Novel Arginine End-Tagging Antimicrobial Peptides to Combat Multidrug-Resistant Bacteria.

The emergence of multidrug-resistant microorganisms has been termed one of the most common global health threats, emphasizing the discovery of new antibacterial agents. To address this issue, we engineered peptides harboring "RWWWR" as a central motif plus arginine (R) end-tagging and then tested them in vitro and in vivo. Our results demonstrate that Pep 6, one of the engineered peptides, shows great potential in combating Escherichia coli bacteremia and the Staphylococcus aureus skin burn infection model, which induces a 62-90% reduction in bacterial burden. Remarkably, after long serial passages of S. aureus and E. coli for 30 days, Pep 6 is still highly efficient in killing pathogens, compared with 64- and 128-fold increase in minimal inhibitory concentrations (MICs) for vancomycin and polymyxin B, respectively. We also found that Pep 6 exhibited robust biofilm-inhibiting activity and eliminated 61.33% of the mature methicillin-resistant Staphylococcus aureus (MRSA) biofilm with concentration in the MIC level. These results suggest that the RWWWR motif and binding of arginine end-tagging could be harnessed as a new agent for combating multidrug-resistant bacteria.

Acute and subchronic toxicity of arprinocid in Sprague-Dawley rats.

We subjected Sprague-Dawley rats to an acute and 13-week subchronic oral toxicity of arprinocid, a nucleoside analogue used as a coccidiostat, according to toxicological guidelines as part of its safety assessment. In the acute study, arprinocid was administered once by oral gavage to rats at doses ranging from 292.4 to 506.0mg/kgb.w. The calculated LD50 was 442.9mg/kgb.w. in males and 378.7mg/kgb.w. in females. In the subchronic study, male and female rats were fed with diets supplemented with 0, 25, 187.5 or 500ppm arprinocid for 13weeks. Significantly lower body weights were noted in the 500ppm group females. The mean body weights of the 500ppm group females were 12.9% lower than that of the controls. Significant differences in haematological and biochemical parameters as well as organ weights were detected between the 500 and 187.5ppm groups. Histopathological observations revealed that 500 and 187.5ppm arprinocid could induce hepatic steatosis and focal hepatocellular necrosis. Slight protein cast in some renal tubules and tubular regeneration were observed in the high dose group of both genders. The dietary no-observed-adverse-effect level (NOAEL) of arprinocid in rats for 13weeks is 25ppm (approximately 1.7mg/kgb.w./day).

Nitazoxanide inhibits the replication of Japanese encephalitis virus in cultured cells and in a mouse model.

BACKGROUND: Japanese encephalitis virus (JEV) has a significant impact on public health. An estimated three billion people in 'at-risk' regions remain unvaccinated and the number of unvaccinated individuals in certain Asian countries is increasing. Consequently, there is an urgent need for the development of novel therapeutic agents against Japanese encephalitis. Nitazoxanide (NTZ) is a thiazolide anti-infective licensed for the treatment of parasitic gastroenteritis. Recently, NTZ has been demonstrated to have antiviral properties. In this study, the anti-JEV activity of NTZ was evaluated in cultured cells and in a mouse model. METHODS: JEV-infected cells were treated with NTZ at different concentrations. The replication of JEV in the mock- and NTZ-treated cells was examined by virus titration. NTZ was administered at different time points of JEV infection to determine the stage at which NTZ affected JEV replication. Mice were infected with a lethal dose of JEV and intragastrically administered with NTZ from 1 day post-infection. The protective effect of NTZ on the JEV-infected mice was evaluated. FINDINGS: NTZ significantly inhibited the replication of JEV in cultured cells in a dose dependent manner with 50% effective concentration value of 0.12 ± 0.04 µg/ml, a non-toxic concentration in cultured cells (50% cytotoxic concentration = 18.59 ± 0.31 µg/ml). The chemotherapeutic index calculated was 154.92. The viral yields of the NTZ-treated cells were significantly reduced at 12, 24, 36 and 48 h post-infection compared with the mock-treated cells. NTZ was found to exert its anti-JEV effect at the early-mid stage of viral infection. The anti-JEV effect of NTZ was also demonstrated in vivo, where 90% of mice that were treated by daily intragastric administration of 100 mg/kg/day of NTZ were protected from a lethal challenge dose of JEV. CONCLUSIONS: Both in vitro and in vivo data indicated that NTZ has anti-JEV activity, suggesting the potential application of NTZ in the treatment of Japanese encephalitis.

Tracing antibacterial compounds from Acalypha australis Linn. by spectrum-effect relationships and semi-preparative HPLC.

Several Acalypha australis Linn. species are used in traditional medicine in Southeast Asia. In this work, the ultra-performance liquid chromatography/mass spectrometry fingerprints and the antibacterial activities of A. australis Linn. were investigated. An in-depth discussion on the reliability of identifying and obtaining potentially active compounds by spectrum-effect relationship and semi-preparative high performance liquid chromatography was conducted. The result shows that gallic acid and a compound with molecular weight of 634.1 in the fingerprints were the main antibacterial compounds. Compared to the crude extract of A. australis Linn., both compounds increase the antibacterial efficacy 10 to 20 times. Compounds with molecular weights of 154.0, 292.0, and 485.1 in the fingerprints were the auxiliary antibacterial compounds. Through the entire isolation procedure, we obtained these antibacterial compounds with purities of 92.53, 87.98, 90.73, 89.36, and 88.14%, respectively. This work provides a general model of the combination of ultra-performance liquid chromatography/mass spectrometry fingerprinting and antibacterial test to study the spectrum-effect relationships of A. australis Linn. This model can be used to discover further the active compounds of this herb.