Efficacy and safety of ceftazidime/avibactam in patients with infections caused by ß-lactamase-producing Gram-negative pathogens: a pooled analysis from the Phase 3 clinical trial programme.

OBJECTIVES: This post hoc pooled analysis evaluated clinical and microbiological outcomes and safety in patients with infections caused by ß-lactamase-producing Gram-negative pathogens across five Phase 3, randomized, controlled, multicentre trials of ceftazidime/avibactam in adults with complicated intra-abdominal infection (cIAI), complicated urinary tract infection (cUTI)/pyelonephritis and nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP). METHODS: In each trial, RECLAIM/RECLAIM 3 (cIAI), REPRISE (cIAI/cUTI), RECAPTURE (cUTI) and REPROVE (NP, including VAP) patients were randomized 1:1 to IV ceftazidime/avibactam (plus metronidazole for patients with cIAI) or comparators (carbapenems in >97% patients) for 5-21 days. Clinical and microbiological responses at the test-of-cure visit were assessed for patients with ESBLs, and/or plasmidic and/or overexpression of chromosomal AmpC, and/or serine carbapenemases without MBLs identified in baseline Gram-negative isolates by phenotypic screening and molecular characterization in the pooled microbiological modified ITT (mMITT) population. RESULTS: In total, 813 patients (ceftazidime/avibactam, n = 389; comparator, n = 424) had ≥1 ß-lactamase-producing baseline pathogen identified, amongst whom 792 patients (ceftazidime/avibactam, n = 379; comparator, n = 413) had no MBLs. The most frequent ß-lactamase-producing pathogens across treatment groups were Escherichia coli (n = 381), Klebsiella pneumoniae (n = 261) and Pseudomonas aeruginosa (n = 53). Clinical cure rates in the pooled non-MBL ß-lactamase-producing mMITT population were 88.1% (334/379) for ceftazidime/avibactam and 88.1% (364/413) for comparators; favourable microbiological response rates were 76.5% (290/379) and 68.8% (284/413), respectively. The safety profile of ceftazidime/avibactam was consistent with previous observations. CONCLUSIONS: This analysis provides supportive evidence of the efficacy and safety of ceftazidime/avibactam in patients with infections caused by ESBLs, AmpC and serine carbapenemase-producing Gram-negative pathogens. TRIAL REGISTRATION: NCT01499290; NCT01726023; NCT01644643; NCT01595438/NCT01599806; NCT01808092.

Antimicrobial Activity of Ceftazidime-Avibactam and Comparators against Pathogens Harboring OXA-48 and AmpC Alone or in Combination with Other ß-Lactamases Collected from Phase 3 Clinical Trials and an International Surveillance Program.

In vitro activities of ceftazidime-avibactam (CAZ-AVI) and key comparators against AmpC-overproducing Enterobacterales and Pseudomonas aeruginosa isolates from four Phase 3 clinical trials and against OXA-48-producing Enterobacterales with multiple resistance mechanisms from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program were evaluated. Susceptibility to CAZ-AVI and comparators was determined by reference broth microdilution methods. Clinical response at test of cure (TOC) was assessed in patients from Phase 3 trials with baseline OXA-48-producing Enterobacterales or AmpC-overproducing Enterobacterales and P. aeruginosa treated with CAZ-AVI or comparators. Against 77 AmpC-overproducing Enterobacterales isolates from Phase 3 trials, meropenem-vaborbactam (98.7% susceptible [S]), CAZ-AVI (96.1% S), and meropenem (96.1% S) had similar in vitro activity and were more active than ceftolozane-tazobactam (24.7% S). Clinical cure rates in patients with baseline AmpC-overproducing Enterobacterales were 80.7% (n = 21/26) and 85.0% (n = 17/20) for CAZ-AVI and comparators. Against 53 AmpC-overproducing P. aeruginosa isolates from Phase 3 trials, CAZ-AVI (73.6% S) was more active in vitro than ceftolozane-tazobactam (58.5% S) and meropenem (37.7% S). Clinical cure rates in patients with baseline AmpC-overproducing P. aeruginosa were 85.7% (n = 12/14) and 75.0% (n = 9/12) for CAZ-AVI and comparators, respectively. Of 113 OXA-48-producing isolates from the ATLAS program, 99.1% were susceptible to CAZ-AVI. Four patients with baseline OXA-48-producing Klebsiella pneumoniae isolates treated with CAZ-AVI in Phase 3 trials were clinical cures at TOC and had favorable microbiological response. CAZ-AVI was among the most active agents against AmpC-overproducing P. aeruginosa and Enterobacterales and had greater in vitro activity against OXA-48-producing Enterobacterales than meropenem-vaborbactam, meropenem, ceftolozane-tazobactam, and other comparators.

