Pipemidic acid, a new antibacterial agent active against Pseudomonas aeruginosa: in vitro properties

Recent Development of Fluoroquinolone Derivatives as Anticancer Agents

Cancer is the second leading cause of death in the world following cardiovascular disease. Its treatment, including radiation therapy and surgical removal of the tumour, is based on pharmacotherapy, which prompts a constant search for new and more effective drugs. There are high costs associated with designing, synthesising, and marketing new substances. Drug repositioning is an attractive solution. Fluoroquinolones make up a group of synthetic antibiotics with a broad spectrum of activity in bacterial diseases. Moreover, those compounds are of particular interest to researchers as a result of reports of their antiproliferative effects on the cells of the most lethal cancers. This article presents the current progress in the development of new fluoroquinolone derivatives with potential anticancer and cytotoxic activity, as well as structure-activity relationships, along with possible directions for further development.

Augmentation of photophysical features and Judd-Ofelt analysis of extensively green glowing terbium (III) complexes with nitrogen donor ancillary ligands

Six green glowing terbium (III) complexes were fabricated via grinding method utilizing a prime organic ligand (L) and nitrogen donor ancillary ligands. Characterization of synthesized complexes was accomplished through various spectroscopic techniques. The significant thermal stability was determined by thermogravimetric analysis while the energy bandgap and Urbach energy were investigated through diffused reflectance spectra of these complexes. The peak observed at 548 nm in emission spectra is responsible for the virescent color of these complexes. Color purity, decay time, quantum yield, and emission intensities of ternary complexes were significantly improved as compared to binary ones due to the synergistic effect of ancillary ligands. Judd-Ofelt parameters were determined by the NIR absorption spectrum, which claims the asymmetric environment around the terbium (III) ion. CCT values advocate the applicability of these complexes in green light-emitting materials as a cool light source. The biological assignments reveal the significance of these complexes as potent antioxidants and antimicrobial agents. The energy transfer process highlights the enhancement of luminescence in these complexes via the synergic effect of ligands. Our investigation portrays that these complexes can be employed in laser technology, display devices, semiconductors, biological fields, and optoelectronic devices.

Development of fluorinated nicotinonitriles and fused candidates as antimicrobial, antibiofilm, and enzyme inhibitors

The antimicrobial assessments of two new series of nicotinonitriles and pyrido[2,3-d]pyrimidines were performed using amoxicillin and nystatin as reference standards. Outstanding antifungal activities were achieved by some target compounds; for instance, compounds 7 and 9 displayed a minimal inhibitory concentration (MIC) value of 1.95 µg/ml toward Candida albicans, compound 11 showed a potent anti-Rhizopus effect (MIC 1.95 µg/ml) and compound 14 elicited remarkable antifungal effects against both Aspergillis niger and C. albicans (MIC 1.95 µg/ml). However, pyrido[2,3-d]pyrimidines 12, 14, and 16 showed moderate antibacterial activities against some gram-negative bacteria. The antibiofilm results of these compounds against resistant strains of Proteus mirabilis were better than those of Pseudomonas aeruginosa. Docking studies of these hits at the DNA gyrase active site revealed affinity and docking scores comparable to that of the reference standards. Gyrase-inhibitory activities revealed that 14 (IC₅₀  = 0.31 µM) is the most potent hit as DNA gyrase A inhibitor; it exhibited 1.66-fold the activity of ciprofloxacin (IC₅₀  = 0.50 µM) and it was a 44.3 times more potent gyrase B inhibitor (IC₅₀  = 0.04 µM) than novobiocin (IC₅₀  = 1.77 µM). Regarding its antifungal activity, it displayed 0.78% of the fluconazole activity as a 14α-demethylase inhibitor. The cytotoxicity of 12, 14, and 16 on human diploid lung fibroblasts (WI38 cells) ensured their safety. Moreover, they are orally bioavailable with no permeation of the blood-brain barrier.

Evaluation of Pipemidic Acid Derivatives for Potential Antimicrobial Activity Application: In silico Studies on Bioactivity

Background:

Pipemidic acid is a broad-spectrum quinolone antibacterial agent for the treatment of chronic urinary tract infections against both gram-positive and gram-negative bacteria. Both quinolone and fluoroquinolone antibiotics have been useful in combating bacterial infections. However, patients suffer severe side effects when they stop taking the medication. The piperazinyl region of pipemidic acid is highly responsible for the side effects.

Objective:

The objective of this study is to design new compounds in which the piperazinyl region is masked by way of conjugation to benzoic acid derivatives.

