Selection of a Potential Synbiotic against Cronobacter sakazakii

Abstract

Cronobacter sakazakii is an opportunistic foodborne pathogen that can be fatal to infants and is commonly associated with powdered infant formula due to contamination in manufacturing processes, hospitals, or homes. This project aimed to select a potential synbiotic, a combination of probiotic strains with a prebiotic product, to inhibit the growth of C.sakazakii in an in vitro dynamic infant gut model (Simulator of the Human Intestinal Microbial Ecosystem). A total of 16 lactic acid bacteria (LAB) were tested for their inhibitory properties against four different C. sakazakii strains by a zone of inhibition test. Lactobacillus and Pediococcus species were able to inhibit the growth (>15-mm inhibition zones) of all C. sakazakii strains tested and only one strain from the two genera exhibited atypical resistance to tetracycline. All C. sakazakii strains and the selected LAB strains, which inhibited C. sakazakii and did not exhibit atypical antibiotic resistance, were grown in Luria-Bertani or MRS broth, respectively, containing 1% dextrose or 1% commercial prebiotic (w/v) to compare their ability to metabolize the prebiotic product. Overall, based on the growth inhibition of C. sakazakii , antibiotic susceptibility, and prebiotic metabolism, 6 out of the 16 LAB were chosen to be part of a potential synbiotic. This study has provided valuable information that will help with the development of a synbiotic that can be used in powdered infant formula to reduce the potential for C. sakazakii related illnesses in infants.

Inhibition of Cronobacter sakazakii in an infant simulator of the human intestinal microbial ecosystem using a potential synbiotic

“…Each SHIME compartment received two treatments spanning 1 week each, with SHIME 1 representing the control for the entire duration of the 2-week treatment period (Table 1). The lactic acid bacteria (LAB) and Vivinal GOS (VGOS), which is a commercial prebiotic substrate incorporated within infant formula, and used as the potential synbiotic in the infant SHIME, were formulated as previously described (Ke et al, 2022). The selected C. sakazakii and LAB strains (Supplementary Table 1) were grown in BHI or MRS broth, respectively, overnight at 37 • C then diluted 1:100 the following day in fresh BHI or MRS broth and incubated for a further 24 h at 37 • C. For the potential synbiotic, hereafter referred to as LAB + VGOS, the overnight cultures of LAB were centrifuged at 14,000 × g for 10 min at room temperature and resuspended in MRS, which did not contain any carbohydrates, containing 1% VGOS.…”