Fosfomycin is a broad-spectrum cell wall active agent that inhibits the MurA enzyme involved in peptidoglycan synthesis and is FDA-approved for treatment of uncomplicated urinary tract infections (UTIs) caused by Escherichia coli and Enterococcus faecalis in women. Data regarding the susceptibility of recent UTI isolates to fosfomycin are limited.

Long-term use of indwelling urinary catheters can lead to urinary tract infections and loss of catheter patency due to encrustation and blockage. Encrustation of urinary catheters is due to formation of crystalline biofilms by urease-producing microorganisms such as Proteus mirabilis. An in vitro catheter biofilm model (CBM) was used to evaluate current methods for maintaining urinary catheter patency. We compared antimicrobial-coated urinary Foley catheters, with both available catheter irrigation solutions and investigational solutions containing NVC-422 (N,N-dichloro-2,2-dimethyltaurine; a novel broad-spectrum antimicrobial). Inoculation of the CBM reactor with 108 colony-forming units of P. mirabilis resulted in crystalline biofilm formation in catheters by 48 h and blockage of catheters within 5 days. Silver hydrogel or nitrofurazone-coated catheters did not extend the duration of catheter patency. Catheters irrigated daily with commercially available solutions such as 0.25 % acetic acid and isotonic saline blocked at the same rate as untreated catheters. Daily irrigations of catheters with 0.2 % NVC-422 in 10 mM acetate-buffered saline pH 4 or Renacidin maintained catheter patency throughout 10-day studies, but P. mirabilis colonization of the CBM remained. In contrast, 0.2 % NVC-422 in citrate buffer (6.6 % citric acid at pH 3.8) resulted in an irrigation solution that not only maintained catheter patency for 10 days but also completely eradicated the P. mirabilis biofilm within one treatment day. These data suggest that an irrigation solution containing the rapidly bactericidal antimicrobial NVC-422 in combination with citric acid to permeabilize crystalline biofilm may significantly enhance catheter patency versus other approved irrigation solutions and antimicrobial-coated catheters.

ABSTRACT Avibactam, a non-β-lactam β-lactamase inhibitor with activity against extended-spectrum β-lactamases (ESBLs), KPC, AmpC, and some OXA enzymes, extends the antibacterial activity of ceftazidime against most ceftazidime-resistant organisms producing these enzymes. In this study, the bactericidal activity of ceftazidime-avibactam against 18 Pseudomonas aeruginosa isolates and 15 Enterobacteriaceae isolates, including wild-type isolates and ESBL, KPC, and/or AmpC producers, was evaluated. Ceftazidime-avibactam MICs (0.016 to 32 μg/ml) were lower than those for ceftazidime alone (0.06 to ≥256 μg/ml) against all isolates except for 2 P. aeruginosa isolates (1 bla VIM -positive isolate and 1 bla OXA-23 -positive isolate). The minimum bactericidal concentration/MIC ratios of ceftazidime-avibactam were ≤4 for all isolates, indicating bactericidal activity. Human serum and human serum albumin had a minimal effect on ceftazidime-avibactam MICs. Ceftazidime-avibactam time-kill kinetics were evaluated at low MIC multiples and showed time-dependent reductions in the number of CFU/ml from 0 to 6 h for all strains tested. A ≥3-log 10 decrease in the number of CFU/ml was observed at 6 h for all Enterobacteriaceae , and a 2-log 10 reduction in the number of CFU/ml was observed at 6 h for 3 of the 6 P. aeruginosa isolates. Regrowth was noted at 24 h for some of the isolates tested in time-kill assays. These data demonstrate the potent bactericidal activity of ceftazidime-avibactam and support the continued clinical development of ceftazidime-avibactam as a new treatment option for infections caused by Enterobacteriaceae and P. aeruginosa , including isolates resistant to ceftazidime by mechanisms dependent on avibactam-sensitive β-lactamases.

