Overview: A new front in the fight against swine respiratory viruses
Respiratory viral diseases threaten animal health and global food security, particularly in intensive pig farming systems. Outbreaks caused by PRRSV, SIV, PRV, and PEDV lead to high piglet mortality, reproductive losses, and substantial economic hardship. Traditional vaccines often fall short due to rapid viral mutation and uneven protection. In response, researchers have turned to the nasal microbiome as a natural line of defense. A wild-type Bacillus subtilis strain, NS12, isolated from outdoor pigs, shows a remarkable capacity to colonize nasal mucosa and directly impede viral infections.
Discovery: A natural nasal probiotic shield
Epidemiological studies revealed that pigs with outdoor access harbored fewer respiratory viruses, closely linked to an enrichment of nasal Bacillus subtilis. The NS12 strain can persist in the nasal mucosa for up to two weeks and secret a potent mix of antiviral metabolites. These substances act as a direct barrier on the mucosal surface, neutralizing a broad panel of enveloped viruses before they reach target cells.
How NS12 protects pigs: two antiviral metabolites
The study identifies two key antiviral compounds produced by NS12:
- Novel surfactin derivatives (C16/C17) — cyclic lipopeptides that disrupt viral envelope phospholipid dynamics and prevent fusion with host membranes. These derivatives are reported to be safer and less cytotoxic than standard surfactin, reducing potential tissue irritation while maintaining antiviral activity.
- Piceatannol — a hydroxylated stilbene phenolic compound that binds to viral envelope lipids, increases lipid saturation, and reduces membrane fluidity. This mechanism blocks viral entry without damaging the virus itself, forming a robust local defense.
Together, these metabolites create a “molecular firewall” on the nasal mucosa, offering a broad-spectrum barrier against enveloped respiratory viruses by targeting the viral envelope rather than specific viral proteins.
Evidence of efficacy: animal and model studies
In controlled experiments, NS12 protected piglets from PRRSV and PEDV infections, lowering viral loads, reducing tissue damage, and improving survival. A mouse model further demonstrated NS12’s cross-species antiviral potential, with strong protection against PRV challenges. These results suggest that NS12’s antiviral action is not limited to a single virus or host species, but may extend to broader respiratory threats.
Implications for sustainable antiviral strategies in livestock
NS12 represents a paradigm shift: a naturally occurring nasal probiotic that blocks viral invasion via metabolite-mediated mechanisms. Unlike vaccines that target specific viral antigens, NS12 works at the level of the viral envelope—derived from host cells—making it harder for viruses to acquire mutation-based resistance. This approach could complement vaccination programs or serve as a standalone strategy where vaccines are less effective.
Future directions: applications and human relevance
Researchers envision deploying NS12 as intranasal probiotic sprays, functional feed additives, or even as the basis for next-generation veterinary antivirals. Because the mechanism targets the viral envelope, there is potential relevance to other mammals, including humans, for respiratory viruses such as influenza and coronaviruses. Ongoing work will need to address safety, dosing, regulatory approval, and long-term ecological impacts of releasing nasal probiotics into farm environments.
Expert perspective
According to Professor Qian Yang, corresponding author of the study, the nasal probiotic NS12 opens new avenues for disease control in pigs and beyond. The concept aligns with a growing interest in microbiome-based strategies that exploit natural host-microbe interactions to improve health and resilience in livestock.
Bottom line
Natural nasal bacteria like Bacillus subtilis NS12 offer a promising, broad-spectrum antiviral approach that complements vaccines and could reduce losses from PRRSV, SIV, PRV, and PEDV. If validated in larger field trials and scaled safely, NS12-based products could become part of a sustainable toolbox to protect animal health and food security—potentially with implications for human respiratory disease prevention as well.
