In vitro evaluation of a new treatment for urinary tract infections caused by nitrate-reducing bacteria

Effects of pH on the Pathogenicity of Escherichia coli and Klebsiella pneumoniae on the Kidney: In Vitro and In Vivo Studies

Urine pH reflects the functional integrity of the body and may influence the virulence of uropathogenic Escherichia coli and Klebsiella pneumoniae, the main causes of urinary tract infections (UTIs). This study evaluated the effects of acidic pH on the pathogenicity of uropathogenic E. coli and K. pneumoniae strains, in vitro and in vivo. Four uropathogenic E. coli and four K. pneumoniae strains were used. Biofilm formation, growth competition indices, motility, and adhesion and invasion of human renal cells were analyzed in media with acidic, neutral, and alkaline pH. A murine lower UTI model was used, with urine adjusted to acidic, neutral, or alkaline pH. At acidic pH, E. coli and K. pneumoniae exhibited higher bacterial concentrations in the kidneys and systemic symptoms, including bacteremia. Alkaline urine pH did not affect bacterial concentrations of any strain. In mice with UTIs caused by E. coli Nu14 and K. pneumoniae HUVR42 and acidic urine pH, histopathological studies of the kidneys showed acute inflammation affecting the urothelium and renal parenchyma, which are traits of acute pyelonephritis. These results indicate that acidic pH could increase the pathogenicity of E. coli and K. pneumoniae in murine models of lower UTI, promoting renal infection and acute inflammation.

Two-dimensional molybdenum disulfide nanosheets evoke nitric oxide-dependent antibacterial effects

Nanomaterials are currently being explored as novel antimicrobial agents. In this study, we first investigated the ability of two-dimensional (2D) molybdenum disulfide (MoS2) nanosheets to trigger neutrophil extracellular traps (NETs) using neutrophil-differentiated HL-60 cells as well as primary human peripheral blood neutrophils. We then addressed whether the MoS2 nanosheets themselves function as antibacterial agents. We found that MoS2 and Na2MoO4 both triggered NETs, as evidenced by the quantification of neutrophil elastase (NE) activity and immunofluorescence staining of extracellular NE, as well as scanning electron microscopy. The release of NETs was found to be nitric oxide (NO)-dependent. We also found that the MoS2 nanosheets but not the soluble salt prompted acellular NO production in the presence of NaNO2. The acellular generation of NO, suggestive of nanozyme properties of the MoS2 nanosheets, was demonstrated by electron paramagnetic resonance analysis. Electrochemical analysis using cyclic voltammetry confirmed the redox transition of the MoS2 nanosheets. Finally, MoS2 nanosheets inhibited the growth of Escherichia coli in the presence of sodium nitrate. Taken together, MoS2 nanosheets triggered cellular effects as well as acellular antibacterial effects, and we provided evidence for nitrite reductase-like properties of MoS2.

Cationic Microbubbles for Non-Selective Binding of Cavitation Nuclei to Bacterial Biofilms

The presence of multi-drug resistant biofilms in chronic, persistent infections is a major barrier to successful clinical outcomes of therapy. The production of an extracellular matrix is a characteristic of the biofilm phenotype, intrinsically linked to antimicrobial tolerance. The heterogeneity of the extracellular matrix makes it highly dynamic, with substantial differences in composition between biofilms, even in the same species. This variability poses a major challenge in targeting drug delivery systems to biofilms, as there are few elements both suitably conserved and widely expressed across multiple species. However, the presence of extracellular DNA within the extracellular matrix is ubiquitous across species, which alongside bacterial cell components, gives the biofilm its net negative charge. This research aims to develop a means of targeting biofilms to enhance drug delivery by developing a cationic gas-filled microbubble that non-selectively targets the negatively charged biofilm. Cationic and uncharged microbubbles loaded with different gases were formulated and tested to determine their stability, ability to bind to negatively charged artificial substrates, binding strength, and, subsequently, their ability to adhere to biofilms. It was shown that compared to their uncharged counterparts, cationic microbubbles facilitated a significant increase in the number of microbubbles that could both bind and sustain their interaction with biofilms. This work is the first to demonstrate the utility of charged microbubbles for the non-selective targeting of bacterial biofilms, which could be used to significantly enhance stimuli-mediated drug delivery to the bacterial biofilm.

