Application of an Environmental Phage-Based Assay (Sample6 Detect HT/L) for the Detection of Listeria spp. in Ice Cream

Abstract

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.

Phage-based forensic tool for spatial visualization of bacterial contaminants in cheese

“…Approximate E. coli inoculation levels, per well, based on serial dilution on lysogeny broth agar: (A) 6.4 × 10 4 cfu, (B) 6.4 × 10 1 cfu, (C) 6.4 × 10 0 cfu, (D) 6.4 × 10 2 cfu, (E) 6.4 × 10 3 cfu, and (F) 0 cfu. cations mainly use phage as an antimicrobial agent, because bacteria die after phage infection; however, the commercial use of bioengineered phage for pathogen detection in dairy products has begun (Arias-Rios et al, 2019). Here, T7 NLC was applied both topically and internally in both LB agar and QF to explore potential application methods of phage in a cheese matrix for the purpose of determining the location of bacterial contaminants.…”

The Application of Bacteriophage Diagnostics for Bacterial Pathogens in the Agricultural Supply Chain: From Farm-to-Fork

“…11,53 The kit was marketed at $16 for a 10 sample kit in 2016 11 ; the assay's reporting time is 6 h and therefore holds potential for production line microbial detection. The Sample 6 Detect HT/L has been recently verified for testing produce such as ice cream, 54 leafy greens, 55 and environmental stainless-steel surfaces, 56 with results comparable with culture methods commercially used and a reduced reporting time. Listeria phage detection holds the potential to improve on gold standard methods in both farm and food processing infrastructures in a variety of matrices.…”