Search

The Gram-negative anaerobe Fusobacterium nucleatum is a major producer of hydrogen sulfide (H 2 S), a volatile sulfur compound that causes halitosis. Here, we dissected the genetic determinants of H 2 S production and its role in bacterial fitness and virulence in this important member of the oral microbiome. F. nucleatum possesses four enzymes, CysK1, CysK2, Hly, and MegL, that presumably metabolize l-cysteine to H 2 S, and CysK1 was previously shown to account for most H 2 S production in vitro , based on correlations of enzymatic activities with gene expression at mid-log phase. Our molecular studies showed that cysK1 and megL were highly expressed at the late exponential growth phase, concomitant with high-level H 2 S production, while the expression levels of the other genes remained substantially lower during all growth phases. Although the genetic deletion of cysK1 without supplementation with a CysK1-catalyzed product, lanthionine, caused cell death, the conditional Δ cysK1 mutant and a mutant lacking hly were highly proficient in H 2 S production. In contrast, a mutant devoid of megL showed drastically reduced H 2 S production, and a cysK2 mutant showed only minor deficiencies. Intriguingly, the exposure of these mutants to various antibiotics revealed that only the megL mutant displayed altered susceptibility compared to the parental strain: partial sensitivity to nalidixic acid and resistance to kanamycin. Most significantly, the megL mutant was attenuated in virulence in a mouse model of preterm birth, with considerable defects in the spread to amniotic fluid and the colonization of the placenta and fetus. Evidently, the l-methionine γ-lyase MegL is a major H 2 S-producing enzyme in fusobacterial cells that significantly contributes to fusobacterial virulence and antibiotic susceptibility. IMPORTANCE Fusobacterium nucleatum is a key commensal anaerobe of the human oral cavity that plays a significant role in oral biofilm development and contributes to additional pathologies at extraoral sites, such as promoting preterm birth and colorectal cancer. Although F. nucleatum is known as a major producer of hydrogen sulfide (H 2 S), its genetic determinants and physiological functions are not well understood. By a combination of bacterial genetics, biochemical methods, and in vivo models of infection, here, we demonstrate that the l-methionine γ-lyase MegL not only is a major H 2 S-producing enzyme of F. nucleatum but also significantly contributes to the antibiotic susceptibility and virulence of this organism.

The objective of this study, for the first time, was to optimize Amazonian cyanobacterial culture conditions for improving cell productivity and lipid content, by analyzing the effect of light intensity and nitrogen concentration, for empirically evaluating biodiesel quality parameters. The strains Synechocystis sp. CACIAM05, Microcystis aeruginosa CACIAM08, Pantanalinema rosaneae CACIAM18, and Limnothrix sp. CACIAM25, were previously identified by morphological and molecular analysis (16S rRNA) and were selected based on their production of chlorophyll a and dry cell weight. Then, factorial planning (2 2 ) with central points was applied, with light intensity and NaNO 3 concentration as independent variables. As response variables, cell productivity and lipid content were determined. Statistical analysis indicated that for all strains, the independent variables were statistically significant for cell productivity. Analysis of the fatty acid composition demonstrated diversity in the composition of the fatty acid profile from the experimental planning assays of each strain. The Biodiesel Analyzer software predicted the biodiesel quality parameters. CACIAM05 and CACIAM25 obtained better parameters with low levels of light intensity and NaNO 3 concentration, whereas CACIAM08 and CACIAM18 obtained better parameters with low NaNO 3 concentrations and high luminous intensity.

Aim: Design and synthesis of novel nalidixic acid derivatives of potent anticancer and topoisomerase II inhibitory activities were our major aim., Materials & Methods: All the newly synthesized nalidixic acid derivatives were submitted to the National Cancer Institute (NCI), Bethesda, USA and were accepted for single dose screening. Further investigation via IC 50 determination of the most potent compound 6a against K-562 and SR leukemia cell lines. Finally, the topoisomerase II inhibitory activity, the cell cycle analysis and molecular docking of 6a were performed in order to identify the possible mechanism of the anticancer activity., Results: Compound 6a showed interesting selectivity against leukemia especially K-562 and SR subpanels with IC 50 35.29 µM and 13.85 µM respectively. Moreover, compound 6a revealed potent topoisomerase IIα and topoisomerase IIβ inhibitory activity compared with known topoisomerase inhibitors such as doxorubicin and topotecan with IC 50 1.30 µM and 0.017 µM respectively. Cell cycle analysis indicated that compound 6a induced cell cycle arrest at G2-M phase leading to inhibition of cell proliferation and apoptosis. Molecular modeling demonstrated that the potent topoisomerase inhibitory activity of 6a was due to the interaction with the topoisomerase II enzyme through coordinate bonding with the magnesium ion Mg 2+ , hydrogen bonding with Asp 545 and arene cation interaction with His 759., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Aim: Exploration of microbes isolated from rhizospheric soil of Crataegus oxycantha for bioactive natural products., Methods and Results: A strain of Streptomyces sp. (C-7) was isolated from rhizospheric soil of C. oxycantha. The 16S rRNA gene sequence of strain C-7 displayed 99% sequence similarity with different Streptomyces species. The highest score was displayed for Streptomyces sp. strain Chy2-8 followed by Streptomyces violarus strain NBRC13104 and Streptomyces arenae strain ISP5293. The position of C-7 in the phylogenetic tree suggested uniqueness of the strain. Nalidixic acid (1), a quinolone antibiotic, was isolated from Streptomyces sp. strain (C-7) for the first time and characterized by NMR and chemically analysed. Compound 1 exhibited antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa. The production of compound 1 was also validated by repeating fermentation of strain C-7 and compound isolation in a separate natural product laboratory with no prior information. Furthermore, Compound 1 showed a cytotoxic effect against human prostate cancer cell line PC3 with an IC 50 11 μg ml -1 ., Conclusion: To the best of our knowledge, this is the first report showing production of nalidixic acid naturally by a strain of Streptomyces sp., Significance and Impact of the Study: In this study, we isolated a strain of Streptomyces sp. producing nalidixic acid, which was otherwise only obtained through chemical synthesis., (© 2018 The Society for Applied Microbiology.)

