Quinolones: a new class of antimicrobial agents with wide potential uses

Engineering Whole-Cell Biosensors for Enhanced Detection of Environmental Antibiotics Using a Synthetic Biology Approach

Bacterial Two component systems have evolved with many intricate sensory apparatuses for external stimuli like light, temperature, oxygen, pH and chemical compounds. Recent studies have shown the potential of two-component regulatory systems (TCSs) of bacteria in creating synthetic regulatory circuits for several applications. Antimicrobial resistance is increasing globally in both developing and developed countries and it is one of the foremost global threats to public health. The resistance level to a broad spectrum of antibiotics is rising every year by 5-10%. In this context, TCSs controlling microbial physiology at the transcriptional level could be an appropriate candidate for monitoring the antibiotics present in the environment. This review provided a wide opportunity to gain knowledge about the TCSs available in diverse species to sense the antibiotics. Further, this review explored the EMeRALD (Engineered Modularized Receptors Activated via Ligand-induced Dimerization) based biosensors to repurpose the sensing modules from the microbial TCSs using the synthetic biology approach.

Co-delivery of norfloxacin and tenoxicam in Ag-TiO2/poly(lactic acid) nanohybrid

A nanohybrid formulation of silver‑titanium dioxide nanoparticles/poly(lactic acid) (Ag-TiO₂/PLA) was designed for Norfloxacin/Tenoxicam (NOR/TENO) targeted delivery to maximize the bioavailability and minimize the side effects of the drugs. Ag-TiO₂ nanoparticles were prepared via Stober method. NOR, TENO and a mixture of NOR/TENO (NT) were loaded onto Ag-TiO₂ nanoparticles and coated by PLA via solution casting. The physical interaction between the drugs and carrier was confirmed by Fourier-transform infrared (FTIR) analysis. X-ray diffraction (XRD) demonstrated that Ag-TiO₂ consists of a cubic phase of Ag with two phases of TiO₂ (anatase and brookite). Ag nanoparticle fine spots coated with TiO₂ were collected to form spheres averaging at 100 nm in size. In-vitro release behavior of drugs was studied at different pH (5.4, 7.4) and the release of drug from NT/Ag-TiO₂/PLA was faster at pH 7.4. Gram-positive and Gram-negative bacteria were used to investigate antibacterial properties of the nanohybrid. Cytotoxicity of the nanohybrid using an MTT assay was studied against different tumor and normal cell lines. It was found that NT/Ag-TiO₂/PLA has an excellent cytotoxic effect against various bacterial cells and tumor cell lines. In addition, antioxidant properties of the nanohybrids were tested using ABTS method and the nanohybrid showed moderate antioxidant activity.

Stability of three commonly compounded extemporaneous enrofloxacin suspensions for oral administration to exotic animals

OBJECTIVE

To evaluate the stability of 3 extemporaneous oral suspensions of enrofloxacin mixed with readily available flavoring vehicles when stored at room temperature (approx 22°C).

DESIGN

Evaluation study.

SAMPLES

3 commonly compounded oral suspensions of enrofloxacin.

PROCEDURES

On day 0, commercially available enrofloxacin tablets were compounded with a mixture of distilled water and corn syrup (formulation A) or cherry syrup (formulation B) flavoring vehicles to create suspensions with a nominal enrofloxacin concentration of 22.95 mg/mL, and 2.27% enrofloxacin injectable solution was compounded with a liquid sweetener (formulation C) to create a suspension with a nominal enrofloxacin concentration of 11.35 mg/mL. Preparations were stored in amber-colored vials at room temperature for 56 days. For each preparation, the enrofloxacin concentration was evaluated with high-performance liquid chromatography at prespecified intervals during the study. The pH, odor, and consistency for all suspensions were recorded at the start and completion of the study.

RESULTS

Relative to the nominal enrofloxacin concentration, the enrofloxacin concentration strength ranged from 95.80% to 100.69% for formulation A, 108.44% to 111.06% for formulation B, and 100.99% to 103.28% for formulation C. A mild pH increase was detected in all 3 suspensions during the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that, when stored in amber-colored vials at room temperature for 56 days, the enrofloxacin concentration strength in all 3 formulations was retained within acceptance criteria of 90% to 110%. Subjectively, cherry syrup flavoring was better at masking the smell and taste of enrofloxacin than were the other mixing vehicles.

