Review of the pharmacokinetic properties of nitrofurantoin and nitroxoline

Novel nitroxoline derivative combating resistant bacterial infections through outer membrane disruption and competitive NDM-1 inhibition

ABSTRACTNew Delhi metallo-β-lactamase-1 (NDM-1) has rapidly disseminated worldwide, leading to multidrug resistance and worse clinical prognosis. Designing and developing effective NDM-1 inhibitors is a critical and urgent challenge. In this study, we constructed a library of long-lasting nitroxoline derivatives and identified ASN-1733 as a promising dual-functional antibiotic. ASN-1733 can effectively compete for Ca2+ on the bacterial surface, causing the detachment of lipopolysaccharides (LPS), thereby compromising the outer membrane integrity and permeability and exhibiting broad-spectrum bactericidal activity. Moreover, ASN-1733 demonstrated wider therapeutic applications than nitroxoline in mouse sepsis, thigh and mild abdominal infections. Furthermore, ASN-1733 can effectively inhibit the hydrolytic capability of NDM-1 and exhibits synergistic killing effects in combination with meropenem against NDM-1 positive bacteria. Mechanistic studies using enzymatic experiments and computer simulations revealed that ASN-1733 can bind to key residues on Loop10 of NDM-1, hindering substrate entry into the enzyme's active site and achieving potent inhibitory activity (Ki = 0.22 µM), even in the presence of excessive Zn2+. These findings elucidate the antibacterial mechanism of nitroxoline and its derivatives, expand their potential application in the field of antibacterial agents and provide new insights into the development of novel NDM-1 inhibitors.

Recurrent UTI in Women-Risk Factors and Management

Urinary tract infections (UTIs) are common in women; more than 50% of women will be diagnosed with a UTI in her lifetime. Many of these women will go on to develop recurrent UTI. Nevertheless, evidence-based prevention of recurrent UTI is under-utilized. Here, the authors provide detailed practical advice on UTI prevention with a thorough review of the evidence. Non-antibiotic prevention measures discussed include increased fluid intake, vaginal estrogen therapy, methenamine, and cranberry. Antibiotic prophyalxis for carefully selected patients is also discussed.

Evaluation of In Vitro Synergistic Effects of Tetracycline with Alkaloid-Related Compounds against Diarrhoeic Bacteria

Diarrhoea remains an important public health concern, particularly in developing countries, and has become difficult to treat because of antibacterial resistance. The development of synergistic antimicrobial agents appears to be a promising alternative treatment against diarrhoeic infections. In this study, the combined effect of tetracycline together with either nitroxoline, sanguinarine, or zinc pyrithione (representing various classes of plant-based compounds) was evaluated in vitro against selected diarrhoeic bacteria (Enterococcus faecalis, Escherichia coli, Listeria monocytogenes, Shigella flexneri, Vibrio parahaemolyticus, and Yersinia enterocolitica). The chequerboard method in 96-well microtiter plates was used to determine the sum of the fractional inhibitory concentration indices (FICIs). Three independent experiments were performed per combination, each in triplicate. It was observed that the combination of tetracycline with either nitroxoline, sanguinarine, or zinc pyrithione produced synergistic effects against most of the pathogenic bacteria tested, with FICI values ranging from 0.086 to 0.5. Tetracycline-nitroxoline combinations produced the greatest synergistic action against S. flexneri at a FICI value of 0.086. The combinations of the agents tested in this study can thus be used for the development of new anti-diarrhoeic medications. However, studies focusing on their in vivo anti-diarrhoeic activity and safety are required before any consideration for utilization in human medicine.

Antibiotics for UTI Prevention After Intradetrusor OnabotulinumtoxinA Injections

IMPORTANCE

Urinary tract infections (UTIs) occur in 8.6% to 48.1% of patients after intradetrusor onabotulinumtoxinA injections.

OBJECTIVE

The objective of this study was to evaluate both choice and duration of antibiotic prophylaxis on the incidence of UTI within 30 days after in-office onabotulinumtoxinA injections.

STUDY DESIGN

We included a single-site, retrospective cohort of 305 patients with overactive bladder or bladder pain syndrome receiving postprocedure prophylactic antibiotics for in-office, 100-unit intradetrusor onabotulinumtoxinA injections from 2019 to 2023. Categories of antibiotic prophylaxis compared included (1) nitrofurantoin 100 mg twice daily for 3 days, (2) nitrofurantoin 100 mg twice daily for 5 days, (3) trimethoprim-sulfamethoxazole 160 mg/800 mg twice daily for 3 days, and (4) "other regimens." Primary outcome was incidence of UTI within 30 days. Variables were compared via χ2 test. Crude/adjusted odds were estimated using binary logistic regression.

RESULTS

Incidence of UTI was 10.4% for 3-day nitrofurantoin, 20.5% for 5-day nitrofurantoin, 7.4% for 3-day trimethoprim-sulfamethoxazole, and 25.7% among "other regimens" (P = 0.023). Differences among primary regimens were substantial but not statistically significant: 3-day trimethoprim-sulfamethoxazole had 31% lower odds of UTI versus 3-day nitrofurantoin (odds ratio [OR], 0.689; P = 0.518). Compared with 3-day nitrofurantoin regimen, the 5-day nitrofurantoin regimen had twice the odds of UTI (OR, 2.22; P = 0.088). Those receiving "other regimens" had nearly 3 times the odds of UTI (OR, 2.98; P = 0.018). Results were similar adjusting for age and race. Overall urinary retention rate was 1.97%.

CONCLUSIONS

Prophylactic antibiotic choice and duration of treatment potentially affect UTI incidence after in-office, intradetrusor onabotulinumtoxinA injections. Nitrofurantoin and trimethoprim-sulfamethoxazole for 3 days have the lowest UTI incidence.

In vitro anti-trypanosomal activity of synthetic nitrofurantoin-triazole hybrids against Trypanosoma species causing human African trypanosomosis

Human African trypanosomosis (HAT) which is also known as sleeping sickness is caused by Trypanosoma brucei gambiense that is endemic in western and central Africa and T. b. rhodesiense that is endemic in eastern and southern Africa. Drugs used for treatment against HAT first stage have limited effectiveness, and the second stage drugs have been reported to be toxic, expensive, and have time-consuming administration, and parasitic resistance has developed against these drugs. The aim of this study was to evaluate the anti-trypanosomal activity of nitrofurantoin-triazole hybrids against T. b. gambiense and T. b. rhodesiense parasites in vitro. This study screened 19 synthesized nitrofurantoin-triazole (NFT) hybrids on two strains of human trypanosomes, and cytotoxicity was evaluated on Madin-Darby bovine kidney (MDBK) cells. The findings in this study showed that an increase in the chain length and the number of carbon atoms in some n-alkyl hybrids influenced the increase in anti-trypanosomal activity against T. b. gambiense and T. b. rhodesiense. The short-chain n-alkyl hybrids showed decreased activity compared to the long-chain n-alkyl hybrids, with increased activity against both T. b. gambiense and T. b. rhodesiense. Incorporation of additional electron-donating substituents in some NFT hybrids showed increased anti-trypanosomal activity than to electron-withdrawing substituents in NFT hybrids. All 19 NFT hybrids tested displayed better anti-trypanosomal activity against T. b. gambiense than T. b. rhodesiense. The NFT hybrid no. 16 was among the best performing hybrids against both T. b. gambiense (0.08 ± 0.04 μM) and T. b.rhodesiense (0.11 ± 0.06 μM), and its activity might be influenced by the introduction of fluorine in the para-position on the benzyl ring. Remarkably, the NFT hybrids in this study displayed weak to moderate cytotoxicity on MDBK cells. All of the NFT hybrids in this study had selectivity index values ranging from 18 to greater than 915, meaning that they were up to 10-100 times fold selective in their anti-trypanosomal activity. The synthesized NFT hybrids showed strong selectivity >10 to T. b. gambiense and T. b. rhodesiense, which indicates that they qualify from the initial selection criteria for potential hit drugs.

Nitroxoline resistance is associated with significant fitness loss and diminishes in vivo virulence of Escherichia coli

IMPORTANCE

Antimicrobial resistance (AMR) poses a global threat and requires the exploration of underestimated treatment options. Nitroxoline, an effective broad-spectrum antibiotic, does not suffer from high resistance rates in the clinics but surprisingly, it is not heavily used yet. Our findings provide compelling evidence that Nitroxoline resistance renders bacteria unable to cause an infection in vivo, thereby reinvigorating the potential of Nitroxoline in combating AMR.

