Quinolones in 2005: an update

Responding to the challenge of untreatable gonorrhea: ETX0914, a first-in-class agent with a distinct mechanism-of-action against bacterial Type II topoisomerases

With the diminishing effectiveness of current antibacterial therapies, it is critically important to discover agents that operate by a mechanism that circumvents existing resistance. ETX0914, the first of a new class of antibacterial agent targeted for the treatment of gonorrhea, operates by a novel mode-of-inhibition against bacterial type II topoisomerases. Incorporating an oxazolidinone on the scaffold mitigated toxicological issues often seen with topoisomerase inhibitors. Organisms resistant to other topoisomerase inhibitors were not cross-resistant with ETX0914 nor were spontaneous resistant mutants to ETX0914 cross-resistant with other topoisomerase inhibitor classes, including the widely used fluoroquinolone class. Preclinical evaluation of ETX0914 pharmacokinetics and pharmacodynamics showed distribution into vascular tissues and efficacy in a murine Staphylococcus aureus infection model that served as a surrogate for predicting efficacious exposures for the treatment of Neisseria gonorrhoeae infections. A wide safety margin to the efficacious exposure in toxicological evaluations supported progression to Phase 1. Dosing ETX0914 in human volunteers showed sufficient exposure and minimal adverse effects to expect a highly efficacious anti-gonorrhea therapy.

Quinolone resistance and ornithine decarboxylation activity in lactose-negative Escherichia coli

Quinolones and fluoroquinolones are widely used to treat uropathogenic Escherichia coli infections. Bacterial resistance to these antimicrobials primarily involves mutations in gyrA and parC genes. To date, no studies have examined the potential relationship between biochemical characteristics and quinolone resistance in uropathogenic E. coli strains. The present work analyzed the quinolone sensitivity and biochemical activities of fifty-eight lactose-negative uropathogenic E. coli strains. A high percentage of the isolates (48.3%) was found to be resistant to at least one of the tested quinolones, and DNA sequencing revealed quinolone resistant determining region gyrA and parC mutations in the multi-resistant isolates. Statistical analyses suggested that the lack of ornithine decarboxylase (ODC) activity is correlated with quinolone resistance. Despite the low number of isolates examined, this is the first study correlating these characteristics in lactose-negative E. coli isolates.

Delafloxacin, a non-zwitterionic fluoroquinolone in Phase III of clinical development: evaluation of its pharmacology, pharmacokinetics, pharmacodynamics and clinical efficacy

Delafloxacin is a fluoroquinolone lacking a basic substituent in position 7. It shows MICs remarkably low against Gram-positive organisms and anaerobes and similar to those of ciprofloxacin against Gram-negative bacteria. It remains active against most fluoroquinolone-resistant strains, except enterococci. Its potency is further increased in acidic environments (found in many infection sites). Delafloxacin is active on staphylococci growing intracellularly or in biofilms. It is currently evaluated as an intravenous and intravenous/oral stepdown therapy in Phase III trials for the treatment of complicated skin/skin structure infections. It was also granted as Qualified Infectious Disease Product for the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia, due to its high activity on pneumococci and atypical pathogens.

Mechanisms involved in quinolone resistance in Mycoplasma mycoides subsp. capri

Mycoplasma mycoides subsp. capri is a causative agent of contagious agalactia in goats. In this study, M. mycoides subsp. capri mutants were selected for resistance to fluoroquinolones (norfloxacin, enrofloxacin and ciprofloxacin) by serial passes in broth with increasing concentrations of antibiotic. Mutations conferring cross-resistance to the three fluoroquinolones were found in the quinolone resistance determining regions of the four genes encoding DNA gyrase and topoisomerase IV. Different mutations in the DNA gyrase GyrA subunit suggest a different mechanism of inhibition between norfloxacin and the other tested fluoroquinolones. The presence of an adenosine triphosphate-dependent efflux system was suggested through the use of the inhibitor orthovanadate.

Rh(III) and Ru(II)-catalyzed site-selective C-H alkynylation of quinolones

C2- and C5-alkynylated quinolone scaffolds are core structures of numerous biologically active molecules. Utilizing TIPS-EBX as an alkynylating agent, we have developed an efficient and site-selective C5 alkynylation of 4-quinolones that is directed by the weakly coordinating carbonyl group. In addition, Ru(II) catalyzed C2-selective alkynylation was successfully realized via N-pyrimidyl group-directed cross-couplings to access valuable C2-alkynylated 4-quinolones. This strategy provides direct access to the C2 or C5 alkynylated 4-quinolones. Furthermore, the reaction was applied to isoquinolones for C3-selective alkynylation.

