Detection of classical enterotoxins of Staphylococcus aureus in raw sheep, goat, camel, and water buffalo milk by ELISA method

A fluorescent aptasensor for Staphylococcus aureus based on strand displacement amplification and self-assembled DNA hexagonal structure

A fluorescent aptasensor for Staphylococcus aureus (S. aureus) is designed, which takes advantage of strand displacement amplification (SDA) technology and unique self-assembled DNA hexagonal structure. In the presence of S. aureus, a partially complementary strand of S. aureus aptamer (cDNA) is competitively released from cDNA/aptamer duplex immobilized on magnetic beads due to the affinity of the aptamer for S. aureus. The addition of primer starts the SDA reaction. With the catalysis of Bsm DNA polymerase and Nb.bpu10I endonuclease, a large number of single-stranded DNA (ssDNA) is produced, which induces the opening of a hairpin probe and the subsequent self-assembly to form a hexagonal structure. The staining of the DNA hexagon with SYBR Green I excites the fluorescence signal, which is used for detection. The aptasensor exhibits a broad linear range from 7 to 7 × 10⁷ CFU/mL, with a detection limit of 1.7 CFU/mL for S. aureus. The sensor shows negligible responses to other bacteria. Moreover, the aptasensor has been applied to detect S. aureus in milk samples, and the results demonstrate the general applicability of the sensor and its prospect in systematic detection of S. aureus in food safety control and medicine-related fields. Graphical abstract The presence of S. aureus can be converted to the formation of unique DNA hexagonal structure and subsequent fluorescent signal by the combination of SDA with self-assembly technology.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.