A quality-by-design evaluated liquid chromatography method development and validation for the separation and quantification of nitroxoline and its impurities

A novel, isocratic, sensitive, stability-indicating high-performance liquid chromatography method was developed for the separation and quantification of related substances in nitroxoline (NTL). The chromatographic separation has been achieved on Inertsil ODS-3 V, (250 × 4.6 mm, 5 μm) at 240 nm using ethylenediamine tetraacetic acid buffer and methanol in the ratio of 60:40 v/v as mobile phase. The performance of the method has been checked as per the International Conference on Harmonization guidelines for specificity, linearity, accuracy, precision, and robustness. Regression analysis showed a correlation coefficient value greater than 0.99 for NTL and its three impurities. The detection limit of impurities was in the range of 0.01% (0.05 μg/mL)-0.22% (1.1 μg/mL) indicating the sensitivity of the newly developed method. The accuracy of the method was established based on the recovery obtained between 94.7% and 104.1% for all the impurities. The percentage relative standard deviation obtained for the repeatability was less than 4.0% at the specification level for all impurities. Forced degradation was performed to establish the stability-indicating nature of the method and to know about the degradation products, the quality of a drug substance changes with time under the influence of stress conditions. Thus, the proposed method was validated and found to be specific, sensitive, linear, accurate, precise, reproducible, and beneficial for routine usage.

Induction of Programmed Cell Death in Acanthamoeba culbertsoni by the Repurposed Compound Nitroxoline

Acanthamoeba is a ubiquitous genus of amoebae that can act as opportunistic parasites in both humans and animals, causing a variety of ocular, nervous and dermal pathologies. Despite advances in Acanthamoeba therapy, the management of patients with Acanthamoeba infections remains a challenge for health services. Therefore, there is a need to search for new active substances against Acanthamoebae. In the present study, we evaluated the amoebicidal activity of nitroxoline against the trophozoite and cyst stages of six different strains of Acanthamoeba. The strain A. griffini showed the lowest IC50 value in the trophozoite stage (0.69 ± 0.01 µM), while the strain A. castellanii L-10 showed the lowest IC50 value in the cyst stage (0.11 ± 0.03 µM). In addition, nitroxoline induced in treated trophozoites of A. culbertsoni features compatibles with apoptosis and autophagy pathways, including chromatin condensation, mitochondrial malfunction, oxidative stress, changes in cell permeability and the formation of autophagic vacuoles. Furthermore, proteomic analysis of the effect of nitroxoline on trophozoites revealed that this antibiotic induced the overexpression and the downregulation of proteins involved in the apoptotic process and in metabolic and biosynthesis pathways.

Insight into the mechanism and toxicology of nitrofurantoin: a metabolomics approach

Safety and effectiveness are the two ends of the balance in drug development that needs to be evaluated. The biotransformation of drugs within a living organism could potentiate biochemical insults in the tissue and compromise the safety of drugs. Nitrofurantoin (NFT) is a cheap clinical antibiotic with a wide array of activities against gram-positive and gram-negative organisms. The NFT scaffold has been utilized to develop other derivates or analogues in the quest to repurpose drugs against other infectious diseases. Several techniques were developed over the years to study the mechanism of NFT metabolism and toxicity, such as voltammetry, chromatographic analysis, protein precipitation, liquid-liquid extraction, etc. Due to limitations in these methods, the mechanism of NFT biotransformation in the cell is poorly understood. Metabolomics has been adopted in drug metabolism to understand the mechanism of drug toxicity and could provide a solution to overcome the limitations of current techniques to determine mechanisms of toxicity. Unfortunately, little or no information regarding the metabolomics approach in NFT metabolism and toxicity is available. Hence, this review highlights the metabolomic techniques that can be adopted in NFT metabolism and toxicological studies to encourage the research community to widely adopt and utilize metabolomics in understanding NFT's metabolism and toxicity.

Antimicrobial Resistance in Bacteria from Meat and Meat Products: A One Health Perspective

According to the 2030 Agenda of the United Nations, one of the sustainable development goals is to ensure sustainable consumption and production patterns. The need to ensure food safety includes, other than microbiological hazards, concerns with antimicrobial-resistant (AMR) bacteria. The emergence of resistant bacteria in the food industry is essentially due to the abusive, and sometimes incorrect, administration of antimicrobials. Although not allowed in Europe, antimicrobials are often administered to promote animal growth. Each time antimicrobials are used, a selective pressure is applied to AMR bacteria. Moreover, AMR genes can be transmitted to humans through the consumption of meat-harbouring-resistant bacteria, which highlights the One Health dimension of antimicrobial resistance. Furthermore, the appropriate use of antimicrobials to ensure efficacy and the best possible outcome for the treatment of infections is regulated through the recommendations of antimicrobial stewardship. The present manuscript aims to give the current state of the art about the transmission of AMR bacteria, particularly methicillin-resistant S. aureus, ESBL-producing Enterobacteriaceae, and vancomycin-resistant Enterococcus spp., along with other ESKAPE bacteria, from animals to humans through the consumption of meat and meat products, with emphasis on pork meat and pork meat products, which are considered the most consumed worldwide.

Antibiotic management of urinary tract infections in the post-antibiotic era: a narrative review highlighting diagnostic and antimicrobial stewardship

BACKGROUND

As one of the most common indications for antimicrobial prescription in the community, the management of urinary tract infections (UTIs) is both complicated by, and a driver of, antimicrobial resistance.

OBJECTIVES

To highlight the key clinical decisions involved in the diagnosis and treatment of UTIs in adult women, focusing on clinical effectiveness and both diagnostic and antimicrobial stewardship as we approach the post-antimicrobial era.

SOURCES

Literature reviewed via directed PubMed searches and manual searching of the reference list for included studies to identify key references to respond to the objectives. A strict time limit was not applied. We prioritised recent publications, randomised trials, and systematic reviews (with or without meta-analyses) where available. Searches were limited to English language articles. A formal quality assessment was not performed; however, the strengths and limitations of each paper were reviewed by the authors throughout the preparation of this manuscript.

CONTENT

We discuss the management of UTIs in ambulatory adult women, with particular focus on uncomplicated infections. We address the diagnosis of UTIs, including the following: definition and categorisation; bedside assessments and point-of-care tests; and the indications for, and use of, laboratory tests. We then discuss the treatment of UTIs, including the following: indications for treatment, antimicrobial sparing approaches, key considerations when selecting a specific antimicrobial agent, specific treatment scenarios, and duration of treatment. We finally outline emerging areas of interest in this field.

IMPLICATIONS

The steady increase in antimicrobial resistance among common uropathogens has had a substantial affect on the management of UTIs. Regarding both diagnosis and treatment, the clinician must consider both the patient (clinical effectiveness and adverse effects, including collateral damage) and the community more broadly (population-level antimicrobial selection pressure).

Nanomechanical changes in probiotic bacteria under antibiotics exposure: Implications on Lactobacillus biofilm formation

Recognition of the microbial cell's surface constituents' biophysical properties is an important research topic, allowing a better understanding of the cell's behaviour under different conditions. Atomic force microscopy (AFM) was employed in this study to analyse the basis of the nanomechanical changes in probiotic bacteria under nitrofurantoin, furazolidone, and nitrofurazone exposure. Recorded significant changes in the two Lactobacillus strains cells morphology, topography, and adhesion parameters resulted in the increase of the cells' longitude (up to 2.58 μm), profile height (by around 0.50 μm), and decrease in the adhesion force (up to 13.58 nN). Young's modulus and adhesion energy decreased within 96 h, however with no negative effect on the cells' morphology or loss of structural integrity. Observed modifications present the mode of action of the 5-nitrofuran derivative antibiotics on probiotic biofilm formation and suggest activation of the multilevel adaptation mechanisms to counteract unfavorable environments. A visual change in bacterial morphology such as an increased surface-to-volume ratio might be a link between molecular-level events and outcomes in individual cells and biofilms. This paper for the first time shows, that these antibiotics affect the properties of non-target microorganisms as lactobacilli, and might impair biofilm formation. However, the degree of such transformations depends on the delivered active substance.