Mechanistic insight into the activity of a sulfone compound dapsone on Propionibacterium (Newly Reclassified as Cutibacterium) Acnes-mediated cytokine production.

Acne remains as the most common skin disease in the United States even despite multiple approved topical and systemic medications available. These treatments available over the counter and by prescription can be classified based on comedolytic, antibacterial and anti-inflammatory activities and are often used in combination. Therefore, understanding of the mechanism of action is critical to achieving the best clinical outcome and synergy. One of the newer acne medications with historical data suggesting both antibacterial and anti-inflammatory activity is dapsone. In order to gain mechanistic insight into the anti-inflammatory activity of dapsone in Propionibacterium (a former genus name recently reclassified as "Cutibacterium") (P. acnes)-driven inflammation, we used two human in vitro models: primary human neonatal epidermal keratinocytes and human monocytes (THP-1). We demonstrate that dapsone suppresses production of specific cytokine signatures interleukin (IL)1α and IL8 in human epidermal keratinocytes and IL1ß, IL6, IL8 and tumor necrosis factor-α in THP-1 cells in response to P. acnes. Using THP-1 cell in vitro model, we show that IL1ß and CASP-1 are regulated by dapsone independently of NFκB activity at transcriptional and post-transcriptional levels, respectively.

The in vitro antimicrobial activity of wound and skin cleansers at nontoxic concentrations.

OBJECTIVE: To determine in vitro antibacterial activity of commercially available skin, wound, and skin/wound cleansers at cell-safe (nontoxic) concentrations. DESIGN: Saline and 19 other commercial wound and skin cleansers were evaluated for cytotoxic effects on mouse dermal fibroblasts. Cells were exposed to serial 10-fold dilutions of each cleanser until treatment-induced cytotoxicity was comparable to the baseline cytotoxicity of unexposed control fibroblasts. Antimicrobial "time-kill" kinetics of these test concentrations of cleansers was tested against methicillin-resistant Staphylococcus aureus. RESULTS: The experimental design allowed calculation of relative cytotoxicity indexes ranging from 0 to 100,000. Shur-Clens Restore Wound Cleanser (ConvaTec, Skillman, New Jersey) and saline were found to be the least toxic (toxicity index: 0); Hibiclens (Mölnlycke Health Care, Norcross, Georgia), Restore Skin Cleanser (Hollister Inc, Libertyville, Illinois), and Betadine Surgical Scrub (Pursue Products LP, Stamford, Connecticut) were found to be the most toxic (toxicity index: 10,000). At noncytotoxic concentrations, NeutroPhase (NovaBay Pharmaceuticals Inc, Emeryville, California) was the most rapidly bactericidal, achieving a 4-log reduction in colony-forming units in less than 1 minute. Puracyn (Innovacyn Inc, Rialto, California) was next at 30 minutes, whereas most of the agents tested required more than 24 hours. CONCLUSIONS: Wound healing depends on controlling bacterial balance while maintaining the viability of the healing tissues. In vitro toxicity indexes provide helpful guidelines subsequent to in vivo evaluations and clinical applications. The study findings suggest that NeutroPhase, in contrast with many commercially available wound cleansers, has rapid bactericidal activity at concentrations that are safe for human cells.

N-chloramines, a promising class of well-tolerated topical anti-infectives.

Antibiotic resistance is a growing public health crisis. To address the development of bacterial resistance, the use of antibiotics has to be minimized for nonsystemic applications in humans, as well as in animals and plants. Possible substitutes with low potential for developing resistance are active chlorine compounds that have been in clinical use for over 180 years. These agents are characterized by pronounced differences in their chlorinating and/or oxidizing activity, with hypochlorous acid (HOCl) as the strongest and organic chloramines as the weakest members. Bacterial killing in clinical practice is often associated with unwanted side effects such as chlorine consumption, tissue irritation, and pain, increasing proportionally with the chlorinating/oxidizing potency. Since the chloramines are able to effectively kill pathogens (bacteria, fungi, viruses, protozoa), their application as anti-infectives is advisable, all the more so as they exhibit additional beneficial properties such as destruction of toxins, degradation of biofilms, and anticoagulative and anti-inflammatory activities. Within the ample field of chloramines, the stable N-chloro derivatives of ß-aminosulfonic acids are most therapeutically advanced. Being available as sodium salts, they distinguish themselves by good solubility and absence of smell. Important representatives are N-chlorotaurine, a natural compound occurring in the human immune system, and novel mono- and dichloro derivatives of dimethyltaurine, which feature improved stability.