Methods:

In silico studies were conducted using AutoDockTools software for ligand-protein docking. The docking scores were compared to the parent pipemidic acid docked to Bacterial DNA (deoxyribonucleic acid) gyrase and GABA (gamma-Aminobutyric acid) receptor from the PDB (Protein Data Bank) database. Sites of metabolism, biological activity, quantum chemical descriptors, and ADME (absorption, distribution, metabolism, and excretion) property predictions for each designed ligand were also evaluated.

Results:

The docking studies and biological activity predictions showed good anti-infective properties (ligand PAR03) whilst also suggesting a reduction in GABA receptor agonist activity. The performance of PAR03 correlates with its electronic properties showing electrophilic character (can generate Reactive Electrophilic Species (RES)).

Conclusion:

The results from this study indicate that modification of the piperazinyl region of pipemidic acid can be an effective way to improve the drug potency whilst also ensuring reduction of the associated side effects.

Naturally Inspired Pyrimidines Analogues for Alzheimer's Disease

Alzheimer's disease (AD) is a multifarious and developing neurodegenerative disorder. The treatment of AD is still a challenge and availability of drug therapy on the basis of symptoms is not up to the mark. In the context of existence, which is getting worse for the human brain, it is necessary to take care of all critical measures. The disease is caused due to multidirectional pathology of the body, which demands the multi-target-directed ligand (MTDL) approach. This gives hope for new drugs for AD, summarized here in with the pyrimidine based natural product inspired molecule as a lead. The review is sufficient in providing a list of chemical ingredients of the plant to cure AD and screen them against various potential targets of AD. The synthesis of a highly functionalized scaffold in one step in a single pot without isolating the intermediate is a challenging task. In few examples, we have highlighted the importance of this kind of reaction, generally known as multi-component reaction. Multi-component is a widely accepted technique by the drug discovery people due to its high atom economy. It reduces multi-step process to a one-step process, therefore the compounds library can be made in minimum time and cost. This review has highlighted the importance of multicomponent reactions by giving the example of active scaffolds of pyrimidine/fused pyrimidines. This would bring importance to the fast as well as smart synthesis of bio-relevant molecules.

Inspiration for revival of old drugs: improving solubility and avoiding hygroscopicity of pipemidic acid by forming two pharmaceutical salts based on charge-assisted hydrogen bond recognitions

Improving solubility and avoiding hygroscopicity of pipemidic acid by forming pharmaceutical salts based on CAHBs.

A New Approach for Improving the Antibacterial and Tumor Cytotoxic Activities of Pipemidic Acid by Including It in Trimethyl-β-cyclodextrin

Pipemidic acid (HPPA) is a quinolone antibacterial agent used mostly to treat gram-negative infections of the urinary tract, but its therapeutic use is limited because of its low solubility. Thus, to improve drug solubility, natural cyclodextrins (CDs) are used for their ability of including guest molecules within their cavities. The aim of this work was to evaluate the antibacterial activity and the preliminary anticancer activity of HPPA included into Heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) as a possible approach for a new innovative formulation. The inclusion complex of HPPA with TRIMEB was prepared in solid state by the kneading method and confirmed by FT-IR and powered X-ray diffraction. The association in aqueous solutions of pipemidic acid with TRIMEB was investigated by UV-Vis spectroscopy. Job's plots have been drawn by UV-visible spectroscopy to confirm the 1:1 stoichiometry of the host⁻guest assembly. The antibacterial activity of HPPA, TRIMEB and of their complex was tested on Escherichia coli, Pseudomonas aeruginosa, and Staphilococcus aureus. The complex was able to increase 47.36% of the median antibacterial activity of the free HPPA against E. coli (IC50 = 249 µM vs. 473 µM). Furthermore, these samples were tested on HepG-2 and MCF-7. After 72 h, the median tumoral cytotoxicity exerted by the complex was increased by 78.08% and 94.27% for HepG-2 and MCF-7 respectively, showing a stronger bioactivity of the complex than the single HAPPA.