Development of a Physiologically Based Pharmacokinetic Model for Nitrofurantoin in Rabbits, Rats, and Humans

Nitrofurantoin (NFT) is a commonly used antibiotic for the treatment of urinary tract infections that can cause liver toxicity. Despite reports of hepatic adverse events associated with NFT exposure, there is still limited understanding of the interplay between NFT exposure, its disposition, and the risk of developing liver toxicity. In this study, we aim to develop a physiologically based pharmacokinetic (PBPK) model for NFT in three different species (rabbits, rats, and humans) that can be used as a standard tool for predicting drug-induced liver injury (DILI). We created several versions of the PBPK model using previously published kinetics data from rabbits, and integrated enterohepatic recirculation (EHR) using rat data. Our model showed that active tubular secretion and reabsorption in the kidney are critical in explaining the non-linear renal clearance and urine kinetics of NFT. We subsequently extrapolated the PBPK model to humans. Adapting the physiology to humans led to predictions consistent with human kinetics data, considering a low amount of NFT to be excreted into bile. Model simulations predicted that the liver of individuals with a moderate-to-severe glomerular filtration rate (GFR) is exposed to two-to-three-fold higher concentrations of NFT than individuals with a normal GFR, which coincided with a substantial reduction in the NFT urinary concentration. In conclusion, people with renal insufficiency may be at a higher risk of developing DILI due to NFT exposure, while at the same time having a suboptimal therapeutic effect with a high risk of drug resistance. Our PBPK model can in the future be used to predict NFT kinetics in individual patients on the basis of characteristics like age and GFR.

Repurposing of Nitroxoline as an Alternative Primary Amoebic Meningoencephalitis Treatment

Among the pathogenic free-living amoebae (FLA), Naegleria fowleri is the etiological agent of a fatal disease known as primary amoebic meningoencephalitis (PAM). Once infection begins, the lesions generated in the central nervous system (CNS) result in the onset of symptoms leading to death in a short period of time. Currently, there is no standardized treatment against the infection, which, due to the high virulence of the parasite, results in a high case fatality rate (>97%). Therefore, it is essential to search for new therapeutic sources that can generate a rapid elimination of the parasite. In recent years, there have already been several successful examples of drug repurposing, such as Nitroxoline, for which, in addition to its known bioactive properties, anti-Balamuthia activity has recently been described. Following this approach, the anti-Naegleria activity of Nitroxoline was tested. Nitroxoline displayed low micromolar activity against two different strains of N. fowleri trophozoites (IC50 values of 1.63 ± 0.37 µM and 1.17 ± 0.21 µM) and against cyst stages (IC50 of 1.26 ± 0.42 μM). The potent anti-parasitic activity compared to the toxicity produced (selectivity index of 3.78 and 5.25, respectively) in murine macrophages and human cell lines (reported in previous studies), together with the induction of programmed cell death (PCD)-related events in N. fowleri make Nitroxoline a great candidate for an alternative PAM treatment.

In silico and in vitro analysis of the mechanisms of action of nitroxoline against some medically important opportunistic fungi

The increasing resistance to antifungal agents associated with toxicity and interactions turns therapeutic management of fungal infections difficult. This scenario emphasizes the importance of drug repositioning, such as nitroxoline - a urinary antibacterial agent that has shown potential antifungal activity. The aims of this study were to discover the possible therapeutic targets of nitroxoline using an in silico approach, and to determine the in vitro antifungal activity of the drug against the fungal cell wall and cytoplasmic membrane. We explored the biological activity of nitroxoline using PASS, SwissTargetPrediction and Cortellis Drug Discovery Intelligence web tools. After confirmation, the molecule was designed and optimized in HyperChem software. GOLD 2020.1 software was used to predict the interactions between the drug and the target proteins. In vitro investigation evaluated the effect of nitroxoline on the fungal cell wall through sorbitol protection assay. Ergosterol binding assay was carried out to assess the effect of the drug on the cytoplasmic membrane. In silico investigation revealed biological activity with alkane 1-monooxygenase and methionine aminopeptidase enzymes, showing nine and five interactions in the molecular docking, respectively. In vitro results exhibited no effect on the fungal cell wall or cytoplasmic membrane. Finally, nitroxoline has potential as an antifungal agent due to the interaction with alkane 1-monooxygenase and methionine aminopeptidase enzymes, which are not the main human therapeutic targets. These results have potentially revealed a new biological target for the treatment of fungal infections. We also consider that further studies are required to confirm the biological activity of nitroxoline on fungal cells, mainly the confirmation of the alkB gene.

Nitrofurantoin: properties and potential in treatment of urinary tract infection: a narrative review

Nitrofurantoin (NF), a wide-spectrum antibiotic accessible since 1953, is utilized widely to treat urinary tract infections as it usually stays active against drug-resistant uropathogen. The use of Nitrofurantoin has increased exponentially since new guidelines have repositioned it as first-line therapy for uncomplicated lower urinary tract infection (UTI). To, although fluoroquinolones are usually used to re-evaluate the first- and second-line therapies for treating uncomplicated UTI, their level of utilization is thought to be inappropriately excessive and will eventually have a detrimental impact; thus, we hypothesize that NF might be the best choice for this condition, because of its low frequency of utilization and its high susceptibility in common UTI pathogens. It can be concluded from this review that NF can be considered as the most effective drug in the treatment of acute urinary infection, but due to the long-term side effects of this drug, especially in elderly patients, it is essential to introduce some criteria for prescribing NF in cases of chronic UTI.

Assessing the urinary concentration of nitrofurantoin and its antibacterial activity against Escherichia coli, Staphylococcus pseudintermedius, and Enterococcus faecium isolated from dogs with urinary tract infections

Nitrofurantoin, a broad-spectrum nitrofuran class antibiotic, is applied as a first-line antibiotic in treating human urinary tract infections (UTIs) due to its great efficacy and high achievable concentration. The interest in using this antibiotic in companion animals has increased due to the growing demand for effective antibiotics to treat UTIs caused by multidrug-resistant bacteria. Currently, the susceptibility interpretations for nitrofurantoin are based on the breakpoints set for humans, while the canine-specific breakpoints are still unavailable. In this study, we assessed the concentration of nitrofurantoin reaching the dog's urine using the recommended oral dosing regimen. In addition, we examined the efficacy of this breakpoint concentration against the common canine UTI pathogens, Escherichia coli, Staphylococcus pseudintermedius, and Enterococcus faecium. Eight experimental beagle dogs were treated with ~5 mg/kg of nitrofurantoin macrocrystal PO 8qh for 7 days. The urine samples were collected via cystocentesis at 2, 4, and 6 h after administration on day 2 and day 7 and used to quantify nitrofurantoin concentrations by ultra-high performance liquid chromatography. The results showed that 26.13-315.87 μg/mL nitrofurantoin was detected in the dogs' urine with a mean and median concentration of 104.82 and 92.75 μg/mL, respectively. Additionally, individual dogs presented with urinary nitrofurantoin concentrations greater than 64 μg/mL for at least 50% of the dosing intervals. This concentration efficiently killed E. coli, and S. pseudintermedius, but not E. faecium strains carrying an MIC₉₀ value equal to 16, 16, and 128 μg/mL, respectively. Taken together, these results suggest that the value of 64 μg/mL may be set as a breakpoint against UTI pathogens, and nitrofurantoin could be an effective therapeutic drug against E. coli and S. pseudintermedius for canine UTIs.

Using evolutionary principles to make clinical decisions: a case series of urinary tract infections

The principles of evolutionary medicine have significant potential to be useful in a wide variety of clinical situations. Despite this, few demonstrations of clinical applications exist. To address this paucity, a case series applying evolutionary medicine principles to urinary tract infections, a common medical condition is presented. This series demonstrates how applying evolutionary medicine principles can be used to augment clinical decision-making.