NVC-422 inactivates Staphylococcus aureus toxins.

Bacterial pathogens have specific virulence factors (e.g., toxins) that contribute significantly to the virulence and infectivity of microorganisms within the human hosts. Virulence factors are molecules expressed by pathogens that enable colonization, immunoevasion, and immunosuppression, obtaining nutrients from the host or gaining entry into host cells. They can cause pathogenesis by inhibiting or stimulating certain host functions. For example, in systemic Staphylococcus aureus infections, virulence factors such as toxic shock syndrome toxin 1 (TSST-1), staphylococcal enterotoxin A (SEA), and staphylococcal enterotoxin B (SEB) cause sepsis or toxic shock by uncontrolled stimulation of T lymphocytes and by triggering a cytokine storm. In vitro, these superantigens stimulate the proliferation of human peripheral blood mononuclear cells (PBMC) and the release of many cytokines. NVC-422 (N,N-dichloro-2,2-dimethyltaurine) is a broad-spectrum, fast-acting topical anti-infective agent against microbial pathogens, including antibiotic-resistant microbes. Using mass spectrometry, we demonstrate here that NVC-422 oxidizes methionine residues of TSST-1, SEA, SEB, and exfoliative toxin A (ETA). Exposure of virulence factors to 0.1% NVC-422 for 1 h prevented TSST-1-, SEA-, SEB-, and ETA-induced cell proliferation and cytokine release. Moreover, NVC-422 also delayed and reduced the protein A- and clumping factor-associated agglutination of S. aureus cultures. These results show that, in addition to its well-described direct microbicidal activity, NVC-422 can inactivate S. aureus virulence factors through rapid oxidation of methionines.

Sulfonyl-polyol N,N-dichloroamines with rapid, broad-spectrum antimicrobial activity.

The discovery and development of antimicrobial agents that do not give rise to resistance remains an ongoing challenge. Our efforts in this regard continue to reveal new potential therapeutic agents with differing physicochemical properties while retaining the effective N,N-dichloroamine pharmacophore as the key antimicrobial warhead. In this Letter, we disclose agents containing polyol units as a water solubilizing group. These sulfonyl-polyol agents show broad spectrum bactericidal and virucidal activity. These compounds show 1 h MBC's of 16-512 µg/mL against Escherichia coli and 4-256 µg/mL against Staphylococcus aureus at neutral pH, and 1-h IC50's of 4.5-32 µM against Adenovirus 5 and 0.7-3.0 µM against Herpes simplex virus 1. The lead compounds were tested in a tissue culture irritancy assay and showed only minimal irritation at the highest concentrations tested.

Real-world in vitro activity of newer antibiotics against Enterobacterales and Pseudomonas aeruginosa, including carbapenem-non-susceptible and multidrug-resistant isolates: a multicenter analysis.

IMPORTANCE: Newer antibiotics against Gram-negative pathogens provide important treatment options, especially for antibiotic-resistant bacteria, but little is known about their use during routine clinical care. To use these agents appropriately, clinicians need to have access to timely susceptibility data. We evaluated 27,531 facility-reported susceptibility results from the BD Insights Research Database to gain a better understanding of real-world testing practices and susceptibility rates for six newer antibiotics. Escherichia coli was the most frequently tested potential pathogen, and ceftazidime-avibactam and ceftolozane-tazobactam had the greatest numbers of susceptibility results. For cefiderocol, eravacycline, imipenem-relabactam, and meropenem-vaborbactam, susceptibility data were available for fewer than 2% of isolates. Susceptibility comparisons should be considered with caution. Ceftazidime-avibactam had the highest susceptibility rates for Enterobacterales while cefiderocol had the highest susceptibility rates for Pseudomonas aeruginosa. New antibiotics have the potential to improve the management of Gram-negative infections, but their use may be hampered by the absence of susceptibility data.

