The newer fluoroquinolones

Label-free liquid crystal-based optical detection of norfloxacin using an aptamer recognition probe in soil and lake water

Norfloxacin (NOX), a broad spectrum fluoroquinolone (FQ) antibiotic, is commonly detected in environmental residues, potentially contributing to biological drug resistance. In this paper, an aptamer recognition probe has been used to develop a label-free liquid crystal-based biosensor for simple and robust optical detection of NOX in aqueous solutions. Stimuli-receptive liquid crystals (LCs) have been employed to report aptamer-target binding events at the LC-aqueous interface. The homeotropic alignment of LCs at the aqueous-LC interface is due to the self-assembly of the cationic surfactant cetyltrimethylammonium bromide (CTAB). In the presence of the negatively charged NOX aptamer, the ordering changes to planar/tilted. On addition of NOX, the aptamer-NOX binding causes redistribution of CTAB at the LC-aqueous interface and the homeotropic orientation is restored. This results in a bright-to-dark optical transition under a polarized optical microscope (POM). This optical transition serves as a visual indicator to mark the presence of NOX. The devised aptasensor demonstrates high specificity with a minimum detection limit of 5 nM (1.596 ppb). Moreover, the application of the developed aptasensor for the detection of NOX in freshwater and soil samples underscores its practical utility in environmental monitoring. This proposed LC-based method offers several advantages over conventional detection techniques for a rapid, feasible and convenient way to detect norfloxacin.

Comparative genomics of quinolone-resistant Escherichia coli from broilers and humans in Norway

BACKGROUND

The usage of fluoroquinolones in Norwegian livestock production is very low, including in broiler production. Historically, quinolone-resistant Escherichia coli (QREC) isolated from Norwegian production animals rarely occur. However, with the introduction of a selective screening method for QREC in the Norwegian monitoring programme for antimicrobial resistance in the veterinary sector in 2014; 89.5% of broiler caecal samples and 70.7% of broiler meat samples were positive. This triggered the concern if there could be possible links between broiler and human reservoirs of QREC. We are addressing this by characterizing genomes of QREC from humans (healthy carriers and patients) and broiler isolates (meat and caecum).

RESULTS

The most frequent mechanism for quinolone resistance in both broiler and human E. coli isolates were mutations in the chromosomally located gyrA and parC genes, although plasmid mediated quinolone resistance (PMQR) was also identified. There was some relatedness of the isolates within human and broiler groups, but little between these two groups. Further, some overlap was seen for isolates with the same sequence type isolated from broiler and humans, but overall, the SNP distance was high.

CONCLUSION

Based on data from this study, QREC from broiler makes a limited contribution to the incidence of QREC in humans in Norway.

Assessment of the impact of intravenous antibiotics treatment on gut microbiota in patients: Clinical data from pre-and post-cardiac surgery

Background and aims

Surgical site infection is a common complication after surgery. Periprocedural antibiotics are necessary to prescribe for preventing or treating infections. The present study aimed to explore the effect of intravenous antibiotics on gut microbiota and menaquinone biosynthesis in patients, especially in elderly patients undergoing cardiac surgery.

Methods

A total of 388 fecal samples were collected from 154 cardiac surgery patients. The V3-V4 hypervariable region of the bacterial 16S rRNA gene was amplified and sequenced on a MiSeq PE300. The gut microbiota diversity of samples was analyzed in terms of α- and β-diversity at the OTU level. The different groups were classified according to antibiotics in combinations and single antibiotics. PICRUSt2 was used for preliminary prediction of the gut microbiota function for menaquinone biosynthesis.

Results

The intravenously administered antibiotics which are excreted via bile represents the main antibiotics that could disturb the gut microbiota's composition in cardiac surgery patients, especially for elderly patients. The effect of antibiotics on gut microbiota is produced after antibiotics treatments over one week. The recovery of gut microbiota to the state of pre-antibiotics may require over two weeks of antibiotics withdrawal. Sex factor doesn't represent as an influencer in gut microbiota composition. Long-term use of cefoperazone-sulbactam may affect coagulation function.

Conclusions

The composition of the gut microbiota had a significant change post-intravenous antibiotics treatment in cardiac surgery patients. The richness and diversity of gut microbiota are increased in elderly patients.