Cathepsin inhibitors nitroxoline and its derivatives inhibit SARS-CoV-2 infection

The severity of the SARS-CoV-2 pandemic and the recurring (re)emergence of viruses prompted the development of new therapeutic approaches that target viral and host factors crucial for viral infection. Among them, host peptidases cathepsins B and L have been described as essential enzymes during SARS-CoV-2 entry. In this study, we evaluated the effect of potent selective cathepsin inhibitors as antiviral agents. We demonstrated that selective cathepsin B inhibitors, such as the antimicrobial agent nitroxoline and its derivatives, impair SARS-CoV-2 infection in vitro. Antiviral activity observed at early stage of virus entry was cell-type dependent and correlated well with the intracellular content and enzymatic function of cathepsins B or L. Furthermore, tested inhibitors were effective against the ancestral SARS-CoV-2 D614 as well as against the more recent BA.1_4 (Omicron). Taken together, our results highlight the important role of host cysteine cathepsin B in SARS-CoV-2 virus entry and show that cathepsin-specific inhibitors, such as nitroxoline and its derivatives, could be used to treat COVID-19. Finally, these results also suggest that nitroxoline has potential to be further explored as repurposed drug in antiviral therapy.

Antimicrobial Activity of Gepotidacin Tested against Escherichia coli and Staphylococcus saprophyticus Isolates Causing Urinary Tract Infections in Medical Centers Worldwide (2019 to 2020)

The in vitro activities of gepotidacin and comparator agents against 3,560 Escherichia coli and 344 Staphylococcus saprophyticus collected from female (81.1%) and male (18.9%) patients with urinary tract infections (UTIs) in a global prospective surveillance program in 2019 to 2020 were determined. Isolates collected from 92 medical centers in 25 countries, including the United States, Europe, Latin America, and Japan, were tested for susceptibility by reference methods in a central monitoring laboratory. Gepotidacin inhibited 98.0% (3,488/3,560 isolates) of E. coli and 100% (344/344 isolates) of S. saprophyticus at gepotidacin concentrations of ≤4 μg/mL and ≤0.25 μg/mL, respectively. This activity was largely unaffected with isolates that demonstrated resistance phenotypes to other oral standard-of-care antibiotics, including amoxicillin-clavulanic acid, cephalosporins, fluoroquinolones, fosfomycin, nitrofurantoin, and trimethoprim-sulfamethoxazole. Gepotidacin also inhibited 94.3% (581/616 isolates) of E. coli isolates with an extended-spectrum β-lactamase-producing phenotype, 97.2% (1,085/1,129 isolates) of E. coli isolates resistant to ciprofloxacin, 96.1% (874/899) of E. coli isolates resistant to trimethoprim-sulfamethoxazole, and 96.3% (235/244 isolates) of multidrug-resistant E. coli isolates at gepotidacin concentrations of ≤4 μg/mL. In summary, gepotidacin demonstrated potent activity against a large collection of contemporary UTI E. coli and S. saprophyticus strains collected from patients worldwide. These data support the further clinical development of gepotidacin as a potential treatment option for patients with uncomplicated UTIs.

Interspecies interaction reduces selection for antibiotic resistance in Escherichia coli

Evolution of microbial traits depends on the interaction of a species with its environment as well as with other coinhabiting species. However, our understanding of the evolution of specific microbial traits, such as antibiotic resistance in complex environments is limited. Here, we determine the role of interspecies interactions on the dynamics of nitrofurantoin (NIT) resistance selection among Escherichia coli. We created a synthetic two-species community comprised of two variants of E. coli (NIT susceptible and resistant) and Bacillus subtilis in minimal media with glucose as the sole carbon source. We show that the presence of B. subtilis significantly slows down the selection for the resistant E. coli mutant when NIT is present and that this slowdown is not due to competition for resources. Instead, the dampening of NIT resistance enrichment is largely mediated by extracellular compounds produced by B. subtilis with the peptide YydF playing a significant role. Our results not only demonstrate the impact of interspecies interactions on the evolution of microbial traits but also show the importance of using synthetic microbial systems in unravelling relevant interactions and mechanisms affecting the evolution of antibiotic resistance. This finding implies that interspecies interactions should be considered to better understand and predict resistance evolution in the clinic as well as in nature.

Effective Treatments of UTI—Is Intravesical Therapy the Future?

Urinary tract infection (UTI) afflicts millions of patients globally each year. While the majority of UTIs are successfully treated with orally administered antibiotics, the impact of oral antibiotics on the host microbiota is under close research scrutiny and the potential for dysbiosis is a cause for concern. Optimal treatment of UTI relies upon the selection of an agent which displays appropriate pharmacokinetic-pharmacodynamic (PK-PD) properties that will deliver appropriately high concentrations in the urinary tract after oral administration. Alternatively, high local concentrations of antibiotic at the urothelial surface can be achieved by direct instillation into the urinary tract. For antibiotics with the appropriate physicochemical properties, this can be of critical importance in cases for which an intracellular urothelial bacterial reservoir is suspected. In this review, we summarise the underpinning biopharmaceutical barriers to effective treatment of UTI and provide an overview of the evidence for the deployment of the intravesical administration route for antibiotics.

Half-Sandwich Ruthenium Arene Complexes Bearing Clinically Approved Drugs as Ligands: The Importance of Metal-Drug Synergism in Metallodrug Design

A novel strategy in metallodrug discovery today is incorporating clinically approved drugs into metal complexes as coordinating ligands. Using this strategy, various drugs have been repurposed to prepare organometallic complexes to overcome the resistance of drugs and to design promising alternatives to currently available metal-based drugs. Notably, the combination of organoruthenium moiety and clinical drug in a single molecule has been shown, in some instances, to enhance pharmacological activity and reduce toxicity in comparison to the parent drug. Thus, for the past two decades, there has been increasing interest in exploiting metal-drug synergism to develop multifunctional organoruthenium drug candidates. Herein, we summarized the recent reports of rationally designed half-sandwich Ru(arene) complexes containing different FDA-approved drugs. This review also focuses on the mode of coordination of drugs, ligand-exchange kinetics, mechanism of action, and structure-activity relationship of organoruthenated complexes containing drugs. We hope this discussion may serve to shed light on future developments in ruthenium-based metallopharmaceuticals.

Susceptibility of Aerococcus urinae and Aerococcus sanguinicola to Standard Antibiotics and to Nitroxoline

Aerococcus urinae and Aerococcus sanguinicola have been increasingly recognized as causative agents of urinary tract infection (UTI) during the last decade. Nitroxoline achieves high urinary concentrations after oral administration and is recommended in uncomplicated UTI in Germany, but its activity against Aerococcus spp. is unknown. The aim of this study was to assess the in vitro susceptibility of clinical Aerococcus species isolates to standard antibiotics and to nitroxoline. Between December 2016 and June 2018, 166 A. urinae and 18 A. sanguinicola isolates were recovered from urine specimens sent to the microbiology laboratory of the University Hospital of Cologne, Germany. Susceptibility to standard antimicrobials was analyzed by disk diffusion (DD) according to EUCAST methodology, nitroxoline was tested by DD and agar dilution. Susceptibility of Aerococcus spp. to benzylpenicillin, ampicillin, meropenem, rifampicin, nitrofurantoin, and vancomycin was 100% and resistance was documented only against ciprofloxacin (20 of 184; 10.9%). MICs of nitroxoline in A. urinae isolates were low (MIC50/90 1/2 mg/L) while significantly higher MICs were observed in A. sanguinicola (MIC50/90 64/128 mg/L). If the EUCAST nitroxoline breakpoint for E. coli and uncomplicated UTI was applied (16 mg/L), 97.6% of A. urinae isolates would be interpreted as susceptible while all A. sanguinicola isolates would be considered resistant. Nitroxoline demonstrated high activity against clinical A. urinae isolates, but low activity against A. sanguinicola. Nitroxoline is an approved antimicrobial for UTI and could be an alternative oral drug to treat A. urinae urinary tract infection, yet clinical studies are needed to demonstrate this potential in vivo. IMPORTANCE A. urinae and A. sanguinicola have been increasingly recognized as causative agents in urinary tract infections. Currently, there are few data available on the activity of different antibiotics against these species and no data on nitroxoline. We demonstrate that clinical isolates in Germany are highly susceptible to ampicillin, while resistance to ciprofloxacin was common (10.9%). Additionally, we show that nitroxoline is highly active against A. urinae, but not against A. sanguinicola, which based on the presented data, should be considered intrinsically resistant. The presented data will help to improve the therapy of urinary tract infections by Aerococcus species.