No decrease in susceptibility to NVC-422 in multiple-passage studies with methicillin-resistant Staphylococcus aureus, S. aureus, Pseudomonas aeruginosa, and Escherichia coli.

Twenty-five serial passages of Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus and 50 passages of methicillin-resistant Staphylococcus aureus resulted in no significant increase in NVC-422 MICs, while ciprofloxacin MICs increased 256-fold for E. coli and 32-fold for P. aeruginosa and S. aureus. Mupirocin, fusidic acid, and retapamulin MICs for MRSA increased 64-, 256-, and 16-fold, respectively. No cross-resistance to NVC-422 was observed with mupirocin-, fusidic acid-, and retapamulin-resistant strains.

Chemical characterization and biological properties of NVC-422, a novel, stable N-chlorotaurine analog.

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.

Antimicrobial Activity of Ceftazidime-Avibactam Against Contemporary Pathogens From Urinary Tract Infections and Intra-abdominal Infections Collected From US Children During the 2016-2019 INFORM Surveillance Program.

BACKGROUND: Antibacterial activity of ceftazidime-avibactam (CAZ-AVI) was evaluated against bacterial isolates from children in the United States with a urinary tract infection (UTI) or intra-abdominal infection (IAI) during the 2016-2019 International Network for Optimal Resistance Monitoring program. Prevalence of isolates and susceptibility to CAZ-AVI in pediatric and adult patients were compared. METHODS: Bacterial isolates were collected from children with a UTI or IAI at 70 US medical centers from 2016 to 2019. The antimicrobial activity of CAZ-AVI and comparator agents was tested by broth microdilution methods. RESULTS: The most prevalent Enterobacterales pathogens in children with UTIs were Escherichia coli (62.5%), Klebsiella pneumoniae (12.1%) and Proteus mirabilis (6.2%). Minimum inhibitory concentration 90% values for CAZ-AVI against Enterobacterales (0.25 µg/mL) and Pseudomonas aeruginosa (4 µg/mL) were identical for children and adults. The most prevalent Enterobacterales pathogens in children with IAIs were E. coli (57.4%), K. pneumoniae (11.1%) and Enterobacter cloacae species complex (9.3%). All isolates of Enterobacterales from pediatric patients with UTI and IAI were susceptible to CAZ-AVI, including extended-spectrum ß-lactamase phenotypes. Susceptibility of P. aeruginosa isolates to CAZ-AVI was 96.2% in children and 98.4% in adults with a UTI: for IAI it was 100% and 97.2%, respectively. CONCLUSIONS: Contemporary UTI and IAI pathogens collected from US children from 2016 to 2019 exhibited similar prevalence and susceptibilities as isolates collected from adult patients. CAZ-AVI exhibited potent activity against these pathogens.

N,N-Dichloroaminosulfonic acids as novel 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.

Quaternary ammonium N,N-dichloroamines as topical, antimicrobial agents.

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.

In vitro activity of telavancin against resistant gram-positive bacteria.

The in vitro activity of telavancin was tested against 743 predominantly antimicrobial-resistant, gram-positive isolates. Telavancin was highly active against methicillin-resistant staphylococci (MIC(90), 0.5 to 1 microg/ml), streptococci (all MICs, < or =0.12 microg/ml), and VanB-type enterococci (all MICs, < or =2 microg/ml). Time-kill studies demonstrated the potent bactericidal activity of telavancin.

Irrigation with N,N-dichloro-2,2-dimethyltaurine (NVC-422) in a citrate buffer maintains urinary catheter patency in vitro and prevents encrustation by Proteus mirabilis.

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 10(8) 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.

Approved Glycopeptide Antibacterial Drugs: Mechanism of Action and Resistance.

The glycopeptide antimicrobials are a group of natural product and semisynthetic glycosylated peptides that show antibacterial activity against Gram-positive organisms through inhibition of cell-wall synthesis. This is achieved primarily through binding to the d-alanyl-d-alanine terminus of the lipid II bacterial cell-wall precursor, preventing cross-linking of the peptidoglycan layer. Vancomycin is the foundational member of the class, showing both clinical longevity and a still preferential role in the therapy of methicillin-resistant Staphylococcus aureus and of susceptible Enterococcus spp. Newer lipoglycopeptide derivatives (telavancin, dalbavancin, and oritavancin) were designed in a targeted fashion to increase antibacterial activity, in some cases through secondary mechanisms of action. Resistance to the glycopeptides emerged in delayed fashion and occurs via a spectrum of chromosome- and plasmid-associated elements that lead to structural alteration of the bacterial cell-wall precursor substrates.