Origins of the Quinolone Class of Antibacterials: An Expanded "Discovery Story"

Published descriptions of the specific lines of research leading to the discovery of therapeutically important medicines, especially major new class medicines, have long provided value to the biopharmaceutical community as models of success, often influencing the strategies and methods of subsequent drug research. Quinolone antibacterials represent one of medicine's most important classes of anti-infective agents; yet in contrast to many other classes of anti-infectives, astonishingly few details concerning the origin of the class or the rationale leading to the selection of the first clinical agent, nalidixic acid, were ever published by the discoverers. Moreover, earlier disclosures of an independent discovery of the quinolone class of antibacterials have been almost entirely overlooked by the scientific literature. This review brings together all the available information from primary literature sources relating to both discoveries and provides for the first time a much fuller, if still partially speculative, story of the earliest years of this important class of drugs.

DNA Topoisomerases

DNA topoisomerases are enzymes that control the topology of DNA in all cells. There are two types, I and II, classified according to whether they make transient single- or double-stranded breaks in DNA. Their reactions generally involve the passage of a single- or double-strand segment of DNA through this transient break, stabilized by DNA-protein covalent bonds. All topoisomerases can relax DNA, but DNA gyrase, present in all bacteria, can also introduce supercoils into DNA. Because of their essentiality in all cells and the fact that their reactions proceed via DNA breaks, topoisomerases have become important drug targets; the bacterial enzymes are key targets for antibacterial agents. This article discusses the structure and mechanism of topoisomerases and their roles in the bacterial cell. Targeting of the bacterial topoisomerases by inhibitors, including antibiotics in clinical use, is also discussed.

Toxicity of ciprofloxacin and sulfamethoxazole to marine periphytic algae and bacteria

Ciprofloxacin and sulfamethoxazole are two antibiotics commonly detected in the aquatic environment, but information on their toxicity towards natural microbial communities is largely absent. In particular no data are available for marine microorganisms. The aim of the current study was therefore to evaluate the chronic toxicity of ciprofloxacin and sulfamethoxazole to natural marine biofilms (periphyton), a complex ecological community comprising a variety of bacterial and algal species. The biofilms were sampled along the Swedish west coast and subsequently exposed over 4 days in a semi-static system to a concentration series of each antibiotic. Effects on the bacterial part of the periphyton community were assessed using Biolog Ecoplates, reflecting total respiration and functional diversity of the bacterial community. Exposure to either antibiotic resulted in a clear concentration-response relationship with EC10 and EC50 values for the inhibition of total carbon source utilization of 46.1nmol/L and 490.7nmol/L for ciprofloxacin, and 56nmol/L and 1073nmol/L for sulfamethoxazole. The NOEC for ciprofloxacin was 26nmol/L, with a minimum significant difference of 19.24%, for sulfamethoxazole it was 140nmol/L with a minimum significant difference of 14%. Multivariate data exploration of the whole carbon source utilization pattern confirmed these results. The data indicate that sulfamethoxazole leads to a general decrease in carbon source utilization, while ciprofloxacin exposure leads to a re-arrangement of the carbon-utilization pattern in the region of 20- 50% effect. This corresponds with the higher specificity of ciprofloxacin for certain bacterial species. Effects on the algal part of the communities were evaluated by analyzing the amount and composition of photosynthetic pigments, and neither ciprofloxacin nor sulfamethoxazole caused any inhibitory effects up to the maximum tested concentration of 9000nmol/L. However, sulfamethoxazole exposure did lead to a significant stimulation (75% above control level) of the total pigment content of the biofilm already at the lowest tested concentration of 5nmol/L. The stimulation then decreased with increasing concentrations to finally return to control level at 3000nmol/L. No shifts in the relative pigment composition were observed, indicating a generally increased algal biomass without major shifts in community composition.

