Antibacterial effect of rose bengal against colistin-resistant gram-negative bacteria.

Increasing drug resistance in Gram-negative bacteria presents significant health problems worldwide. Despite notable advances in the development of a new generation of ß-lactams, aminoglycosides, and fluoroquinolones, it remains challenging to treat multi-drug resistant Gram-negative bacterial infections. Colistin (polymyxin E) is one of the most efficacious antibiotics for the treatment of multiple drug-resistant Gram-negative bacteria and has been used clinically as a last-resort option. However, the rapid spread of the transferable gene, mcr-1 which confers colistin resistance by encoding a phosphoethanolamine transferase that modifies lipid A of the bacterial membrane, threatens the efficacy of colistin for the treatment of drug-resistant bacterial infections. Colistin-resistant strains of Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae often reduce their susceptibility to other anti-Gram-negative bacterial agents. Thus, drugs effective against colistin-resistant strains or methods to prevent the acquisition of colistin-resistance during treatment are urgently needed. To perform cell-based screenings of the collected small molecules, we have generated colistin-resistant strains of E. coli, A. baumannii, K. pneumoniae, P. aeruginosa, and S. enterica Typhimurium. In-house MIC assay screenings, we have identified that rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is the only molecule that displays unique bactericidal activity against these strains at low concentrations under illumination conditions. This article reports the antibacterial activity of a pharmaceutical-grade rose bengal against colistin-resistant Gram-negative bacteria.

Antibacterial Activity of Pharmaceutical-Grade Rose Bengal: An Application of a Synthetic Dye in Antibacterial Therapies.

Rose bengal has been used in the diagnosis of ophthalmic disorders and liver function, and has been studied for the treatment of solid tumor cancers. To date, the antibacterial activity of rose bengal has been sporadically reported; however, these data have been generated with a commercial grade of rose bengal, which contains major uncontrolled impurities generated by the manufacturing process (80-95% dye content). A high-purity form of rose bengal formulation (HP-RBf, >99.5% dye content) kills a battery of Gram-positive bacteria, including drug-resistant strains at low concentrations (0.01-3.13 µg/mL) under fluorescent, LED, and natural light in a few minutes. Significantly, HP-RBf effectively eradicates Gram-positive bacterial biofilms. The frequency that Gram-positive bacteria spontaneously developed resistance to HP-RB is extremely low (less than 1 × 10-13). Toxicity data obtained through our research programs indicate that HP-RB is feasible as an anti-infective drug for the treatment of skin and soft tissue infections (SSTIs) involving multidrug-resistant (MDR) microbial invasion of the skin, and for eradicating biofilms. This article summarizes the antibacterial activity of pharmaceutical-grade rose bengal, HP-RB, against Gram-positive bacteria, its cytotoxicity against skin cells under illumination conditions, and mechanistic insights into rose bengal's bactericidal activity under dark conditions.

Quality of life patient-reported outcomes for locally advanced cutaneous melanoma.

Locally advanced cutaneous melanoma has marked quality-of-life implications; however, the patient experience of symptom management and subsequent impact on quality of life has not been well described. This study aims to address the impact on patients of advanced cutaneous melanoma through qualitative interviews. Adults with stage IIIB, IIIC, or IV (M1a) cutaneous melanoma were recruited from two cancer centers in the USA and one in Australia. Telephone interviews were conducted to assess how locoregionally advanced cutaneous melanoma impacted everyday life. Interviews were recorded, transcribed, and coded for qualitative analysis. Twenty-two melanoma patients were interviewed, mean age 69.7 years (range: 52-83), 64% male. The study included stage IIIB (36%), stage IIIC (59%), and stage IV M1a (5%) patients. Emotional health/self-perception issues were the most commonly identified (41% of patient impact expressions), including worry, concern, embarrassment, self-consciousness, fear, and thoughts of death. Limitations of lifestyle and activities were also identified (28% of expressions) including leisure and social activities, physical functioning, general functioning, and personal care. Coping strategies such as modified clothing choices, increased use of pain and/or anti-inflammatory medications, and avoidance/protection from the sun represented 20% of all impact expressions. Ratings of the degree of difficulty patients experienced (using an 11-point numerical rating scale) ranged from 0.0 to 10.0 (mean 5.7, SD 2.9). Condition-related and treatment-related factors were well characterized in patients with locally advanced cutaneous melanoma. This provides a strong foundation for assessment of how cutaneous melanoma impacts quality of life.

Phase 2 Study of Intralesional PV-10 in Refractory Metastatic Melanoma.

PURPOSE: This international, multicenter, single-arm trial assessed efficacy and safety of intralesional rose bengal (PV-10) in 80 patients with refractory cutaneous or subcutaneous metastatic melanoma. METHODS: Sixty-two stage III and 18 stage IV melanoma patients with disease refractory to a median of six prior interventions received intralesional PV-10 into up to 20 cutaneous and subcutaneous lesions up to four times over a 16-week period and were followed for 52 weeks. Objectives were to determine best overall response rate in injected target lesions and uninjected bystander lesions, assess durability of response, and characterize adverse events. RESULTS: For target lesions, the best overall response rate was 51 %, and the complete response rate was 26 %. Median time to response was 1.9 months, and median duration of response was 4.0 months, with 8 % of patients having no evidence of disease after 52 weeks. Response was dependent on untreated disease burden, with complete response achieved in 50 % of patients receiving PV-10 to all of their disease. Response of target lesions correlated with bystander lesion regression and the occurrence of locoregional blistering. Adverse events were predominantly mild to moderate and locoregional to the treatment site, with no treatment-associated grade 4 or 5 adverse events. CONCLUSIONS: Intralesional PV-10 yielded durable local control with high rates of complete response. Toxicity was confined predominantly to the injection site. Cutaneous bystander tumor regression is consistent with an immunologic response secondary to ablation. This intralesional approach for local disease control could be complementary to current and investigational treatments for melanoma.

