Significance and Impact of the Study: Staphylococcus epidermidis infections are frequently associated with biofilms that are difficult to eradicate with conventional antibiotics. The new biofilm inhibitors from Actinomycete will have a great value in the prevention and treatment of dairy cow mastitis and other biofilm-related infections. AbstractThis study sought to identify novel and nontoxic biofilm inhibitors from the Actinomycete library for attenuating biofilm formation by Staphylococcus epidermidis. After investigating the antibiofilm activities of spent media from 185 Actinomycete strains using two S. epidermidis strains (ATCC 35984 and a clinical strain 5-121-2) as target bacteria, three strains of tested Actinomycete (TRM 46200, TRM 41337, and TRM 46814) showed a significant inhibition against S. epidermidis biofilm formation without affecting the growth of planktonic cells. The characteristics of three strains of supernatants suggested that hydrophilic compound possibly extracellular peptides or proteins from these three strains, confer the biofilm reduction in S. epidermidis. An attempt was made to assess their effects on biofilm components and cell surface hydrophobicities in order to disclose acting mechanisms. The crude proteins from spent media of three strains degraded not only exopolysaccharides but also extracellular DNA in S. epidermidis biofilm. The active substances in crude proteins caused S. epidermidis cells to become less hydrophobic. Given these results, the metabolites from Actinomycete strains should keep further attention as potential antibiofilm agents against biofilm formation of S. epidermidis, even biofilm infections of the other bacteria.

As a natural potential resource, Tamarix ramosissima has been widely used as barbecue skewers for a good taste and unique flavor. The polyphenolics in the branch bark play a key role in the quality improvement. The purposes of the present work were to explore the polyphenolic composition of T. ramosissima bark extract and assess their potential antioxidant and antimicrobial activities. Hispidulin and cirsimaritin from T. ramosissima bark extract were first identified in the Tamarix genus reported with UPLC-MS analysis. Isorhamnetin (36.91 μg/mg extract), hispidulin (28.79 μg/mg extract) and cirsimaritin (13.35 μg/mg extract) are rich in the bark extract. The extract exhibited promising antioxidant activity with IC50 values of 117.05 μg/mL for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 151.57 μg/mL for hydroxyl radical scavenging activities, as well as excellent reducing power with an EC50 of 93.77 μg/mL. The bark extract showed appreciable antibacterial properties against foodborne pathogens. Listeria monocytogenes was the most sensitive microorganism with the lowest minimum inhibitory concentration (MIC) value of 5 mg/mL and minimum bactericidal concentration (MBC) value of 10 mg/mL followed by S. castellani and S. aureus among the tested bacteria. The T. ramosissima bark extract showed significantly stronger inhibitory activity against Gram-positive than Gram-negative bacteria. Nevertheless, this extract failed to show any activity against tested fungi. Overall, these results suggested that T. ramosissima shows potential in improving food quality due to its highly efficacious antioxidant and antibacterial properties.

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