Activity of the old antimicrobial nitroxoline against Mycobacterium abscessus complex isolates

OBJECTIVES

The old antimicrobial nitroxoline is approved to treat urinary tract infection (UTI) and is currently rediscovered for treatment of drug resistant pathogens. Mycobacteria of the Mycobacterium abscessus complex (MYABS) are rapid-growing nontuberculous mycobacteria that are associated with difficult to treat infections of the lungs in patients with pulmonary disorders such as cystic fibrosis. In this study we assessed the in vitro activity of nitroxoline against molecularly characterized drug-resistant MYABS isolates from clinical samples to address potential repurposing of nitroxoline in difficult-to-treat MYABS infection.

METHODS

The isolates originated from clinical samples collected between 2010 and 2019 at the University Hospital of Cologne, Germany (N=16; 10/16 M. abscessus Spp. abscessus, 4/16 M. abscessus Spp. massiliense, 2/16 M. abscessus Spp. bolletii). Nitroxoline activity was compared to standard antimicrobials recommended for treatment of MYABS infection. For drug susceptibility testing of nitroxoline and comparators broth microdilution was performed based on current Clinical and Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Nitroxoline yielded a MIC₉₀ of 4 mg/L (range 2-4 mg/L), which is two twofold dilutions below the current EUCAST susceptibility breakpoint of ≤ 16 mg/L (limited to uncomplicated UTI and Escherichia coli). Resistance to other antimicrobials was common in our cohort (16/16 isolates resistant to ciprofloxacin, imipenem and doxycycline; 12/16 isolates resistant to tobramycin; 9/16 isolates resistant to cefoxitin; 7/16 isolates resistant to clarithromycin; 2/16 isolates resistant to amikacin).

CONCLUSION

Nitroxoline has a promising in vitro activity against drug-resistant MYABS isolates. Future studies should investigate this finding with macrophage and in vivo models.

Nitrofurantoin failure in males with an uncomplicated urinary tract infection: a primary care observational cohort study

BACKGROUND

Nitrofurantoin is the first-choice antibiotic treatment for uncomplicated urinary tract infections (UTIs) in males according to the Dutch primary care UTI guideline. However, prostate involvement may be undetected and renders this treatment less suitable.

AIM

To compare the nitrofurantoin failure fraction with that found with use of other antibiotics in adult males diagnosed by their GP with an uncomplicated UTI, as well as GP adherence to the Dutch primary care UTI guideline.

DESIGN AND SETTING

Retrospective observational cohort study using routine healthcare data for males seeking care at GP practices participating in the Julius GP Network from 2014 to 2020.

METHOD

Medical records were screened for signs and symptoms of complicated UTIs, antibiotic prescriptions, and referrals. Treatment failure was defined as prescription of a different antibiotic within 30 days after initiation of antibiotic therapy and/or acute hospital referral. The effects of age and comorbidities on failure were assessed using multivariable logistic regression.

RESULTS

Most UTI episodes in males were uncomplicated (n = 6805/10 055 episodes, 68%). Nitrofurantoin  was prescribed in 3788 (56%) of uncomplicated UTIs, followed by ciprofloxacin (n = 1887,  28%), amoxicillin/clavulanic acid (n = 470,  7%), and trimethoprim/sulfamethoxazole (n = 285, 4%). Antibiotic failure occurred in  25% (95% confidence interval [CI] = 23 to 26), 10% (95% CI = 9 to 12), 20% (95% CI = 16 to 24), and 14% (95% CI = 10 to 19) of episodes, respectively. The nitrofurantoin failure fraction increased with age. Comorbidities, adjusted for age, were not associated with nitrofurantoin failure.

CONCLUSION

Nitrofurantoin failure was common in males with uncomplicated UTI and increased with age.

Prevalence and Antimicrobial Resistance of Bacterial Uropathogens Isolated from Dogs and Cats

Bacterial urinary tract infection (UTI) is a common diagnosis in companion animal practice and is one of the leading reasons for antimicrobial prescriptions. We analysed 1862 samples from the urinary tract of dogs and cats, submitted to a veterinary microbiological diagnostic laboratory in 2019 and 2020 in Germany. Susceptibility of 962 uropathogenic isolates to 15 antimicrobials, suggested as first- and second-line treatment options for UTI, was determined according to CLSI recommendations. Bacterial growth of uropathogens was detected in 43.9% of dog and in 38.5% of cat samples. Escherichia (E.) coli was the most frequently isolated pathogen (48.4%), followed by Enterococcus spp. (11.9%) and coagulase-positive staphylococci (CoPS; 11.5%). Females were more likely to exhibit a positive microbiological culture. Regarding first-line antibiotics, 93.4% of the most commonly isolated uropathogenic species were susceptible to the first-line antibiotics amoxicillin/clavulanic acid (AMC) and 87.6% to trimethoprim-sulfamethoxazole (SXT), while 76.1% showed decreased susceptibility to ampicillin (AMP). Multidrug resistance (MDR) was detected in 11.9% of E. coli, 50.4% of enterococci, and 42.7% of CoPS; 90.6% of these isolates were susceptible to nitrofurantoin (NIT). Our data indicate that empiric treatment of UTI with AMC or SXT could be recommended and is preferable to treatment with AMX. NIT should be considered for the treatment of MDR uropathogens.

Assessing Clinical Potential of Old Antibiotics against Severe Infections by Multi-Drug-Resistant Gram-Negative Bacteria Using In Silico Modelling

In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria.

Core/Double-Sheath Composite Fibers from Poly(ethylene oxide), Poly(L-lactide) and Beeswax by Single-Spinneret Electrospinning

The conventional approach for preparation of core-sheath fibers is coaxial electrospinning. Single-spinneret electrospinning of emulsions is a much less common method to obtain core-sheath fibers. Core-sheath structure may be generated by electrospinning of homogeneous blend solutions; however, reports on such cases are still scarce. Herein, the preparation of nanofibrous composites from poly(ethylene oxide) (PEO), poly(L-lactide) (PLA) and beeswax (BW) by single-spinneret electrospinning of their homogeneous blend solutions in chloroform is reported. The produced fibers had core/double-sheath structure with a PEO core, PLA inner sheath and BW outer sheath. This original fiber structure was evidenced by transmission electron microscopy, selective extraction of BW or PEO, and X-ray photoelectron spectroscopy. The PLA/BW double sheath led to hydrophobicity of the PEO/PLA/BW mats. The tensile tests revealed that PEO/PLA/BW mats had substantially improved mechanical behavior as compared to PEO, PLA and PEO/BW mats. PEO/PLA/BW mats can be used as drug carriers as evidenced by the one-pot incorporation of the model drug 5-nitro-8-hydroxyquinoline (NQ) into the fibrous materials. Microbiological tests showed that PEO/PLA/BW/NQ had antimicrobial activity. Therefore, the new materials are promising for wound healing applications.

Stability study of extemporaneously compounded nitrofurantoin oral suspensions for pediatric patients

AIM

To evaluate the stability of nitrofurantoin suspended in different extemporaneously compounded vehicles after storage at 4°C and at 25°C. To formulate an effective, readily available vehicle that can guarantee extended stability and precise dosing.

Chelation in Antibacterial Drugs: From Nitroxoline to Cefiderocol and Beyond

In the era of escalating antimicrobial resistance, the need for antibacterial drugs with novel or improved modes of action (MOAs) is a health concern of utmost importance. Adding or improving the chelating abilities of existing drugs or finding new, nature-inspired chelating agents seems to be one of the major ways to ensure progress. This review article provides insight into the modes of action of antibacterial agents, class by class, through the perspective of chelation. We covered a wide scope of antibacterials, from a century-old quintessential chelating agent nitroxoline, currently unearthed due to its newly discovered anticancer and antibiofilm activities, over the commonly used antibacterial classes, to new cephalosporin cefiderocol and a potential future class of tetramates. We show the impressive spectrum of roles that chelation plays in antibacterial MOAs. This, by itself, demonstrates the importance of understanding the fundamental chemistry behind such complex processes.