In renal proximal tubule cells, the organic anion transporters 1 and 3 (OAT1 and OAT3) in the basolateral membrane and the multidrug resistance-associated protein 4 (MRP4) in the apical membrane share substrates and co-operate in renal drug secretion. We hypothesized that recently identified MRP4 inhibitors dantrolene, glafenine, nalidixic acid, and prazosin also interact with human OAT1 and/or OAT3 stably transfected in human embryonic kidney 293 cells. These four drugs were tested as possible inhibitors of p -[ 3 H]aminohippurate (PAH) and [ 14 C]glutarate uptake by OAT1, and of [ 3 H]estrone-3-sulfate (ES) uptake by OAT3. In addition, we explored whether these drugs decrease the equilibrium distribution of radiolabeled PAH, glutarate, or ES, an approach intended to indirectly suggest drug/substrate exchange through OAT1 and OAT3. With OAT3, a dose-dependent inhibition of [ 3 H]ES uptake and a downward shift in [ 3 H]ES equilibrium were observed, indicating that all four drugs bind to OAT3 and may possibly be translocated. In contrast, the interaction with OAT1 was more complex. With [ 14 C]glutarate as substrate, all four drugs inhibited uptake but only glafenine and nalidixic acid shifted glutarate equilibrium. Using [ 3 H]PAH as a substrate of OAT1, nalidixic acid inhibited but dantrolene, glafenine, and prazosin stimulated uptake. Nalidixic acid decreased equilibrium content of [ 3 H]PAH, suggesting that it may possibly be exchanged by OAT1. Taken together, OAT1 and OAT3 interact with the MRP4 inhibitors dantrolene, glafenine, nalidixic acid, and prazosin, indicating overlapping specificities. At OAT1, more than one binding site must be assumed to explain substrate and drug-dependent stimulation and inhibition of transport activity., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)

Penicillins remain first-line agents for treatment of group B Streptococcus (Streptococcus agalactiae; GBS) infections; however, several reports have confirmed the existence of GBS with reduced penicillin susceptibility (PRGBS). Because no selective agar plates for detection of PRGBS are available to date, in this investigation, we developed the selective agar plate for detection of PRGBS. We used 19 genetically well-confirmed PRGBS isolates and 38 penicillin-susceptible GBS isolates identified in Japan. For preparation of trial PRGBS-selective agar plates, we added 1 of antimicrobial agents (among oxacillin, ceftizoxime, and ceftibuten) to a well-established GBS-selective agar plate. Among 12 trial PRGBS-selective agar plates, Muller-Hinton agar containing 128 μg/mL ceftibuten with 5% sheep blood, 8 μg/mL gentamicin, and 12 μg/mL nalidixic acid was the most appropriate selective agar for PRGBS, showing 100% sensitivity and 81.6% specificity. In cases of potential nosocomial spread of PRGBS, the selective agar plate could be useful and reliable., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Considering the medical, biotechnological, and economical importance of actinobacteria, there is a continuous need to improve the tools for genetic engineering of a broad range of these microorganisms. Intergeneric conjugation has proven to be a valuable yet imperfect tool for this purpose. The natural resistance of many actinomycetes to nalidixic acid (Nal) is generally exploited to eliminate the sensitive Escherichia coli donor strain following conjugation. Nevertheless, Nal can delay growth and have other unexpected effects on the recipient strain. To provide an improved alternative to antibiotics, we propose a postconjugational counterselection using a diaminopimelic acid (DAP) auxotrophic donor strain. The DAP-negative phenotype was obtained by introducing a dapA deletion into the popular methylase-negative donor strain E. coli ET12567/pUZ8002. The viability of ET12567 and its ΔdapA mutant exposed to DAP deprivation or Nal selection were compared in liquid pure culture and after mating with Streptomyces coelicolor. Results showed that death of the E. coli ΔdapA Nal-sensitive donor strain occurred more efficiently when subjected to DAP deprivation than when exposed to Nal. Our study shows that postconjugational counterselection based on DAP deprivation circumvents the use of antibiotics and will facilitate the transfer of plasmids into actinomycetes with high biotechnological potential, yet currently not accessible to conjugative techniques.

The dnaQ gene of Escherichia coli encodes the ε subunit of DNA polymerase III, which provides the 3' → 5' exonuclease proofreading activity of the replicative polymerase. Prior studies have shown that loss of ε leads to high mutation frequency, partially constitutive SOS, and poor growth. In addition, a previous study from our laboratory identified dnaQ knockout mutants in a screen for mutants specifically defective in the SOS response after quinolone (nalidixic acid) treatment. To explain these results, we propose a model whereby, in addition to proofreading, ε plays a distinct role in replisome disassembly and/or processing of stalled replication forks. To explore this model, we generated a pentapeptide insertion mutant library of the dnaQ gene, along with site-directed mutants, and screened for separation of function mutants. We report the identification of separation of function mutants from this screen, showing that proofreading function can be uncoupled from SOS phenotypes (partially constitutive SOS and the nalidixic acid SOS defect). Surprisingly, the two SOS phenotypes also appear to be separable from each other. These findings support the hypothesis that ε has additional roles aside from proofreading. Identification of these mutants, especially those with normal proofreading but SOS phenotype(s), also facilitates the study of the role of ε in SOS processes without the confounding results of high mutator activity associated with dnaQ knockout mutants., (Copyright © 2015 Whatley and Kreuzer.)

The detection of Listeria monocytogenes from food is currently carried out using a double enrichment. For the ISO methodology, this double enrichment is performed using half-Fraser and Fraser broths, in which the overgrowth of L. innocua can occur in samples where both species are present. In this study, we analyzed the induction of phages and phage tails of Listeria spp. in these media and in two brain heart infusion (BHI) broths (BHIM [bioMérieux] and BHIK [Biokar]) to identify putative effectors. It appears that Na2HPO4 at concentrations ranging from 1 to 40 g/liter with an initial pH of 7.5 can induce phage or phage tail production of Listeria spp., especially with 10 g/liter of Na2HPO4 and a pH of 7.5, conditions present in half-Fraser and Fraser broths. Exposure to LiCl in BHIM (18 to 21 g/liter) can also induce phage and phage tail release, but in half-Fraser and Fraser broths, the concentration of LiCl is much lower (3 g/liter). Low phage titers were induced by acriflavine and/or nalidixic acid. We also show that the production of phages and phage tails can occur in half-Fraser and Fraser broths. This study points out that induction of phages and phage tails could be triggered by compounds present in enrichment media. This could lead to a false-negative result for the detection of L. monocytogenes in food products., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

K-12 Escherichia coli cells grown in static media containing a critical phosphate (Pi) concentration ≥25 mM maintained a high polyphosphate (polyP) level in stationary phase, impairing biofilm formation, a phenomenon that is triggered by polyP degradation. Pi concentration in human urine fluctuates according to health state. Here, the influence of environmental Pi concentration on the occurrence of virulence traits in uropathogenic E. coli (UPEC) isolated from acute prostatitis patients was evaluated. After a first screening, 3 isolates were selected according to differential biofilm formation profiles depending on media Pi concentration. For each isolate, biofilm positive and negative conditions were established. Regardless of the isolate, biofilm formation capacity was accompanied with curli and cellulose production and expression of some key virulence factors associated with adhesion. When the selected isolates were grown in their non-biofilm-forming condition, low concentrations of nalidixic acid and ciprofloxacin induced biofilm formation. Interestingly, similar to laboratory strains, polyP degradation induced biofilm formation in the selected isolates. Data demonstrated the complexity of UPEC responses to environmental Pi and the importance of polyP metabolism in the virulence of clinical isolates.