Renaissance of antibiotics against difficult infections: Focus on oritavancin and new ketolides and quinolones

Lipoglycopeptide, ketolide, and quinolone antibiotics are currently in clinical development, with specific advantages over available molecules within their respective classes. The lipoglycopeptide oritavancin is bactericidal against MRSA, vancomycin-resistant enterococci, and multiresistant Streptococcus pneumoniae, and proved effective and safe for the treatment of acute bacterial skin and skin structure infection (ABSSSI) upon administration of a single 1200 mg dose (two completed phase III trials). The ketolide solithromycin (two phase III studies recruiting for community-acquired pneumonia) shows a profile of activity similar to that of telithromycin, but in vitro data suggest a lower risk of hepatotoxicity, visual disturbance, and aggravation of myasthenia gravis due to reduced affinity for nicotinic receptors. Among quinolones, finafloxacin and delafloxacin share the unique property of an improved activity in acidic environments (found in many infection sites). Finafloxacin (phase II completed; activity profile similar to that of ciprofloxacin) is evaluated for complicated urinary tract and Helicobacter pylori infections. The other quinolones (directed towards Gram-positive pathogens) show improved activity on MRSA and multiresistant S. pneumoniae compared to current molecules. They are in clinical evaluation for ABSSSI (avarofloxacin (phase II completed), nemonoxacin and delafloxacin (ongoing phase III)), respiratory tract infections (zabofloxacin and nemonoxacin (ongoing phase III)), or gonorrhea (delafloxacin).

Molecular Investigation of Quinolone Resistance of Quinolone Resistance-Determining Region in Streptococcus pneumoniae Strains Isolated from Iran Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Method

Objectives

The resistance of Streptococcus pneumoniae to the recently available antibiotic treatment has been a growing problem. The aim of the study was to determine the quinolone-resistant strains and detect the presence of mutations in the quinolone resistance-determining regions of the gyrA, parE, and parC genes.

Methods

In this study, for the first time in Iran, the polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method was used to investigate the presence of mutations at quinolone resistance-determining regions of topoisomerase IV and DNA gyrase on 82 S. pneumoniae strains, among them 45 clinical samples were from patients and 37 from healthy carriers (control group).

Results

In clinical samples, 34 (75.56%) strains contained mutations in the parC gene, 31 (68.89%) carried mutations in the gyrA gene, and 14 (31.11%) had parE gene mutations. Antibiotic susceptibility test was performed using the CLSI (Clinical and Laboratory Standards Institute) criteria on three different generations of quinolone family, with nalidixic acid (82.22%) showing the highest resistance and levofloxacin (42.22%) the least resistance.

Conclusion

Results indicated that there is a significant correlation between quinolone resistance development and mutations in the parE gene as well as in the parC and gyrA genes.

Supramolecular assemblies of triblock copolymers with hexanuclear molybdenum clusters for sensing antibiotics in aqueous solutions via energy transfer

Water soluble hexanuclear molybdenum cluster assembled with triblock copolymer gives luminescent response on ion-pairing with difloxacin through energy transfer.

A copper-mediated cross-coupling approach for the synthesis of 3-heteroaryl quinolone and related analogues

An efficient and practical method for the direct cross-coupling between quinolones and a range of azoles was developed via copper-mediated C–H functionalization.

Formulation development and stability studies of norfloxacin extended-release matrix tablets

The aim of this research was to develop a new hydrophilic matrix system containing norfloxacin (NFX). Extended-release tablets are usually intended for once-a-day administration with benefits to the patient and lower discontinuation of the therapy. Formulations were developed with hydroxypropylmethylcellulose or poly(ethylene oxide) as hydrophilic polymers, with different molecular weights (MWs) and concentrations (20 and 30%). The tablets were found to be stable (6 months at 40 ± 2°C and 75 ± 5% relative humidity), and the film-coating process is recommended to avoid NFX photodegradation. The dissolution profiles demonstrated an extended-release of NFX for all developed formulations. Dissolution curves analyzed using the Korsmeyer exponential equation showed that drug release was controlled by both drug diffusion and polymer relaxation or erosion mechanisms. A more erosion controlled system was obtained for the formulations containing lower MW and amount of polymer. With the increase in both MW and amount of polymer in the formulation, the gel layer became stronger, and the dissolution was more drug-diffusion dependent. Formulations containing intermediate MW polymers or high concentration (30%) of low MW polymers demonstrated a combination of extended and complete in vitro drug release. This way, these formulations could provide an increased bioavailability in vivo.