Characterization of PACs profile and bioactivity of a novel nutraceutical combining cranberry extracts with different PAC-A oligomers, D-mannose and ascorbic acid: An in vivo/ex vivo evaluation of dual mechanism of action on intestinal barrier and urinary epithelium

In this paper, an A-type procyanidin (PAC)-rich cranberry extract (CB-B) was obtained mixing different extracts and was formulated with D-mannose and ascorbic acid to obtain a novel nutraceutical (URO-F) aimed at preventing non-complicated bacterial urinary tract infections (UTIs). To assess the bioactivity of CB-B and URO-F, urine samples collected from six healthy volunteers undergoing a 2-days oral consumption of 0.41 g/day of CB-B or 10 g/day of URO-F (corresponding to 72 mg/day of PACs) were tested against uropathogenic E. coli (UPEC) incubated on urinary bladder epithelial cells (T24). Urinary markers of CB-B and URO-F consumption were assessed in the same urine output by UPLC-QTOF-based untargeted metabolomics approach. CB-B and URO-F were evaluated for their ability to promote the intestinal barrier function by restoring the trans-epithelial electrical resistance (TEER) and to inhibit the production of inflammatory cytokines in intestinal epithelial Caco2 cells. CB-B was characterized by a high PAC-A content (70% of total PACs) and a broad distribution of different PACs polymers (dimers-hexamers). Urine from subjects consuming CB-B and URO-F showed a significant effect in reducing the adhesion of UPEC to urothelium in vitro, supporting their efficacy as anti-adhesive agents after oral intake. CB-B inhibited the release of cytokine IL-8, and both products were effective in restoring the TEER. Overall, our results show that the beneficial effects of CB-B and URO-F on UTIs are not only due to the antiadhesive activity of cranberry on UPEC in the urothelium, but also to a multi-target activity involving anti-inflammatory and permeability-enhancing effects on intestinal epithelium.

Nitric oxide for the prevention and treatment of viral, bacterial, protozoal and fungal infections

Although the antimicrobial potential of nitric oxide (NO) is widely published, it is little used clinically. NO is a key signalling molecule modulating vascular, neuronal, inflammatory and immune responses. Endogenous antimicrobial activity is largely mediated by high local NO concentrations produced by cellular inducible nitric oxide synthase, and by derivative reactive nitrogen oxide species including peroxynitrite and S-nitrosothiols. NO may be taken as dietary substrate (inorganic nitrate, L-arginine), and therapeutically as gaseous NO, and transdermal, sublingual, oral, intranasal and intravenous nitrite or nitrate. Numerous preclinical studies have demonstrated that NO has generic static and cidal activities against viruses (including β-coronaviruses such as SARS-CoV-2), bacteria, protozoa and fungi/yeasts  in vitro. Therapeutic effects have been seen in animal models  in vivo, and phase II trials have demonstrated that NO donors can reduce microbial infection. Nevertheless, excess NO, as occurs in septic shock, is associated with increased morbidity and mortality. In view of the dose-dependent positive and negative effects of NO, safety and efficacy trials of NO and its donors are needed for assessing their role in the prevention and treatment of infections. Trials should test dietary inorganic nitrate for pre- or post-exposure prophylaxis and gaseous NO or oral, topical or intravenous nitrite and nitrate for treatment of mild-to-severe infections, including due to SARS-CoV-2 (COVID-19). This review summarises the evidence base from  in vitro, in vivo and early phase clinical studies of NO activity in viral, bacterial, protozoal and fungal infections.

Nitric oxide for the prevention and treatment of viral, bacterial, protozoal and fungal infections

Although the antimicrobial potential of nitric oxide (NO) is widely published, it is little used clinically. NO is a key signalling molecule modulating vascular, neuronal, inflammatory and immune responses. Endogenous antimicrobial activity is largely mediated by high local NO concentrations produced by cellular inducible nitric oxide synthase, and by derivative reactive nitrogen oxide species including peroxynitrite and S-nitrosothiols. NO may be taken as dietary substrate (inorganic nitrate, L-arginine), and therapeutically as gaseous NO, and transdermal, sublingual, oral, intranasal and intravenous nitrite or nitrate. Numerous preclinical studies have demonstrated that NO has generic static and cidal activities against viruses (including β-coronaviruses such as SARS-CoV-2), bacteria, protozoa and fungi/yeasts  in vitro. Therapeutic effects have been seen in animal models  in vivo, and phase II trials have demonstrated that NO donors can reduce microbial infection. Nevertheless, excess NO, as occurs in septic shock, is associated with increased morbidity and mortality. In view of the dose-dependent positive and negative effects of NO, safety and efficacy trials of NO and its donors are needed for assessing their role in the prevention and treatment of infections. Trials should test dietary inorganic nitrate for pre- or post-exposure prophylaxis and gaseous NO or oral, topical or intravenous nitrite and nitrate for treatment of mild-to-severe infections, including due to SARS-CoV-2 (COVID-19). This review summarises the evidence base from  in vitro, in vivo and early phase clinical studies of NO activity in viral, bacterial, protozoal and fungal infections.

