Current Cronobacter spp. Researches on Prevalence, Control, and Detection

Inactivation of Cronobacter sakazakii in powdered infant formula with probiotics and metagenomic analysis

In the present study, proper manual for powdered infant formula with probiotics (PIF-P) to prevent the contamination of Cronobacter sakazakii was investigated. First, the population of C. sakazakii and LAB in three different PIF-P samples were quantitatively analyzed after reconstituted with hydrothermal treatments. When C. sakazakii was inoculated into reconstituted infant formula with probiotics (RIF-P), it was immediately reduced below the detection limit by 60-65 °C hydrothermal treatment whereas reduction levels of LAB was 1-2 log CFU/g. When heat resistance of C. sakazakii inoculated to PIF-P with 4 h drying was compared with that inoculated to RIF-P samples, the heat resistance of C. sakazakii increased significantly after the inoculation in PIF-P with drying. Metagenomic analysis revealed that Lactobacillus and Bifidobacterium were dominant genus in all three groups and there was no significant difference in the microbial community of untreated PIF sample and hydrothermal treated samples.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01503-x.

Growth Inhibition of Cronobacter sakazakii in Experimentally Contaminated Powdered Infant Formula by Kefir Supernatant

Kefir is a type of fermented milk containing lactic and acetic acid bacteria and yeast. In this study, we evaluated the antimicrobial activity of kefir supernatant against Cronobacter sakazakii in powdered infant formula (PIF). In a spot-on-lawn test, the growth of 20 C. sakazakii strains, including 10 clinical and 10 food isolates, was completely inhibited in the presence of kefir supernatant. Significant differences in the diameters of inhibition zones were observed upon treatment with kefir compared with the results for Lactobacillus kefiri and Candida kefyr culture supernatants or solutions of lactic and acetic acid and ethyl alcohol in the agar well diffusion test (P < 0.05). The addition of 100 μl of kefir supernatant to 1 ml of nutrient broth completely inhibited the growth of C. sakazakii, as evaluated by spectrophotometry. The antimicrobial activity of kefir supernatant in experimentally contaminated PIF was also tested; we found no viable C. sakazakii cells remaining in PIF rehydrated with 30% kefir supernatant solution for 1 h, demonstrating that the antimicrobial activity of kefir supernatant against C. sakazakii could be applied in real food samples.