The management of infection and colonization due to methicillin-resistant Staphylococcus aureus: A CIDS/CAMM position paper

Methicillin-resistant Staphylococcus aureus (MRSA) is being seen with greater frequency in most hospitals and other health care facilities across Canada. The organism may cause life-threatening infections and has been associated with institutional outbreaks. Several studies have confirmed that MRSA infection is associated with increased morbidity and mortality compared with infections caused by susceptible strains, even when the presence of comorbidities is accounted for. Treatment of MRSA infection is complicated by the fact that these organisms are resistant to multiple antimicrobial agents, so treatment options are limited. The effectiveness of decolonization therapy (attempting to eradicate MRSA carriage) is also uncertain. This paper reviews the medical management of MRSA infections, discusses the potential role of decolonization and provides an overview of evidence to support recommended infection control practices.

Ocular toxicity of fluoroquinolones

The ocular toxicity of fluoroquinolones and the risks of their use in the treatment of ocular infection were reviewed. Systematic identification, selection, review and synthesis of published English-language studies relating to fluoroquinolone use and safety in animals and humans was conducted. Although not free of complications, fluoroquinolones are generally safe when used to treat ocular infection. Ocular toxicity appears to be dose-dependent and results from class-effects and specific fluoroquinolone structures. Phototoxicity and neurotoxicity have been reported, and toxic effects on ocular collagen may be associated with Achilles tendinopathy. Corneal precipitation may provide an advantageous drug depot but delay healing and result in corneal perforation in approximately 10% of cases. Although human toxicity studies are limited, the current recommended dose for intracameral injection of ciprofloxacin is less than 25 microg. Intravitreal injections of ciprofloxacin 100 microg, ofloxacin 50 microg/mL, trovafloxacin 25 microg or less, moxifloxacin 160 microg/0.1 mL or less and pefloxacin 200 microg/0.1 mL are considered safe.

Simple, rapid determination of enrofloxacin and ciprofloxacin in bovine milk and plasma by high-performance liquid chromatography with fluorescence detection

A rapid and simple procedure for determination of enrofloxacin and ciprofloxacin in bovine milk and plasma is described. Protein precipitation from both milk and plasma samples was achieved by addition of acetonitrile and phosphoric acid. Acetonitrile was removed with methylene chloride, leaving enrofloxacin and ciprofloxacin in the acidic aqueous extract. The aqueous extract was analyzed by high-performance liquid chromatography (HPLC) with fluorescence detection. The limit of quantitation (LOQ) for enrofloxacin and ciprofloxacin in milk was found to be 2ng/ml. LOQ for enrofloxacin and ciprofloxacin in plasma was found to be 1ng/ml. Linear calibration curves were obtained with correlation coefficient (r(2)) >/=0.99. Analysis of quality control (QC) samples gave results within +/-10% of the nominal values. Inter-assay precision for the analysis of milk QC samples were in the ranges: 4.63-12.49% (for enrofloxacin) and 4.67-9.86% (for ciprofloxacin). Inter-assay precision for the analysis of plasma QC samples were in the ranges: 6.60-17.31% (for enrofloxacin) and 6.14-13.87% (for ciprofloxacin). Intra-assay precision for the analysis of milk QC samples were in the following ranges: 3.65-7.21% (for enrofloxacin) and 1.58-14.28% (for ciprofloxacin). Intra-assay precision for the analysis of plasma QC samples were in the following ranges: 2.17-16.95% (for enrofloxacin) and 3.31-16.31% (for ciprofloxacin). The effectiveness of protein precipitants other than phosphoric acid was investigated. The method described has been applied to a study of the pharmacokinetics of enrofloxacin and ciprofloxacin in lactating dairy cows and beef steers.