The Bactericidal Tandem Drug, AB569: How to Eradicate Antibiotic-Resistant Biofilm Pseudomonas aeruginosa in Multiple Disease Settings Including Cystic Fibrosis, Burns/Wounds and Urinary Tract Infections

The life-threatening pandemic concerning multi-drug resistant (MDR) bacteria is an evolving problem involving increased hospitalizations, billions of dollars in medical costs and a remarkably high number of deaths. Bacterial pathogens have demonstrated the capacity for spontaneous or acquired antibiotic resistance and there is virtually no pool of organisms that have not evolved such potentially clinically catastrophic properties. Although many diseases are linked to such organisms, three include cystic fibrosis (CF), burn/blast wounds and urinary tract infections (UTIs), respectively. Thus, there is a critical need to develop novel, effective antimicrobials for the prevention and treatment of such problematic infections. One of the most formidable, naturally MDR bacterial pathogens is Pseudomonas aeruginosa (PA) that is particularly susceptible to nitric oxide (NO), a component of our innate immune response. This susceptibility sets the translational stage for the use of NO-based therapeutics during the aforementioned human infections. First, we discuss how such NO therapeutics may be able to target problematic infections in each of the aforementioned infectious scenarios. Second, we describe a recent discovery based on years of foundational information, a novel drug known as AB569. AB569 is capable of forming a "time release" of NO from S-nitrosothiols (RSNO). AB569, a bactericidal tandem consisting of acidified NaNO₂ (A-NO₂ ^-) and Na₂-EDTA, is capable of killing all pathogens that are associated with the aforementioned disorders. Third, we described each disease state in brief, the known or predicted effects of AB569 on the viability of PA, its potential toxicity and highly remote possibility for resistance to develop. Finally, we conclude that AB569 can be a viable alternative or addition to conventional antibiotic regimens to treat such highly problematic MDR bacterial infections for civilian and military populations, as well as the economical burden that such organisms pose.

Symptoms, risk factors, diagnosis and treatment of urinary tract infections

Urinary tract infection (UTI) is a common microbial infection found in all ages and sexes which involves inflammation of the urinary tract. These infections can range from simple bladder inflammation, that is, cystitis, to severe cases of uroseptic shock. UTI ranks as the number 1 infection that leads to a prescription of antibiotics after a doctor's visit. These infections are sometimes distressing and even life threatening, and both males (12%) and females (40%) have at least one symptomatic UTI throughout their lives. Diagnostic failures in case of bacterial infections are the main contributing factor in improper use of antibiotics, delay in treatment and low survival rate in septic conditions. So, early diagnosis and appropriate therapy with antibiotics are the most significant requirements for preventing complicated UTI conditions such as urosepsis. This review article summarises the symptoms of the UTIs and the associated risk factors to it. The various conventional and recent diagnostic methods were also discussed in this review, along with treatment therapies with or without antibiotics.

Urinary tract infection: recent insight into the evolutionary arms race between uropathogenic Escherichia coli and our immune system

Urinary tract infections (UTIs) are among the most common bacterial infections worldwide. Humans evolved various immune-dependent and independent defense mechanisms, while pathogens evolved multiple virulence factors to fight back. This article summarizes recent findings regarding the arms race between hosts and pathogens in UTIs. It was recently reported that macrophage subsets regulate neutrophil-mediated defense in primary UTIs but seem to subvert adaptive immunity upon re-infection. Moreover, some bacterial strains can survive inside macrophages, leading to recurrent infections. Inflammasome activation results in infected host cell death and pathogen release, facilitating the removal of intracellular bacteria. As a counteraction, some bacteria evolved mechanisms to disrupt inflammasome activation. Mucosal-associated invariant T cells are further effectors that can lyse infected epithelial cells and release intracellular bacteria. Once released, the bacteria are phagocytosed by neutrophils. However, some bacteria can inhibit neutrophil migration and deprive neutrophils of nutrients. Furthermore, the complement system, considered generally bactericidal, is exploited by the bacteria for cellular invasion. Another weapon against UTI is antimicrobial peptides, e.g. ribonuclease 7, but its production is inhibited by certain bacterial strains. Thus the arms race in UTI is ongoing, and knowing the enemy's methods can help in developing new drugs to win the race.

Host-Derived Nitric Oxide and Its Antibacterial Effects in the Urinary Tract

Urinary tract infection (UTI) is one of the most common bacterial infections in humans, and the majority are caused by uropathogenic Escherichia coli (UPEC). The rising antibiotic resistance among UPEC and the frequent failure of antibiotics to effectively treat recurrent UTI and catheter-associated UTI motivate research on alternative ways of managing UTI. Abundant evidence indicates that the toxic radical nitric oxide (NO), formed by activation of the inducible nitric oxide synthase, plays an important role in host defence to bacterial infections, including UTI. The major source of NO production during UTI is from inflammatory cells, especially neutrophils, and from the uroepithelial cells that are known to orchestrate the innate immune response during UTI. NO and reactive nitrogen species have a wide range of antibacterial targets, including DNA, heme proteins, iron-sulfur clusters, and protein thiol groups. However, UPEC have acquired a variety of defence mechanisms for protection against NO, such as the NO-detoxifying enzyme flavohemoglobin and the NO-tolerant cytochrome bd-I respiratory oxidase. The cytotoxicity of NO-derived intermediates is nonspecific and may be detrimental to host cells, and a balanced NO production is crucial to maintain the tissue integrity of the urinary tract. In this review, we will give an overview of how NO production from host cells in the urinary tract is activated and regulated, the effect of NO on UPEC growth and colonization, and the ability of UPEC to protect themselves against NO. We also discuss the attempts that have been made to develop NO-based therapeutics for UTI treatment.