Isocratic Resolution of Fluoroquinolone-Based Antibiotics on the Phenylethyl-Bonded Phase under Nonaqueous Elution: A Consideration of the Separation Mechanism

This paper reports the isocratic resolution of 10 fluoroquinolone-based antibiotics and their precursors on the phenylethyl-bonded phase under the elution of the nonaqueous mobile phase composed of acetonitrile, methanol, acetic acid, and triethylamine. Most of the analytes were baseline resolved within 10 minutes. The interaction simulation and Fourier-transform infrared spectroscopy (FTIR) data indicated that the carbonyl-containing group, a secondary or tertiary amine of an analyte, was heavily involved in the retention, resulting in retention with residual silanol groups on the stationary phase. In some cases, the elution reversal or resolution enhancement of analytes was observed when the volume of acidic or basic additive in the mobile phase was dominant. However, the π-π complexation interaction between the fluorine-attached phenyl group of the analyte and the phenylethyl moiety on the stationary phase was not observed. Consequently, the resolution could not be reproduced either on the other stationary phase modified with C₁₈, phenyl, or phenylhexyl moiety under the same chromatographic conditions or under the aqueous elution.

Synthesis and in vitro antimicrobial activity screening of new pipemidic acid derivatives

This article describes the synthesis and antimicrobial activity evaluation of new pipemidic acid derivatives. New compounds were obtained on the basis of Mannich reaction of 4,5-disubstituted 1,2,4-triazole-3-thiones with pipemidic acid. Antimicrobial tests revealed high antibacterial activity of obtained derivatives. Gram-negative rods belonging to Enterobacteriaceae family were particularly most sensitive to new pipemidic acid derivatives. Synthesized compounds exhibited very strong activity towards Proteus mirabilis ATCC 12453, Salmonella typhimurium ATCC 14028 and Escherichia coli ATCC 25922. The minimum inhibitory concentrations of new pipemidic acid derivatives which inhibited the growth of these bacteria were 0.98-7.81 µg/ml, 0.98-7.81 µg/ml and 0.98-3.91 µg/ml, respectively. The antibacterial activity of newly synthesized pipemidic acid derivatives in many cases was far better than the activity of substances used as positive controls (nitrofurantoin, cefuroxime, ampicillin and pipemidic acid).

Nanoparticles with high payloads of pipemidic acid, a poorly soluble crystalline drug: drug-initiated polymerization and self-assembly approach

Nowadays, biodegradable polymers such as poly(lactic acid) (PLA), poly(D,L-lactic-co-glycolic acid) (PLGA) and poly(ε-caprolactone) (PCL) remain the most common biomaterials to produce drug-loaded nanoparticles (NPs). Pipemidic acid (PIP) is a poorly soluble antibiotic with a strong tendency to crystallize. PIP incorporation in PLA/PLGA NPs was challenging because of PIP crystals formation and burst release. As PIP had a poor affinity for the NPs, an alternative approach to encapsulation was used, consisting in coupling PIP to PCL. Thus, a PCL-PIP conjugate was successfully synthesized by an original drug-initiated polymerization in a single step without the need of catalyst. PCL-PIP was characterized by NMR, IR, SEC and mass spectrometry. PCL-PIP was used to prepare self-assembled NPs with PIP contents as high as 27% (w/w). The NPs were characterized by microscopy, DLS, NTA and TRPS. This study paves the way towards the production of NPs with high antibiotic payloads by drug-initiated polymerization. Further studies will deal with the synthesis of novel polymer-PIP conjugates with ester bonds between the drug and PCL. PIP can be considered as a model drug and the strategy developed here could be extended to other challenging antibiotics or anticancer drugs and employed to efficiently incorporate them in NPs.

Removal of antibiotics in wastewater by enzymatic treatment with fungal laccase - Degradation of compounds does not always eliminate toxicity

In this study, the performance of immobilised laccase (Trametes versicolor) was investigated in combination with the mediator syringaldehyde (SYR) in removing a mixture of 38 antibiotics in an enzymatic membrane reactor (EMR). Antibiotics were spiked in osmosed water at concentrations of 10μg·L(-1) each. Laccase without mediator did not reduce the load of antibiotics significantly. The addition of SYR enhanced the removal: out of the 38 antibiotics, 32 were degraded by >50% after 24h. In addition to chemical analysis, the samples' toxicity was evaluated in two bioassays (a growth inhibition assay and the Microtox assay). Here, the addition of SYR resulted in a time-dependent increase of toxicity in both bioassays. In cooperation with SYR, laccase effectively removes a broad range of antibiotics. However, this enhanced degradation induces unspecific toxicity. If this issue is resolved, enzymatic treatment may be a valuable addition to existing water treatment technologies.

Synthesis and antibacterial evaluation of amino acid-antibiotic conjugates

Amino acid conjugates of quinolone, metronidazole and sulfadiazine antibiotics were synthesized in good yields using benzotriazole methodology. All the conjugates were screened for their antibacterial activity using methods adapted from the Clinical and Laboratory Standards Institute. Antibiotic conjugates were tested for activity in four medically relevant organisms; Staphylococcus aureus (RN4220), Escherichia coli (DH5α), Pseudomonas aeruginosa (PAO1), and Bacillus subtilis (168). Several antibiotic conjugates show promising results against several of the strains screened.

