Iron-enriched Aspergillus oryzae as an alternative to iron sulphate to limit iron accumulation, growth and motility of the enteric pathogen S. Typhimurium

Excess unabsorbed iron in the gastrointestinal tract may select for enteric pathogens and increase the incidence and severity of infectious disease. Aspergillus oryzae (Ao) is a filamentous fungus that has the ability to accumulate and store large amounts of iron, and when used as a supplement or fortificant, has similar absorption to ferrous sulphate (FeSO4) in humans. The objective of this study was to determine the effect of iron-enriched Ao (Ao iron) compared with FeSO4 on iron accumulation, growth and motility of the Gram-negative enteric pathogen, S. Typhimurium. S. Typhimurium was cultured in media containing no added iron or 1 mu M elemental iron as either Ao iron or FeSO4. S. Typhimurium cultured with FeSO4 accumulated more iron than those cultured with Ao iron. Genes regulated by the iron-activated transcriptional repressor, Fur, did not differ between control and Ao iron, but decreased in S. Typhimurium cultured with FeSO4 compared with both groups. Growth of S. Typhimurium was greater when cultured with FeSO4 compared with Ao iron and control. S. Typhimurium swam faster, had greater acceleration and travelled further when cultured with FeSO4 compared with Ao iron and control; swim speed, acceleration and distance travelled did not differ between Ao iron and control. These findings provide evidence that Ao iron reduces the virulence of a common enteric pathogen in vitro. Further research is required to determine whether iron-enriched Ao is a suitable iron supplement to improve iron delivery in areas with a high infection burden.