Molecular characteristics of fluoroquinolone-resistant Escherichia coli isolated from suckling piglets with colibacillosis

Objectives

Colibacillosis is a frequent enteric disease in the pig industry that causes significant economic losses. The objective of this study was to investigate the molecular characteristics of fluoroquinolone (FQ)-resistant E. coli isolates from suckling piglets with colibacillosis.

Results

A total of 43 FQ-resistant E. coli isolates were tested in this study and all isolates showed multi-drug resistance (MDR) and mutations in quinolone resistance determining regions (gyrA or parC). Especially, FQ-resistant E. coli isolates with double mutations in both gyrA and parC were shown a high FQs minimum inhibitory concentration (≥ 64 mg/L for ciprofloxacin, ≥ 128 mg/L for enrofloxacin, and ≥ 256 mg/L for norfloxacin). Among 43 FQ-resistant E. coli isolates, 12 (27.9%) were showed plasmid-mediated quinolone resistance (PMQR) positive E. coli. Prevalence of PMQR gene, aac(6’)-Ib-cr, qnrS, and qepA, were identified in 7, 3, and 2 E. coli isolates, respectively. We identified the following in PMQR-positive E. coli isolates: the tetracycline resistance genes tetD (12 isolates, 100.0%), tetE (12 isolates, 100.0%), tetA (11 isolates, 91.7%), and tetB (1 isolate, 8.3%); β-lactamases–encoding blaCMY-2 (10 isolates, 83.3%), blaTEM-1 (7 isolates, 58.3%), blaOXA-1 (7 isolates, 58.3%), blaSHV-1 (3 isolates, 16.7%), and blaAAC-2 (1 isolate, 8.3%); and the chloramphenicol resistance genes (10 isolates, 83.3%); the sulfonamide resistance genes sul1 (9 isolates, 75.0%) and sul2 (10 isolates, 83.3%); the aminoglycoside modifying enzyme gene aac(3)-II (2 isolates, 16.7%). The F4 (7 isolates, 58.3%), LT:STb:EAST1 (5 isolates, 41.7%), and paa (3 isolates, 25.0%) were most common fimbrial antigen, combinations of toxin genes, and non-fimbrial adhesins genes, respectively. All PMQR-positive E. coli carried class I integrons but only 4 isolates carried the gene cassette. The most prevalent plasmid replicon was FIB (9 isolates, 75.0%), followed by FIC, HI1, and N (7 isolates, 58.3%), respectively.

Conclusions

Because FQ-resistant E. coli can serve as a reservoir of FQ resistant genetic determinants that can be transferred to pathogenic bacteria in humans or pigs, this represents a public health hazard.

Systemic quinolones and risk of retinal detachment III: a nested case-control study using a US electronic health records database

Background

Quinolones are popular antibiotics that are known for their potency, broad coverage, and reasonable safety. Concerns have been raised about a possible association between quinolones and retinal detachment (RD).

Methods

We conducted a nested case–control study using electronic health records (EHR) from the Health Facts® Database. The initial cohort included all patients who were admitted between 2000 and 2016, with no history of eye disease, and had a minimum medical history of one year. Eligible cases comprised inpatients who were first admitted with a primary diagnosis of RD between 2010 and 2015. Each eligible case was matched without replacement to five unique controls by sex, race, age, and period-at-risk. We used conditional logistic regression to calculate RD risk, adjusting for exposure to other medications, and major risk factors.

Results

We identified 772 cases and 3860 controls. Whereas our primary analysis of all subjects revealed no quinolone-associated RD risk, elevated but non-significant risks were noted in African Americans (ciprofloxacin and levofloxacin), those aged 56–70 years old (moxifloxacin), and women (ciprofloxacin).

Conclusion

Our study did not identify an elevated RD risk within 30 days following systemic administration of quinolone antibiotics. Suggestions of increased risk observed in some population subgroups warrant further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00228-021-03260-4.