We analyzed formation of single-stranded DNA (ssDNA) related to SOS induction in nalidixilate (Nal)-treated Escherichia coli, using immunofluorescence microscopy accompanied by computer analysis. We found enhancement of both ssDNA concentrations and cells having ssDNA foci that often localized around cellpoles. Analyzing several mutants deficient in DNA repair or replication, we found, after Nal treatment, that recN, recA, uvrD and dnaB failed to increase ssDNA concentration and that recG and particularly ruvA only partially enhanced it. In Nal-treated recB mutant, despite its failure in SOS induction, ssDNA foci positive cells increased with a slight enhancement of its concentration. These observations suggest the existence of a cellular process that sequesters genotoxic ssDNA as inert form, offering a new concept for SOS suppressor genes action., (© 2013.)

The Fenton-like degradation of nalidixic acid was studied in this work. The effects of Fe(3+) concentration and initial H(2)O(2) concentration were investigated. Increasing the initial H(2)O(2) concentration enhances the degradation and mineralization efficiency for nalidixic acid, while Fe(3+) shows an optimal concentration of 0.25 mM. A complete removal of nalidixic acid and a TOC removal of 28 % were achieved in 60 min under a reaction condition of [Fe(3+)] =0.25 mM, [H(2)O(2)] =10 mM, T=35 °C, and pH=3. LC-MS analysis technique was used to analyze the possible degradation intermediates. The degradation pathways of nalidixic acid were proposed according to the identified intermediates and the electron density distribution of nalidixic acid. The Fenton-like degradation reaction of nalidixic acid mainly begins with the electrophilic attack of hydroxyl radical towards the C3 position which results in the ring-opening reaction; meanwhile, hydroxyl radical attacking to the branched alkyl groups of nalidixic acid leads to the oxidation at the branched alkyl groups.

For the first time in this work, uniform molecularly imprinted polymer (MIP) nanoparticles were prepared using nalidixic acid as a template. The MIP nanoparticles were successfully synthesized by precipitation polymerization applying methacrylic acid (MAA) as a functional monomer and trimethylolpropane trimethacrylate (TRIM) as a cross-linking monomer at different mole ratios. The morphology, binding, recognition, selectivity, and in vitro release behaviors of obtained particles were studied. The produced polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetric. Furthermore, their morphology was analyzed accurately by scanning electron microscopy, photon correlation spectroscopy, and Brunauer-Emmett-Teller analysis. The nanospheres and microspheres with mean diameter values of 94 nm, 256 nm, and 1.2 µm were obtained using nalidixic acid-MAA-TRIM various mole ratios. Among the MIPs, the product with nalidixic acid-MAA-TRIM mole ratio of 1:12:12 established nanospheres with the lowest polydispersity index (0.003), an average pore diameter (12 nm), and the highest specific surface area (280 m(2) g(-1)) and selectivity factor (10.4). Results from binding experiments demonstrated that the imprinted nanospheres with a 94-nm mean diameter and a binding capacity of 28 mg of nalidixic acid per gram of polymer had higher specific affinity to nalidixic acid in contrast with the other imprinted nanospheres, microspheres, and nonimprinted particles. However, the binding performance of imprinted nanospheres in human serum was estimated using high-performance liquid chromatography analysis (binding approximately 98% of nalidixic acid). In addition, release experiments proved to be successful in the controlled release of nalidixic acid during a long period. The 20% of loaded nalidixic acid was released from the imprinted nanospheres within the first 20 h, whereas the remaining 80% was released in the after 120 h. The nalidixic acid release kinetics from the MIPs was highly affected by properties of the particles., (Copyright © 2012 John Wiley & Sons, Ltd.)

Dissemination of plasmid-mediated quinolone resistance among pathogenic bacteria is a concern for public health because of decreased sensitivity to fluoroquinolones and increased potentials to develop high fluoroquinolone resistance. Two qnrS1-positive isolates of Salmonella enterica Corvallis (468) and Typhimurium (484) from imported seafood (Thailand and Vietnam) were tested for quinolone sensitivity using disk agar diffusion and the Sensititre system. The presence of qnr genes, qnr-carrying plasmids, and mutations in the quinolone resistance determining regions were also determined. Minimal inhibitory concentrations of nalidixic acid for isolates 468 and 484 were 8 and 16 μg mL(-1) , respectively, and those of ciprofloxacin were 1 and 2 μg mL(-1), respectively. Disk agar diffusion indicated that isolate 468 was moderately resistant to moxifloxacin, and isolate 484 was resistant to moxifloxacin and moderately resistant to norfloxacin. Isolates 468 and 484 carried a mutation on parC, but not on gyrA, gyrB, or parE. Sequences of qnrS1-carrying plasmids from isolates 468 and 484, sized 10,039 and 10,047 bp, were nearly identical (> 99% similarity) to each other and to published sequences of plasmids from clinical isolates of Salmonella Typhimurium isolated in the United Kingdom and Taiwan, indicating a dissemination of qnrS1-carrying plasmids among different serovars of Salmonella from geographically separated sources. This is the first complete sequence of a qnrS1-carrying plasmid from imported seafood isolate of S. enterica., (© 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)

The biodegradability of different wastewater samples originated from the industrial production of three pharmaceuticals (naproxen, acyclovir, and nalidixic acid) was performed through the standard Zahn-Wellens test. Moreover, the wastewater composition before and during the test was evaluated in terms of parent compounds and main metabolites by LC/MS, and the biodegradability of the parent compounds was also assessed by performing extra Zahn-Wellens tests on synthetic solutions. The results, besides showing the relatively good biodegradability of acyclovir and naproxen, evidenced the masking role of the organic matrices, especially in the case of nalidixic acid. The latter compound showed to be recalcitrant and persistent, despite the apparently good performance of the Zahn-Wellens test. Deeper evaluation evidenced that the biodegradation of high concentrations of organic solvents and other biodegradable compound tended to "hide" the lack of removal of the target compound., (Copyright 2009 Elsevier Ltd. All rights reserved.)