Determination of marbofloxacin in plasma samples by high-performance liquid chromatography using fluorescence detection

A simple and sensitive HPLC method has been developed for the determination of marbofloxacin (MAR) in plasma. Sample preparations were carried out by adding phosphate buffer (pH 7.4, 0.1 M), followed by extraction with trichloromethane. MAR and the internal standard, enrofloxacin (ENR), were separated on a reversed-phase column and eluted with aqueous solution-acetonitrile (80:20). The fluorescence of the column effluent was monitored at lambda(ex) = 338 and lambda(em) = 425 nm. The retention times were 2.20 and 3.30 min for MAR and ENR, respectively. The method was shown to be linear from 15 to 1500 ng/ml (r2 = 0.999). The detection limit was 15 ng/ml. Mean recovery was determined as 90% by the analysis of plasma standards containing 150, 750, and 1500 ng/ml. Inter- and intra-assay precisions were 3.3% and 2.7%, respectively.

Fluoroquinolones in animal health

The fluoroquinolones are a series of synthetic antibacterial agents that are undergoing extensive investigation for both human and veterinary use in the treatment of a variety of bacterial infections. These agents work through the inhibition of DNA gyrase, interfering with the supercoiling of bacterial chromosomal material. As a result, these agents are rapidly bactericidal primarily against gram-negative bacteria, mycoplasma, and some gram-positive bacteria, with most having little to no activity against group D streptococci and obligate anaerobic bacteria. Resistance develops slowly and is almost always chromosomal and not plasmid-mediated. However, development of resistance to the fluoroquinolones and transfer of that resistance among animal and human pathogens have become a hotly debated issue among microbiologists. The fluoroquinolones are a current antimicrobial class whose use in veterinary medicine is being scrutinized. From a pharmacokinetic perspective, these agents are variably but well absorbed from the gastrointestinal tract and almost completely absorbed from parenteral injection sites, and they are well distributed to various tissues in the body. The fluoroquinolones are metabolized and renally excreted, with many of them having approximately equal excretion by the hepatic and the renal excretory systems. The primary toxicity observed at therapeutic doses involves the gastrointestinal system and phototoxicity, although at higher doses central nervous system toxicity and ocular cataracts are observed. Administration to immature animals may result in erosive arthropathies at weight-bearing joints, and administration of high doses to pregnant animals results in maternotoxicity and occasionally embryonic death. The fluoroquinolones are approved for indications such as urinary tract infections and soft tissue infections in dogs and cats and colibacillosis in poultry. Approval for bovine respiratory disease in the United States is being sought. Other indications for which the fluoroquinolones have been used in animal health include deep-seated infections, prostatitis, and other bacterial infections resistant to standard antimicrobial therapy.

The role of new antibiotics for the treatment of infections in the emergency department

Treatment of infectious diseases comprises a large part of emergency medicine practice. The management of infectious diseases in the emergency department is often different than in other settings because of the types of infectious presentations and the frequent necessity of empiric treatment decisions. This paper examines the new antimicrobials and their role for the treatment of infections in the ED.

Acute renal failure secondary to ciprofloxacin use

We report on a 22-year-old woman with a continent urinary diversion in whom acute renal failure developed on ciprofloxacin therapy for pelvic osteomyelitis. Renal failure resolved rapidly once the drug was withheld. Because ciprofloxacin is used extensively by the urological community, we believe that it is important to be aware of this potential complication of therapy. We review the literature on the association of ciprofloxacin and renal failure.

Controlled trial of ciprofloxacin in short-term chemotherapy for pulmonary tuberculosis

The study was undertaken in patients with newly diagnosed bacteriologically positive pulmonary tuberculosis. The patients were randomly allocated to receive one of two regimens. In one of the regimens, patients received 2 months of daily treatment with streptomycin, isoniazid, rifampin, and pyrazinamide (SHRZ) followed by isoniazid plus rifampin for 4 months (4 HR). In the other regimen, patients received 2 months of daily streptomycin, isoniazid, pyrazinamide, and ciprofloxacin (SHZ Cipro) followed by isoniazid plus ciprofloxacin for 4 months. All patients in the SHRZ/HR regimens and all but one in the SHZ Cipro/H Cipro regimens had a favorable bacteriologic response during chemotherapy. In the patients in the SHZ Cipro/H Cipro regimen, ciprofloxacin was well tolerated during the period of treatment. After chemotherapy, one (5.9 percent) of 17 patients in the SHRZ/HR group and three (16.6 percent) of 18 patients in the SHZ Cipro/H Cipro group relapsed bacteriologically.