Fluoroquinolones: Blessings Or Curses

Fluoroquinolones are one of the world's most valuable and popularly used categories of antimicrobial agents. This paper attempts to review the substantial progress of fluoroquinolones from their discovery to black box warning. Antibiotic drug choice will remain difficult in the presence of increasing resistance, but the introduction of fluoroquinolones has created a new and exciting era in antimicrobial treatment. These are a synthetic heterogeneous group of compounds used in both hospital and community practices to treat numerous severe infections. The era of quinolone antibiotics began with the serendipitous discovery of the quinolone prototype in 1962. The chronological development of fluoroquinolone reported that nalidixic acid was the first quinolone that gained popular choice for the treatment of urinary tract infection. The subsequent agents like levofloxacin, ofloxacin, norfloxacin, gatifloxacin, moxifloxacin, clinafloxacin, sparfloxacin, and ciprofloxacin were derived through side chain and nuclear manipulation from basic pharmacophore. The fluoroquinolone motifs have been found as a milestone, effective in certain infections that are respiratory tract infection, urinary tract infection, bone disorders, meningococcal and mycobacterial infections, sexually transmitted diseases, skin infections, etc. Fluoroquinolones are first entirely man-made antibiotics that exhibit antibacterial activity through the inhibition of topoisomerase II, topoisomerase IV and deoxyribonucleic acid gyrase, which is vital for chromosome replication and function. The post-marketing surveillance pointed out the favorable side effects associated with fluoroquinolones such as phototoxicity, QT interval prolongation and anaphylaxis. The discovery, development and clinical use of fluoroquinolone antibiotics in the last century contributed to a decline in morbidity and mortality rates.

Systemic quinolones and risk of acute liver failure III: A nested case-control study using a US electronic health records database

BACKGROUND AND AIM

Quinolones are globally popular antibiotics with proven potency, broad coverage, and reasonable safety. However, some concerns were raised as to their possible association with acute liver failure (ALF). The aim of this study is to assess ALF risk within 30 days of receiving a systemically administered quinolone antibiotic, in individuals with no history of liver/diseases.

METHODS

We conducted a nested case-control study using electronic health records from the Cerner Health Facts. The initial cohort (n = 35 349 943) included all patients who were admitted between 2000 and 2016, with no history of liver diseases, and had a minimum medical history of one year. Eligible cases were inpatients who were first diagnosed with ALF between 2010 and 2015. Using incidence density sampling, each case was matched with up to five unique controls by sex, race, age at index encounter, and period-at-risk. We used conditional logistic regression to calculate the odds ratio and 95% confidence interval for ALF risk, upon adjusting for exposure to other medications, and major confounders (diabetes mellitus and alcohol abuse). We used the STROBE Statement for reporting on our study.

RESULTS

We identified 3151 cases and 15 657 controls. Our primary analysis did not reveal an association between quinolones and ALF risk. However, some risk was identified among those with no or few comorbidities, those ≤ 60 years of age, women, men, African Americans, and Caucasians.

CONCLUSION

Although our study does not suggest an overall association between quinolones and ALF, elevated risks seen in some subgroups warrant further investigation.

Systemic quinolones and risk of acute liver failure I: Analysis of data from the US FDA adverse event reporting system

Background and Aim

Quinolones are a potent and globally popular group of antibiotics that are used to treat a wide range of infections. Some case reports have raised concern about their possible association with acute hepatic failure (AHF). Data from the US FDA Adverse Event Reporting System were evaluated for signals of AHF in association with systemically administered quinolone antibiotics.

Methods

AHF reports between 1969 and 2019q2, with a focus on 2010–2019q2, were analyzed. Specifically, AHF reports linked to non‐quinolone antibiotics of known hepatotoxicity were compared to reports with non‐quinolone, non‐hepatotoxic (reference) antibiotics; and AHF reports with quinolones were also compared to reports with the same group of reference antibiotics. Two disproportionality signal detection techniques (proportional reporting ratio, PRR, and empirical Bayes geometric mean, EBGM) were used to assess the AHF signal for both analyses.

Results

Only ciprofloxacin showed a marginal and significant AHF signal (PRR: 1.85 [1.21, 2.81]; EBGM: 1.54 [1.06, 1.81]); moxifloxacin, levofloxacin, and ofloxacin showed weak and nonsignificant signals.

Conclusion

Further pharmacovigilance studies are required to confirm the association between ciprofloxacin and AHF seen in the present analysis.