In South Africa, for the years 2003-2007, the Enteric Diseases Reference Unit received 510 human isolates of Salmonella Typhi, of which 27 were nalidixic acid-resistant [minimum inhibitory concentrations (MICs) 128-512 microg/ml] with reduced susceptibility to ciprofloxacin (MICs 0.125-0.5 microg/ml). Pulsed-field gel electrophoresis analysis of 19 available isolates differentiated them into five DNA pattern types; multiple-locus variable-number tandem repeat analysis differentiated the isolates into 10 types. This level of genetic diversity suggested that resistant strains usually emerged independently of one another. A 16- to 32-fold decrease in nalidixic acid MIC and a 2- to 8-fold decrease in ciprofloxacin MIC, was observed in the presence of an efflux pump inhibitor. All isolates were negative by PCR screening for qnr genes. Seven resistant isolates were further analysed for mutations in the quinolone resistance-determining region of gyrA, gyrB, parC and parE. No amino-acid mutations were identified in GyrB and ParE; all isolates showed amino-acid mutations in both GyrA and ParC. We conclude that amino-acid mutations in GyrA and ParC in combination with active efflux of antibiotic out of the bacterial cell are the probable mechanisms conferring quinolone resistance.

The quinolones exert their anti-bacterial activity by binding to DNA gyrase A (GyrA), an essential enzyme in maintenance of DNA topology within bacterial cell. The mutations conferring resistance to quinolones arise within the quinolone-resistance-determining region (QRDR) of GyrA. Therefore, quinolones interaction with wild and mutated GyrA can provide the molecular explanation for resistance. Resistant strains of Salmonella enterica of our hospital have shown mutations in the QRDR of GyrA of serine 83 (to phenylalanine or tyrosine) or aspartic acid 87 (to glycine or tyrosine). In order to understand the association between observed resistance and structural alterations of GyrA with respect to quinolone binding, we have studied the interaction of mutated QRDR of GyrA with nalidixic acid and ciprofloxacin by molecular modeling using GLIDE v4. Analysis of interaction parameters like G-score has revealed reduced interaction between nalidixic acid/ciprofloxacin with QRDR of GyrA in all four mutated cases of resistant strains. The mutation of Ser83 to Phe or Tyr shows least binding for nalidixic acid, while Asp87 to Gly or Tyr exhibits minimal binding for ciprofloxacin. The study also highlights the important role of arginines at 21, 91 and His at 45, which form strong hydrogen bonds (at < 3 A) with quinolones. The hydrophilic OH group of Serine 83, which is in close proximity to the quinolone binding site is replaced by aromatic moieties of Tyr or Phe in mutated GyrA. This replacement leads to steric hindrance for quinolone binding. Therefore, quinolone resistance developed by Salmonella appears to be due to the decreased selectivity and affinity of nalidixic acid/ciprofloxacin to QRDR of GyrA.

Remediation of pharmaceutical wastewater, containing nalidixic acid (NXA; 38 mg/L), a quinolone antibacterial agent commonly used in human and veterinary medicine, and characterized as having mainly 725 mg/L dissolved organic carbon (DOC), 3400 mg/L chemical oxygen demand, and around 4 g/L NaCl, was studied. A prior biodegradability study (Zahn-Wellens test) had demonstrated that the matrix was biodegradable after a rather long biomass adaptation period. After 4 days of treatment in an immobilized biomass reactor (IBR), 96% of the original DOC was removed by the biological treatment however, more than 50% of NXA was adsorbed on the biomass. As development of chronic toxicity in the IBR is possible after long exposure to NXA, adsorption and biomass stability during continuous exposure to NXA were studied in different cycles for one month. Afterthe biotreatment, the effluent was treated by solar photo-Fenton. Total degradation of NXA and reduction in toxicity were observed. The intermediates formed during degradation by biotreatment and subsequent photo-Fenton were studied by liquid chromatography-time-of-flight mass spectrometry.

Serratia marcescens is a nosocomial agent with a natural resistance to a broad spectrum of antibiotics, making the treatment of its infections very challenging. This study examines the influence of salicylate, sucrose, temperature, and pH variability on membrane permeability and susceptibility of S. marcescens to norfloxacin (hydrophilic fluoroquinolone) and nalidixic acid (hydrophobic quinolone). Resistance of wild-type S. marcescens UOC-67 (ATCC 13880) to norfloxacin and nalidixic acid was assessed by minimal inhibitory concentration (MIC) assays after growth in the presence of various concentrations of sucrose and salicylate and different temperatures and pH values. Norfloxacin and nalidixic acid accumulation was determined in the absence and presence of (i) carbonyl cyanide m-chlorophenylhydrazone (CCCP), a proton-motive-force collapser, and (ii) Phe-Arg beta-naphthylamide (PAbetaN), an efflux pump inhibitor. Accumulation of norfloxacin decreased when S. marcescens was grown in high concentrations of salicylate (8 mmol/L) and sucrose (10% m/v), at high temperature (42 degrees C), and at pH 6, and it was restored in the presence of CCCP because of the collapse of proton-gradient-dependent efflux in S. marcescens. Although nalidixic acid accumulation was observed, it was not affected by salicylate, sucrose, pH, or temperature changes. In the absence of PAbetaN, and either in the presence or absence of CCCP, a plateau was reached in the nalidixic acid accumulation for all environmental conditions. With the addition of 20 mg/L PAbetaN nalidixic acid accumulation is restored for all environmental conditions, suggesting that this quinolone is recognized by a yet to be identified S. marcescens pump that does not use proton motive force as its energy source.

A fluoroquinolone prodrug, PA2808, was prepared and shown to convert to the highly active parent drug PA2789. In vitro and in vivo activation of PA2808 by alkaline phosphatase was demonstrated using disk diffusion and rat lung infection models. The water solubility of PA2808 showed a marked increase compared to PA2789 over a pH range suitable for aerosol drug delivery. A total of 48 analogues based on PA2789 were prepared and screened against a panel of Gram-positive and Gram-negative pathogens. Incorporating a cyclopropane-fused pyrrolidine (amine) at C-7 resulted in some of the most active analogues.

