IntroductionCertain strains of Cronobacter sakazakii can cause serious invasive infections in children, mainly those <2 months old and fed with powdered infant formula (PIF). The infectious dose of C. sakazakii is unknown but evidence suggests that it is approximately 1000 colony forming units (CFU). PIF is currently considered safe if its end-product C. sakazakii level is <1 CFU/g. In this study, we determined the lag time, generation time (GT), and growth rate of five pooled C. sakazakii isolates to evaluate the factors affecting contamination levels in reconstituted PIF.Methods1.71 log CFU/ml of C. sakazakii were inoculated into 100 and 3000 ml of reconstituted PIF and incubated at 22 and 35°C. Growth was evaluated over a 24-h period. ComBase was used for modeling.ResultsIn 3000 ml, the growth rate was 0.45 ± 0.02 log CFU/h with a lag phase of 3 ± 0.05 h and GT of 0.67 h at 22°C, while the growth rate was 0.73 ± 0.01 log CFU/h with a lag phase of 0.45 ± 0.03 h and GT of 0.41 h at 35° C.ConclusionCronobacter sakazakii grows rapidly in reconstituted PIF, especially at 35° C.

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Background: Dairy products are common sources of Listeria outbreaks, and early detection of the pathogen is critical to prevent outbreaks of illnesses and financial losses for dairy producers. Objective: This study aimed to evaluate Sample6 Detect HT/L for effective detection of Listeria monocytogenes and L. innocua in ice cream. Methods: Performance of the Sample6 DETECT HT/L was compared with U.S. Food and Drug Administration (FDA) Bacteriological Analytical Manual (BAM) Chapter 10 method for detection of Listeria spp. in ice cream using an unpaired study design. Results: R2-enriched samples tested with Sample6 Detect HT/L performed as well as the reference method at all time points tested from 15 to 24 h. R2 is a proprietary blend for use with the test kit that helps with early detection. All the dPODC values (Sample6 Detect HT/L presumptive and confirmed results) equaled zero, indicating 100% concordance between the methods. Both Sample6 Detect HT/L and FDA BAM results showed low dPODC values, with confidence intervals indicating no significant differences between Sample6 Detect HT/L and reference method results. Conclusions: Sample6 Detect HT/L is suitable to detect Listeria spp. in ice cream, even with a 12 h enrichment. Sample6 Detect HT/L demonstrated equivalent detection of L. monocytogenes and L. innocua from R2-enriched samples as expected with 15 and 18 h enrichment when compared with the 24 h FDA BAM method for L. monocytogenes. Highlights: These results indicate that Sample6 Detect HT/L, primarily developed for environmental samples, can be used to detect Listeria spp. in ice cream with less incubation time, resulting in faster detection.

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Background: Early and accurate detection of Listeria in foods is vital. Current methods require 24 h enrichment for detection. Objective: This study aimed to demonstrate enhanced early detection of Listeria in mixed leafy greens using Sample6 DETECT™ HT/L, a phage-based detection system. Methods: A method comparison between the reference method (U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 10) for the detection of Listeria spp. and the Sample6 DETECT HT/L using a new proprietary R2 Medium was performed in mixed leafy greens. Results: Using the R2 Medium enrichment with Sample6 DETECT HT/L, detection of L. innocua was possible at 12 h (with a centrifugation step), and L. monocytogenes was detected by 18 h, with equivalent performance as the 24 h enrichments using the reference method detection. The Sample6 DETECT HT/L gave an equivalent performance for L. innocua at 15 h as the reference method at 24 h. Detection was accomplished by the addition of reagents in the kit, following the package insert, and reading results in a detection chamber using a 96-well plate reader that detects a fluorescent signal. Conclusions: Results indicate the new R2 Medium and Sample6 DETECT HT/L allowed for earlier detection of Listeria spp. in mixed leafy greens. Highlights: Sample6 DETECT HT/L with the new R2 Medium allowed the early detection of Listeria spp. and may be applied in other food matrices and environmental samples.