Hydrogen Sulfide Sensing through Reactive Sulfur Species (RSS) and Nitroxyl (HNO) in Enterococcus faecalis

Recent studies of hydrogen sulfide (H2S) signaling implicate low molecular weight (LMW) thiol persulfides and other reactive sulfur species (RSS) as signaling effectors. Here, we show that a CstR protein from the human pathogen Enterococcus faecalis ( E. faecalis), previously identified in Staphylococcus aureus ( S. aureus), is an RSS-sensing repressor that transcriptionally regulates a cst-like operon in response to both exogenous sulfide stress and Angeli's salt, a precursor of nitroxyl (HNO). E. faecalis CstR reacts with coenzyme A persulfide (CoASSH) to form interprotomer disulfide and trisulfide bridges between C32 and C61', which negatively regulate DNA binding to a consensus CstR DNA operator. A Δ cstR strain exhibits deficiency in catheter colonization in a catheter-associated urinary tract infection (CAUTI) mouse model, suggesting sulfide regulation and homeostasis is critical for pathogenicity. Cellular polysulfide metabolite profiling of sodium sulfide-stressed E. faecalis confirms an increase in both inorganic polysulfides and LMW thiols and persulfides sensed by CstR. The cst-like operon encodes two authentic thiosulfate sulfurtransferases and an enzyme we characterize here as an NADH and FAD-dependent coenzyme A (CoA) persulfide reductase (CoAPR) that harbors an N-terminal CoA disulfide reductase (CDR) domain and a C-terminal rhodanese homology domain (RHD). Both cysteines in the CDR (C42) and RHD (C508) domains are required for CoAPR activity and complementation of a sulfide-induced growth phenotype of a S. aureus strain lacking cstB, encoding a nonheme FeII persulfide dioxygenase. We propose that S. aureus CstB and E. faecalis CoAPR employ orthogonal chemistries to lower CoASSH that accumulates under conditions of cellular sulfide toxicity and signaling.

Non-surgical management of recurrent urinary tract infections in women

One in three women will experience a clinically significant urinary tract infection (UTI) by age twenty-four and almost half will have at least one in their lifetime. Recurrent UTIs (rUTIs) are defined as having greater than two infections in a 6-month period, or three infections over twelve months, with complete resolution for at least two weeks. These may be due to relapse from incomplete treatment (persistence) or re-infection (new source). It may be difficult to distinguish between the two, where the same organism is cultured. There are several risk factors for rUTIs including an impairment of the body's immune system and virulence factors. Reversible or treatable causes are sought and excluded in the patient's initial review. Patient's with rUTI are often complex and difficult to manage. The long-term management options in women are multimodal and should focus on prevention of relapse and recurrence. Behavioural factors include adequate hydration, care with sexual hygiene, reducing one's body mass index (BMI) and post-void residual (PVR) volume. There are several non-antimicrobial options for rUTIs which have become a multi-billion-dollar business. Unfortunately, there are numerous studies which fail to show any major benefit or having conflicting data. Vaccines are currently being explored as a prevention strategy, delivered through injection, intra-nasal sprays, or vaginal suppositories, which are made from combinations of heat killed uro-pathogenic strains. There are no widely available vaccines at present due to limited clinical success. It is well established that appropriate antibiotic therapy results in higher rates of symptom relief and bacterial eradication in women with uncomplicated cystitis. There are several options for antimicrobial use which have been shown to be highly effective in reducing the risk of rUTI in women. The pain and discomfort of the UTI must be balanced with the cost and risk of developing resistance when using antimicrobials. Continuous prophylaxis, pre- and post-coital voiding, and self-starting are the three commonly accepted options for prophylaxis. The choice between these will depend upon patient preference, cultures and previous pattern of infection. Intra-vesical instillation of hyaluronic acid and chondroitin sulphate have been used for glycosaminoglycan (GAG) layer replenishment for many indications, including interstitial cystitis, overactive bladder syndrome, radiation cystitis and prevention of rUTI. At present, intra-vesical therapies are reserved for only those with the most unresponsive rUTIs. The principles of treating rUTI are to break the cycle and to treat any reversible causes. With our ever-expanding research knowledge, there are now many useful products that may be used for the successful treatment of rUTI. A management plan including a combination of a non-antimicrobial and selective antimicrobial regime for a minimum of six months should be considered. It is a prudent clinician that clearly defines this management plan, with reassurance of a finite period of therapy.