Tributyltin (TBT) is a toxic agent used in marine antifouling paints. Among the bacterial flora of a polluted harbor, TBT-resistant strains of Pseudomonas stutzeri have been isolated. In the strain 5MP1 (TBT minimum inhibitory concentration (MIC) > or =1000 mg l(-1)), TBT resistance was found to be associated with the presence of the operon tbtABM, homologous to the resistance-nodulation-cell division (RND) efflux pump family, as demonstrated by cloning in Escherichia coli. TbtABM exhibited the greatest homology (60.9-84.9%) with the TtgDEF and SrpABC systems, both involved in aromatic compound tolerance in P. putida. TbtABM conferred multidrug resistance (MDR) including to n-hexane, nalidixic acid, chloramphenicol, and sulfamethoxazole (antibiotic MICsx4 for the E. coli host strain carrying the operon). By polymerase chain reaction amplification and hybridization experiments, the presence of tbtABM was detected in the TBT-sensitive P. stutzeri 3MP1 (TBT MIC 25 mg l(-1)). However, the latter strain did not seem to express TbtABM. This is the first description of a MDR efflux pump in P. stutzeri, and of a new kind of substrate, TBT, for the RND family of transporters.

Purpose: To investigate the corneal and scleral permeability of nalidixic acid and synthesized fluoroquinolones and their in vivo pharmacokinetics in rabbits., Methods: The corneal and scleral permeability coefficients of ciprofloxacin, norfloxacin, cinoxacin, enoxacin, and ofloxacin were determined in rabbits using high performance liquid chromatography (HPLC). The aqueous humor levels of norfloxacin and ciprofloxacin were measured separately by topical instillation of 0.3% solutions of the two drugs onto rabbit eyes., Results: Nalidixic acid had a higher corneal permeability coefficient (17.3 +/- 3.56 x 10(-6) cm/second) than all other drugs tested (p < 0.01). Corneal permeability coefficients in rabbits among ciprofloxacin, norfloxacin, cinoxacin, enoxacin, and ofloxacin were not significantly different (p > 0.1). Comparing the corneal and scleral permeability coefficients, only values for nalidixic acid were not significantly different (17.35 +/- 3.56 x l0(-6) cm/second versus 22.69 +/- 5.19 x 10(-6) cm/second, p > 0.05), while all other drugs had scleral permeability coefficients 8 to 10 times greater than corneal permeability coefficients. The mean aqueous humor concentration of norfloxacin and ciprofloxacin at 60 minutes to 180 minutes after instillation was around 0.3 microg/mL, a value higher than MIC90 of most bacteria.

Context: Group B streptococcus (GBS) is the most common cause of early-onset neonatal sepsis in developed countries, and determination of the GBS colonization status in pregnant patients near term is essential for the provision of prophylactic measures to prevent early-onset disease., Objectives: To determine if GBS recovery rates and/or result turnaround times for vaginal or combined vaginal/rectal swab specimens from pregnant patients near term are enhanced if swabs are inoculated initially onto selective versus nonselective agar media, in addition to the standard Centers for Disease Control and Prevention method., Design: Prospective laboratory analysis., Setting: Urban health region/centralized diagnostic microbiology laboratory., Patients: Pregnant women presenting for routine obstetrical care and collection of vaginal or combined vaginal/rectal swab specimens for GBS testing at 35 to 37 weeks' gestation., Intervention: Culture of specimens directly onto selective (5% sheep blood with colistin and nalidixic acid) or nonselective (5% sheep blood) agar media, in addition to LIM broth enrichment and terminal subculture., Main Outcome Measures: Group B streptococcus recovery rate and culture result turnaround time., Results: A total of 639 specimens were tested, with 128 (20%) positive for GBS. Sixty-three isolates were recovered on direct agar media at 24 hours, of which 16 (12.5%) were isolated on selective plates only. An additional 38 isolates were recovered at 48 hours from direct plates. Twenty-seven (21.1%) isolates that failed to grow on direct plates were recovered from the LIM broth subculture only. Three (2.3%) isolates not recovered from LIM broths were detected at 48 hours on the direct selective (2 isolates) and nonselective (1 isolate) agar plates. A 24-hour result turnaround time was achieved for 63 (49.2%) and 47 (36.7%) of the 128 culture-positive specimens for direct selective and nonselective plates, respectively (chi2 = 76.63, P <.001)., Conclusions: Use of direct selective agar media, in addition to LIM broth enrichment, for the determination of the GBS colonization status in pregnant patients near term results in decreased turnaround time for reporting positive results.

The binding of quinolones, nalidixic acid (Nal), oxolinic acid (Oxo) with double stranded polynucleotides was undertaken by using UV-melting, UV-Vis absorption, fluorescence and CD spectroscopic techniques. The binding of Nal or Oxo to the polynucleotides under low-salt buffer conditions were determined for poly (dA).(dT), poly [d(A-T)], poly (dG).(dC), poly [d(G-C)] and E. coli DNA. The fluorescence data were analyzed using a previously established two step mechanism with two different DNA-Drug complexes [Rajeswari et al., Biochemistry 26, 6825-31 (1987)]. The first complex [DN](1) with a binding constant K(1), is formed where the interactions are 'nonspecific' and complex [DN](2) with a binding constant K(2), is formed where the interactions are "specific" which involve (additional) hydrophobic type of interactions like 'stacking' of the drug and the overall association constant is represented as K(=K(1)K(2)). The order of binding for Nal and Oxo is: poly [d(G-C)] > poly [d(A- T)] > E. coli > poly (dG).(dC) > poly (dA).(dT). Interaction of quinolones seems to be preferential in the alternating G, C or A, T stretches of DNA than those of non-alternating. Within any alternating or non-alternating in DNA sequences the G, C rich sequences have distinctly greater binding than A, T sequences. The overall association constant data (K) reveal higher binding of Oxo to DNA compared to Nal to any given polynucleotide investigated; which also explains the higher antibacterial potency of Oxo. Changes in the absorption difference spectra and in circular dichroic spectra also manifest these results. As the melting temperatures of the polynucleotides were only marginally raised in presence of the quinolone, we rule out the possibility of 'classical intercalation' of the drug. Amino group of guanine facilitates the binding of quinolones and therefore has the greater binding with the DNA. However, poly (dG).(dC) is known to exist in 'A' conformation which is not adopted by quinolones as in the case of poly (dA).(dT). Present results suggest that Nal or Oxo bind to DNA in a non-classical fashion which is partially stacking in nature.

