Antibiofilm potential of luteolin against multidrug-resistant Staphylococcus aureus isolated from dairy goats and farm environments.

Staphylococcus aureus (S. aureus) is a prominent pathogen responsible for mastitis in dairy goats, and capable of contaminating farm environments. Luteolin is a naturally derived flavonoid found in many plant types. To our best of knowledge, this study involved the initial investigation into the prevalence of S. aureus and screened the multidrug-resistant (MDR) S. aureus from raw milk samples and farm environments. Furthermore, we explored the antimicrobial and antibiofilm activities of luteolin against MDR S. aureus. Antibiofilm activity was evaluated via crystal violet staining and confocal laser scanning microscopy (CLSM). Bacterial morphology and biofilm microstructure were observed via scanning electron microscopy (SEM), and the antibiofilm mechanisms were further explored based on extracellular polymeric substance (EPS) production, extracellular DNA (eDNA) content, and quantitative reverse transcription PCR (qRT-PCR). In total, 28 and 43 S. aureus isolates were isolated from raw milk and environmental samples, respectively. Raw milk samples had the highest prevalence of S. aureus (58.33%), followed by sewage sludge (35.42%), soil (27.78%), excrement (19.44%), bulk tank (12.50%), milking parlor (11.11%), and feed (7.50%). Among the isolated strains, 40 isolates (56.34%) expressed the MDR phenotype. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of luteolin against MDR S. aureus were 8-32 µg/mL and 16-64 µg/mL, respectively. Compared to that in the untreated control isolate, the number of dead cells increased, while the auto-aggregation and cell surface hydrophobicity decreased. Moreover, the cell membrane dissolved with the increase in luteolin concentration. Luteolin down-regulated the transcription of seven biofilm related genes: icaA, icaD, icab, hld, hla, agrA and RNAIII. These results indicated that S. aureus coexisted in raw milk and goat farm environments, and also suggested the potential of luteolin as a promising antibiofilm agent against MDR S. aureus.

Echinacea Polyphenols Inhibit NLRP3-Dependent Pyroptosis, Apoptosis, and Necroptosis via Suppressing NO Production during Lipopolysaccharide-Induced Acute Lung Injury.

PANoptosis is an intricate programmed death pathway that involves the interaction between pyroptosis, apoptosis, and necroptosis. We systematically explored the protective effect of Echinacea polyphenols (EPP) against the lipopolysaccharide (LPS)-induced acute lung injury (ALI) and the underlying mechanisms both in vitro and in vivo. We noted that EPP pretreatment could significantly alleviate LPS-induced lung tissue injury and pulmonary edema. EPP inhibited the PANoptosis by regulating the expression of nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome, gasdermin D, caspase-8, caspase-3, and mixed lineage kinase domain-like protein. Meanwhile, a comparative study of EPP and inducible nitric oxide synthase inhibitor S-methylisothiourea sulfate indicated that EPP may play a preprotective role in inhibiting PANoptosis via reducing the activity of inducible nitric oxide synthase and the production of nitric oxide (NO) during ALI. Our results clearly indicated that PANoptosis existed in LPS-induced ALI, and EPP pretreatment could provide obvious protective effects to LPS-induced ALI by inhibiting PANoptosis, which may be related to NO production.

Antimicrobial and antibiofilm activity of isoorientin against carbapenem non-sensitive Escherichia coli from raw milk of goats.

Carbapenemase-producing E. coli is a grave public health concern as the potential emergence of resistant strains and their transmission. Isoorientin belongs to a potential antimicrobial flavonoid compound existing in several plants, while the research on the antimicrobial activity of isoorientin is limited thus far. We evaluated the antimicrobial and antibiofilm effects of isoorientin against biofilm-forming carbapenem non-sensitive Escherichia coli (E. coli) from raw milk of goats, and explored its molecular mechanisms. Isoorientin showed obvious antimicrobial ability with the minimum inhibitory concentration (MIC), and it exhibited synergistic activity with traditional antimicrobials against the carbapenem non-sensitive E. coli. Isoorientin could also significantly inhibit the carbapenem non-sensitive E. coli biofilm formation and destroy the established biofilms, with the percentage of inhibition ranging from 27.8% to 75% at MIC, and the corresponding percentage of eradication ranging from 15.3% to 61.6%, respectively. Confocal laser scanning microscopy (CLSM) observation and scanning electron microscopy (SEM) images indicated that the E. coli biofilm reduced in thickness with increasing concentrations of isoorientin. Dose-dependent decrease in eDNA revealed that isoorientin interacted with the extracellular polymeric substances (EPS) of the biofilm. qRT-PCR assay for the biofilm-forming associated genes further confirmed the above results. Overall, these results concluded that the isoorientin has significant antimicrobial and antibiofilm activity against carbapenem non-sensitive E. coli, and has potential application in prevention of food contamination and spoilage.

Escherichia coli (E. coli) has been the major foodborne bacteria that can cause diarrhea, gastroenteritis, and some complications, and also used as fecal bacteria pollution indicator in food. Carbapenems are considered as the last resort to life-threatening E. coli infections. We evaluated the antimicrobial and antibiofilm effects of isoorientin against biofilm-forming carbapenem non-sensitive E. coli from raw milk of goats, and explored its molecular mechanisms. This study firstly demonstrated the potential antimicrobial and antibiofilm properties of isoorientin against the carbapenem non-sensitive E. coli for the first time, and it has the properties of inhibiting the biofilm formation and destroying the preformed biofilms. Therefore, isoorientin is a promising biofilm inhibitor for curtailing drug resistant foodborne pathogens, and this study could provide a scientific basis for its practical application of isoorientin.