Thiosemicarbazide Derivatives Decrease the ATPase Activity of Staphylococcus aureus Topoisomerase IV, Inhibit Mycobacterial Growth, and Affect Replication in Mycobacterium smegmatis

Compounds targeting bacterial topoisomerases are of interest for the development of antibacterial agents. Our previous studies culminated in the synthesis and characterization of small-molecular weight thiosemicarbazides as the initial prototypes of a novel class of gyrase and topoisomerase IV inhibitors. To expand these findings with further details on the mode of action of the most potent compounds, enzymatic studies combined with a molecular docking approach were carried out, the results of which are presented herein. The biochemical assay for 1-(indol-2-oyl)-4-(4-nitrophenyl) thiosemicarbazide (4) and 4-benzoyl-1-(indol-2-oyl) thiosemicarbazide (7), showing strong inhibitory activity against Staphylococcus aureus topoisomerase IV, confirmed that these compounds reduce the ability of the ParE subunit to hydrolyze ATP rather than act by stabilizing the cleavage complex. Compound 7 showed better antibacterial activity than compound 4 against clinical strains of S. aureus and representatives of the Mycobacterium genus. In vivo studies using time-lapse microfluidic microscopy, which allowed for the monitoring of fluorescently labelled replisomes, revealed that compound 7 caused an extension of the replication process duration in Mycobacterium smegmatis, as well as the growth arrest of bacterial cells. Despite some similarities to the mechanism of action of novobiocin, these compounds show additional, unique properties, and can thus be considered a novel group of inhibitors of the ATPase activity of bacterial type IIA topoisomerases.

Phenotypic and genotypic profile of the antimicrobial resistance of bacterial isolates and evaluation of physical and chemical potability indicators in groundwater in Brazil

The aquatic environment has received increasing attention regarding the evolution of bacterial resistance, either as a source of resistance genes or as a matrix for the dissemination of these genes. We evaluated the physicochemical, microbiological and antimicrobial resistance characteristics of 160 samples from alternative water well solutions. According to Ordinance 2914/2011 - MS, 44 (27.5%) samples were considered unsafe if at least one physicochemical parameter exceeded permissible limits. Escherichia coli were found in 30.6% of the unregistered housing estates (UHE) and 1.9% of the local sanitary surveillance system (RW). The total of 158 bacterial strains were isolated from 13 (25%) RW and 68 (63%) UHE, 132 of which (83.5%) were obtained from UHE samples. In the investigation of resistance genes, tetA, qnrS and qnrB genes were detected in three, one and eight isolates, respectively. Our results emphasize the importance of constant surveillance and control of the quality of water supplies.

An sRNA Screen for Reversal of Quinolone Resistance in Escherichia coli

In light of the rising prevalence of antimicrobial resistance (AMR) and the slow pace of new antimicrobial development, there has been increasing interest in the development of adjuvants that improve or restore the effectiveness of existing drugs. Here, we use a novel small RNA (sRNA) screening approach to identify genes whose knockdown increases ciprofloxacin (CIP) sensitivity in a resistant strain of Escherichia coli 5000 sRNA constructs were initially screened on a gyrA S83L background, ultimately leading to 30 validated genes whose disruption reduces CIP resistance. This set includes genes involved in DNA replication, repair, recombination, efflux, and other regulatory systems. Our findings increase understanding of the functional interactions of DNA Gyrase, and may aid in the development of new therapeutic approaches for combating AMR.

Dual Glycation-Inflammation Modulation, DPP-IV and Pancraetic Lipase Inhibitory Potentials and Antiproliferative Activity of Novel Fluoroquinolones

Paramount efforts by pharmaceutical industry to identify new targets for obesity-diabetes (Diabesity) pharmacological intervention have led to a number of agents developed and directed at DPP IV [dipeptidyl peptidase IV] enzyme inhibition thereby enhancing endogenous insulinotropic incretins. Besides antioxidative-antiinflammtory molecules that inhibit accumulation of advanced glycation end products (AGEs) can be good candidates for ameliorating diabetic complications. Fluoroquinolones (FQs) have been identified recently as potent inhibitors of pancreatic lipase (PL). The suggested association between obesity and colorectal cancer initiated the evaluation of antiproliferative activity of the new FQs and TFQs against a panel of obesity related colorectal cells (HT29, HCT116, SW620 CACO2 and SW480). The aim of the current study is to examine the potential of newly synthesized FQs and triazolofluoroquinolones (TFQs) derivatives as dual inhibitors for glycation and inflammation, DPP IV inhibitors, PL inhibitors for dual management of obesity and diabetes, as well as antiprolifertaive efficacy against colorectal cancer cell lines. Sulforodamine B (SRB) colorimetric assay revealed that some derivatives exhibited unselective cytotoxity against HT29, HCT116, SW620 CACO2 and SW480. The superior antiglycation activity of the reduced derivatives 4a and 4b over that of aminoguanidine with respective IC50 (μM) values of 3.05±0.33 and 8.51±3.21; none of the tested synthetic compounds could perform equally effectively to Diprotin A, a dose dependent inhibitor of DPP IV. Compounds 4a, 5a, 3b, 4b and 5b demonstrated anti-inflammatory IC50 values exceeding that of indomethacin. Compounds 3a and 4a showed IC50 lower than 10 μM as PL inhibitors. In conclusion, FQ and TFQ derivatives may unveil new antiobesity and anticancer agents in the future. Our research qualifies FQs and TFQs as promising candidates for the development of related α-dicarbonyl scavengers as therapeutic agents to protect cells against carbonyl stress.