It is rocket science - why dietary nitrate is hard to 'beet'! Part II: further mechanisms and therapeutic potential of the nitrate-nitrite-NO pathway

Dietary nitrate (found in green leafy vegetables such as rocket and in beetroot) is now recognized to be an important source of nitric oxide, via the nitrate-nitrite-NO pathway. Dietary nitrate confers several cardiovascular beneficial effects on blood pressure, platelets, endothelial function, mitochondrial efficiency and exercise. Having described key twists and turns in the elucidation of the pathway and the underlying mechanisms in Part I, we explore the more recent developments which have served to confirm mechanisms, extend our understanding, and discover new properties and potential therapeutic uses of the pathway in Part II. Even the established dependency on low oxygen states for bioactivation of nitrite has recently been challenged. Dietary nitrate appears to be an important component of 'healthy diets', such as the DASH diet to lower blood pressure and the Mediterranean diet, with its potential to lower cardiovascular risk, possibly through beneficial interactions with a range of other constituents. The World Cancer Research Foundation report strong evidence for vegetables including spinach and lettuce (high nitrate-containing) decreasing cancer risk (mouth, pharynx, larynx, oesophagus and stomach), summarized in a 'Nitrate-Cancer Risk Veg-Table'. The European Space Agency recommends that beetroot, lettuce, spinach and rocket (high-nitrate vegetables) are grown to provide food for long-term space missions. Nitrate, an ancient component of rocket fuel, could support sustainable crops for healthy humans.

Urinary alkalisation for symptomatic uncomplicated urinary tract infection in women

BACKGROUND

Uncomplicated urinary tract infection (UTI) is the most common bacterial infection in women, characterised by dysuria and urinary frequency. Urinary alkalisers are widely used in some countries for the symptomatic treatment of uncomplicated UTI, and they are recommended in some national formularies. However, there is a lack of empirical evidence to support their use for UTI and some healthcare guidelines advise against their use.

OBJECTIVES

We aimed to look at the benefits and harms of the use of urinary alkalisers for the treatment of uncomplicated UTIs in adult women.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 19 January 2016 through contact with the Trials Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs on the use of (any) urinary alkalisers (either exclusively or non-exclusively) for the symptomatic treatment of uncomplicated UTI amongst women aged 16 and over, were included. Studies were eligible if they included patients whose diagnosis of UTI was decided by symptoms alone, or positive urine dipstick test or urine culture; and patients with recurrent UTI, provided patients had no symptoms of UTI in the two weeks prior to the onset of symptoms that lead them to seek medical advice. Studies were ineligible if they studied patients with complicated UTIs; immune-compromising conditions; acute pyelonephritis; or chronic conditions such as interstitial cystitis.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed and screened papers, and this was repeated by two separate authors (independently). An additional investigator acted as arbitrator, where necessary. There were no papers which fulfilled the inclusion criteria for this review, and therefore no data extraction was performed.

MAIN RESULTS

Our search identified 172 potential studies for inclusion. However, following assessment none fulfilled the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

Until relevant evidence is generated from randomised trials, the safety and efficacy of urinary alkalisers for the symptomatic treatment of uncomplicated UTI remains unknown.

Role of Hypoxia Inducible Factor-1α (HIF-1α) in Innate Defense against Uropathogenic Escherichia coli Infection

Uropathogenic E. coli (UPEC) is the primary cause of urinary tract infections (UTI) affecting approximately 150 million people worldwide. Here, we revealed the importance of transcriptional regulator hypoxia-inducible factor-1 α subunit (HIF-1α) in innate defense against UPEC-mediated UTI. The effects of AKB-4924, a HIF-1α stabilizing agent, were studied using human uroepithelial cells (5637) and a murine UTI model. UPEC adherence and invasion were significantly reduced in 5637 cells when HIF-1α protein was allowed to accumulate. Uroepithelial cells treated with AKB-4924 also experienced reduced cell death and exfoliation upon UPEC challenge. In vivo, fewer UPEC were recovered from the urine, bladders and kidneys of mice treated transurethrally with AKB-4924, whereas increased bacteria were recovered from bladders of mice with a HIF-1α deletion. Bladders and kidneys of AKB-4924 treated mice developed less inflammation as evidenced by decreased pro-inflammatory cytokine release and neutrophil activity. AKB-4924 impairs infection in uroepithelial cells and bladders, and could be correlated with enhanced production of nitric oxide and antimicrobial peptides cathelicidin and β-defensin-2. We conclude that HIF-1α transcriptional regulation plays a key role in defense of the urinary tract against UPEC infection, and that pharmacological HIF-1α boosting could be explored further as an adjunctive therapy strategy for serious or recurrent UTI.

Urinary tract infection (UTI), commonly caused by uropathogenic E.coli (UPEC), affects more than 150 million people worldwide, resulting in 14 million hospital visits per year and an estimated total cost of 6 billion dollars in direct health care. Due to the high prevalence of UTI and rapid emergence of antibiotic-resistant bacteria, new effective strategies to prevent and treat UTI are urgently needed. Here, we describe a global regulatory role of transcription factor hypoxia-inducible factor-1 (HIF-1) in innate antimicrobial defense against UPEC. HIF-1 stabilization reduces UPEC attachment to and invasion of uroepithelial cells, and protects bladders from UPEC-mediated cytotoxicity in vivo. In the murine UTI model, we found normal bladder HIF-1 expression is required for efficient UPEC clearance, since HIF-1-deficient mice suffer more severe infection than normal mice. Further studies showed that key elements of host protection provided by HIF-1 regulation are uroepithelial cell nitric oxide and antimicrobial peptide production. This study provides valuable insight into the importance of HIF-1 in supporting host immunity during UTI and its potential as a therapeutic target.