Transcript Profiling of Nitroxoline-Treated Biofilms Shows Rapid Up-regulation of Iron Acquisition Gene Clusters

Bacterial biofilms are surface-attached communities of slow- or non-replicating cells embedded within a protective matrix of biomolecules. Unlike free-floating planktonic bacteria, biofilms are innately tolerant to conventional antibiotics and are prevalent in recurring and chronic infections. Nitroxoline, a broad-spectrum biofilm-eradicating agent, was used to probe biofilm viability. Transcript profiling (RNA-seq) showed that 452 of 2594 genes (17.4%) in methicillin-resistant Staphylococcus aureus (MRSA) biofilms were differentially expressed after a 2 h treatment of nitroxoline. WoPPER analysis and time-course validation (RT-qPCR) revealed that gene clusters involved in iron acquisition (sbn, isd, MW2101, MW0695, fhu, and feo) were rapidly up-regulated following nitroxoline treatment, which is indicative of iron starvation in MRSA biofilms. In addition, genes related to oligopeptide transporters and riboflavin biosynthesis were found to be up-regulated, while genes related to carotenoid biosynthesis and nitrate assimilation were down-regulated. RT-qPCR experiments revealed that iron uptake transcripts were also up-regulated in established Staphylococcus epidermidis and Acinetobacter baumannii biofilms following nitroxoline treatment. Overall, we show RNA-seq to be an ideal platform to define cellular pathways critical for biofilm survival, in addition to demonstrating the need these bacterial communities have for iron.

Antimicrobial activity of clioquinol and nitroxoline: a scoping review

Clioquinol and nitroxoline, two drugs with numerous pharmacological properties fallen into disuse for many decades. The first was considered dangerous due to contraindications and the second mainly because was taken as ineffective, despite its known antibacterial activity. In the last decades, the advances in pharmaceutical chemistry, molecular biology, toxicology and genetics allowed to better understand the cellular action of these compounds, some toxicological issues and/or activity scopes. Thus, a new opportunity for these drugs to be considered as potential antimicrobial agents has arisen. This review contemplates the trajectory of clioquinol and nitroxoline from their emergence to the present day, emphasizing the new studies that indicate the possibility of reintroduction for specific cases.

Activity of Drug Combinations against Mycobacterium abscessus Grown in Aerobic and Hypoxic Conditions

Infections caused by Mycobacterium abscessus (Mab), an environmental non-tuberculous mycobacterium, are difficult to eradicate from patients with pulmonary diseases such as cystic fibrosis and bronchiectasis even after years of antibiotic treatments. In these people, the low oxygen pressure in mucus and biofilm may restrict Mab growth from actively replicating aerobic (A) to non-replicating hypoxic (H) stages, which are known to be extremely drug-tolerant. After the exposure of Mab A and H cells to drugs, killing was monitored by measuring colony-forming units (CFU) and regrowth in liquid medium (MGIT 960) of 1-day-old A cells (A1) and 5-day-old H cells (H5). Mab killing was defined as a lack of regrowth of drug-exposed cells in MGIT tubes after >50 days of incubation. Out of 18 drugs tested, 14-day treatments with bedaquiline-amikacin (BDQ-AMK)-containing three-drug combinations were very active against A1 + H5 cells. However, drug-tolerant cells (persisters) were not killed, as shown by CFU curves with typical bimodal trends. Instead, 56-day treatments with the nitrocompounds containing combinations BDQ-AMK-rifabutin-clarithromycin-nimorazole and BDQ-AMK-rifabutin-clarithromycin-metronidazole-colistin killed all A1 + H5 Mab cells in 42 and 56 days, respectively, as shown by lack of regrowth in agar and MGIT medium. Overall, these data indicated that Mab persisters may be killed by appropriate drug combinations.

Does Protocatechuic Acid Affect the Activity of Commonly Used Antibiotics and Antifungals?

The aim of this study is to evaluate the efficiency of protocatechuic acid (PCA) in enhancing the commonly used drugs used to fight against nosocomial infection. These drugs are represented by routinely used antibiotics, synthetic chemotherapeutic agents with an antimicrobial spectrum, and antifungals. Three concentrations of PCA were added to 12 types of commercial disks used for antibiotic and antifungal susceptibility and tested against bacterial and yeast strains represented by Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. The results proved that PCA increased up to 50% of the antibacterial activity, especially that of levofloxacin against Staphylococcus aureus and Escherichia coli. These formulations will lead to new drug design ideas containing a smaller amount of antibiotics with the same effectiveness.

In vitro Activity of Repurposed Nitroxoline Against Clinically Isolated Mycobacteria Including Multidrug-Resistant Mycobacterium tuberculosis

Antimicrobial treatment options for mycobacterial infections are limited due to intrinsic resistance and the emergence of acquired resistance in Mycobacterium tuberculosis. Isolates resisting first- and second line drugs are raising concerns about untreatable infections and make the development of new therapeutic strategies more pressing. Nitroxoline is an old oral antimicrobial that is currently repurposed for the treatment of urinary tract infection (UTI). In this study, we report the in vitro activity of nitroxoline against 18 clinical isolates of M. tuberculosis complex (MTBC) (M. tuberculosis N = 16, M. bovis BCG N = 1, M. bovis sp. bovis N = 1). Since nitroxoline achieves high concentrations in the urinary tract, we included all MTBC-isolates from urinary samples sent to our laboratory between 2008 and 2021 (University Hospital of Cologne, Germany). Isolates from other sources (N = 7/18) were added for higher sample size and for inclusion of drug-resistant M. tuberculosis isolates (N = 4/18). Based on our clinical routine the fluorescence-based liquid media system BACTEC MGIT 960 was used for susceptibility testing of nitroxoline and mainstay antitubercular drugs. Nitroxoline yielded a MIC₉₀ of 4 mg/L for MTBC. In all M. tuberculosis isolates nitroxoline MICs were at least two twofold dilutions below the current EUCAST susceptibility breakpoint of ≤16 mg/L (limited to E. coli and uncomplicated UTI). In vitro activity of nitroxoline can be considered excellent, even in multidrug-resistant isolates. Future studies with in vivo models should evaluate a potential role of nitroxoline in the treatment of tuberculosis in the era of drug resistance.

In Vitro Activity of Nitroxoline in Antifungal-Resistant Candida Species Isolated from the Urinary Tract

Infections by drug-resistant fungi are increasingly reported worldwide; however, only few novel antifungals are being developed. The old antimicrobial nitroxoline is currently repurposed for oral treatment of bacterial urinary tract infections (UTI). Previously, antifungal activity has been demonstrated and in contrast to many antifungals nitroxoline reaches high urinary concentrations. In this study, the activity of nitroxoline was assessed in vitro in a collection of yeasts from the German National Reference Centre for Invasive Fungal Infections. Susceptibility was determined by broth microdilution (BMD) and disk diffusion (DD). The collection comprised 45 Candida isolates originating from the urinary tract. MICs of amphotericin, anidulafungin and azoles were analyzed using EUCAST BMD. Among the collection isolates, resistance to antifungals was common, e.g., for fluconazole the MIC_50/90 was 16/>64 mg/L; in contrast MIC_50/90 of nitroxoline was 2/2 mg/L (MIC range 0.25-4 mg/L), which is at least two dilutions below the EUCAST breakpoint for uncomplicated UTI defined for E. coli (susceptible ≤ 16mg/L). Activity of nitroxoline was high irrespective of resistance to other agents. As BMD is labor-intensive, DD was investigated as an alternative method using three different agars. Nitroxoline disks produced large inhibition zones on all agars (≥19mm), but the correlation of MICs and zone diameters was low, with the highest correlation recorded for the CLSI recommended agar for antifungal DD (Pearson's r = -0,52). In conclusion, isolates of different Candida species are highly susceptible to nitroxoline, which could be a promising antimicrobial to treat candiduria caused by multidrug resistant yeasts.

In vitro activity of nitroxoline against carbapenem-resistant Acinetobacter baumannii isolated from the urinary tract

BACKGROUND

The old antimicrobial nitroxoline is currently repurposed for oral treatment of uncomplicated urinary tract infections (UTIs).

OBJECTIVES

To investigate the in vitro activity of nitroxoline against carbapenem-resistant Acinetobacter baumannii (CRAb).

METHODS

From an international collection of previously well-characterized clinical A. baumannii isolates, 34 isolates from urinary tract sources with different carbapenem-resistance mechanisms were selected. Nitroxoline activity was analysed with broth microdilution (BMD), disc diffusion (DD) and within an in vitro biofilm model. MICs of meropenem and imipenem were assessed with BMD. Susceptibility to ciprofloxacin and trimethoprim/sulfamethoxazole was investigated using DD. Escherichia coli ATCC 25922 and A. baumannii NCTC 13304 were used for quality control.