Determination of fluoroquinolone antibiotics through the fluorescent response of Eu(III) based nanoparticles fabricated by layer-by-layer technique

The present work introduces the determination of fluoroquinolone antibiotics (FQs) in aqueous solutions through the fluorescent response of Eu(TTA)3 and [Eu(TTA)(3)1] (TTA(-) and 1 are thenoyltrifluoroacetonate and phosphine oxide derivative) complexes encapsulated into the polyelectrolyte capsules fabricated through layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI). The variation of luminescent core, polyelectrolyte deposition and concentration conditions reveals two modes of fluorescent response on FQs of diverse structure namely the sensitization and quenching of Eu(III) centered luminescence. The obtained regularities reveal the ternary complex formation and the ligand exchange occurring at the interface of polyelectrolyte coated [Eu(TTA)(3)1] based colloids as the reasons of the diverse fluorescent response of Eu(III) centered luminescence on FQs. The factors affecting the fluorescent response have been revealed, which are: the content of luminescent core, the mode of polyelectrolyte deposition, concentration and structure of FQs. The discrimination of moxifloxacin and lomefloxacin from levofloxacin, ofloxacin, difloxacin, perfloxacin through the quenching of Eu(III) luminescence in PSS-[Eu(TTA)(3)1] colloids has been revealed.

Fungal keratitis responsive to moxifloxacin monotherapy

PURPOSE

To report 5 cases of culture-proven fungal keratitis that resolved with moxifloxacin monotherapy.

METHODS

Case reports and review of medical literature. Five patients with fungal keratitis were treated with topical moxifloxacin.

RESULTS

All 5 patients had resolution of their infection with topical moxifloxacin monotherapy.

CONCLUSIONS

Topical fluoroquinolone agents may have significant antifungal properties. However, the vast majority of fungal keratitis patients cannot be cured with fluoroquinolone monotherapy. An initial response of keratitis to topical fluoroquinolone therapy should not lead to the assumption that the infection is bacterial because the possibility of fungal infection cannot be ruled out on that basis.

Moxifloxacin safety: an analysis of 14 years of clinical data

Background

Moxifloxacin, a fluoroquinolone antibiotic, is used for the treatment of respiratory tract, pelvic inflammatory disease, skin, and intra-abdominal infections. Its safety profile is considered favorable in most reviews but has been challenged with respect to rare but potentially fatal toxicities (e.g. hepatic, cardiac, or skin reactions).

Objective

To analyze and compare the safety profile of moxifloxacin versus comparators in the entire clinical database of the manufacturer.

Setting

Data on the valid-for-safety population from phase II–IV actively controlled studies (performed between 1996 and 2010) were analyzed. Studies were either double blind (n = 22 369) or open label (n = 7635) and included patients with indications that have been approved in at least one country [acute bacterial sinusitis, acute exacerbation of chronic bronchitis, community-acquired pneumonia, uncomplicated pelvic inflammatory disease, complicated and uncomplicated skin and skin structure infections, and complicated intra-abdominal infections] (n = 27 824) and patients with other indications (n = 2180), using the recommended daily dose (400 mg) and route of administration (oral, intravenous/oral, intravenous only). The analysis included patients at risk (age ≥65 years, diabetes mellitus, renal impairment, hepatic impairment, cardiac disorders, or body mass index <18 kg/m²). Patients with known contraindications were excluded from enrollment by study protocol design, but any patient having entered a study, even if inappropriately, was included in the analysis.

Main Outcome Measure

Crude incidences and relative risk estimates (Mantel-Haenszel analysis) of patients with any adverse event (AE), adverse drug reaction (ADR), serious AE (SAE), serious ADR (SADR), treatment discontinuation due to an AE or ADR, and fatal outcomes related to an AE or ADR.

Results

Overall incidence rates of AEs were globally similar in the moxifloxacin and comparator groups. By filtering the data for differences in disfavor of moxifloxacin (i) at ≥2.5% for events with an incidence ≥2.5% or at ≥2-fold for events with an incidence <2.5% in one or both groups and (ii) affecting ≥10 patients in either group, we observed slightly more (i) AEs in double-blind intravenous-only and open-label oral studies, (ii) SAEs in double-blind intravenous-only studies, (iii) ADRs and SADRs in open-label oral studies, (iv) SADRs in open-label intravenous/oral studies, and (v) premature discontinuation due to AEs in open-label intravenous-only studies. The actual numbers of SADRs (in all studies) were small, with clinically relevant differences noted only in intravenous/oral studies and mainly driven by ‘gastrointestinal disorders’ (15 versus 7 patients) and ‘changes observed during investigations’ (23 versus 7 patients [asymptomatic QT prolongation: 11 versus 4 patients in double-blind studies]). Analysis by comparator (including another fluoroquinolone) did not reveal medically relevant differences, even in patients at risk. Incidence rates of hepatic disorders, tendon disorders, clinical surrogates of QT prolongation, serious cutaneous reactions, and Clostridium difficile-associated diarrhea were similar with moxifloxacin and comparators.

