Nitrofurantoin 100 mg versus 50 mg prophylaxis for urinary tract infections, a cohort study

Flemish consensus statement on the prevention, diagnosis and treatment of urinary tract infections in older nursing home residents

BACKGROUND

Urinary tract infections (UTIs) are one of the most commonly reported infections in Belgian nursing home residents. In older adults, UTI diagnosis and management is complex, often leading to over-diagnosis and irrational antimicrobial use, stressing the need for a guideline approach.

OBJECTIVES AND METHODS

A consensus statement on the prevention, diagnosis and treatment of UTIs in older adults residing in nursing homes was developed in a collaborative effort between the Flemish Hospital Outbreak Support Teams, the Flemish Agency for Care and Health, the Association of the Flemish Coordinating and Advising General Practitioners, the Belgian Association of Urology, the Belgian Society for Gerontology and Geriatrics and PhD researchers based on a combination of clinical expertise, (inter)national guidelines and peer-reviewed studies.

RESULTS

Optimizing fluid intake, appropriate toilet behaviour and posture, mobilization and local estrogen therapy in women are of proven value in UTI prevention, whereas the use of cranberry and probiotics is not to be advocated. The importance of avoiding bladder catheterization is stressed. In older nursing home residents, the diagnosis of UTIs remains challenging, mostly due to atypical systemic symptoms. A consensus diagnostic algorithm for UTI among residents with and without a urinary catheter was developed, including the presence of suggestive clinical symptoms and a positive urine culture. Urine dipsticks have a high negative but a low positive predictive value. C-reactive protein point-of-care testing is not recommended. Asymptomatic bacteriuria should not be screened for, in order to avoid unnecessary triggers for treatment. In cystitis, nitrofurantoin is the primary choice for treatment, with fosfomycin as an alternative; in prostatitis and uncomplicated pyelonephritis a fluoroquinolone is the advocated empirical antimicrobial.

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.

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.

CpxA/R-Controlled Nitroreductase Expression as Target for Combinatorial Therapy against Uropathogens by Promoting Reactive Oxygen Species Generation

The antibiotic resistances emerged in uropathogens lead to accumulative treatment failure and recurrent episodes of urinary tract infection (UTI), necessitating more innovative therapeutics to curb UTI before systematic infection. In the current study, the combination of amikacin and nitrofurantoin is found to synergistically eradicate Gram-negative uropathogens in vitro and in vivo. The mechanistic analysis demonstrates that the amikacin, as an aminoglycoside, induced bacterial envelope stress by introducing mistranslated proteins, thereby constitutively activating the cpxA/R two-component system (Cpx signaling). The activation of Cpx signaling stimulates the expression of bacterial major nitroreductases (nfsA/nfsB) through soxS/marA regulons. As a result, the CpxA/R-dependent nitroreductases overexpression generates considerable quantity of lethal reactive intermediates via nitroreduction and promotes the prodrug activation of nitrofurantoin. As such, these actions together disrupt the bacterial cellular redox balance with excessively-produced reactive oxygen species (ROS) as "Domino effect", accelerating the clearance of uropathogens. Although aminoglycosides are used as proof-of-principle to elucidate the mechanism, the synergy between nitrofurantoin is generally applicable to other Cpx stimuli. To summarize, this study highlights the potential of aminoglycoside-nitrofurantoin combination to replenish the arsenal against recurrent Gram-negative uropathogens and shed light on the Cpx signaling-controlled nitroreductase as a potential target to manipulate the antibiotic susceptibility.

Molecular Basis of Interactions between the Antibiotic Nitrofurantoin and Human Serum Albumin: A Mechanism for the Rapid Drug Blood Transportation

Nitrofurantoin is an antimicrobial agent obtained through the addition of a nitro group and a side chain containing hydantoin to a furan ring. The interactions of the antibiotic with human serum albumin (HSA) have been investigated by fluorescence, UV-VIS, Fourier transform infrared spectroscopy (FTIR) spectroscopy, and protein-ligand docking studies. The fluorescence studies indicate that the binding site of the additive involves modifications of the environment around Trp214 at the level of subdomain IIA. Fluorescence and UV-VIS spectroscopy, displacement studies, and FTIR experiments show the association mode of nitrofurantoin to HSA, suggesting that the primary binding site of the antibiotic is located in Sudlow’s site I. Molecular modeling suggests that nitrofurantoin is involved in the formation of hydrogen bonds with Trp214, Arg218, and Ser454, and is located in the hydrophobic cavity of subdomain IIA. Moreover, the curve-fitting results of the infrared Amide I’ band indicate that the binding of nitrofurantoin induces little change in the protein secondary structure. Overall, these data clarify the blood transportation process of nitrofurantoin and its rapid transfer to the kidney for its elimination, hence leading to a better understanding of its biological effects and being able to design other molecules, based on nitrofurantoin, with a higher biological potential.