Purpose.: Viral conjunctivitis is a highly contagious infection often causing major epidemics. A safe broad-spectrum antiviral agent is needed to treat this unmet medical need. The purpose of this study is to demonstrate that in vitro NVC-422 is a safe, broad-spectrum topical virucidal agent with activity against ophthalmic viral pathogens. Methods.: The virucidal activity of NVC-422 against several serotypes of human adenovirus (HAdV), coxsackievirus A24, enterovirus 70, and herpes simplex-virus-1 (HSV-1) was tested in standard in vitro titer reduction assays with or without tears. An in vitro irritancy score for NVC-422 was determined using the MatTek EpiOcular tissue system. Results.: NVC-422 reduced the viral titer of HAdV-5, HAdV-8, HAdV-19, HAdV-37, and HSV-1 by at least 4 logs after 1 hour incubation at 250 μM. Incubation of coxsackievirus A24 and enterovirus 70 with 2.5 mM NVC-422 for 1 hour reduced the viral titer by 4 logs and 4.5 logs, respectively. The virucidal activity of NVC-422 is maintained in the presence of 10% synthetic tears. In the EpiOcular corneal tissue model, NVC-422 was nonirritating at concentrations up to 41 mM. Conclusions.: NVC-422 has potent, rapid in vitro virucidal activity against major causes of conjunctivitis. Its broad-spectrum virucidal activity combined with favorable safety profile validates NVC-422 as a potential new therapeutic agent against viral conjunctivitis.

Structure stability/activity relationships (SXR) of a new class of N,N-dichloroamine compounds were explored to improve antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans while maintaining aqueous solution stability. This study identified a new class of solution-stable and topical antimicrobial agents. These agents are sulfone-stabilized and possess either a quaternary ammonium or sulfonate appendages as a water solubilizing group. Several unique challenges were confronted in the synthesis of these novel compounds which are highlighted in the discussion.

During oxidative burst, neutrophils selectively generate HOCl to destroy invading microbial pathogens. Excess HOCl reacts with taurine, a semi-essential amino acid, resulting in the formation of the longer-lived biogenerated broad-spectrum antimicrobial agent, N-chlorotaurine (NCT). In the presence of an excess of HOCl or under moderately acidic conditions, NCT can be further chlorinated, or it can disproportionate to produce N,N-dichlorotaurine (NNDCT). In the present study, 2,2-dimethyltaurine was used to prepare a more stable N-chlorotaurine, namely, N,N-dichloro-2,2-dimethyltaurine (NVC-422). In addition, we report on the chemical characterization, in vitro antimicrobial properties, and cytotoxicity of this compound. NVC-422 was shown effectively to kill all 17 microbial strains tested, including antibiotic-resistant Staphylococcus aureus and Enterococcus faecium. The minimum bactericidal concentration of NVC-422 against Gram-negative and Gram-positive bacteria ranged from 0.12 to 4 μg/ml. The minimum fungicidal concentrations against Candida albicans and Candida glabrata were 32 and 16 μg/ml, respectively. NVC-422 has an in vitro cytotoxicity (50% cytotoxicity = 1,440 μg/ml) similar to that of NNDCT. Moreover, our data showed that this agent possesses rapid, pH-dependent antimicrobial activity. At pH 4, NVC-422 completely killed both Escherichia coli and S. aureus within 5 min at a concentration of 32 μg/ml. Finally, the effect of NVC-422 in the treatment of an E. coli-infected granulating wound rat model was evaluated. Treatment of the infected granulating wound with NVC-422 resulted in significant reduction of the bacterial tissue burden and faster wound healing compared to a saline-treated control. These findings suggest that NVC-422 could have potential application as a topical antimicrobial.