β-Cyclodextrin inclusion complex to improve physicochemical properties of pipemidic acid: characterization and bioactivity evaluation

The aptitude of cyclodextrins (CDs) to form host-guest complexes has prompted an increase in the development of new drug formulations. In this study, the inclusion complexes of pipemidic acid (HPPA), a therapeutic agent for urinary tract infections, with native β-CD were prepared in solid state by kneading method and confirmed by FT-IR and ¹H NMR. The inclusion complex formation was also characterized in aqueous solution at different pH via UV-Vis titration and phase solubility studies obtaining the stability constant. The 1:1 stoichiometry was established by a Job plot and the inclusion mechanism was clarified using docking experiments. Finally, the antibacterial activity of HPPA and its inclusion complex was tested on P. aeruginosa, E. coli and S. aureus to determine the respective EC_50s and EC_90s. The results showed that the antibacterial activity of HPPA:β-CD against E. coli and S. aureus is higher than that of HPPA. Furthermore, HPPA and HPPA:β-CD, tested on human hepatoblastoma HepG2 and MCF-7 cell lines by MTT assay, exhibited, for the first time, antitumor activities, and the complex revealed a higher activity than that of HPPA. The use of β-CD allows an increase in the aqueous solubility of the drug, its bioavailability and then its bioactivity.

Inhaled antibiotics for Gram-negative respiratory infections

Several disease states create conditions that lead to opportunistic Gram-negative respiratory infections. Inhalation is the most direct and, until recently, underutilized means of antimicrobial drug targeting for respiratory tract infections. All approved antimicrobial agents for administration by inhalation are indicated for Pseudomonas aeruginosa infections in patients with cystic fibrosis. These inhaled therapies have directly contributed to a significant reduction in exacerbations and hospitalizations in this patient population over the last few decades. The relentless adaptation of pathogenic organisms to current treatment options demands that the pharmaceutical industry continue designing next-generation antimicrobial agents over 70 years after they were first introduced. Recent technological advances in inhalation devices and drug formulation techniques have broadened the scope of antimicrobial structural classes that can be investigated by inhalation; however, there is an urgent need to discover novel compounds with improved resistance profiles relative to those drugs that are already marketed.

High-throughput screens for small-molecule inhibitors of Pseudomonas aeruginosa biofilm development

Pseudomonas aeruginosa is both a model biofilm-forming organism and an opportunistic pathogen responsible for chronic lung infections in cystic fibrosis (CF) patients and infections in burn patients, among other maladies. Here we describe the development of an efficient high-throughput screen to identify small-molecule modulators of biofilm formation. This screen has been run with 66,095 compounds to identify those that prevent biofilm formation without affecting planktonic bacterial growth. The screen is a luminescence-based attachment assay that has been validated with several strains of P. aeruginosa and compared to a well-established but low-throughput crystal violet staining biofilm assay. P. aeruginosa strain PAO1 was selected for use in the screen both because it forms robust biofilms and because genetic information and tools are available for the organism. The attachment-inhibited mutant, strain PAO1 DeltafliC, was used as a screening-positive control. We have also developed and validated a complementary biofilm detachment assay that can be used as an alternative primary screen or secondary screen for the attachment screening-positive compounds. We have determined the potencies of 61 compounds against biofilm attachment and have identified 30 compounds that fall into different structural classes as biofilm attachment inhibitors with 50% effective concentrations of less than 20 microM. These small-molecule inhibitors could lead to the identification of their relevant biofilm targets or potential therapeutics for P. aeruginosa infections.

The influence of magnesium stearate on the characteristics of mucoadhesive microspheres

