Evaluation of a latex agglutination kit for the detection of human antibodies to the lipopolysaccharide of Escherichia coli O157, following infection with verocytotoxin-producing E. coli O157

A novel multiplex PCR method for the detection of virulence-associated genes of Escherichia coli O157:H7 in food

Shiga toxin-producing Escherichia coli O157:H7 (E. coli O157:H7) strains are foodborne infectious agents that cause a number of life-threatening diseases, including hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Shiga toxin 1 (stx1), shiga toxin 2 (stx2), or a combination of both are responsible for most clinical symptoms of these diseases. Hence, various diagnostic methods have been developed so far to detect shiga toxins such as cell culture, ELISA, Rapid Latex Agglutination (RPLA) and hybridization, but due to high costs and labor time in addition to low sensitivity, they have not received much attention. The aim of this study was to develop a complete, rapid and reliable multiplex PCR (mPCR) method by using two pairs of specific primers to detect either the stx1 or the stx2 gene confirms the presence of E.coli O157:H7. The study results show that stx1F/stx1R primers are specific for stx1 and primers stx2F/stx2R are specific for stx2 genes in E. coli O157:H7. The mPCR method with two pairs of primers for amplifying the stx1, stx2 target genes to detect E. coli O157:H7 in food has been set up successfully. Complete method performed well in both types of food matrices with a detection limit of 3 CFU/25 g or mL of food samples. Tests on 180 food samples have shown a specificity value of 93.75 % (95 % confidence interval [CI], 82.83–100), a sensitivity of 100 % (95 % CI, 83.79–99.85 %), and an accuracy of 96.66 % (CI 95 %, 83.41–99.91 %). Interestingly, results indicate that the mPCR performed as well as the traditional culture methods and can reduce the diagnosis time to 2 days. Finally, complete mPCR method was applied to natural samples covering a wide variety of food types proving that the mPCR method was a rapid and reliable screening method for detection of E. coli O157:H7 in food and environmental samples.

Development of a latex agglutination test for norovirus detection

Norovirus (NoV) is the leading cause of acute gastroenteritis worldwide. Currently, reverse transcription polymerase chain reaction (RT-PCR) is used commonly to detect NoVs in both clinical and environmental samples. However, RT-PCR requires expensive equipment and cannot be performed on site. In this study, a latex agglutination test (LAT) using antibody-labeled latex beads for detecting NoVs was developed. Two kinds of polyclonal antibodies, one generated from synthetic peptides and the other from E. coli-expressed NoV capsid proteins, were used to develop the LAT. Each of these polyclonal antibodies was immobilized on the surface of latex beads and tested for the ability to detect NoVs. Under optimized conditions, our LAT detected GII.4 NoV at concentrations as low as 3.3x10(5) RT-PCR units/ml in stool samples. The detection limit for the LAT was approximately 1.7 103 RT-PCR units. Forty-eight stool samples were tested for NoVs using this LAT. In comparison with an RT-PCR assay, the sensitivity and specificity of the LAT were 35% and 100%, respectively. With further optimization, this LAT used with appropriate antibodies could be applied for convenient detection of NoVs in clinical diagnosis and food monitoring.