Rapid identification and susceptibility testing of uropathogenic microbes via immunosorbent ATP-bioluminescence assay on a microfluidic simulator for antibiotic therapy

The incorporation of pathogen identification with antimicrobial susceptibility testing (AST) was implemented on a concept microfluidic simulator, which is well suited for personalizing antibiotic treatment of urinary tract infections (UTIs). The microfluidic device employs a fiberglass membrane sandwiched between two polypropylene components, with capture antibodies immobilized on the membrane. The chambers in the microfluidic device share the same geometric distribution as the wells in a standard 384-well microplate, resulting in compatibility with common microplate readers. Thirteen types of common uropathogenic microbes were selected as the analytes in this study. The microbes can be specifically captured by various capture antibodies and then quantified via an ATP bioluminescence assay (ATP-BLA) either directly or after a variety of follow-up tests, including urine culture, antibiotic treatment, and personalized antibiotic therapy simulation. Owing to the design of the microfluidic device, as well as the antibody specificity and the ATP-BLA sensitivity, the simulator was proven to be able to identify UTI pathogen species in artificial urine samples within 20 min and to reliably and simultaneously verify the antiseptic effects of eight antibiotic drugs within 3-6 h. The measurement range of the device spreads from 1 × 10(3) to 1 × 10(5) cells/mL in urine samples. We envision that the medical simulator might be broadly employed in UTI treatment and could serve as a model for the diagnosis and treatment of other diseases.

Tuning the direct growth of Agseeds into bimetallic Ag@Cu nanorods on surface functionalized electrochemically reduced graphene oxide: enhanced nitrite detection

The significant challenges in the growth of 1D nanostructure on reduced graphene oxide surface were addressed. It enabled the electrooxidation of the nitrite ion (NO₂⁻) with high sensitivity and good detection limit of 1 nM.

A capacitive touch screen sensor for detection of urinary tract infections in portable biomedical devices

Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria. However, the urine sampling and analysis required for these methods can be both time-consuming and complex. This work proposes a capacitive touch screen sensor (CTSS) concept as feasible alternative for a portable UTI detection device. Finite element method (FEM) simulations were conducted with a CTSS model. An exponential response of the model to increasing amounts of E. coli and liquid samples was observed. A measurable capacitance change due to E. coli presence and a tangible difference in the response given to urine and water samples were also detected. Preliminary experimental studies were also conducted on a commercial CTSS using liquid solutions with increasing amounts of dissolved ions. The CTSS was capable of distinguishing different volumes of liquids, also giving an exponential response. Furthermore, the CTSS gave higher responses to solutions with a superior amount of ions. Urine samples gave the top response among tested liquids. Thus, the CTSS showed the capability to differentiate solutions by their ionic content.

Control of pathogen growth and biofilm formation using a urinary catheter that releases antimicrobial nitrogen oxides

Antibacterial nitrogen oxides including nitric oxide are formed from nitrite under acidic conditions. In a continuous-flow model of the urinary bladder we used the retention cuff of an all-silicone Foley catheter as a depot for export of nitrogen oxides. The cuff was filled with sodium nitrite (50mM) and an acidic buffer solution (pH 3.6) and the growth of nine common uropathogens in the surrounding artificial urine was measured along with biofilm formation on the catheter surface. In experiments with control catheters (NaCl) bacteria grew readily and biofilm developed within hours in five of nine strains. In contrast, with test catheters bacterial counts were markedly reduced and biofilm formation by Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter cloace was prevented, whereas Escherichia coli and Staphylococcus aureus were unaffected. We conclude that antibacterial nitrogen oxides generated in the retention cuff of a urinary catheter diffuse into urine and prevent the growth of urinary pathogens and biofilm formation. Although promising, future studies will reveal if this novel approach can be clinically useful for the prevention of catheter-associated urinary tract infections.

Management of recurrent urinary tract infections in healthy adult women

Recurrence after urinary tract infection (rUTI) is common in adult women. The majority of recurrences are believed to be reinfection from extraurinary sources such as the rectum or vagina. However, uropathogenic Escherichia coli are now known to invade urothelial cells and form quiescent intracellular bacterial reservoirs. Management of women with frequent symptomatic rUTI can be particularly vexing for both patients and their treating physicians. This review addresses available and promising management strategies for rUTI in healthy adult women.