Microspheres containing the mucoadhesive polymer chitosan hydrochloride, with matrix polymer Eudragit RS, pipemidic acid as a model drug and agglomeration preventing agent magnesium stearate were prepared by the solvent evaporation method. The amount of magnesium stearate was varied and the following methods were used for microsphere evaluation: sieve analysis, drug content and dissolution determination, scanning electron microscopy, x-ray diffractometry, DSC and FTIR spectroscopy. The results showed that average particle size decreased with increasing amount of magnesium stearate used for microsphere preparation. This is probably a consequence of stabilization of the emulsion droplets with magnesium stearate. Higher pipemidic acid content in the microspheres was observed in larger particle size fractions and when higher amounts of magnesium stearate were used. It was also found that these two parameters significantly influenced the dissolution rate. The important reason for the differences in drug content in microspheres of different particle sizes is the diffusion of pipemidic acid from the acetone droplets in liquid paraffin during the preparation procedure. The physical state of pipemidic acid changed from crystalline to mostly amorphous with its incorporation in microspheres, as shown by x-ray diffractometry and differential scanning calorimetry. No differences were observed in the physical state of pipemidic acid and in microsphere shape and surface between different size fractions of microspheres, prepared with different amounts of magnesium stearate. Additionally, no correlation between the physical state of the drug in different microspheres and their biopharmaceutical properties was found.

Drug resistance in bacteria: history, genetics and biochemistry

The significance of the discovery of prontosil in 1932 as the initiating step in the development of the modern era of antimicrobial chemotherapy is reviewed. The history of the discovery and the development of chemotherapeutic agents, from penicillin in 1929 to present-day antibiotics, are summarized. The various mechanisms by which bacteria are able to overcome the protective effects of these therapeutic agents (from the sulphonamides to the new fluoroquinolones) and develop resistance to them are discussed in detail. Attempts to elucidate the mechanisms by which resistance to chemotherapeutic agents develops are vital to the future of antimicrobial chemotherapy.

A review of the antimicrobial activity of the fluoroquinolones

The evolution of the fluoroquinolones is described, and structure-activity relationships outlined. The in-vitro antimicrobial activities of ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin against a wide range of organisms are critically reviewed. In-vitro factors influencing fluoroquinolone activity are discussed. Reports of the acquisition of resistance to the fluoroquinolones are evaluated. Finally, possible future directions for this group of antibiotics are discussed.

In vitro and in vivo antibacterial activities of KB-5246, a new tetracyclic quinolone

The in vitro and in vivo antibacterial activities of KB-5246, a tetracyclic quinolone, were compared with those of ciprofloxacin, ofloxacin, and norfloxacin. KB-5246 demonstrated a broad antibacterial spectrum. The in vitro activity of KB-5246 against gram-negative bacteria was higher than that of ofloxacin or norfloxacin and was comparable to that of ciprofloxacin. KB-5246 demonstrated the greatest activity against gram-positive bacteria of the four agents tested. Among Streptococcus pyogenes strains resistant to 1.56 micrograms of norfloxacin per ml, there were 26 strains susceptible to 0.2 micrograms of KB-5246 per ml. Similarly, among the Staphylococcus aureus and Staphylococcus epidermidis strains resistant to 3.13 micrograms of norfloxacin per ml, there were 23 S. aureus and 11 S. epidermidis strains susceptible to 0.39 micrograms of KB-5246 per ml. Among the Streptococcus pneumoniae and Enterococcus faecalis strains resistant to 12.5 micrograms of norfloxacin per ml, there were 5 S. pneumoniae and 10 E. faecalis strains susceptible to 0.39 micrograms of KB-5246 per ml. KB-5246 had bactericidal activity at the MIC. KB-5246 demonstrated excellent antibacterial activity against various systemic infections in mice. After oral administration, KB-5246 was as active as ofloxacin and about two times more active than norfloxacin.

In vitro and in vivo antibacterial activities of AT-4140, a new broad-spectrum quinolone

AT-4140, 5-amino-1-cyclopropyl-6,8-difluoro-1,4-dihydro-7-(cis-3,5- dimethyl-1-piperazinyl)-4-oxoquinoline-3-carboxylic acid, showed broad and potent antibacterial activity. Its MICs for 90% of the strains tested were 0.1 to 0.78 micrograms/ml against gram-positive organisms, such as members of the genera Staphylococcus, Streptococcus, and Enterococcus, and 0.0125 to 1.56 micrograms/ml against gram-negative organisms, such as members of the family Enterobacteriaceae and the genera Pseudomonas, Branhamella, Campylobacter, Haemophilus, and Neisseria. Its MICs were 0.025 to 0.78 micrograms/ml against glucose nonfermenters, such as members of the genera Xanthomonas, Acinetobacter, Alcaligenes, Moraxella, Flavobacterium, and Brucella; 0.2 to 0.78 micrograms/ml against anaerobes, such as Clostridium perfringens and Bacteroides fragilis; 0.0125 to 0.05 micrograms/ml against Legionella spp.; 0.0125 to 0.2 micrograms/ml against Mycoplasma spp.; 0.031 to 0.063 micrograms/ml against Chlamydia spp.; and 0.1 to 0.3 micrograms/ml against Mycobacterium spp. The potencies of AT-4140 against gram-negative organisms were comparable to those of ciprofloxacin and higher than those of ofloxacin, enoxacin, and norfloxacin. The potencies of AT-4140 against gram-positive organisms, glucose nonfermenters, anaerobes, Mycoplasma spp., Chlamydia spp., and Mycobacterium spp. were generally higher than those of the quinolones with which AT-4140 was compared. AT-4140 showed good oral efficacy against systemic infections with Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Escherichia coli, and Pseudomonas aeruginosa in mice. Its efficacy was better when a daily dose was given once than when it was given in two doses. Good efficacies of the orally administered drug were also observed in pulmonary, dermal, and urinary tract infection models in mice. The in vivo efficacies of AT-4140 were equal to or better than those of ciprofloxacin, ofloxacin, enoxacin, and norfloxacin.

