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.

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