Viability and gene transcription of Campylobacter jejuni in infant milk formulas

Abstract

This study simulated the contamination of two varieties of infant milk formulas (homemade and commercial) with 10³ and 10⁴ CFU/mL of Campylobacter jejuni, that were kept under refrigeration (4-7ºC) for up to 48 hours. The aim of this study was to verify the maintenance of the viability and ability of Campylobacter jejuni to produce transcripts of virulence and resistance to stress conditions during periods of 0 (after preparation), 24 and 48 hours. C. jejuni remained viable during all analyzed stages and the presence of coliforms was not detected. In general, the counts reduced 1 log cycle after 48 hours for all samples, except the 10⁴ CFU/mL inoculum of commercial formula, which reduced 2 log cycles, indicating greater injury of C. jejuni in this food matrix. C. jejuni showed to be more adapted to homemade matrix, due to high transcription of the gene related to cell invasion, ciaB, and more susceptible in the commercial matrix, due to the high transcription  of genes related to conditions of stress tolerance (dnaJ, p19, sodB). The low infective dose of C. jejuni coupled with greater vulnerability of children less than five years indicate the need for care in the preparation and maintenance of infant formulas, to prevent the use of contaminated raw material and cross-contamination, especially in homemade formulations.