In vitro and in vivo antibacterial activities of T-3262, a new fluoroquinolone

T-3262, a new fluoroquinolone, showed a broad spectrum of activity against gram-positive and gram-negative bacteria. T-3262 had most potent activity against gram-positive cocci, such as Staphylococcus, Streptococcus, and Enterococcus spp. The MICs of T-3262 for 90% of strains tested were between 0.05 and 1.56 micrograms/ml. Against members of the family Enterobacteriaceae and Pseudomonas aeruginosa, the activities of T-3262 were almost equal to those of ciprofloxacin. Obligate anaerobes were also susceptible to T-3262. T-3262 was bactericidal for one strain each of Staphylococcus aureus, Escherichia coli, and P. aeruginosa at concentrations near its MIC; and fluoroquinolones, including T-3262, inhibited DNA gyrase activity at low concentrations. The 50% effective dose of T-3262 after oral administration against systemic infections with S. aureus in mice was about 6 times lower than that of ofloxacin and about 20 times lower than that of norfloxacin.

In vitro and in vivo activity of NY-198, a new difluorinated quinolone

NY-198 [1-ethyl-6,8-difluoro-1,4-dihydro-7-(3-methyl-1-piperazinyl)-4-oxo-3- quinolinecarboxylic acid hydrochloride] is a new difluorinated quinolone characterized by the presence of a C-methyl group at the 3 position of the piperazine moiety. It has a broad antibacterial spectrum. The in vitro antibacterial activity of NY-198 was almost the same as those of ofloxacin and norfloxacin, but far exceeded that of pipemidic acid. NY-198 was more active than norfloxacin against Pseudomonas maltophilia, Acinetobacter calcoaceticus, and anaerobic microorganisms. Cross resistance was not observed between NY-198 and various antibiotics including methicillin, gentamicin, and ampicillin. NY-198 had bactericidal activity at the MIC or slightly higher than the MIC. It showed excellent antibacterial activity against various systemic infections in mice. After oral administration, NY-198 was two times more active than or as active as ofloxacin and two to four times more active than norfloxacin.

Nalidixic acid-resistant mutations of the gyrB gene of Escherichia coli

DNA fragments of 3.4 kb containing the gyrB gene were cloned from Escherichia coli KL-16 and from spontaneous nalidixic acid-resistant mutants. The mutations (nal-24 and nal-31) had been determined to be in the gyrB gene by transduction analysis. Nucleotide sequence analysis of the cloned DNA fragments revealed that nal-24 was a G to A transition at the first base of the 426th codon of the gyrB gene, resulting in an amino acid change from aspartic acid to asparagine, and nal-31 was an A to G transition at the first base of the 447th codon, resulting in an amino acid change from lysine to glutamic acid. This indicates tha mutations in the gyrB gene are responsible for nalidixic acid resistance.

The in vitro and in vivo activity of ciprofloxacin

The antibacterial activity of ciprofloxacin (Bay o 9867) was compared with those of norfloxacin, nalidixic acid, trimethoprim-sulfamethoxazole, cefaclor, sisomicin and cefotaxime in in vitro and mouse protection studies. Approximately 300 clinical isolates of clinically important gram-positive and gram-negative species were used. The median MICs of ciprofloxacin against gram-positive and gram-negative bacteria ranged from less than or equal to 0.015-1 mg/l. Ciprofloxacin was 2-8 fold more active than norfloxacin and 100-fold more active than nalidixic acid. It also had a wider spectrum of activity against gram-positive organisms including even enterococci. No cross-resistance was observed between ciprofloxacin and beta-lactam antibiotics or aminoglycosides. Only acidic pH conditions decreased its activity. Ciprofloxacin showed rapid bactericidal action against organisms in both the logarithmic and stationary growth phases. In mouse protection studies (intraperitoneal infection) ciprofloxacin was significantly more effective than norfloxacin, ampicillin, trimethoprim-sulfamethoxazole, and also showed excellent activity against Pseudomonas infections.