RESULTS

All isolates were carbapenem resistant (MIC90 >32 mg/L for meropenem and imipenem) and most isolates were resistant to ciprofloxacin (33/34) and trimethoprim/sulfamethoxazole (31/34). Nitroxoline yielded MIC50/90 values of 2/2 mg/L (MIC range 1-2 mg/L) and inhibition zone diameters ranging from 20 to 26 mm. In contrast, for definite eradication of biofilm-associated CRAb in vitro, higher nitroxoline concentrations (≥16 to ≥128 mg/L) were necessary for all isolates.

CONCLUSIONS

Nitroxoline showed excellent in vitro activity against a collection of CRAb despite high resistance rates to other antimicrobials for parental and oral therapy of A. baumannii UTI. Currently, nitroxoline is recommended for the treatment of uncomplicated UTI in Germany with a EUCAST breakpoint limited to uncomplicated UTI and E. coli (S ≤16 mg/L). Nitroxoline could be a promising drug for oral treatment of lower UTI caused by CRAb. More data are warranted to correlate these findings with in vivo success rates.

Therapeutic Efficacy of Orally Administered Nitrofurantoin against Animal African Trypanosomosis Caused by Trypanosoma congolense Infection

Animal African trypanosomosis (AAT) leads to emaciation and low productivity in infected animals. Only six drugs are commercially available against AAT; they have severe side effects and face parasite resistance. Thus, the development of novel trypanocidal drugs is urgently needed. Nitrofurantoin, an antimicrobial, is used for treating bacterial urinary tract infections. Recently, we reported the trypanocidal effects of nitrofurantoin and its analogs in vitro. Furthermore, a nitrofurantoin analog, nifurtimox, is currently used to treat Chagas disease and chronic human African trypanosomiasis. Thus, this study was aimed at evaluating the in vivo efficacy of nitrofurantoin in treating AAT caused by Trypanosoma congolense. Nitrofurantoin was orally administered for 7 consecutive days from 4 days post-infection in T. congolense-infected mice, and the animals were observed for 28 days. Compared to the control group, the treatment group showed significantly suppressed parasitemia at 6 days post-infection. Furthermore, survival was significantly prolonged in the group treated with at least 10 mg/kg nitrofurantoin. Moreover, 100% survival and cure was achieved with a dose of nitrofurantoin higher than 30 mg/kg. Thus, oral nitrofurantoin administration has potential trypanocidal efficacy against T. congolense-induced AAT. This preliminary data will serve as a benchmark when comparing future nitrofurantoin-related compounds, which can overcome the significant shortcomings of nitrofurantoin that preclude its viable use in livestock.

Nitroxoline and its derivatives are potent inhibitors of metallo-β-lactamases

Carbapenemases such as metallo-β-lactamases (MBLs) are spreading among Gram-negative bacterial pathogens. Infections due to these multidrug-resistant bacteria constitute a major global health challenge. Therapeutic strategies against carbapenemase producing bacteria include β-lactamase inhibitor combinations. Nitroxoline is a broad-spectrum antibiotic with restricted indication for urinary tract infections. In this study, we report on nitroxoline as an inhibitor of MBLs. We investigate the structure-activity relationships of nitroxoline derivatives considering in vitro MBL inhibitory potency in a fluorescence based assay using purified recombinant MBLs, NDM-1 and VIM-1. We investigated the most potent nitroxoline derivative in combination with imipenem against clinical isolates as well as transformants producing MBL by broth microdilution and time-kill kinetics. Our findings demonstrate that nitroxoline derivatives are potent MBL inhibitors and in combination with imipenem overcome MBL-mediated carbapenem resistance.

OUP accepted manuscript

Nitrofurantoin, a broad-spectrum antibiotic available since 1953, is used widely for the treatment of urinary tract infections as it often retains activity against drug-resistant uropathogens. It is contraindicated in pregnant women at term, and in neonates. Like trimethoprim/sulfamethoxazole, nitrofurantoin carries a warning for patients with known sensitivity to oxidant drugs, notably glucose-6-phosphate dehydrogenase (G6PD) deficiency, in whom it may cause haemolytic anaemia. This is a barrier to uptake in tropical regions where there is a high burden of antimicrobial resistance and where G6PD deficiency is common. Early studies of erythrocyte survival following nitrofurantoin suggest it is less likely to cause oxidant haemolysis in individuals with G6PD deficiency than primaquine. Here we review reports of haemolysis associated with nitrofurantoin from the published literature and from USA (FDA Adverse Event Reporting System; FAERS) and European (VigiBase) pharmacovigilance databases. In total, 318 episodes of haemolytic anaemia were reported and 10 deaths, with 42 (13%) in individuals with confirmed or highly probable G6PD deficiency, out of at least 245 million exposures. A causal link between death and exposure was not reported and a precise risk estimation in G6PD-deficient individuals was not possible as there are few reports from regions where this enzymopathy is most prevalent. The evidence suggests a total daily dose of 200 mg nitrofurantoin may be used for short (3–5 day) course urinary tract infection treatment without G6PD screening when accompanied by appropriate advice. Pharmacovigilance in countries with high prevalence of G6PD-deficiency is recommended to monitor for serious adverse events.

OUP accepted manuscript

Background

With increasing resistance to common antibiotics the treatment of urinary tract infections has become challenging and alternative therapeutic options are needed. In the present study, we evaluate the activity of three older and less frequently used antibiotics against MDR Enterobacterales.

Methods

Susceptibility of mecillinam, temocillin and nitroxoline was assessed in Enterobacterales isolated from urinary specimens with elevated MICs of third-generation cephalosporins. Susceptibility was determined by the recommended reference MIC methods and additionally by disc diffusion. All isolates were characterized for common β-lactamases by phenotypic and molecular assays.

Results

In total 394 Enterobacterales were included. The most common resistance mechanisms were ESBLs (n = 273), AmpC (n = 132), carbapenemases [n = 12, including OXA-48-like (n = 8), VIM (n = 2), KPC (n = 1) and NDM (n = 1)] or others (n = 2). Resistance was observed in 59% of isolates to ceftazidime, in 41% to piperacillin/tazobactam and in 54% to ciprofloxacin. In comparison, resistance was less frequent against mecillinam (15%), temocillin (13%) or nitroxoline (2%). Mecillinam showed higher activity in Enterobacter spp., Escherichia coli and in OXA-48-like-producing isolates compared with temocillin, which was more active in Proteus mirabilis and in ESBL-producing isolates. Activity of nitroxoline was high against all isolates, including carbapenemase-producing isolates. Correlation between disc diffusion and MIC methods was good for mecillinam and moderate for temocillin and nitroxoline.

Conclusions

Mecillinam, temocillin and nitroxoline show good to excellent in vitro activity in MDR Enterobacterales. The activity of mecillinam and temocillin was higher in certain species and restricted depending on β-lactamase production while nitroxoline showed universally high activity irrespective of species or β-lactamase present.

Alterations in chromosomal genes nfsA, nfsB, and ribE are associated with nitrofurantoin resistance in Escherichia coli from the United Kingdom

Antimicrobial resistance in enteric or urinary Escherichia coli is a risk factor for invasive E. coli infections. Due to widespread trimethoprim resistance amongst urinary E. coli and increased bacteraemia incidence, a national recommendation to prescribe nitrofurantoin for uncomplicated urinary tract infection was made in 2014. Nitrofurantoin resistance is reported in <6% urinary E. coli isolates in the UK, however, mechanisms underpinning nitrofurantoin resistance in these isolates remain unknown. This study aimed to identify the genetic basis of nitrofurantoin resistance in urinary E. coli isolates collected from north west London and then elucidate resistance-associated genetic alterations in available UK E. coli genomes. As a result, an algorithm was developed to predict nitrofurantoin susceptibility. Deleterious mutations and gene-inactivating insertion sequences in chromosomal nitroreductase genes nfsA and/or nfsB were identified in genomes of nine confirmed nitrofurantoin-resistant urinary E. coli isolates and additional 11 E. coli isolates that were highlighted by the prediction algorithm and subsequently validated to be nitrofurantoin-resistant. Eight categories of allelic changes in nfsA, nfsB, and the associated gene ribE were detected in 12412 E. coli genomes from the UK. Evolutionary analysis of these three genes revealed homoplasic mutations and explained the previously reported order of stepwise mutations. The mobile gene complex oqxAB, which is associated with reduced nitrofurantoin susceptibility, was identified in only one of the 12412 genomes. In conclusion, mutations and insertion sequences in nfsA and nfsB were leading causes of nitrofurantoin resistance in UK E. coli. As nitrofurantoin exposure increases in human populations, the prevalence of nitrofurantoin resistance in carriage E. coli isolates and those from urinary and bloodstream infections should be monitored.

