Abstract
Organic acid and essential oils (EOs), well-known antimicrobials, could also possess antiviral activity, a characteristic which has not been completely addressed up to now. In this study, the effect of two organic acids (formic acid and sodium salt of coconut fatty acid distillates) and two single EO compounds (thymol and cinnamaldehye) was evaluated against porcine epidemic diarrhea virus (PEDV). The concentration used for each compound was established by cytotoxicity assays in Vero cells. The antiviral activity was then evaluated at three multiplicities of infection (MOIs) through visual cytopathic effect (CPE) evaluation and an alamarBlue assay as well as real-time reverse-transcription PCR (RT-qPCR) and viral titration of cell supernatants. Formic acid at at a dose of 1,200 ppm was the only compound which showed antiviral activity, with a weak reduction of CPE caused by PEDV. Through the alamarBlue fluorescence assay, we showed a significant anti-CPE effect of formic acid which could not be observed by using an inverted optical microscope. RT-qPCR and infectivity analysis also showed that formic acid significantly reduced viral RNA and viral titers in a PEDV MOI-dependent manner. Our results suggest that the antiviral activity of formic acid could be associated to its inhibitory effect on viral replication. Further studies are required to explore the anti-PEDV activity of formic acid under field conditions alone or together with other antiviral agents.
Highlights
Organic acids and essential oils (EOs) are among the most effective alternatives to antibiotics [1], providing solutions to the antimicrobial resistance (AMR) problem [2]
Due to high cytotoxicity showed by the compounds tested, a single concentration of each product was used to evaluate the anti-porcine epidemic diarrhea virus (PEDV) activity; 1,200 ppm for formic acid, 64 ppm for sodium salt of coconut fatty acid distillates, 150 ppm for thymol and 75 ppm for cinnamaldehyde
The inclusion of 1,200 ppm of formic acid reduced cytopathic effect (CPE) to 62.5% in the wells exposed to PEDV at a MOI of 0.005, a significant reduction compared to non-treated control wells (p < 0.05)
Summary
Organic acids and essential oils (EOs) are among the most effective alternatives to antibiotics [1], providing solutions to the antimicrobial resistance (AMR) problem [2]. Compared to other cost-effective alternatives, organic acids and EOs have received particular attention due to their potential benefits to health and growth of the host [3, 4], associated to the modulation of gut microbiota and immune response [5,6,7,8] Apart from their known activity against bacteria, even with drug or multi-drug resistant profiles [9,10,11,12], studies using human viruses have shown that they may have antiviral properties [13,14,15,16]. Among the viral enteric diseases of swine, porcine epidemic diarrhea (PED) is worth mentioning causing devastating economic losses for pig industry. The etiological agent, porcine epidemic diarrhea virus (PEDV), is a coronavirus (CoV) which is an enveloped virus with a
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