Conclusion

The safety of moxifloxacin is essentially comparable to that of standard therapies for patients receiving the currently registered dosage and for whom contraindications and precautions of use (as in the product label) are taken into account.

Antibiotic Resistance Mechanisms in the Intensive Care Unit

Antibiotic resistance is increasingly recognised as a major threat to global health, with few new antimicrobial agents in development. The intensive care unit provides a unique environment for the growth and spread of drug-resistant organisms. Knowledge of the pathogenesis and mechanisms of resistance of drug-resistant organisms provides a conceptual framework which underpins the clinical manifestation of infections caused by these organisms, and is crucial for the intensivist to understand. Particular importance lies in the prevention of infection and the control of drug-resistant pathogens. The major resistance mechanisms of these organisms will be highlighted, focusing on specific gram-positive (meticillin-resistant Staphylococcus aureus and glycopeptide-resistant Enterococci), gram-negative ( Pseudomonas aeruginosa, Acinetobacter baumannii and multi-drug resistant Enterobacteriaceae) organisms, and then placed in historical and clinical context.

Plasmid-Mediated Quinolone Resistance; Interactions between Human, Animal, and Environmental Ecologies

Resistance to quinolones and fluoroquinolones is being increasingly reported among human but also veterinary isolates during the last two to three decades, very likely as a consequence of the large clinical usage of those antibiotics. Even if the principle mechanisms of resistance to quinolones are chromosome-encoded, due to modifications of molecular targets (DNA gyrase and topoisomerase IV), decreased outer-membrane permeability (porin defect), and overexpression of naturally occurring efflux, the emergence of plasmid-mediated quinolone resistance (PMQR) has been reported since 1998. Although these PMQR determinants confer low-level resistance to quinolones and/or fluoroquinolones, they are a favorable background for selection of additional chromosome-encoded quinolone resistance mechanisms. Different transferable mechanisms have been identified, corresponding to the production of Qnr proteins, of the aminoglycoside acetyltransferase AAC(6′)-Ib-cr, or of the QepA-type or OqxAB-type efflux pumps. Qnr proteins protect target enzymes (DNA gyrase and type IV topoisomerase) from quinolone inhibition. The AAC(6′)-Ib-cr determinant acetylates several fluoroquinolones, such as norfloxacin and ciprofloxacin. Finally, the QepA and OqxAB efflux pumps extrude fluoroquinolones from the bacterial cell. A series of studies have identified the environment to be a reservoir of PMQR genes, with farm animals and aquatic habitats being significantly involved. In addition, the origin of the qnr genes has been identified, corresponding to the waterborne species Shewanella sp. Altogether, the recent observations suggest that the aquatic environment might constitute the original source of PMQR genes, that would secondly spread among animal or human isolates.

Cutaneous leukocytoclastic vasculitis associated with levofloxacin therapy

Many cases of cutaneous vasculitis are drug-induced with histology revealing leukocytoclastic vasculitis (LCV). We present a case of levofloxacin-associated LCV successfully treated with prednisone and cessation of the offending drug. Although case reports describe a link between LCV and older fluoroquinolones, such as ciprofloxacin and ofloxacin, recent reports have implicated the newer fluoroquinolone levofloxacin. Recognition of fluoroquinolone-induced cutaneous vasculitis is important as continuation or re-exposure of the offending agent may have life-threatening consequences.