Single- and multiple-dose pharmacokinetics of pipemidic acid in normal human volunteers

The pharmacokinetic profile of pipemidic acid was studied in two groups of young healthy volunteers by using a new, sensitive, high-pressure liquid chromatography procedure for quantitation of pipemidic acid in biological fluids. After oral or intravenous administration, the disposition of pipemidic acid may be described as a one- or a two-compartment open model, respectively. Oral bioavailability was 93.1 +/- 11% (mean +/- standard error). After administration of a 100-mg tablet, 13.4 +/- 2.7% was bound to serum proteins at the time of peak drug concentration in serum. Excretion of pipemidic acid in saliva was negligible, the saliva/serum ratio being about 0.32. At steady state after the twice-daily administration of a 500-mg tablet, which is a recommended dosage regimen, a peak drug concentration in serum of 4.3 +/- 0.5 micrograms/ml was attained in 1.2 +/- 0.1 h. The apparent volume of distribution was 1.9 +/- 0.2 liters/kg, and the elimination half-life was 3.4 +/- 0.2 h. The renal clearance was 4.3 +/- 0.7 ml/min per kg, and the total clearance was 6.3 +/- 0.5 ml/min per kg. Despite a considerable water load, the minimum concentration in urine at the end of a dosing interval averaged 100 micrograms/ml, which widely exceeds the known MIC of pipemidic acid against bacteria commonly causing urinary tract infections.

In vitro and in vivo antibacterial activity of AT-2266

AT-2266 [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3-carbo xylic acid] showed a broad spectrum of antibacterial activity against gram-positive and gram-negative microorganisms, including Pseudomonas aeruginosa. The in vitro antibacterial activity of AT-2266 was in general comparable to that of norfloxacin, but much higher than that of pipemidic or nalidixic acid. The 90% minimal inhibitory concentrations (MIC90s) of AT-2266 for P. aeruginosa resistant to gentamicin (MIC range, 25 to greater than 200 microgram/ml) and Enterobacteriaceae resistant to nalidixic acid (25 to greater than 1,600 micrograms/ml) were 3.13 and 12.5 micrograms/ml, respectively. The to nalidixic acid (25 to 1,600 micrograms/ml) were 3.13 and 12.5 micrograms/ml, respectively. The MICs of AT-2266 were only slightly affected by the addition of horse serum or sodium cholate, by the pH of the medium, and by inoculum size. AT-2266 was sodium cholate, by the pH of the medium, and by inoculum size. AT-2266 was bactericidal at concentrations near its MIC value. The 50% effective doses of AT-2266 after oral administration against systemic infections in mice were about 1/2 those of norfloxacin, about 1/10 those of pipemidic acid, and between 1/20 and 1/40 those of nalidixic acid.

Activity of AT-2266 compared with those of norfloxacin, pipemidic acid, nalidixic acid, and gentamicin against various experimental infections in mice

AT-2266 (1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1, 8-naphthyridine-3-carboxylic acid) showed marked activity in vivo when administered orally to mice bearing systemic, pulmonary, dermal, or urinary tract infections due to variety of organisms. The activity of AT-2266 was uniformly higher than those of norfloxacin, pipemidic acid, and nalidixic acid against all of the infections. The activity of AT-2266 administered orally was almost comparable to that of gentamicin administered subcutaneously against urinary tract infections due to gram-negative organisms but was generally lower against other infections. AT-2266 exhibited significant activity against infections due to gentamicin-resistant and nalidixic acid-resistant organisms.