Safety and efficacy of lomefloxacin versus cefaclor in the treatment of acute exacerbations of chronic bronchitis

In two multicenter trials, lomefloxacin and cefaclor were compared as treatments for acute bacterial exacerbations of chronic bronchitis. In total, 522 adult outpatients were enrolled at 50 centers in the United States. Patients were randomized to treatment groups receiving either 400 mg lomefloxacin orally once daily (n = 259) or 250 mg cefaclor every 8 hours (n = 263) for 7-10 days. Both groups were comparable in terms of age, severity of exacerbation, smoking history, theophylline use, and baseline pathogens. The most common baseline pathogens were Haemophilus influenzae, found in 32% of patients in the lomefloxacin group and in 29% in the cefaclor group, Pseudomonas aeruginosa (13% and 16%, respectively), Moraxella (Branhamella) catarrhalis (12% and 13%), and Streptococcus pneumoniae (10% in both groups). Bacterial eradication rates 1-4 days after the completion of treatment for all patients with baseline pathogens were 81.8% in the lomefloxacin group and 62.7% in the cefaclor group (p less than 0.001). Clinical success (disappearance or improvement of presenting signs and symptoms) was noted in 80.0% of patients in the lomefloxacin group and 64.7% in the cefaclor group (p = 0.002). Eradication rates for the subgroup of patients who had pathogens susceptible in vitro to both study drugs and who completed treatment were 97.1% for lomefloxacin and 84.6% for cefaclor (p = 0.002). Clinical success rates in this subgroup were 92.4% for lomefloxacin and 90.1 for cefaclor (p = 0.585). Treatment-related adverse events were reported for 7% of patients in the lomefloxacin group and 5% in the cefaclor group. The most common adverse events in both groups were nausea and diarrhea. Six patients were withdrawn from treatment with lomefloxacin and four from the cefaclor group because of adverse events. There was no clinical or laboratory evidence of theophylline interaction with either treatment. Once-daily oral administration of 400 mg lomefloxacin was an effective, well-tolerated alternative to 250 mg of cefaclor three times daily in the treatment of acute exacerbations of chronic bronchitis.

Ciprofloxacin in typhoid fever

The study covers 78 children with typhoid fever who were hospitalized in April & May 1990. Serious complications were present in 32% (toxemia 22%, ileus 25% and myocarditis 8%). Blood cultures were positive in 30 of 49 tested. Others were diagnosed by positive Widal test. In vitro cultures of S. typhi were resistant to chloramphenicol (90%), ampicillin (93%) and co-trimoxazole (97%). However all were highly sensitive to ciprofloxacin and moderately sensitive to cephalexin and gentamycin. Ciprofloxacin alone or in combination was given in 73 of the 78 children and found to be remarkably effective in controlling the disease and preventing relapse. No serious side effects were noted. The cohort is being followed up for possible long term adverse effects.

Relevance of ionic effects on norfloxacin uptake by Escherichia coli

The uptake of the quinolone drug norfloxacin by Escherichia coli was investigated at initial rate kinetics at different pH and monovalent/divalent metal ion concentration. The results support a simple diffusion mechanism for quinolone incorporation into cells. The uptake process decreases under acidic conditions. The presence of Na+ or K+ ions does not affect the results to an appreciable extent, whereas divalent ions cause a dramatic decrease in drug incorporation. The antibacterial activity, evaluated under identical experimental conditions, shows a direct relationship with the uptake data. As a general explanation for the above results it is suggested that the ability of the drug to penetrate into cells is a function of its net charge. The molecule in the zwitterionic form exhibits maximum permeation properties, whereas the uptake is remarkably reduced when the drug bears a net charge as a result of ionization or complex formation with bivalent ions. These results allow further insight into the mechanism of quinolone access to the intracellular compartment.