In vitro inhibition of human liver cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzymes by rose bengal: system-dependent effects on inhibitory potential.

1. Rose bengal (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein) is being developed for the treatment of cutaneous melanoma and hepatocellular carcinoma. Interestingly, rose bengal can generate singlet oxygen species upon exposure to light. 2. We evaluated rose bengal as an in vitro inhibitor of cytochrome P450 (CYP) or UDP-glucuronosyltransferase (UGT) enzymes in both human liver microsomes (HLM) and cryopreserved human hepatocytes (CHHs) under both yellow light and dark conditions. 3. Rose bengal directly inhibited CYP3A4/5 and UGT1A6 in HLM under yellow light with inhibitor concentration that causes 50% inhibition (IC50) values of 0.072 and 0.035 µM, respectively; whereas much less inhibition was observed in the dark with the IC50 values increasing 43- and 120-fold, respectively. To determine if a more physiologically-relevant test system could be protected from such an effect, rose bengal was evaluated as an inhibitor of CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 3A4/5 and UGT enzymes in CHH. All IC50 values were similar (64 ± 8 µM) and little to no effect of light on inhibitory potential was observed. 4. Given the IC50 values in CHH increased an order of magnitude compared to HLM and the atypical pharmacokinetics of the drug, the risk of rose bengal to cause clinically relevant drug-drug interactions is likely low, particularly when administered to cancer patients on an intermittent schedule.

Chemoablation of metastatic melanoma using intralesional Rose Bengal.

To study the effects of intralesional Rose Bengal for chemoablation of metastatic melanoma. Twenty-six target lesions in 11 patients with locoregionally recurrent disease were injected with the agent PV-10 (10% w/v Rose Bengal in saline) at a dose of 0.5 ml/cc lesion volume. An additional 28 untreated lesions were observed for potential bystander effect. The treatment was well tolerated and an objective response was observed in 12 target lesions, with an additional seven lesions remaining static over at least 12 weeks of observation. In this dose-evaluation study, response rate was dose dependent, increasing to 69% after higher dose injections. Nontarget lesions exhibited a 27% objective response rate that increased to 44% in patients exhibiting a positive response of target lesions. These findings indicate that intralesional Rose Bengal is nontoxic and could benefit patients with metastatic melanoma.

Intensity-modulated, stepped frequency cw lidar for distributed aerosol and hard target measurements.

A compact frequency-modulated, continuous wave (FM-cw) lidar system for measurement of distributed aerosol plumes and hard targets is presented. The system is based on intensity modulation of a laser diode and quadrature detection of the return signals. The advantages of using laser diode amplitude modulation and quadrature detection is a large reduction in the hardware required for processing and storing return signals as well as the availability of off-the-shelf integrated electronic components from the wireless and telecommunication communities. Equations to invert the quadrature signal components and determine spatial distributions of multiple targets are derived. Spatial scattering intensities are used to extract aerosol backscatter coefficients, which can then be directly compared to microphysics aerosol models for environmental measurements. Finally, results from laboratory measurements with a monostatic FM-cw lidar system with both hard targets and aerosols are discussed.

Topical rose bengal: pre-clinical evaluation of pharmacokinetics and safety.

BACKGROUND AND OBJECTIVES: Rose bengal (RB) is a potent photosensitizer that has largely been overlooked as a potential photodynamic therapy (PDT) agent. In this study, the feasibility of topical delivery of RB to the epidermis has been evaluated. STUDY DESIGN/MATERIALS AND METHODS: Topical formulations of RB were assessed on murine and rabbit skin for pharmacokinetic properties, cutaneous toxicity, and photosensitization. RESULTS: Hydrophilic formulations (

Phase sensitive demodulation in multiphoton microscopy.

Multiphoton laser scanning microscopy offers advantages in depth of penetration into intact samples over other optical sectioning techniques. To achieve these advantages it is necessary to detect the emitted light without spatial filtering. In this nondescanned (nonconfocal) approach, ambient room light can easily contaminate the signal, forcing experiments to be performed in absolute darkness. For multiphoton microscope systems employing mode-locked lasers, signal processing can be used to reduce such problems by taking advantage of the pulsed characteristics of such lasers. Specifically, by recovering fluorescence generated at the mode-locked frequency, interference from stray light and other ambient noise sources can be significantly reduced. This technology can be adapted to existing microscopes by inserting demodulation circuitry between the detector and data collection system. The improvement in signal-to-noise ratio afforded by this approach yields a more robust microscope system and opens the possibility of moving multiphoton microscopy from the research lab to more demanding settings, such as the clinic.