Uropathogenic Escherichia coli Shows Antibiotic Tolerance and Growth Heterogeneity in an In Vitro Model of Intracellular Infection

Uropathogenic Escherichia coli (UPEC), the major causative agent of urinary tract infections, can invade different types of host cells. To compare the pharmacodynamic properties of antibiotics against intra- and extracellular UPEC, an in vitro model of intracellular infection was established in J774 mouse macrophages infected by the UPEC strain CFT073. We tested antibiotics commonly prescribed against urinary tract infections (gentamicin, ampicillin, nitrofurantoin, trimethoprim, sulfamethoxazole, and ciprofloxacin) and the investigational fluoroquinolone finafloxacin. The metabolic activity of individual bacteria was assessed by expressing the fluorescent reporter protein TIMERbac within CFT073. Concentration-response experiments revealed that all tested antibiotics were much less effective against intracellular bacteria than extracellular ones. Most antibiotics, except fluoroquinolones, were unable to reach a bactericidal effect intracellularly at clinically achievable concentrations. Ciprofloxacin and finafloxacin killed 99.9% of extracellular bacteria at concentrations around the MIC, while for intracellular bacteria, concentrations more than 100× over the MIC were required to achieve a bactericidal effect. Time-kill curves showed that finafloxacin was more rapidly bactericidal in acidic medium than at neutral pH, while the reverse observation was made for ciprofloxacin. Intracellularly, kill curves showed biphasic kinetics for both fluoroquinolones, suggesting the presence of drug-tolerant subpopulations. Flow cytometry analysis of TIMERbac fluorescence revealed a marked heterogeneity in intracellular growth of individual bacteria, suggesting that the presence of subpopulations reaching a state of metabolic dormancy was the main reason for increased antibiotic tolerance of intracellular UPEC.

Retrospective Review on the Safety and Efficacy of Nitrofurantoin for the Treatment of Cystitis in the Veteran Population With or Without Renal Insufficiency

Background

The emergence of antimicrobial resistance in uropathogens has generated interest in the use of nitrofurantoin in controversial populations, such as in males and those with renal dysfunction. The purpose of this study was to compare the efficacy and safety of nitrofurantoin for the treatment of cystitis in males and females with variable degrees of renal dysfunction.

Methods

A retrospective chart review was conducted in adult patients who received nitrofurantoin for acute cystitis in the outpatient setting. The primary outcome was clinical cure compared between males and females and across various renal function groups (creatinine clearances [CrCl] >60 mL/min, 30-60 mL/min, and <30 mL/min) following nitrofurantoin treatment. The secondary outcome was adverse events.

Results

A total of 446 patients were included, with 278 females and 168 males. The overall clinical cure rate was 86.5% (95% CI, 83.0%-89.4%; n = 386). The clinical cure rate did not vary between genders (odds ratio [OR], 0.6; 95% CI 0.35-1.04; P = .085) or between patients with a CrCl >60 mL/min compared with those with CrCl 30-60 mL/min (OR, 1.01; 95% CI, 0.40-2.44; P = 1). The 1 patient with a CrCl <30 mL/min was not included in the analysis. A history of benign prostatic hyperplasia (OR, 0.5; 95% CI, 0.26-0.99; P = .045) or cirrhosis (OR, 0.21; 95% CI, 0.06-0.82; P = .025) was associated with decreased odds of clinical cure. Adverse events occurred in 2% (n = 9) of patients.

Conclusions

There was no statistically significant difference in clinical cure with nitrofurantoin between genders or various renal functions.

Risk factors for treatment failure in women with uncomplicated lower urinary tract infection

Given rising antibiotic resistance and increasing use of delayed prescription for uncomplicated lower urinary tract infections (UTI), patients at risk for treatment failure should be identified early. We assessed risk factors for clinical and microbiological failure in women with lower UTI. This case-control study nested within a randomized clinical trial included all women in the per-protocol population (PPP), those in the PPP with microbiologically confirmed UTI, and those in the PPP with UTI due to Escherichia coli. Cases were women who experienced clinical and/or microbiologic failure; controls were those who did not. Risk factors for failure were assessed using multivariate logistic regression. In the PPP, there were 152 clinical cases for 307 controls. Among 340 women with microbiologically confirmed UTI, 126 and 102 cases with clinical and microbiological failure were considered with, respectively, 214 and 220 controls. Age ≥52 years was independently associated with clinical (adjusted OR 3.01; 95%CI 1.84-4.98) and microbiologic failure (aOR 2.55; 95%CI 1.54-4.25); treatment with fosfomycin was associated with clinical failure (aOR 2.35; 95%CI 1.47-3.80). The association with age persisted among all women, and women with E. coli-related UTI. Diabetes was not an independent risk factor, nor were other comorbidities. Postmenopausal age emerged as an independent risk factor for both clinical and microbiological treatment failure in women with lower UTI and should be considered to define women at-risk for non-spontaneous remission, and thus for delayed antibiotic therapy; diabetes mellitus was not associated with failure.

Antifungal activity of nitroxoline against Candida auris isolates

OBJECTIVES

To investigate the in vitro activity of nitroxoline against a molecularly characterized collection of clinical Candida auris isolates.

METHODS

Thirty-five clinical isolates of C. auris from diverse sources representing all five different C. auris clades were included in the study. Nitroxoline activity was assessed using broth microdilution. Additionally, susceptibility testing by disc diffusion was assessed on RPMI-1640 and Müller-Hinton agar plates. Minimal inhibitory concentrations of the antifungals fluconazole, voriconazole, amphotericin B and anidulafungin were determined.

RESULTS

Nitroxoline MICs ranged from 0.125 to 1 mg/L (MIC_50/90 0.25/0.5 mg/L). Compared with amphotericin B (MIC >1 mg/L in 4/35 isolates), anidulafungin (MIC >0.06 mg/L in 26/35 isolates) and fluconazole (MIC >4 mg/L in 31/35 isolates), in vitro activity of nitroxoline was high. Isolates belonging to clade I had marginally lower nitroxoline MICs (range 0.125-0.5 mg/L, mean MIC 0.375 mg/L) compared with clade III (range 0.5-1 mg/L, mean MIC 0.7 mg/L; p = 0.0094). The correlation of MIC and inhibition zones by disc diffusion was good when using RPMI-agar for disc diffusion, with a Pearson's correlation coefficient of -0.74 (95% CI -0.86 to -0.54).

CONCLUSIONS

Nitroxoline has excellent in vitro activity against C. auris isolates, with MICs of 0.125-1 mg/L (for comparison, the EUCAST breakpoint for uncomplicated urinary tract infection with Escherichia coli is ≤ 16 mg/L). It is an approved, well-tolerated antimicrobial that achieves high urinary concentrations after oral administration and could be a useful treatment option in C. auris candiduria.

Repurposing of Antimicrobial Agents for Cancer Therapy: What Do We Know?

The substantial costs of clinical trials, the lengthy timelines of new drug discovery and development, along the high attrition rates underscore the need for alternative strategies for finding quickly suitable therapeutics agents. Given that most approved drugs possess more than one target tightly linked to other diseases, it encourages promptly testing these drugs in patients. Over the past decades, this has led to considerable attention for drug repurposing, which relies on identifying new uses for approved or investigational drugs outside the scope of the original medical indication. The known safety of approved drugs minimizes the possibility of failure for adverse toxicology, making them attractive de-risked compounds for new applications with potentially lower overall development costs and shorter development timelines. This latter case is an exciting opportunity, specifically in oncology, due to increased resistance towards the current therapies. Indeed, a large body of evidence shows that a wealth of non-cancer drugs has beneficial effects against cancer. Interestingly, 335 drugs are currently being evaluated in different clinical trials for their potential activities against various cancers (Redo database). This review aims to provide an extensive discussion about the anti-cancer activities exerted by antimicrobial agents and presents information about their mechanism(s) of action and stage of development/evaluation.