Information on V. cholerae eltor isolated in the focus of cholera in Kazan in 2001 at different periods of the outbreak is presented. The identity of strains isolated from patients, vibriocarriers and environmental objects, including their antibioticograms (sensitivity to cyprofloxacin and resistance to trimethoprim--sulfamethoxazole, streptomycin, furazolidone and nalidixic acid, which may be regarded as markers), is shown. Variable tandem repetitions in the DNA of 30 isolates strains of different origin have been determined. The results of this determination make it possible to classify all these strains as one genotype, which confirms the suggestion on the circulation of one subclone of the infective agent of cholera in the focus. As revealed in this investigation, the isolated strains are labile with respect to diagnostic phage eltor, while ctx+ strains are resistant to phage eltor ctx+.

Pseudomonas aeruginosa has been implicated as a foodborne and waterborne pathogen and is now considered a primary infectious agent. In the present study, the survival of P. aeruginosa inoculated in mineral water was evaluated by drop counts on Pseudomonas Agar Base (PAB), PAB with CN supplement X107, PAB with cetrimide, PAB with nalidixic acid, and these media with added FeSO(4). Initial counts, before starvation, were the same in all media tested. Following this period, P. aeruginosa became sensitive to PAB with added cetrimide. The addition of FeSO(4) did not improve the recovery of stressed P. aeruginosa but gave colonies a typical dark brown colour being easily differentiated from other species that can grow at 42 degrees C. The modified Pseudomonas agar medium was also tested with several P. aeruginosa strains, other species of Pseudomonas, and other genera. Only P. aeruginosa strains (pyocyanin positive) produced the typical colonies. Our results demonstrate that Pseudomonas agar with ferrous sulphate, used for the differentiation of P. aeruginosa colonies, and nalidixic acid, used as an inhibitor of Gram-positive bacteria, might be a useful medium for the detection of injured P. aeruginosa in mineral water.

As revealed in this study, S. sonnei population is represented by two clusters with respect to the sensitivity to different antibiotics. A higher degree of diversity was observed with respect to the action of streptomycin, kefzol, ampicillin, chloramphenicol and kanamycin in comparison with the action of gentamicin, nevigramon, rafampicin, tetracycline and polymyxin. The level of diversity of S. sonnei with respect to the sensitivity to antibiotics under study underwent essential changes during the calendar year. The distributions obtained study quite closely corresponded to changes in Sonne dysentery morbidity observed within the year period: the first cluster corresponded to the period of morbidity between the seasons and the second one, to the seasonal period of morbidity. The minimal coefficient of diversity fell on May while the maximum--on September. The minimal level of S. sonnei diversity, as a rule, corresponds to the minimum biosystems stability.

The influence of salicylic acid on the permeability and susceptibility of Serratia marcescens to both nalidixic acid and ciprofloxacin was studied, as well as the effect of salicylate on outer membrane proteins and lipopolysaccharide. As salicylic acid concentration increased, ciprofloxacin accumulation decreased with a concomitant, previously observed, reduction in the porin content of the outer membrane. Resistance to ciprofloxacin and nalidixic acid was enhanced when bacteria grew in the presence of salicylic acid.

Studies of complexation equilibria of the antibiotic anions nalidixate and cinoxacinate with [Cu(phen)]2+ and [Cu(bipy)]2+ are reported. These studies indicate that the stability of this type of complex is strongly related to the metal environment. A correlation between the stability constants, determined here, with the sigma donation character of the ligand is proposed. This study shows that the stability constant for the reaction between the quinolones and the moiety [Cu(N-N)]2+ is dependent on the coordinate diamine to the metal ion. This is in agreement with previous studies where other physical properties as their electronic absorption spectra in the visible region, display similar behavior. These results suggest that inside the living cells, a possible interaction with some metal ion will be strongly controlled by the type of ligand bound to the cation.

A case of presumed interaction between warfarin and nalidixic acid is reported in an 84 year-old female in whom INR rose from 1.9 to 9.6 after start of treatment with nalidixic acid. The interaction may be caused by several factors: 1) Nalidixic acid may displace warfarin from plasma proteins and thereby increase the anticoagulant effect. 2) The fluoroquinolone drug enoxacin reduces the hepatic clearance of the R-stereomere of warfarin but without prolongation of the prothrombin time ratio. 3) Fluoroquinolones may affect the vitamin-K producing bacteria in the gut and thereby influence the vitamin-K: warfarin ratio in plasma. Only some patients develop hypoprothrombinaemia during concomitant therapy with warfarin and quinolone antimicrobials. It is hypothesized that the interaction may partly be related to age, sex or concomitant disease. Frequent control of INR in patients treated with both warfarin and quinolone antimicrobials is recommended.

A previously published liquid chromatographic (LC) method for determining residues of flumequine (FLU) and nalidixic (NAL), oxolinic (OXO), and piromidic (PIR) acids in catfish tissue was applied to salmon and shrimp muscle. Identities of all 4 residues in salmon and shrimp were confirmed by gas chromatography/mass spectrometry (GC/MS). The tissue is homogenized with acetone, the acetone extract is defatted with hexane, and the quinolones are extracted into chloroform. The extract is further purified by first partitioning into base and then back-extracting from a solution acidified to pH 6.0. Analytes are determined by LC with simultaneous UV and fluorescence detection. Muscle tissue was fortified with each quinolone at 5, 10, 20, 40, and 80 ng/g. Average recoveries and relative standard deviations (RSDs) for salmon, which represent an average of the 5 levels for each analyte, ranged from 75.9 to 90.8% and from 2.25 to 6.40%, respectively. Average recoveries and RSDs for shrimp ranged from 81.3 to 91.2% and from 7.34 to 10.7%, respectively. Identities of OXO, FLU, NAL, and PIR were confirmed in extracts of salmon and shrimp tissue fortified at 10 ng/g by determination of decarboxylated quinolones by GC/MS. Four diagnostic ions were monitored for OXO, FLU, and PIR, and 5 ions were monitored for NAL. All ion relative abundances were within 10% of those calculated for standard decarboxylated quinolones. Optimum conditions for decarboxylation and GC/MS confirmation are given.