Pharmacokinetic and pharmacodynamic testing of marbofloxacin administered as a single injection for the treatment of bovine respiratory disease

New approaches in Pharmacokinetic/Pharmacodynamic (PK/PD) integration suggested that marbofloxacin, a fluoroquinolone already licensed for the treatment of bovine respiratory disease at a daily dosage of 2 mg/kg for 3-5 days, would be equally clinically effective at 10 mg/kg once (Forcyl(®)), whilst also reducing the risk of resistance. This marbofloxacin dosage regimen was studied using mutant prevention concentration (MPC), PK simulation, PK/PD integration and an in vitro dynamic system. This system simulated the concentration-time profile of marbofloxacin in bovine plasma established in vivo after a single 10 mg/kg intramuscular dose and killing curves of field isolated Pasteurellaceae strains of high (minimum inhibitory concentration (MIC) MIC ≤ 0.03 μg/mL), average (MIC of 0.12-0.25 μg/mL) and low (MIC of 1 μg/mL) susceptibility to marbofloxacin. The marbofloxacin MPC values were 2- to 4-fold the MIC values for all Mannheimia haemolytica, Pasteurella multocida tested. Marbofloxacin demonstrated a concentration-dependent killing profile with bactericidal activity observed within 1 h for most strains. No resistance development (MIC ≥ 4 μg/mL) was detected in the dynamic tests. Target values for risk of resistance PK/PD surrogates (area under the curve (AUC) AUC(24 h) /MPC and T(>MPC) /T(MSW) ratio) were achieved for all clinically susceptible pathogens. The new proposed dosing regimen was validated in vitro and by PK/PD integration confirming the single-injection short-acting antibiotic concept.

Antimicrobials in urogenital infections

Urinary tract infections (UTIs) and male genital infections are amongst the most prevalent infections. A prudent antibiotic policy therefore has a large impact on society. The clinical classification in uncomplicated cystitis, uncomplicated pyelonephritis, complicated UTI and genital infections is useful, also for the right choice of antibiotic treatment. In this regard pharmacokinetic and pharmacodynamic aspects have to be considered. Nowadays in uncomplicated cystitis antibiotics exclusively reserved for this indication are preferred, such as fosfomycin trometamol, nitrofurantoin and pivmecillinam, in order to reduce antibiotic pressure in this extremely frequent entity. In complicated UTI a broad bacterial spectrum has to be considered. Different antibiotic substances should be used for treatment, such as penicillins, with β-lactamase inhibitors, cephalosporins or carbapenems, fluoroquinolones, aminoglycosides or cotrimoxazole, if tested susceptible. For genital infections the pharmacokinetic properties of the antibiotics should especially be considered, such as in prostatitis, where mainly fluoroquinolones and macrolides show sufficient pharmacokinetic parameters for treatment of bacterial infections. Furthermore in genital infections fastidious organisms, such as Chlamydia or Mycoplasma spp. have to be considered with respect to their antimicrobial susceptibility.

Ciprofloxacin safety in paediatrics: a systematic review

OBJECTIVE

To determine the safety of ciprofloxacin in paediatric patients in relation to arthropathy, any other adverse events (AEs) and drug interactions.

METHODS

A systematic search of MEDLINE, EMBASE, CINAHL, CENTRAL and bibliographies of relevant articles was carried out for all published articles, regardless of design, that involved the use of ciprofloxacin in any paediatric age group ≤ 17 years. Only articles that reported on safety were included.

RESULTS

105 articles met the inclusion criteria and involved 16 184 paediatric patients. There were 1065 reported AEs (risk 7%, 95% CI 3.2% to 14.0%). The most frequent AEs were musculoskeletal AEs, abnormal liver function tests, nausea, changes in white blood cell counts and vomiting. There were six drug interactions (with aminophylline (4) and methotrexate (2)). The only drug related death occurred in a neonate who had an anaphylactic reaction. 258 musculoskeletal events occurred in 232 paediatric patients (risk 1.6%, 95% CI 0.9% to 2.6%). Arthralgia accounted for 50% of these. The age of occurrence of arthropathy ranged from 7 months to 17 years (median 10 years). All cases of arthropathy resolved or improved with management. One prospective controlled study estimated the risk of arthropathy as 9.3 (OR 95% CI 1.2 to 195). Pooled safety data of controlled trials in this review estimated the risk of arthropathy as 1.57 (OR 95% CI 1.26 to 1.97).