In vitro antibacterial properties of AT-2266, a new pyridonecarboxylic acid

AT-2266, 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridine-3 -carboxylic acid, is a new pyridonecarboxylic acid derivative with broad and potent antibacterial activity. It inhibited some gram-positive bacteria, such as staphylococci and Bacillus subtilis, and most gram-negative bacteria, including Serratia marcescens, Pseudomonas aeruginosa, Haemophilus influenzae, and Campylobacter jejuni, at concentrations of 0.1 to 0.78 microgram/ml, and most gram-positive bacteria, glucose-nonfermenters, and Mycoplasma pneumoniae at concentrations of 1.56 to 12.5 micrograms/ml. Most of the clinical isolates tested were as susceptible to AT-2266 as were laboratory strains. The antibacterial potency of AT-2266 was higher than those of pipemidic acid and nalidixic acid and similar to that of norfloxacin. AT-2266 was not cross-resistant with antibiotics and inhibited most highly nalidixic acid-resistant bacteria at concentrations of 1.56 to 3.13 micrograms/ml. Its activity was barely affected by the addition of horse serum or sodium cholate but weakened by lowering the medium pH or increasing the inoculum size. AT-2266 was bactericidal at concentrations near its minimal inhibitory concentrations. Frequencies of mutants resistant to 10 micrograms of AT-2266 per ml were lower than 4.0 x 10(-9).

In vitro and in vivo activity of DL-8280, a new oxazine derivative

DL-8280, 9-fluoro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-2,3-dihydro-7H- pyrido-(1,2,3-de)1,4-benzoxazine-6-carboxylic acid, is a new nalidixic acid analog with a broad spectrum of antibacterial activity against gram-negative and gram-positive bacteria, including obligate anaerobes. The activity of DL-8280 against Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, Neisseria gonorrhoeae, and Clostridium perfringens was roughly comparable to that of norfloxacin and far exceeded that of pipemidic acid and nalidixic acid. DL-8280 had greater activity against Staphylococcus spp., Streptococcus spp., Pseudomonas maltophilia, Acinetobacter spp., and Bacteroides fragilis than did norfloxacin, pipemidic acid, and nalidixic acid. Nalidixic acid-resistant Enterobacteriaceae, ampicillin-resistant gonococci, and clindamycin-resistant obligate anaerobes were also susceptible to DL-8280. The activity of DL-8280 was affected very little by inoculum size, and its action was bactericidal at two times the minimal inhibitory concentrations at most. Administered orally to mice experimentally infected with Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Proteus mirabilis, Serratia marcescens, or P. aeruginosa, DL-8280 was 2 to 7 times more effective than norfloxacin and 7 to more than 50 times more active than pipemidic acid.

Resistance of Pseudomonas aeruginosa PAO to nalidixic acid and low levels of beta-lactam antibiotics: mapping of chromosomal genes

Resistance to high concentrations of nalidixic acid in Pseudomonas aeruginosa PAO was due to mutations in one locus designated nalA, which was mapped by transduction between hex-9001 and leu-10. The nalA mutants were cross-resistant to pipemidic acid, a nalidixic acid analog, at relatively low concentrations. Replicative DNA synthesis was resistant to both drugs in permeabilized cells of nalA mutants. A locus coding for low-level resistance to nalidixic acid, nalB, was cotransducible with pyrB, proC, and met-28. The nalB mutants were also resistant to low levels of pipemidic acid, novobiocin, and beta-lactam antibiotics (e.g., carbenicillin, azlocillin, and cefsulodin), but not to other drugs, such as gentamicin, rifampin, kanamycin, or tetracycline. In nalB mutants, DNA replication showed wild-type sensitivity to nalidixic acid, whereas carbenicillin-induced filamentation required higher drug levels than in the wild-type strain. Thus, nalB mutations appear to decrease cell permeability to some antibiotics. The sensitivity of replicative DNA synthesis to nalidixic acid and novobiocin was very similar in P. aeruginosa and Escherichia coli; by contrast, the concentrations of these drugs needed to inhibit growth of P. aeruginosa were higher than those reported for E. coli by one or two orders of magnitude.

New nalidixic acid resistance mutations related to deoxyribonucleic acid gyrase activity

In Escherichia coli K-12 mutants which had a new nalidixic acid resistance mutation at about 82 min on the chromosome map, cell growth was resistant to or hypersusceptible to nalidixic acid, oxolinic acid, piromidic acid, pipemidic acid, and novobiocin. Deoxyribonucleic acid gyrase activity as tested by supercoiling of lambda phage deoxyribonucleic acid inside the mutants was similarly resistant or hypersusceptible to the compounds. The drug concentrations required for gyrase inhibition were much higher than those for cell growth inhibition but similar to those for inhibition of lambda phage multiplication. Transduction analysis with lambda phages carrying the chromosomal fragment of the tnaA-gyrB region suggested that one of the mutations, nal-31, was located on the gyrB gene.

Comparative activities of AM-715 and pipemidic and nalidixic acids against experimentally induced systemic and urinary tract infections

Dose for dose, AM-715 was at least five times as active as pipemidic acid and nalidixic acid against systemic and urinary bladder-kidney infections in mice.