Flavone inhibits Staphylococcus aureus virulence via inhibiting the sae two component system

Trans-cinnamaldehyde nanoemulsion reduces Salmonella Enteritidis biofilm on steel and plastic surfaces and downregulates expression of biofilm associated genes

Salmonella Enteritidis is a major poultry-associated foodborne pathogen that can form sanitizer-tolerant biofilms on various surfaces. The biofilm-forming capability of S. Enteritidis facilitates its survival on farm and food processing equipment. Conventional sanitization methods are not completely effective in killing S. Enteritidis biofilms. This study investigated the efficacy of a Generally Recognized as Safe phytochemical Trans-cinnamaldehyde (TC), and in its nanoemulsion form (TCNE), for inhibiting S. Enteritidis biofilm formation and inactivating mature biofilms developed on polystyrene and stainless-steel surfaces. Moreover, the effect of TC on Salmonella genes critical for biofilm formation was studied. TCNE was prepared using a high energy sonication method with Tween 80. For biofilm inhibition assay, S. Enteritidis was allowed to form biofilms either in the presence or absence of sub-inhibitory concentration (SIC; 0.01 %) of TCNE at 25°C and the biofilm formed was quantified at 24-h intervals for 48 h. For the inactivation assay, S. Enteritidis biofilms developed at 25°C for 48 h were exposed to TCNE (0.5, 1 %) for 1, 5, and 15 min, and surviving S. Enteritidis in the biofilm were enumerated. SIC of TCNE inhibited S. Enteritidis biofilm by 45 % on polystyrene and 75 % on steel surface after 48 h at 25°C compared to control (P < 0.05). All TCNE treatments rapidly inactivated S. Enteritidis mature biofilm on polystyrene and steel surfaces (P < 0.05). The lower concentration of TCNE (0.5 %) reduced S. Enteritidis counts by 1.5 log CFU/ml as early as 1 min of exposure on both polystyrene and stainless-steel surfaces. After 15 min of exposure, TCNE at concentration of 0.5 or 1 % reduced S. Enteritidis count significantly by 4.5 log CFU or 6 log CFU/ml on polystyrene or stainless-steel surfaces. TC downregulated the expression of S. Enteritidis genes (hilA, hilC, flhD, csgA, csgD, sdiA) responsible for biofilm formation (P < 0.05). Results suggest that TCNE has potential as a natural disinfectant for controlling S. Enteritidis biofilms on common farm and food processing surfaces, such as plastic and steel.

Synergistic Antibacterial Mechanism of Benzyl Isothiocyanate and Resveratrol Against Staphylococcus aureus Revealed by Transcriptomic Analysis and Their Application in Beef

This study aims to elucidate the synergistic antibacterial mechanism of benzyl isothiocyanate (BITC) and resveratrol (RES) on Staphylococcus aureus (S. aureus) at the transcriptional level. Compared with the individuals, the combination of BITC and RES (BITC_RES) reduced S. aureus growth, inhibited biofilm formation, and increased cell membrane disruption. The transcriptomic results showed that the BITC_RES group presented 245 and 1150 more DEGs than the BITC group and the RES group, respectively. In addition, some other key genes in the BITC_RES group, including serine protease (splA, splE), Sae regulatory system (saeR, saeS, tsaE, sau300), accessory gene regulator protein C (agrC), cysteine protease (sspB), glutamyl endopeptidase (sspA), and hemolysin toxin family-related genes (hly, lukDv, lukEv), and the relative expression of these 12 genes was downregulated by 2.2-259.8-fold, 0.8-259.8-fold and 1.2-158.2-fold greater than those in the BITC group and the RES group, respectively. Finally, a synergistic antimicrobial effect of this combination was also observed in fresh lean beef at 4 °C and 25 °C. These findings provide information for future studies on the synergistic antimicrobial effects of BITC and RES on S. aureus.

Fitness cost and compensatory evolution of penicillin-induced resistant Staphylococcus aureus

Staphylococcus aureus is a widespread pathogen in nature, with staphylococcal enterotoxins being a major cause of foodborne illness. The extensive use of antibiotics on farms has contributed to the spread of antibiotic-resistant S. aureus. Understanding the fitness cost and compensatory evolution of antibiotic-resistant isolates is crucial for assessing the consequences of resistance acquisition and predicting the potential spread of resistant mutants in various environments. In this study, penicillin (PEN) was used to induce resistance in antibiotic-sensitive S. aureus, resulting in PEN-resistant mutants. We evaluated and compared the growth and thermal inactivation characteristics at different temperatures, virulence potential, and relative fitness of S. aureus isolates before and after PEN exposure under various stress conditions. The results revealed that PEN induction led to the acquisition of multidrug resistance and cross-resistance in S. aureus. Compared to the parent sensitive isolates, PEN-resistant S. aureus exhibited altered biological characteristics, including reduced phenotypes related to invasion (hemolysis activity, serum resistance) and toxin production (staphyloxanthin formation), but increased characteristics linked to colonization (biofilm formation) and gene transfer (autolytic activity). Fitness advantages were either maintained or enhanced in resistant isolates, with PEN serial passaging showing a more pronounced effect in improving fitness and driving compensatory evolution. These findings underscore the importance of investigating fitness costs and compensatory evolution following resistance acquisition to better understand the risks posed by resistant S. aureus to the food chain and human health.

Anti-virulence potential of patuletin, a natural flavone, against Staphylococcus aureus: In vitro and In silico investigations

Staphylococcus aureus is a highly prevalent and aggressive human pathogen causing a wide range of infections. This study aimed to explore the potential of Patuletin, a rare natural flavone, as an anti-virulence agent against S. aureus. At a sub-inhibitory concentration (1/4 MIC), Patuletin notably reduced biofilm formation by 27 % and 23 %, and decreased staphyloxanthin production by 53 % and 46 % in Staphylococcus aureus isolate SA25923 and clinical isolate SA1, respectively. In order to gain a more comprehensive understanding of the in vitro findings, several in silico analyses were conducted. Initially, a 3D-flexible alignment study demonstrated a favorable structural similarity between Patuletin and B70, the co-crystallized ligand of CrtM, an enzyme that plays a pivotal role in the biosynthesis of staphyloxanthin. Molecular docking highlighted the strong binding of Patuletin to the active site of CrtM, with a high affinity of -20.95 kcal/mol. Subsequent 200 ns molecular dynamics simulations, along with MM-GBSA, ProLIF, PLIP, and PCAT analyses, affirmed the stability of the Patuletin-CrtM complex, revealing no significant changes in CrtM's structure upon binding. Key amino acids crucial for binding were also identified. Collectively, this study showcased the effective inhibition of CrtM activity by Patuletin in silico and its attenuation of key virulence factors in vitro, including biofilm formation and staphyloxanthin production. These findings hint at Patuletin's potential as a valuable therapeutic agent, especially in combination with antibiotics, to counter antibiotic-resistant Staphylococcus aureus infections.

Development of a dual fluorescent reporter system to identify inhibitors of Staphylococcus aureus virulence factors

IMPORTANCE

Staphylococcus aureus is a formidable pathogen responsible for a wide range of infections, and the emergence of antibiotic-resistant strains has posed significant challenges in treating these infections. In this study, we have established a novel dual reporter system capable of concurrently monitoring the activities of two critical virulence regulators in S. aureus. By incorporating both reporters into a single screening platform, we provide a time- and cost-efficient approach for assessing the activity of compounds against two distinct targets in a single screening round. This innovative dual reporter system presents a promising strategy for the identification of molecules capable of modulating virulence gene expression in S. aureus, potentially expediting the development of antivirulence therapies.