid (cefotiam) is approximately ten times more active than cefoxitin or cefuroxime against non-selected bacterial isolates. Cefotiam is also significantly more active than cefoxitin or cefoperazone against mezlocillin- and piperacillin-resistant cultures. The determination of susceptibility to cefotiam gives reliable results with 30 microgram discs. Inhibition zones of up to 12 mm (corresponding to MIC superior or equal to 64 microgram/ml) should be considered as resistance and zones larger or equal to 18 mm (corresponding to MIC inferior or equal to 8 microgram/ml) as susceptibility.     

Fluorimetric determination of norfloxacin in plasma and urine samples after thin-layer chromatographic separation

A thin-layer chromatographic (TLC) assay for the determination of norfloxacin (1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7- (piperazinyl)-3-quinolinecarboxylic acid), a new antibacterial agent, in human plasma and urine is described. Norfloxacin was extracted from plasma samples using commercial cartridges, urine samples were simply diluted with methanol. Plasma extracts or urine samples were applied to TLC plates (silica gel). Chromatography was performed with a mobile phase consisting of methanol, ethanol and water, the atmosphere in the tank being saturated with ammonia. The fluorescence intensity of norfloxacin was enhanced by dipping the plate into a paraffin/citric acid mixture. Peaks were quantified by fluorimetric measurement (excitation 313 nm/emission 390 nm, cut-off filter). The method showed acceptable precision and linearity in the range of 0.01 to 4 micrograms/ml for plasma and 1 to 100 micrograms/ml for urine. The assay was shown to be applicable to human plasma and urine samples.     

Novel amino-substituted 3-quinolinecarboxylic acid antibacterial agents: synthesis and structure-activity relationships

A series of novel 3-quinolinecarboxylic acid derivatives have been prepared and their antibacterial activity evaluated. These derivatives are characterized by fluorine attached to the 6-position and substituted amino groups appended to the 1- and 7-positions. Structure-activity relationship studies indicate that antibacterial potency is greatest when the 1-substituent is methylamino and the 7-substituent is either 4-methyl-1-piperazinyl, 16, or 1-piperazinyl, 21. Derivatives 16 and 21, the 1-methylamino analogues of pefloxacin and norfloxacin, respectively, show comparable in vitro and in vivo antibacterial potency to these two known agents. The activity (vs. Escherichia coli Vogel) of 16 (amifloxacin) is the following: in vitro MIC (microgram/mL) = 0.25; in vivo (mice) PD50 (mg/kg) = 1.0 (po), 0.6 (sc).     

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.     

诺氟沙星锌抗大鼠实验性胃溃疡作用研究

目的 :研究诺氟沙星锌 (NF -Zn)的抗胃溃疡作用。方法 :采用大鼠的多种急、慢性胃溃疡模型 ,体外中和盐酸实验和抗幽门螺旋杆菌 (Hp)实验 ,评价药物的抗胃溃疡作用。结果 :NF -Zn能明显防止乙醇、水杨酸和应激所致的急性胃溃疡 ,明显促进醋酸浸渍所致慢性胃溃疡的愈合 ,降低胃酸的分泌 ,提高胃液的pH值。体外实验表明 ,NF -Zn具有明显的制酸作用 ,并能明显抑制Hp 的生长 ,其MIC50 为0 5μg/ml。结论 :NF -Zn具有制酸、保护胃粘膜和抑制Hp 的作用     

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 influence of norfloxacin and metronidazole on the disposition of mycophenolate mofetil

The objective of this study was to investigate the effect of concurrent antibiotic administration on the disposition of mycophenolic acid (MPA) and mycophenolic acid glucuronide (MPAG) after oral administration of mycophenolate mofetil (MMF) in healthy subjects. Eleven healthy subjects were enrolled. The study was divided into 4 treatment periods. Subjects received MMF as a single oral 1-g dose alone and were then randomized to 3 antibiotic treatment periods. The 3 periods included norfloxacin, metronidazole, and a combination of norfloxacin and metronidazole. Antibiotic treatment was started 3 days prior to each MMF pharmacokinetic study day and was given for a total of 5 days. On day 4 of each antibiotic phase, subjects received a single 1-g oral dose of MMF. Plasma and urine samples were obtained over 48 hours after the MMF dose in all treatment periods and were quantitatively measured for MPA and MPAG. Pharmacokinetic parameters for MPA and MPAG were determined for all periods. Compared to MMF alone, the area under the plasma concentration versus time curve (AUC) of MPA was reduced by an average of 10%, 19%, and 33% when given with norfloxacin, metronidazole, and norfloxacin plus metronidazole, respectively. The AUC of MPAG was also reduced on average by 10%, 27%, and 41% in the corresponding periods. The combination of norfloxacin and metronidazole significantly reduced the AUC of MPA and MPAG in healthy subjects. This likely occurs as a result of reduced enterohepatic recirculation.     

Pharmacokinetic-pharmacodynamic modelling of the convulsant interaction between norfloxacin and biphenyl acetic acid in rats

Fluoroquinolones (FQs) are associated with a low incidence of central nervous system (CNS) side effects, possibly leading to convulsions, especially when co-administered with nonsteroidal anti-inflammatory drugs (NSAIDS). Although the in vivo pro-convulsant activity of NSAIDS is essentially unknown, the convulsant potential of FQs is traditionally evaluated by in vitro gamma-aminobutyric acid (GABA) binding experiments in the presence of 4-biphenyl acetic acid (BPAA), the active metabolite of fenbufen. The aim of this study was therefore to investigate the BPAA-norfloxacin convulsant interaction in vivo. Male Sprague-Dawley rats (n = 27) were given BPAA orally, at various doses 1 h before norfloxacin infusion, which was maintained until the onset of maximal seizures, when cerebrospinal fluid (CSF) and plasma samples were collected for analysis. An inhibitory E(max) effect model with a baseline effect parameter was fitted to the norfloxacin versus BPAA concentrations in the CSF, previously shown to be part of the biophase. This model includes three parameters: the concentrations of norfloxacin in the absence of BPAA (C(CSF0, Nor)), and when BPAA concentration tends toward infinity (C(CSFbase, Nor)), and the BPAA concentration for which half of the maximal effect is observed (C(CSF50, BPAA)). The maximal proconvulsant effect of BPAA is given by the C(CSF0, Nor) / C(CSFbase, Nor) ratio, estimated to approximately 6 in this study. Derived models were developed in plasma to account for the non-linear CSF diffusion of norfloxacin and protein binding of BPAA. In conclusion this study has shown that the convulsant interaction between norfloxacin and BPAA in rats, can be adequately characterized by modelling of the CSF concentrations of the two drugs at the onset of activity, following their administration in various proportions.