Comparative Study of Shigella flexneri Identiefication with Colorimetric Assay Based on Gold Nanoparticles and Electrophoresis Method

Shigella is a Gram-negative enteric bacilli that causes serious problems in advanced and developing countries. The purpose of this study was to evaluate colorimetric assay based on gold nanoparticles for rapid detection of S. flexneri using ipaH gene amplification products.
To identify the genus Shigella, the specific primers were used to amplify ipaH gene with polymerase chain reaction (PCR) method. Then, single-stranded probe was used to connect to the specific region of the PCR product. After addition of gold nanoparticles, the color changing was observed visually in the solution and imaged with scanning electron microscope (SEM). To examine the sensitivity of new method, a range of different concentrations of PCR products was used and the results were compared with gel electrophoresis method.
The hybridization of probes with amplified products of ipaH gene caused the accumulation of gold nanoparticles which resulted in color changing in the reaction solution from red to purple, but no color changing was observed in the negative control. Then, the accumulation of gold nanoparticles was approved with SEM.
Discussion and Because of the specificity of ipaH gene in S. flexneri, the colorimetric assay with high sensitivity can be used for specific detection of S. flexneri in the clinical specimen and food samples.