The aim of this pilot study was to demonstrate the possible inhibitory effect of probenecid on the renal glucuronidation and on the renal clearance of nalidixic acid in a human volunteer. Under acidic urine conditions, hardly any nalidixic acid is excreted unchanged (0.2%). It is excreted as acyl glucuronide (53.4%), 7-hydroxymethylnalidixic acid (10.0%), the latter's acyl glucuronide 30.9%, and 7-carboxynalidixic acid (4.2%). Under probenecid co-medication the renal glucuronidation of nalidixic acid is reduced from 53% to 16%; the renal clearance of both nalidixic acid and 7-hydroxymethylnalidixic acid are reduced (p < 0.001); the intrinsic t1/2 of the metabolite 7-hydroxymethylnalidixic acid increased from 0.48 h to 4.24 h. The amount of acyl glucuronidation of 7-hydroxymethylnalidixic acid was not altered. The in vitro protein binding of both acyl glucuronides was increased, while no effect on the unconjugated compounds was seen. Nalidixic acid had no effect on the maximal renal excretion rate of probenecid acyl glucuronide.

Objective: To demonstrate that the human kidney is capable not only of filtering and secreting drugs and their metabolites, but also of carrying out conjugation reactions such as acyl glucuronidation, N-glucuronidation, and glycination., Data Sources: Plasma concentrations and renal excretion rates of drugs are measured and renal clearance is calculated in a series of selected pharmacokinetic studies in healthy human volunteers (some studies were conducted in the authors' laboratory and others were reported in the literature). BACKGROUND THEORY: It is generally agreed that the liver plays the dominant role in drug metabolism, and that the function of the kidneys is limited to excretion of parent drug and metabolites. This can be easily understood when a metabolite is present in both plasma and urine. When the metabolite is present in urine but is not measurable in plasma, then the possibility exists that the metabolite is formed by the kidneys., Results: "Simple" excretion by the kidneys is demonstrated for sulfatroxazole/sulfamethoxazole. Ether glucuronides of codeine are formed in the liver, and the resulting glucuronide is excreted by the kidneys. Possible formation of N1- and N2-glucuronides by the kidneys is demonstrated for sulfadimethoxine, sulfametomidine, and sulfaphenazole. Acyl glucuronidation of probenecid and nalidixic acid is carried out by the kidneys. The acyl glucuronidation of probenecid shows a capacity-limited formation/excretion rate of 46 mg/h, which is subject dependent. During this process, the acyl glucuronidation of co-administered nalidixic acid is reduced from 53 to 16 percent compared with that of nalidixic acid alone. Probenecid and its acyl glucuronidation do not inhibit the ether glucuronidation of codeine in the liver, but only interfere with the active tubular secretion process. The acyl glucuronidation of the nonsteroidal antiinflammatory drug naproxen and its metabolite, O-desmethylnaproxen, may be carried out by the liver and kidneys. Glycination of benzoic acid and salicylic acid is carried out in both the liver and kidneys., Conclusions: It is difficult to recognize renal drug metabolism in the intact human body (in vivo); the glucuronides or conjugates must be measured via direct HPLC analysis. In cases where the metabolite is present in high concentrations in urine but not in blood, there may be an indication that the kidneys are responsible for the formation of the metabolite. Impaired kidney function not only affects renal excretion but may also affect renal metabolism.

The diffusion rates of nalidixic acid, ofloxacin and ofloxacin's two optically active isomers through OmpF channels were measured in proteoliposomes and compared with the rates of beta-lactams. The four quinolones showed high diffusion rates, exceeding that of cephaloridine and being comparable to imipenem. There was no significant difference in diffusion rate between nalidixic acid and ofloxacin, or between the two optically active isomers. The diffusion rates of enoxacin and norfloxacin were also estimated to be higher than many beta-lactams.

PD 117596 is a novel quinolone compound that is being investigated for use as an antibacterial agent. Early investigations demonstrated a significant phototoxic liability associated with this compound. These studies were undertaken to investigate the mechanism of phototoxicity using an in vitro model. In the UVA region, PD 117596 was found to be a more efficient producer of singlet oxygen than rose bengal, ciprofloxacin, nalidixic acid, or PD 118879, another quinolone under investigation. The quantum yield of photoreaction for PD 117596 was relatively low (phi = 0.021); however, it was approximately 10-fold higher than other tested quinolones. In vitro studies using a mouse erythrocyte model were used to further investigate the mechanism of phototoxicity. PD 117596-induced photohemolysis was found to be oxygen dependent with a relatively rapid onset that progressed even after removal of light. Preirradiation of the compound prevented subsequent hemolytic or photohemolytic action. BHA, BHT, alpha-tocopherol, and the iron chelator DTPA were all found to be effective at ameliorating the photohemolytic response. The photohemolytic response was markedly enhanced when D2O was substituted for H2O in the incubation medium, indicating a singlet oxygen-mediated mechanism of action. A rise in thiobarbituric acid products was noted within 1 hr of irradiation and was maximal at the time of onset of overt photohemolysis. These data suggest that singlet oxygen production by irradiated PD 117596 is responsible for secondary changes in mouse red blood cells including lipid peroxidation and ultimately results in cellular lysis.

DNA breakdown occurred in Escherichia coli KL16 exposed to nalidixic acid, ciprofloxacin or norfloxacin. However DNA breakdown does not seem to be the cause of the lethality of the 4-quinolones because it still occurred under conditions which abolished the lethality of nalidixic acid. Furthermore, no correlation was found between the amount of DNA breakdown and the rate of death of bacteria caused by the three 4-quinolones. Similarly, DNA breakdown did not occur when recB or recC mutants were treated with nalidixic acid despite both mutants being killed by the drug, again suggesting that DNA breakdown is not the cause of bacterial death. Since recB and recC mutants lack exonuclease V, this enzyme may be responsible for the DNA breakdown observed in bacteria treated with 4-quinolones.

Plasma levels of active naphthyridine were measured in healthy old (mean age 77.3 years) and young (mean age 25.4 years) subjects following oral administration of 1 Gm nalidixic acid. The plasma levels of active naphthyridine, i.e., nalidixic acid and its metabolite 7-hydroxynalidixic acid, were generally higher in the old group, particularly in the elimination phase. Significant variations in the pharmacokinetic parameters were obtained between the two groups of volunteers. The plasma half-life of active naphthyridine averaged 11.5 hours in old subjects and 2.7 hours in the younger group. Diminished renal function in the geriatric group may explain the slower elimination of the drug in the old subjects. The mean values of the other parameters calculated were: apparent volume of distribution, 0.55 (old) and 0.47 (young) liter/kg body weight; area under the curve, 327.7 (old) and 156.3 (young) micrograms/ml x hr; total body clearance 2.9 (old) and 8.3 (young) liters/hr; absorption rate constant, 0.29 (old) and 0.52 (young) hr. -1

A sensitive and highly selective thin-layer chromatographic method for determining plasma levels of nalidixic acid is presented. Plasma (50 microliter) was acidified with 50 microliter M orthophosphoric acid and extracted with 100 microliter toluene. A 40-microliter aliquot of the extract was spotted onto the thin-layer plate with the aid of a Desaga Autospotter and, after irrigation, the nalidixic acid on the plate was converted into a fluorescent compound by exposing the plates to hydrogen chloride gas for 10 min and then to strong ultraviolet radiation from a mercury lamp for 10 min. The fluorescence was measured quantitatively using a spectrofluorimeter equipped with a thin-layer chromatogram scanning attachment.

