Salmonella Heidelberg Strain Responses to Essential Oil Components

Salmonella are one of the more prominent foodborne pathogens that represent a major health risk to humans. Salmonella serovar Heidelberg strains are increasingly becoming an important public health concern, since they have been identified as one of the primary Salmonella serovars responsible for human outbreaks. Over the years, Salmonella Heidelberg isolates have exhibited higher rates of resistance to multiple antimicrobial agents compared to other Salmonella serovars. Essential oils (EOs) have been widely used as alternatives to chemical-based antimicrobials. In the current research, five EOs were screened to determine their antimicrobial activity against 15 S. Heidelberg strains from different sources. Oils tested were R(+)-limonene, orange terpenes, cold compressed orange oil, trans-cinnamaldehyde and carvacrol. EOs were stabilized in nutrient broth by adding 0.15% (w/v) agar. Tube dilution assays and minimal inhibitory concentrations (MIC) were determined by observing color changes in samples during exposure to EOs. Carvacrol and trans-cinnamaldehyde completely inhibited the growth of S. Heidelberg strains, while R(+)-limonene and orange terpenes did not show any inhibitory activity against the strains tested. Cold compressed orange oil only inhibited growth of two of the strains exhibiting an MIC of 1%. All S. Heidelberg isolates evaluated exhibited similar responses to the respective EOs. The use of all natural antimicrobials such as specific EOs offers the potential to limit the majority of S. Heidelberg isolates that may occur in food production.