Purpose: The objective of this study was to investigate the synergistic effect of gums on the growth and antibiotic susceptibility of foodborne pathogens.
Methods: Batches of 200 ml sterilized tryptic soy broth containing 0.5% gums were inoculated at 0.05% and plated on tryptic soy agar to determine initial bacterial counts and then final counts after incubation at 37°C for 16 h. Antibiotic activity was determined by disc diffusion on tryptic soy agar containing 0.5% gums.
Results: Amongst antibiotics tested, treatment with carrageenan-maltodextrin (52.00±2.00 mm) and pectin (51.00±1.00 mm) resulted in a two-fold increase in susceptibility of Salmonella enterica to imipenem 10 μg, compared to the control (25.33±1.00 mm). Treatment with locust bean and agar also led to a two-fold increase in susceptibility of Salmonella enterica to cefixime and xanthan also increased susceptibility of Escherichia coli O157:H7 to doripenem. Compared to control, addition of locust bean, pectin and xanthan led to the highest growth inhibition of Salmonella enterica, Escherichia coli O157:H7, Staphylococcus aureus and Listeria monocytogenes, respectively. Bacterial survival decreased in the presence of all gums with pectin showing a 2.68±0.10 log CFU ml-1 reduction during refrigerated storage.
Significance: These findings suggest that carrageenan, pectin, locust bean and agar could potentially be used in combination with antimicrobial agents to improve their efficacy in the treatment of Salmonella enterica and Escherichia coli O157:H7 infections resulting in early recovery. Additionally, these gums could be used together with other ingredients to preserve food, thus, reducing dependence on chemicals and promoting food safety.