Treatment of Acute Necrotizing Fasciitis Using Negative Pressure Wound Therapy and Adjunctive NeutroPhase Irrigation Under the Foam.

Necrotizing fasciitis is a complication of a bacterial infection that activates the immune system in perifascial planes. This case report highlights initial diagnostic failures that delay early treatment, which causes profoundly negative consequences. Antimicrobial control with abolition of the inciting bacteria does not neutralize the subsequent endopathologic ravages. A new therapeutic technique, which combines negative pressure wound therapy (NPWT) and a pure hypochlorous acid solution 0.01% (NeutroPhase, NovaBay Pharmaceuticals Inc, Emeryville, CA) along with debridement and antibiotics is described in this study. It is believed that the combination of neutralization of the toxins produced by bacteria with NeutroPhase along with the NPWT action of removing exudates is effective in saving the patient.

Broad-spectrum virucidal activity of (NVC-422) N,N-dichloro-2,2-dimethyltaurine against viral ocular pathogens in vitro.

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.

Efficacy of NVC-422 against Staphylococcus aureus biofilms in a sheep biofilm model of sinusitis.

BACKGROUND: Bacterial biofilms are a major obstacle in management of recalcitrant chronic rhinosinusitis. NVC-422 is a potent, fast-acting, broad-spectrum, nonantibiotic, antimicrobial with a new mechanism of action effective against biofilm bacteria in in vitro conditions. The aim of this study was to investigate the safety and efficacy of NVC-422 as local antibiofilm treatment in a sheep model of rhinosinusitis. METHODS: After accessing and occluding frontal sinus ostia in 24 merino sheep via staged endoscopic procedures, S. aureus clinical isolate was instilled in frontal sinuses. Following biofilm formation, ostial obstruction was removed and sinuses irrigated with 0.1% and 0.5% NVC-422 in 5 mM acetate isotonic saline at pH 4.0. Sheep were monitored for adverse effects and euthanized 24 hours after treatment. Frontal sinuses were assessed for infection and changes in mucosa after the treatment. S. aureus biofilms were identified with Baclight-confocal scanning microscopy protocol and the biofilm biomass assayed by applying the COMSTAT2 program to recorded image stacks. RESULTS: After 2 irrigations with 0.1% NVC-422, S. aureus biofilm biomass was reduced when compared to control sinuses (p = 0.0001), though this effect was variable in samples. NVC-422 0.5% solution irrigations reduced biofilm even more significantly and consistently over all samples (p < 0.0001). NVC-422 0.5% was also more effective than 0.1% NVC-422, vehicle control, and normal saline sinus irrigations in reducing biofilm biomass (p < 0.05 for all subgroups). No adverse events were observed in sheep after sinus irrigations with 0.1% and 0.5% NVC-422 solutions. CONCLUSION: NVC-422 is an effective topical agent against S. aureus biofilms, with dose-dependent efficacy in this animal model of biofilm-associated sinusitis.

N-chlorotaurine, a long-lived oxidant produced by human leukocytes, inactivates Shiga toxin of enterohemorrhagic Escherichia coli.

N-chlorotaurine (NCT), the main representative of long-lived oxidants produced by granulocytes and monocytes, is known to exert broad-spectrum microbicidal activity. Here we show that NCT directly inactivates Shiga toxin 2 (Stx2), used as a model toxin secreted by enterohemorrhagic Escherichia coli (EHEC). Bacterial growth and Stx2 production were both inhibited by 2 mM NCT. The cytotoxic effect of Stx2 on Vero cells was removed by ≥5.5 mM NCT. Confocal microscopy and FACS analyses showed that the binding of Stx2 to human kidney glomerular endothelial cells was inhibited, and no NCT-treated Stx2 entered the cytosol. Mass spectrometry displayed oxidation of thio groups and aromatic amino acids of Stx2 by NCT. Therefore, long-lived oxidants may act as powerful tools of innate immunity against soluble virulence factors of pathogens. Moreover, inactivation of virulence factors may contribute to therapeutic success of NCT and novel analogs, which are in development as topical antiinfectives.