The kinetics of the conversion of nalidixic acid to the 7-hydroxymethyl derivative (M-HNA) by isolated liver microsomes of several common laboratory animal species was studied under optimal conditions. The order of activity was (from greatest activity to least): monkey greater than rabbit greater than mouse greater than rat greater than dog greater than cat. The formation of 7-HNA followed apparent Michaelis-Menton kinetics in all species except the cat; the substrate concentration at half-maximal velocity was highest with mouse microsomes, while the maximum velocity was greatest with monkey microsomes. Cat, dog, mouse and rabbit microsomes formed an additional metabolite, which was identified as 6-hydroxynalidixic acid, 1-ethyl-1,4-dihydro-6-hydroxy-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid (6-HNA); in the cat, this was the major microsomal metabolite.

The effect of food on the bioavailability of two single lots of commercial tablets and one trial tablet of nalidixic acid, varying widely in drug dissolution characteristics, was determined in healthy male subjects after oral administration. Four subjects received, in a crossover fashion, a single 250 mg dose in an uncoated tablet during periods of fasting and non-fasting. Significant differences in Cmax, Tmax and AUC0-8 were observed between the tablet having the fastest dissolution rate and the other tablets tested, when administered postprandially. Both Cmax and AUC0-8 were significantly increased after administration of the two tablets exhibiting the poorer dissolution characteristics to the non-fasting subjects. However, food was not observed to affect any of the bioavailability parameters after postprandial administration of the tablet exhibiting the fastest dissolution rate. The improvement of bioavailability of the two tablets exhibiting the poorer dissolution by food intake was ascribable to enhanced dissolution of nalidixic acid resulting from vigorous mixing and agitation in the digestive tract. It was concluded that the effect of food on the bioavailability of nalidixic acid from uncoated tablets varies with formulation factors, especially with dissolution characteristics.

The pharmacokinetics and cantharides-induced blister fluid levels of norfloxacin were studied after a single 400 mg oral dose. The mean maximum serum level was 1.45 mg/l and occurred 1.5 h after administration. The serum half-life of norfloxacin was found to be 3.5 h. After 24 h 27% of the administered dose was recovered in the urine as microbiologically active compound. High urine levels were found. Rapid blister fluid penetration occurred, the maximum level (occurring between 2-3 h) was about 1 mg/l. Thereafter the blister fluid level exceeded the serum level, both declining in parallel.

The distribution in the dog prostate and other tissues of ciprofloxacin, a quinoline carboxylic acid derivative, was investigated in an experimental model. The concentrations in prostatic tissue, prostatic interstitial fluid (PIF), and prostatic secretion (PS) were lower than the corresponding plasma (P) concentrations, as would be expected for an acidic compound. The experiments were carried out under steady state conditions during intravenous infusion in one group of dogs and following gastric administration in another group. During steady state the ciprofloxacin concentrations were significantly higher in PS than in PIF, and the median PS/P ratios were significantly higher than the PIF/P ratios. These concentrations and ratios were compared with those of two other quinoline carboxylic acid derivatives, rosoxacin and norfloxacin. The concentrations of ciprofloxacin in prostatic tissue, PIF, PS, and urine were several times higher than the minimum inhibitory concentrations for most gram-negative pathogens that cause bacterial prostatitis and urinary tract infections. Clinical trials of ciprofloxacin in these diseases are therefore indicated.

Nalidixic acid is metabolized by hydroxylation to 7-hydroxymethylnalidixic acid[[ and then by oxidation to 7-carboxynalidixic acid.[[ The half-lives of the two elimination phases of nalidixic acid are 0.75 and 2.5 h. The apparent half-lives of the metabolite 7-hydroxymethylnalidixic acid are 2.5 and 5.5 h. Plasma protein binding of nalidixic acid is 95% and that of 7-hydroxymethylnalidixic acid 65%. The renal clearance of nalidixic acid varies between 2 and 25 ml/min and that of 7-hydroxymethylnalidixic acid between 37 and 162 ml/min. Of nalidixic acid 42% is glucuronidated and 40% hydroxylated. Of the hydroxy metabolite 57% is glucuronidated and 32% excreted unchanged. 7-Carboxynalidixic acid is excreted in the urine and is not glucuronidated. The variations in the glucuronidation/hydroxylation ratio of nalidixic acid and the glucuronidation/renal excretion ratio of the 7-hydroxymethyl metabolite belong to a normal distribution.

A technique is described to obtain renal interstitial fluid (RIF) from rabbits after implantation of diffusion chambers with permeable membranes of 0.45 mu porosity in both kidneys. Pharmacokinetic studies were conducted two to three weeks after implantation. No difference in gentamicin concentrations, as measured microbiologically, was seen between RIF withdrawn from the left and right kidney chambers at the same points in time. Simultaneous drug concentrations were determined in RIF and serum of rabbits after oral administration of ampicillin or nalidixic acid and after intramuscular injection of gentamicin. Ampicillin concentrations in RIF peaked at two hours with about one fourth of the peak concentration measured in serum at one hour. These curves crossed at 3.45 hours. In RIF, the maximum concentration of gentamicin found at two hours was again approximately one fourth of the serum peak level determined at half an hour. The gentamicin curves crossed at 3.15 hours. No levels of nalidixic acid could be detected microbiologically in serum and RIF. In collected urine, however, concentrations of this drug could be measured for several sampling periods. Our results show that this diffusion chamber technique can be useful in the pharmacokinetic examination of drugs, also with respect to their distribution in the kidneys.

Nalidixic acid and hydroxynalidixic acid penetrate the placenta during labour. During the first 24 h of life the serum concentrations of nalidixic acid and nalidixic acid plus hydroxynalidixic acid decline slowly and show individual differences. The changed kinetic parameter in the newborn, especially the delayed elimination of nalidixic acid as well as nalidixic acid plus hydroxynalidixic acid lead to the consequence of recommendation of a very strong therapeutic indication in the peripartal period.