Loop-mediated isothermal amplification (LAMP) has been widely used to detect many infectious diseases. However, minor inconveniences during the steps of adding reaction ingredients and lack of simple color results hinder point-of-care detection. We therefore invented a fluorometric paper-based LAMP by incorporating LAMP reagents, including a biotinylated primer, onto a cellulose membrane paper, with a simple DNA fluorescent dye incubation that demonstrated rapid and accurate results parallel to quantitative polymerase chain reaction (qPCR) methods. This technology allows for instant paper strip detection of methicillin-resistant Staphylococcus aureus (MRSA) in the laboratory and clinical samples. MRSA represents a major public health problem as it can cause infections in different parts of the human body and yet is resistant to commonly used antibiotics. In this study, we optimized LAMP reaction ingredients and incubation conditions following a central composite design (CCD) that yielded the shortest reaction time with high sensitivity. These CCD components and conditions were used to construct the paper-based LAMP reaction by immobilizing the biotinylated primer and the rest of the LAMP reagents to produce the ready-to-use MRSA diagnostic device. Our paper-based LAMP device could detect as low as 10 ag (equivalent to 1 copy) of the MRSA gene mecA within 36−43 min, was evaluated using both laboratory (individual cultures of MRSA and non-MRSA bacteria) and clinical blood samples to be 100% specific and sensitive compared to qPCR results, and had 35 day stability under 25°C storage. Furthermore, the color readout allows for quantitation of MRSA copies. Hence, this device is applicable for point-of-care MRSA detection.

Chlamydia trachomatis is the major bacterial sexually transmitted disease worldwide. The clinical symptoms are broad, and chronic C. trachomatis infections could lead to blindness, ectopic pregnancy, sterility in males and females, and a higher risk of the development of cervical cancer. The result indicates the potential usefulness of our crude DNA lysis coupled loop-mediated isothermal amplification with hydroxynaphthol blue for a simple, rapid, specific, sensitive and cost-effective assay for C. trachomatis detection from suspected specimens. This assay offers an alternative in the clinical diagnosis of C. trachomatis in resource-limited health-care facilities and clinical laboratories in developing countries, and in field tests.

Staphylococcus aureus strains carrying enterotoxin A gene (sea) causes food poisoning and cannot be distinguished from non-pathogenic strains by the culture method. Here, we developed a rapid, specific and sensitive visual detection of sea using loop-mediated isothermal amplification (LAMP) combined with nanogold probe (AuNP) or styryl dye (STR). LAMP-AuNP and LAMP-STR can detect as low as 9.7 fg (3.2 sea copies) and 7.2 sea copies, respectively, which were lower than PCR (97 fg or 32 sea copies). The excellent performance of these new assays was demonstrated in food samples using crude DNA lysates. While the culture method detected 10 4 CFU/g in ground pork and 10 CFU/mL in milk in 5-7 days, LAMP-AuNP could detect down to 10 CFU/g for both samples in 27 minutes. Analyzing 80 pork and milk samples revealed that the LAMP-AuNP showed 100% sensitivity, 97-100% specificity and 97.5-100% accuracy, which were superior to the culture method, and comparable to PCR but without requirement of a thermal cycler. Furthermore, our LAMP-AuNP detect sea at a range below the food safety control (<100 CFU/g). The LAMP-STR quantitated sea in 10-1,000 CFU (7.2-720 copies). Our crude DNA lysis combined with LAMP-AuNP/STR present effective point-of-care detection and facilitate appropriate control strategies. Staphylococcus aureus strains with the staphylococcal enterotoxin A gene (sea) bacteriophage, are a common cause of foodborne disease and outbreaks worldwide including the United States and countries of the European Union 1-5. In Thailand, one of the largest outbreaks occurred in 2009 reporting 573 illnesses due to consumption of contaminated sticky rice custard 6. S. aureus is commonly found in soil, water, air, as well as human respiratory tract and skin. The sea toxin is relatively heat stable (e.g. up to 100 °C for 30 min) therefore, food contamination generally occurs when cooking is performed without sufficient hygiene. Frequently reported contaminated foods include dairy products (milk, cheese, ice cream, etc.), and meat 7,8. Importantly, contaminated food may not be easily identified by sensory evaluation such as odor or appearance. Clinical symptoms from sea food poisoning include vomiting, abdominal cramps, diarrhea, and dysentery, often within 1-6 h after consumption. Occasional symptoms include sweating, chills, rectal bleeding, and shock 9-11. The severity of illness depends on the concentration of the toxin. Consumption of merely 20-100 ng of sea toxin can cause clinical symptoms and >100 ng may be fatal, therefore a sensitive method of sea detection is important for food safety control. Detection is usually

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A rapid, highly sensitive, and quantitative colorimetric paper‐based analytical device (PAD) based on silver nanoplates (AgNPls) and loop‐mediated isothermal amplification (LAMP) is presented. It is shown that cauliflower‐like concatemer LAMP products can mediate crystal etching of AgNPls, with a threefold signal enhancement versus linear dsDNA. Methicillin‐resistant Staphylococcus aureus (MRSA), an antimicrobial resistant bacterium that poses a formidable risk with persistently high mortality, is used as a model pathogen. Due to the excellent color contrast provided by AgNPls, the PAD allows qualitative analysis by the naked eye and quantitative analysis using a smartphone camera, with detection limits down to a single copy in just 30 min, and a linear response from 1 to 104 copies (R2 = 0.994). The entire assay runs in situ on the paper surface, which drastically simplifies operation of the device. This is the first demonstration of single copy detection using a colorimetric readout, and the developed PAD shows great promise for translation into an ultrasensitive gene‐based point‐of‐care test for any infectious disease target, via modification of the LAMP primer set.