Impetigo is a highly contagious bacterial skin infection affecting children worldwide that is caused by the Gram-positive bacteria Staphylococcus aureus, Streptococcus pyogenes, or both. Staphylococcus species can quickly develop drug resistance rendering mupirocin, fusidic acid, and erythromycin ineffective. Preclinical and clinical studies demonstrated that NVC-422 (N, N-dichloro-2, 2-dimethyltaurine) rapidly kills pathogens without the development of drug resistance. 129 patients with clinically diagnosed impetigo were randomized to three dose groups (0.1, 0.5, or 1.5% NVC-422 topical gel) in a study conducted at 2 centers; 125 patients (97%) had microbiologically confirmed infection. Treatment was administered three times a day (TID) for 7 days to all randomized subjects. Response was measured at the completion of treatment (Day 8) and 1 week post treatment (Day 15) by the Skin Infection Rating Scale (SIRS) and by microbiological response. A total of 120 subjects (96%) completed all 7 days of treatment and were assessed at end of treatment (EOT). Clinical response rate at EOT in the PPC population was excellent in each of the dose groups (84.6%, 87.2%, and 92.3% in the 0.1%, 0.5% and 1.5% dose groups respectively). The majority of the infections were caused by S. aureus, alone (106/125, 85%) of which approximately 10% were MRSA. There were no clinical recurrences in any treatment groups. Treatment-emergent adverse events were seen in 5.4% of the subjects (7/129) and were mild to moderate and resolved. NVC-422 topical gel administered TID was well tolerated, with high rates of clinical and microbiological responses for treating impetigo.

Antimicrobial compounds with broad-spectrum activity and minimal potential for antibiotic resistance are urgently needed. Toward this end, we prepared and investigated a novel series of N-chloroheterocycles. Of the compounds examined, the N-chloroamine series were found superior over N-chloroamide series in regards to exhibiting high antimicrobial activity, low cytotoxicity, and long-term aqueous stability.

A series of backbone modified and sulfonic acid replacement analogs of our topical, clinical candidate (iii) were synthesized. Their antimicrobial activities and aqueous stabilities at pH 4 and pH 7 were determined, and has led us to identify quaternary ammonium N,N-dichloroamines as a new class of topical antimicrobial agents.

2-Dichloroamino-2-methyl-propane-1-sulfonic acid sodium salt (2a), a stable derivative of endogenous N,N-dichlorotaurine (1), has been identified and is under development as a topical antimicrobial agent. Structure-activity relationships of analogs were explored to achieve optimal antimicrobial activity with minimal mammalian toxicity while maintaining the desired stability. All the analogs synthesized showed antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans in the range of 1-128 microg/mL and cytotoxicity against mammalian L929 cells in the range 80-1900 microg/mL.

OBJECTIVE:Hypochlorous acid (HOCl), a major inorganic bactericidal compound of innate immunity, is effective against a broad range of microorganisms. Owing to its chemical nature, HOCl has never been used as a pharmaceutical drug for treating infection. In this article, we describe the chemical production, stabilization, and biological activity of a pharmaceutically useful formulation of HOCl.METHODS:Stabilized HOCl is in the form of a physiologically balanced solution in 0.9% saline at a pH range of 3.5 to 4.0. Chlorine species distribution in solution is a function of pH. In aqueous solution, HOCl is the predominant species at the pH range of 3 to 6. At pH values less than 3.5, the solution exists as a mixture of chlorine in aqueous phase, chlorine gas, trichloride (Cl(3) (-)), and HOCl. At pH greater than 5.5, sodium hypochlorite (NaOCl) starts to form and becomes the predominant species in the alkaline pH. To maintain HOCl solution in a stable form, maximize its antimicrobial activities, and minimize undesirable side products, the pH must be maintained at 3.5 to 5.RESULTS:Using this stabilized form of HOCl, the potent antimicrobial activities of HOCl are demonstrated against a wide range of microorganisms. The in vitro cytotoxicity profile in L929 cells and the in vivo safety profile of HOCl in various animal models are described.CONCLUSION:On the basis of the antimicrobial activity and the lack of animal toxicity, it is predicted that stabilized HOCl has potential pharmaceutical applications in the control of soft tissue infection.