Successful Use of Octreotide Therapy for Refractory Levofloxacin-Induced Hypoglycemia: A Case Report and Literature Review

Fluoroquinolones are commonly prescribed antimicrobials that have been implicated in alterations of glucose metabolism. We report a case of refractory fluoroquinolone-induced hypoglycemia in a patient with type-2 diabetes mellitus on glipizide that was successfully treated with octreotide. A patient was admitted with hypoglycemia after having been initiated on levofloxacin therapy. Despite treating the hypoglycemia supportively with multiple boluses of 25 g of dextrose, a continuous dextrose infusion, and glucagon, the patient experienced repeated episodes of rebound hypoglycemia. The persistent hypoglycemia was eventually reversed with the administration of subcutaneous octreotide. Clinicians should be cognizant of this adverse effect of fluoroquinolones, as well as predisposing risk factors, and consider octreotide as an adjunctive therapy for refractory hypoglycemia cases.

In Vitro Comparison of Antibacterial and Antibiofilm Activities of Selected Fluoroquinolones against Pseudomonas aeruginosa and Methicillin-Resistant Staphylococcus aureus

An in vitro overview of the inhibitory effects of selected fluoroquinolones against planktonic and biofilm cells of the methicillin-resistant Staphylococcus aureus (MRSA) strain American type culture collection (ATCC) 43300 and the Pseudomonas aeruginosa strain ATCC 27853 was carried out. Biofilm cells of both strains were less susceptible to the selected antibiotics than their planktonic counterparts. In addition, certain antibiotics were more effective against biofilm cells, while others performed better on the planktonic cells. Against P. aeruginosa, ciprofloxacin was the most potent on both planktonic and biofilm cells, whereas ofloxacin was the least potent on both biofilm and planktonic cells. Moxifloxacin and gatifloxacin were the most potent against both planktonic and biofilm MRSA bacteria, however, not in the same order of activity. Norfloxacin was the least active when tested against both planktonic and biofilm cells. The results of this work are expected to provide insight into the efficacy of various fluoroquinolones against MRSA and Pseudomonas aeruginosa biofilms. This study could form the basis for future clinical studies that could recommend special guidelines for the management of infections that are likely to involve bacteria in their biofilm state.

Antiadhesive and antibacterial properties of pillar[5]arene-based multilayers

A new type of coating, based on carboxylato-pillar[5]arene/poly(allylamine hydrochloride) multilayer films, for the sustained release of antibiotics with in vitro antiadhesive and antimicrobial activity against Gram-positive and Gram-negative bacteria is described.

Review of Properties and Analytical Methods for the Determination of Norfloxacin

The first-generation quinolones have their greatest potency against Gram-negative bacteria, but newly developed molecules have exhibited increased potency against Gram-positive bacteria, and existing agents are available with additional activity against anaerobic microorganisms. Norfloxacin is a broad-spectrum antimicrobial fluoroquinolone used against Gram-positive and Gram-negative organisms (aerobic organisms). There are different analytical methods available to determine norfloxacin applied in quality control of this medicine in order to ensure its effectiveness and safety. The authors present an overview of the fourth generation of quinolones, followed by the properties, applications, and analytical methods of norfloxacin. These results show several existing analytical techniques that are flexible and broad-based methods of analysis in different matrices. This article focuses on bionalytical and pharmaceutical quality-control applications, such as thin-layer chromatography, microbiological assay, spectrophotometry, capillary electrophoresis (CE), and high-performance liquid chromatography (HPLC).