CONCLUSION

Musculoskeletal AEs occur due to ciprofloxacin use. However, these musculoskeletal events are reversible with management. It is recommended that further prospective controlled studies should be carried out to evaluate the safety of ciprofloxacin, with particular focus on the risk of arthropathy.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

Cellular accumulation of fluoroquinolones is not predictive of their intracellular activity: studies with gemifloxacin, moxifloxacin and ciprofloxacin in a pharmacokinetic/pharmacodynamic model of uninfected and infected macrophages

Fluoroquinolones enter eukaryotic cells but the correlation between cellular accumulation and activity remains poorly established. Gemifloxacin is known to accumulate to a larger extent than most other fluoroquinolones in tissues. Using murine J774 macrophages and human THP-1 monocytes, we show that gemifloxacin accumulates more than ciprofloxacin and even moxifloxacin. Whilst showing indistinguishable kinetics of accumulation in J774 macrophages, gemifloxacin was released at an approximately two-fold slower rate than ciprofloxacin and its release was only partial. Gemifloxacin was also a weaker substrate than ciprofloxacin for the efflux transporter Mrp4 active in J774 macrophages. In cells infected with Listeria monocytogenes or Staphylococcus aureus (typical cytoplasmic and phagolysosomal organisms, respectively), gemifloxacin was equipotent to moxifloxacin and ciprofloxacin in concentration-dependent experiments if data are normalised based on the minimum inhibitory concentration (MIC) in broth. Thus, larger cellular concentrations of gemifloxacin than of moxifloxacin or ciprofloxacin were needed to obtain a similar target effect. Fractionation studies showed a similar subcellular distribution for all three fluoroquinolones, with approximately two-thirds of the cell-associated drug recovered in the soluble fraction (cytosol). These data suggest that cellular accumulation of fluoroquinolones is largely a self-defeating process as far as activity is concerned, with the intracellular drug made inactive in proportion to its accumulation level. Whilst these observations do not decrease the intrinsic value of fluoroquinolones for the treatment of intracellular infections, they indicate that ranking fluoroquinolones based on cell accumulation data without measuring the corresponding intracellular activity may lead to incorrect conclusions regarding their real potential.

Quinolones: from antibiotics to autoinducers

Since quinine was first isolated, animals, plants and microorganisms producing a wide variety of quinolone compounds have been discovered, several of which possess medicinally interesting properties ranging from antiallergenic and anticancer to antimicrobial activities. Over the years, these have served in the development of many synthetic drugs, including the successful fluoroquinolone antibiotics. Pseudomonas aeruginosa and related bacteria produce a number of 2-alkyl-4(1H)-quinolones, some of which exhibit antimicrobial activity. However, quinolones such as the Pseudomonas quinolone signal and 2-heptyl-4-hydroxyquinoline act as quorum-sensing signal molecules, controlling the expression of many virulence genes as a function of cell population density. Here, we review selectively this extensive family of bicyclic compounds, from natural and synthetic antimicrobials to signalling molecules, with a special emphasis on the biology of P. aeruginosa. In particular, we review their nomenclature and biochemistry, their multiple properties as membrane-interacting compounds, inhibitors of the cytochrome bc₁ complex and iron chelators, as well as the regulation of their biosynthesis and their integration into the intricate quorum-sensing regulatory networks governing virulence and secondary metabolite gene expression.

Contrasting effects of acidic pH on the extracellular and intracellular activities of the anti-gram-positive fluoroquinolones moxifloxacin and delafloxacin against Staphylococcus aureus

In contrast to currently marketed fluoroquinolones, which are zwitterionic, delafloxacin is an investigational fluoroquinolone with an anionic character that is highly active against Gram-positive bacteria. We have examined the effect of acidic pH on its accumulation in Staphylococcus aureus and in human THP-1 cells, in parallel with its activity against extracellular and intracellular S. aureus. Moxifloxacin was used as a comparator. Delafloxacin showed MICs 3 to 5 log(2) dilutions lower than those of moxifloxacin for a collection of 35 strains with relevant resistance mechanisms and also proved to be 10-fold more potent against intracellular S. aureus ATCC 25923. In medium at pH 5.5, this difference was further enhanced, with the MIC decreasing by 5 log(2) dilutions. In infected cells incubated in acidic medium, the relative potency was 10-fold higher than that at neutral pH and the maximal relative efficacy reached a bactericidal effect at 24 h. These results can be explained by a 10-fold increase in delafloxacin accumulation in both bacteria and cells at acidic pH, making delafloxacin one of the most efficient drugs tested in this model. Opposite effects were seen for moxifloxacin with respect to both activity and accumulation. As reported for zwitterionic fluoroquinolones, delafloxacin was found associated with the soluble fraction in homogenates of eukaryotic cells. Taken together, these properties may confer to delafloxacin an advantage for the eradication of S. aureus in acidic environments, including intracellular infections.