Biomedical evaluation of a novel nitrogen oxides releasing wound dressing

Chronic wounds are a major cause for both suffering and economical losses. Management of chronic non-healing wounds requires multipronged approach. They are polymicrobial and agonizing for the patient due to associated pain. Moist dressing providing antimicrobial action is a highly desirable chronic wound management option. Here we report a hydrogel based dressing that possesses the antimicrobial properties of acidified sodium nitrite and the homeostatic property of a hydrogel. The dressing was developed by combining citric acid cross-linked cotton gauze and sodium nitrite loaded gelatin. The cotton gauze was cross-linked with citric acid by pad-dry-curing in presence of nano-titania catalyst. The cotton gauze-gelatin hydrogel combination was gamma-irradiated and freeze-dried. At the time of application, the freeze-dried dressing is wetted by sodium nitrite solution. The dressing has a fluid uptake ability of 90 % (w/v) and the water vapour evaporation rate was estimated to be 2,809 ± 20 g/m(2)/day. The dressing showed significant antimicrobial activity against both planktonic and biofilm forms and was effective during consecutive re-uses. Cytotoxicity study showed inhibition of fibroblasts, but to a lesser extent than clinically administered concentrations of antiseptic like povidone iodine. Storage at 37 °C over a 3 month period resulted in no significant loss of its antimicrobial activity.

Impact of pH on activity of trimethoprim, fosfomycin, amikacin, colistin and ertapenem in human urine

OBJECTIVE

Although major impairment of activity at lower pH values has been reported for fluoroquinolones, acidification is a widely recommended practice for the prophylaxis and treatment of uncomplicated urinary tract infections (UTIs). Until now, there is little evidence for the influence of pH on the activity on other antimicrobial classes in urine.

METHODS

Bacterial growth curves of Staphylococcus aureus (ATCC 29213), Klebsiella oxytoca (ATCC 700324), Proteus mirabilis (ATCC 14153), Escherichia coli (ATCC 25922) and Enterococcus faecalis (ATCC 29212) were performed in Mueller-Hinton broth and in pooled human urine with a pH of between 5.0 and 8.0. Bacterial killing of trimethoprim, fosfomycin, amikacin, colistin and ertapenem against the five strains (where appropriate) was determined consecutively at concentrations equal to the MIC.

RESULTS

While no difference in the bacterial growth of E. coli, S. aureus, P. mirabilis and K. oxytoca was observed at different pH values, bacterial growth of E. faecalis was significantly reduced at low pH. Acidification to pH 5 impaired the antimicrobial activity of all investigated antibiotics, i.e. the net effect of bacterial growth and killing resulted in increased colony-forming units/ml at the end of the experiment.

CONCLUSION

The present in vitro findings indicate that acidification of urine during the treatment of UTIs should be carefully considered. While growth curves of one strain supports the concept of therapeutic or prophylactic acidification during UTIs, the most common pathogen, E. coli, was not affected by low pH. Independent of the investigated strain or antibiotic, pH values below 6 lead to a reduction of antimicrobial activity.

Inorganic nitrite therapy: historical perspective and future directions

Over the past several years, investigators studying nitric oxide (NO) biology and metabolism have come to learn that the one-electron oxidation product of NO, nitrite anion, serves as a unique player in modulating tissue NO bioavailability. Numerous studies have examined how this oxidized metabolite of NO can act as a salvage pathway for maintaining NO equivalents through multiple reduction mechanisms in permissive tissue environments. Moreover, it is now clear that nitrite anion production and distribution throughout the body can act in an endocrine manner to augment NO bioavailability, which is important for physiological and pathological processes. These discoveries have led to renewed hope and efforts for an effective NO-based therapeutic agent through the unique action of sodium nitrite as an NO prodrug. More recent studies also indicate that sodium nitrate may also increase plasma nitrite levels via the enterosalivary circulatory system resulting in nitrate reduction to nitrite by microorganisms found within the oral cavity. In this review, we discuss the importance of nitrite anion in several disease models along with an appraisal of sodium nitrite therapy in the clinic, potential caveats of such clinical uses, and future possibilities for nitrite-based therapies.

Chemioprevenzione Delle Infezioni Urinarie Nel Mieloleso

Il presente studio si è posto l'obiettivo di valutare l'efficacia di un trattamento “naturale” a lungo termine per la profilassi delle infezioni urinarie in soggetti affetti da mielolesione e vescica neurologica. La scelta è caduta su di un prodotto commerciale a base di L-Metionina + Cranberry (avente cioè sia azione antimicrobica grazie all'azione di ostacolo all'adesività batterica da parte della proantocianidine, sia azione stabilizzante l'acidità urinaria): ACIDIF (Biohealth-Italia).

The nitrate-nitrite-nitric oxide pathway in physiology and therapeutics

The inorganic anions nitrate (NO3-) and nitrite (NO2-) were previously thought to be inert end products of endogenous nitric oxide (NO) metabolism. However, recent studies show that these supposedly inert anions can be recycled in vivo to form NO, representing an important alternative source of NO to the classical L-arginine-NO-synthase pathway, in particular in hypoxic states. This Review discusses the emerging important biological functions of the nitrate-nitrite-NO pathway, and highlights studies that implicate the therapeutic potential of nitrate and nitrite in conditions such as myocardial infarction, stroke, systemic and pulmonary hypertension, and gastric ulceration.