Simultaneous Semimechanistic Population Analyses of Levofloxacin in Plasma, Lung, and Prostate To Describe the Influence of Efflux Transporters on Drug Distribution following Intravenous and Intratracheal Administration

Levofloxacin (LEV) is a broad-spectrum fluoroquinolone used to treat pneumonia, urinary tract infections, chronic bacterial bronchitis, and prostatitis. Efflux transporters, primarily P-glycoprotein (P-gp), are involved in LEV's tissue penetration. In the present work, LEV free lung and prostate interstitial space fluid (ISF) concentrations were evaluated by microdialysis in Wistar rats after intravenous (i.v.) and intratracheal (i.t.) administration (7 mg/kg of body weight) with and without coadministration of the P-gp inhibitor tariquidar (TAR; 15 mg/kg administered i.v.). Plasma and tissue concentration/time profiles were evaluated by noncompartmental analysis (NCA) and population pharmacokinetics (popPK) analysis. The NCA showed significant differences in bioavailability (F) for the control group (0.4) and the TAR group (0.86) after i.t. administration. A four-compartment model simultaneously characterized total plasma and free lung (compartment 2) and prostate (compartment 3) ISF concentrations. Statistically significant differences in lung and prostate average ISF concentrations and levels of kidney active secretion in the TAR group from those measured for the control group (LEV alone) were observed. The estimated population means were as follows: volume of the central compartment (V1), 0.321 liters; total plasma clearance (CL), 0.220 liters/h; TAR plasma clearance (CLTAR), 0.180 liters/h. The intercompartmental distribution rate constants (K values) were as follows: K12, 8.826 h(-1); K21, 7.271 h(-1); K13, 0.047 h(-1); K31, 7.738 h(-1); K14, 0.908 h(-1); K41, 0.409 h(-1); K21 lung TAR (K21LTAR), 8.883 h(-1); K31 prostate TAR (K31PTAR), 4.377 h(-1). The presence of P-gp considerably impacted the active renal secretion of LEV but had only a minor impact on the efflux from the lung following intratracheal dosing. Our results strongly support the idea of a role of efflux transporters other than P-gp contributing to LEV's tissue penetration into the prostrate.

Biological evaluation and molecular modelling study of thiosemicarbazide derivatives as bacterial type IIA topoisomerases inhibitors

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC(50) below 15 μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32 μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.

Appropriate use of fluoroquinolones in children

With the increasing resistance to antibiotics among common bacterial pathogens, challenges associated with the use of fluoroquinolones (FQs) in paediatrics have emerged. The majority of FQs have favourable pharmacokinetic properties, although these properties can differ in children compared with adults. Moreover, all FQs have broad antimicrobial activity both against Gram-positive and Gram-negative bacteria. However, only some FQs for which adequate studies are available have been approved for use in children in a limited number of clinical situations owing to the supposed risk of development of severe musculoskeletal disorders, as demonstrated in juvenile animals. Recent short- and long-term evaluations appear to indicate that, at least for levofloxacin, this risk, if present at all, is marginal. This marginal risk could lead to more frequent use of FQs in children, even to treat diseases for which several other drugs with documented efficacy, safety and tolerability are considered the first-line antibiotics. However, for most of the FQs, adequate long-term studies of safety are not available. This indicates that the use of FQs should be limited to selected respiratory infections (including tuberculosis), exacerbation of lung disease in cystic fibrosis, central nervous system infections, enteric infections, febrile neutropenia, as well as serious infections attributable to FQ-susceptible pathogen(s) in children with life-threatening allergies to alternative agents. When considering diseases that could benefit from the use of FQs, particular attention must be paid to the choice of drug and its dosage, considering that not all of the FQs have been evaluated in different diseases.

Probing bacterial uptake of glycosylated ciprofloxacin conjugates

Mono- and disaccharide-functionalised conjugates of the fluoroquinolone antibiotic ciprofloxacin have been synthesised and used as chemical probes of the bacterial uptake of glycosylated ciprofloxacin. Their antimicrobial activities against a panel of clinically relevant bacteria were determined: the ability of these conjugates to inhibit their target DNA gyrase and to be transported into the bacteria was assessed by using in vivo and in vitro assays. The data suggest a lack of active uptake through sugar transporters and that although the addition of monosaccharides is compatible with the inhibition of DNA gyrase, the addition of a disaccharide results in a significant decrease in antimicrobial activity.

