Mycotoxins are secondary metabolites that are known to be toxic to humans and animals. Omics tools are important to establish prevention, control and mitigation strategies of mycotoxins in food.

Escherichia coli O157:H7, a Shiga-toxin-producing E. coli (STEC), is an important pathogen related to foodborne disease that is responsible for a growing number of outbreaks worldwide and has been detected in processed meats, dairy, and fresh vegetables. Although culturing is the gold standard method for detection of this bacterium, molecular methods based on nucleic acid amplification techniques such as PCR are becoming more common because of their rapidity, sensitivity, and specificity. However, to ensure reliable results among the several alternative PCR protocols (e.g., commercial kits and reference methods), different measurement assurance tools, including validated methods, reference materials, and proficiency tests, among others, are required. Herein, we present a digital PCR method validation for E. coli O157:H7 detection and quantification using seven specific gene sequences; this method quantified nucleic acids from different E. coli serotypes, with a detection range of 6.6 to 7900 copies/µL and a repeatability standard deviation over the concentration range of 1% to 13.6%. The relative standard uncertainty was 3.5–14.6%, and the detection limit was 0.27 copies/µL. Subsequently, two batches of a candidate reference material based on E. coli O157:H7 genomic DNA were then produced and characterized for evaluation of copy number concentration with the validated ddPCR method, with assigned values of 164,770 ± 9251 and 172 ± 9 copies/μL. Thus, this study demonstrated the development of a validated method and reference material for dPCR and qPCR detection of E. coli O157:H7, a key STEC responsible for food poisoning.

Infection with human immunodeficiency virus (HIV)-1 leads to acquired immunodeficiency syndrome (AIDS) if left untreated. According to UN figures, approximately 39 million people globally were living with HIV in 2022, with 76% of those individuals accessing antiretroviral therapy. Measurement of plasma viral RNA load using calibrated nucleic acid amplification tests (like reverse transcription quantitative PCR, RT-qPCR) is routinely performed to monitor response to treatment and ultimately prevent viral transmission. RNA quantities measured by commercial tests can vary over many orders of magnitude, from trace single copy levels to, in cases, over 10 ⁹ /mL of plasma, presenting an analytical challenge for calibrating across a broad measurement range. Interlaboratory study CCQM-P199 “HIV-1 RNA copy number quantification” (April to September 2019) was conducted under the auspices of the Consultative Committee for Amount of Substance (CCQM) Nucleic Acid analysis Working Group (NAWG), with the aims of supporting national metrology institutes (NMIs) and designated institutes (DIs) development of the capacity and evaluating candidate reference measurement procedures for applied viral nucleic acid measurements. Thirteen laboratories participated in CCQM-P199 and were requested to report the RNA copy number concentration, expressed in copies per microliter, of the HIV-1 group specific antigen ( gag ) gene of in vitro transcribed RNA molecules at low (≈ 10 ³ /μL) and high concentration (≈ 10 ⁹ /μL) (Study Materials 1 and 2, linked by gravimetric dilution) and purified genomic RNA from cultured virus (Study Material 3). Study Materials 1 and 3 were measured by participants using one-step reverse transcription digital PCR (RT-dPCR) (Bio-Rad reagents) and/or two-step RT-dPCR with alternative cDNA synthesis reagents. Study Material 2 was measured by both RT-dPCR (one-step) ( n = 4) and orthogonal methods: single molecule flow cytometric counting ( n = 2), high performance liquid chromatograph (HPLC) ( n = 1) and isotype dilution-mass spectrometry (ID-MS) ( n = 1). Interlaboratory reproducibilities (expressed as %CV) were 21.4 %, 15.3 % and 22.0 % for Study Materials 1, 2 and 3 respectively. Analysis of overdispersion showed that the interlaboratory variation for all three Study Materials was not accounted for in their reported uncertainties, indicating uncharacterized sources of variation remain. Although the mean values of RT-dPCR and orthogonal method results were not statistically significantly different ( p = 0.46), the extrapolated mean Study Material 2 results were higher than mean Study Material 1 results (1196 vs . 808 /μL; p < 0.05). Follow-up analysis of Study Material 2 purity by ultra-performance liquid chromatography (UPLC) indicated higher molecular weight (MW) impurities constituted 16.6 % of the molecules, which are hypothesised to be the cause of the HPLC and ID-MS results being higher than the majority of Study Material 1 and 2 results. This study demonstrates that reproducible measurement of RNA templates was achieved by metrology laboratories, illustrating the potential of RT-dPCR combined with complimentary orthogonal approaches to support traceability and precision of contemporary methods for RNA quantification. This study also highlighted that detailed characterization of RNA materials and sources of bias affecting measurements such as RT efficiency is needed to further establish RT-dPCR as a primary reference measurement procedure for RNA copy number quantification.

Escherichia coli O157:H7, a Shiga toxin-producing E. coli (STEC) is an important pathogen related to foodborne disease that is responsible for a growing number of outbreaks worldwide and has been detected in processed meats, dairy, and fresh vegetables. Although culturing is the gold standard method for detection of this bacteria, molecular methods based on nucleic acid amplification techniques such as PCR are becoming more common because of their rapidity, sensitivity, and specificity. However, to ensure reliable results among the several alternative PCR protocols (e.g., commercial kits and reference methods), different measurement assurance tools, including validated methods, reference materials, and proficiency tests among others, are required. Herein, we present a digital PCR method validation for E. coli O157:H7 detection and quantification using seven gene sequences; this method quantified nucleic acids from different E. coli serotypes, with a detection range between 6.6 to 7,900 copies/µL and a repeatability standard deviation over the concentration range of between 1% to 13.6%. The relative standard uncertainty was 3.5%–14.6%, and the detection limit was 0.27 copies/µL. Subsequently two batches of a candidate reference material based on E. coli O157:H7 genomic DNA were then produced and characterized for evaluation of copy number concentration with the validated dPCR method, with assigned values of 164,770 ± 9,251 and 172 ± 9 copies/μL. Thus, this study demonstrated the development a validated method and reference material for dPCR and qPCR detection of E. coli O157:H7, a key STEC responsible for food poisoning.