Current Developments in Diagnostic Assays for Laboratory Confirmation and Investigation of Botulism.

Detection of botulinum neurotoxin or isolation of the toxin-producing organism is required for the laboratory confirmation of botulism in clinical specimens. In an effort to reduce animal testing required by the gold standard method of botulinum neurotoxin detection, the mouse bioassay, many technologies have been developed to detect and characterize the causative agent of botulism. Recent advancements in these technologies have led to improvements in technical performance of diagnostic assays; however, many emerging assays have not been validated for the detection of all serotypes in complex clinical and environmental matrices. Improvements to culture protocols, endopeptidase-based assays, and a variety of immunological and molecular methods have provided laboratories with a variety of testing options to evaluate and incorporate into their testing algorithms. While significant advances have been made to improve these assays, additional work is necessary to evaluate these methods in various clinical matrices and to establish standardized criteria for data analysis and interpretation.

Evaluation of Specimen Types and Saliva Stabilization Solutions for SARS-CoV-2 Testing.

Identifying SARS-CoV-2 infections through aggressive diagnostic testing remains critical to tracking and curbing the spread of the COVID-19 pandemic. Collection of nasopharyngeal swabs (NPS), the preferred sample type for SARS-CoV-2 detection, has become difficult due to the dramatic increase in testing and consequent supply strain. Therefore, alternative specimen types have been investigated that provide similar detection sensitivity with reduced health care exposure and the potential for self-collection. In this study, the detection sensitivity of SARS-CoV-2 in nasal swabs (NS) and saliva was compared to that of NPS using matched specimens from two outpatient cohorts in New York State (total n = 463). The first cohort showed only a 5.4% positivity, but the second cohort (n = 227) had a positivity rate of 41%, with sensitivity in NPS, NS, and saliva of 97.9%, 87.1%, and 87.1%, respectively. Whether the reduced sensitivity of NS or saliva is acceptable must be assessed in the settings where they are used. However, we sought to improve on it by validating a method to mix the two sample types, as the combination of nasal swab and saliva resulted in 94.6% SARS-CoV-2 detection sensitivity. Spiking experiments showed that combining them did not adversely affect the detection sensitivity in either. Virus stability in saliva was also investigated, with and without the addition of commercially available stabilizing solutions. The virus was stable in saliva at both 4°C and room temperature for up to 7 days. The addition of stabilizing solutions did not enhance stability and, in some situations, reduced detectable virus levels.

One-step pentaplex real-time polymerase chain reaction assay for detection of zika, dengue, chikungunya, West nile viruses and a human housekeeping gene.

BACKGROUND: Recent emergence of Zika virus (ZIKV), and the global spread of dengue (DENV), chikungunya (CHIKV) and West Nile viruses (WNV) raised urgent need of accurate and affordable molecular diagnosis of these clinically indistinguishable arboviral infections. OBJECTIVES: We established a pentaplex real-time reverse transcription PCR (rRT-PCR) assay (CII-ArboViroPlex rRT-PCR) for specific and sensitive detection of the African and American genotypes of ZIKV, all four serotypes of DENV, CHIKV, WNV and a housekeeping gene as internal control in single reaction. STUDY DESIGN: Specific primers and probe sets were designed for ZIKV, DENV, CHIKV, WNV and RNase P (housekeeping gene) and tested for in-vitro transcribed RNA standards, virus cultures, clinical samples positive for ZIKV, DENV, CHIKV and WNV and limit of detection (LOD) were determined for each. Results Using ten-fold serially diluted in-vitro transcribed RNA, CII- ArboViroPlex rRT-PCR assay has LOD of 100 RNA copies/reaction (Rn) for ZIKV in serum or urine, 100 RNA copies/Rn for DENV in serum, and 10 RNA copies/Rn for CHIKV and WNV in serum. LODs from sera spiked with quantitated viral stocks were 2.6 × 102 GEQ/Rn for ZIKV, 2.2 × 101 GEQ/Rn for DENV-1, 9.4 × 100 GEQ/Rn for DENV-2, 2.3 × 102 GEQ/Rn for DENV-3, 1.4 × 103 GEQ/Rn for DENV-4, 2.7 × 102 GEQ/Rn for CHIKV, and 1.05 × 101 GEQ/Rn for WNV. CONCLUSIONS: The CII-ArboViroPlex rRT-PCR assay is a quantitative one-step pentaplex rRT-PCR assay for the molecular detection and differential diagnosis of ZIKV, DENV, CHIKV, WNV and a human housekeeping gene control in a single- PCR reaction.

Molecular Characterization of Clostridium botulinum Harboring the bont/B7 Gene.

Clostridium botulinum produces botulinum neurotoxin (BoNT), which is the causative agent of botulism, a rare but serious disease that can result in death if not treated. Infant botulism occurs when C. botulinum colonizes the intestinal tract of infants and produces BoNT. It has been proposed that infants under the age of 1 year are uniquely susceptible to colonization by C. botulinum as their intestinal microbiota is not fully developed and provides little competition, allowing C. botulinum to thrive and produce BoNT in the gut. There are seven well-characterized serotypes (A-G) of BoNT identified by the ability of specific antitoxins to neutralize BoNTs. Molecular technology has allowed researchers to narrow these further into subtypes based on nucleic acid sequences of the botulinum toxin (bont) gene. One of the most recently recognized subtypes for bont/B is subtype bont/B7. We identified through whole genome sequencing five C. botulinum isolates harboring bont/B7 from CDC's strain collection, including patient isolates and an epidemiologically linked isolate from an opened infant formula container. In this study, we report the results of whole genome sequencing analysis of these C. botulinum subtype bont/B7 isolates. Average nucleotide identity and high quality single nucleotide polymorphism (hqSNP) analysis resulted in two major clades. The epidemiologically linked isolates differed from each other by 2-6 hqSNPs, and this clade separated from the other isolates by 95-119 hqSNPs, corroborating available epidemiological evidence.

Implementing the Bruker MALDI Biotyper in the Public Health Laboratory for C. botulinum Neurotoxin Detection.

Currently, the gold standard method for active botulinum neurotoxin (BoNT) detection is the mouse bioassay (MBA). A Centers for Disease Control and Prevention-developed mass spectrometry (MS)-based assay that detects active BoNT was successfully validated and implemented in a public health laboratory in clinical matrices using the Bruker MALDI-TOF MS (Matrix-assisted laser desorption ionization-time of flight mass spectrometry) Biotyper. For the first time, a direct comparison with the MBA was performed to determine MS-based assay sensitivity using the Bruker MALDI Biotyper. Mice were injected with BoNT/A, /B, /E, and /F at concentrations surrounding the established MS assay limit of detection (LOD) and analyzed simultaneously. For BoNT/B, /E, and /F, MS assay sensitivity was equivalent or better than the MBA at 25, 0.3, and 8.8 mLD50, respectively. BoNT/A was detected by the MBA between 1.8 and 18 mLD50, somewhat more sensitive than the MS method of 18 mLD50. Studies were performed to compare assay performance in clinical specimens. For all tested specimens, the MS method rapidly detected BoNT activity and serotype in agreement with, or in the absence of, results from the MBA. We demonstrate that the MS assay can generate reliable, rapid results while eliminating the need for animal testing.