Fragment-to-hit-to-lead discovery of a novel pyridylurea scaffold of ATP competitive dual targeting type II topoisomerase inhibiting antibacterial agents

The discovery and optimization of a new class of bacterial topoisomerase (DNA gyrase and topoisomerase IV) inhibitors binding in the ATP domain are described. A fragment molecule, 1-ethyl-3-(2-pyridyl)urea, provided sufficiently potent enzyme inhibition (32 μM) to prompt further analogue work. Acids and acid isosteres were incorporated at the 5-pyridyl position of this fragment, bridging to a key asparagine residue, improving enzyme inhibition, and leading to measurable antibacterial activity. A CF3-thiazole substituent at the 4-pyridyl position improved inhibitory potency due to a favorable lipophilic interaction. Promising antibacterial activity was seen versus the Gram-positive pathogens Staphylococcus aureus and Streptococcus pneumoniae and the Gram-negative pathogens Haemophilus influenzae and Moraxella catarrhalis . Precursor metabolite incorporation and mutant analysis studies support the mode-of-action, blockage of DNA synthesis by dual target topoisomerase inhibition. Compound 35 was efficacious in a mouse S. aureus disease model, where a 4.5-log reduction in colony forming units versus control was demonstrated.

Pharmacokinetics of moxifloxacin and high-dose levofloxacin in severe lower respiratory tract infections

This study evaluated the pharmacokinetics of intravenous moxifloxacin 400 mg once and levofloxacin 500 mg twice daily in patients with lower respiratory tract infections (LRTIs) and assessed their pharmacodynamic adequacy against common respiratory pathogens. Eighteen patients with LRTIs hospitalised in general wards were included. Serial blood samples were obtained at steady state and concentrations were determined using HPLC. Pharmacokinetic variables were estimated by a two-compartment model. The characteristic pharmacodynamic parameter for fluoroquinolones (AUC(0-24)/MIC) was calculated. Peak and trough concentrations were, respectively, 4.81 ± 1.03 and 0.59 ± 1.13 mg/L for moxifloxacin and 6.42 ± 1.08 and 0.79 ± 0.39 mg/L for levofloxacin. Pharmacokinetic data for moxifloxacin and levofloxacin, respectively, were: CL, 10.27 ± 1.24 and 22.66 ± 6.62 L/h; t1/2, 13.43 ± 5.12 and 6.75 ± 1.34 h; Vss, 163.03 ± 53.88 and 170.73 ± 39.59 L; and AUC(0-24), 39.38 ±5.28 and 47.06 ± 14.09 mg·h/L. The pharmacodynamic target was attained in all patients by both antibiotics against the majority of respiratory pathogens. Moxifloxacin proved to be pharmacodynamically efficacious against Gram-positive bacteria with MICs ≤ 0.79 mg/L and Gram-negative bacteria with MICs ≤ 0.32 mg/L. These MIC thresholds for levofloxacin were 1.1 mg/L and 0.38 mg/L, respectively. Moxifloxacin and high-dose levofloxacin show a favourable pharmacokinetic profile in plasma of patients with severe LRTIs, without significant interpatient variability. They ensure optimal pharmacodynamic exposure against the majority of microbes involved in these infections. However, the predicted efficacy against Gram-negative bacteria with MICs ≥ 0.5 mg/L appears to be low.

Activity of JNJ-Q2, a novel fluoroquinolone, tested against Neisseria gonorrhoeae, including ciprofloxacin-resistant strains

JNJ-Q2 is a broad-spectrum fluoroquinolone with activity against Gram-positive and -negative pathogens. The in vitro activity of JNJ-Q2 was evaluated when tested against Neisseria gonorrhoeae isolates, including 31 ciprofloxacin-resistant strains with documented mutations in the quinolone resistance determining region. MIC values were determined using reference agar dilution methods using ciprofloxacin, penicillin, ceftriaxone, tetracycline, and azithromycin as comparators. All isolates were inhibited by ≤0.25 μg/mL of JNJ-Q2 (range, 0.004-0.25 μg/mL; MIC(50/90), 0.03/0.25 μg/mL) which was 8-fold (MIC(50)) and 32-fold more potent (MIC(90)) compared to ciprofloxacin. Few strains were susceptible to penicillin (3.0%) and tetracycline (6.1%), and with the use of the European Committee on Antimicrobial Susceptibility Testing interpretive criteria, 13.6% were resistant to azithromycin. All strains were susceptible to ceftriaxone, the most potent agent (MIC(90), 0.06 μg/mL) followed by JNJ-Q2 (MIC(90), 0.25 μg/mL). JNJ-Q2 appears to be a potent fluoroquinolone when tested against contemporary multidrug-resistant N. gonorrhoeae.