Allylic nitro compounds as nitrite donors

Allylic nitro compounds were synthesized and evaluated as organic sources of nitrite and nitric oxide. Unactivated allylic nitro compounds do not spontaneously release nitrite and nucleophile promoted nitrite release is slow. However, 2-(nitromethyl)-cyclohex-1-ene-3-one spontaneously dissociates in buffer (pH = 7.4) to release nitrite with a kobs = 1.6 x 10(-5) s(-1). In the presence of L-cysteine, this compound rapidly yields nitrite and reacts with hemoglobin similarly to sodium nitrite. Structural modifications and the nature and amount of nucleophile modulate the rate of nitrite release. In the presence of L-cysteine and ascorbic acid, this compound forms nitric oxide. Together, these results reveal a new structural architecture for the tunable liberation of nitrite and nitric oxide from organic compounds.

Uropathogenic Escherichia Coli and Tolerance to Nitric Oxide: The Role of Flavohemoglobin

PURPOSE

NO has an important role as part of the innate host response against bacterial infections. Flavohemoglobin, which is encoded by the hmp gene, protects Escherichia coli against nitrosative stress. We compared the NO tolerance of UPEC and nonpathogenic strains, and examined the involvement of flavohemoglobin.

MATERIALS AND METHODS

The E. coli K12 derivates HB101 and DH5alpha represent nonpathogenic strains, while J96 and IA2 represent UPEC strains. HB101 was used as the host for a pBR322 plasmid carrying the hmp gene. Bacterial tolerance to NO was evaluated by determining cfu. Flavohemoglobin expression was examined using Northern and Western blot analysis.

RESULTS

In the stationary growth phase, J96 was significantly more tolerant to DETA/NO (Alexis Biochemical, Lausen, Switzerland) (1 mM) compared to HB101 (47% +/- 11% vs 6.4% +/- 3.1% cfu). In the exponential growth phase DETA/NO exposure resulted in 98% +/- 4.6% cfu for J96 and 74% +/- 7.6% cfu for IA2 compared to 15% +/- 5.9% for HB101 and 21% +/- 12% for DH5alpha. HB101 over expressing hmp showed increased tolerance to DETA/NO (0.5 mM) compared to WT HB101 (106% +/- 5.6% vs 67 +/- 6.2%, p <0.01). Northern and Western blot analysis demonstrated increased flavohemoglobin expression after DETA/NO exposure and the strongest expression in HB101 carrying hmp on a multicopy plasmid.

CONCLUSIONS

UPEC strains were significantly more tolerant to DETA/NO than nonpathogenic strains, which suggests a correlation between virulence and NO tolerance. Flavohemoglobin expression increased after DETA/NO exposure in UPEC and in nonpathogenic strains.

Intravesical nitric oxide delivery for prevention of catheter-associated urinary tract infections

The use of indwelling urinary catheters is a major risk factor for urinary tract infection; and despite the availability of numerous preventive regimens, this condition is still extremely common. In earlier studies we have demonstrated the inhibitory effects of nitrite and ascorbic acid on bacterial growth in urine. When combined, these compounds generate antibacterial reactive nitrogen species, including the gas nitric oxide. We have now tested in a laboratory model of the urinary bladder whether filling of the catheter retention balloon with nitrite and ascorbic acid would generate measurable amounts of NO outside the membrane and whether this would affect bacterial growth in the surrounding urine. Two strains of Escherichia coli, one strain isolated from a patient (U1106024) and one reference strain (ATCC 25922), were tested. Nitric oxide gas was generated in the silicone balloon and readily diffused into the urine. When control catheters with ascorbic acid but without nitrite were used, bacterial counts increased from 9.0 x 10(5) to 2.0 x10(8) CFU/ml (strain U1106024) and from 2.5 x 10(6) to 2.7 x 10(8) CFU/ml (strain ATCC 25922) after 24 h. In contrast, in test catheters with ascorbic acid and nitrite, both strains tested were effectively killed. The NO donor {DETA NONOate, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate} also showed antibacterial activity in the same model, thereby supporting a central role of NO in achieving the observed effects. Future clinical trials will reveal whether this novel approach for the intravesical delivery of an antibacterial gas could be used to prevent catheter-associated infections.

Emerging drugs for bacterial urinary tract infections

Bacterial urinary tract infections (UTIs) are frequent infections in the outpatient as well as in the nosocomial setting. The stratification into uncomplicated and complicated UTIs has proven to be clinically useful. Bacterial virulence factors on the one side and the integrity of the host defence mechanisms on the other side determine the course of the infection. In uncomplicated UTIs, Escherichia coli is the leading organism, whereas in complicated UTIs, the bacterial spectrum is much broader, including Gram-negative, Gram-positive and often multiresistant organisms. The therapy of uncomplicated UTIs is almost exclusively antibacterial, whereas in complicated UTIs the complicating factors also have to be treated. There are two predominant aims in the antimicrobial treatment of both uncomplicated and complicated UTIs: i) rapid and effective response to therapy and prevention of recurrence of the individual patient treated; and ii) prevention of emergence of resistance to chemotherapy in the microbial environment. The aim of this review is to highlight the existing, and to describe emerging, treatment options for UTIs.