Development of a Serotype-Specific DNA Microarray for Identification of Some Shigella and Pathogenic Escherichia coli Strains

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Abstract
Shigella and pathogenic Escherichia coli are major causes of human infectious diseases and are responsible for millions of cases of diarrhea worldwide every year. A convenient and rapid method to identify highly pathogenic serotypes of Shigella and E. coli is needed for large-scale epidemiologic study, timely clinical diagnosis, and reliable quarantine of the pathogens. In this study, a DNA microarray targeting O-serotype-specific genes was developed to detect 15 serotypes of Shigella and E. coli , including Shigella sonnei ; Shigella flexneri type 2a; Shigella boydii types 7, 9, 13, 16, and 18; Shigella dysenteriae types 4, 8, and 10; and E. coli O55, O111, O114, O128, and O157. The microarray was tested against 186 representative strains of all Shigella and E. coli O serotypes, 38 clinical isolates, and 9 strains of other bacterial species that are commonly present in stool samples and was shown to be specific and reproducible. The detection sensitivity was 50 ng genomic DNA or 10 4 CFU per ml in mock stool specimens. This is the first report of a microarray for serotyping Shigella and pathogenic E. coli . The method has a number of advantages over traditional bacterial culture and antiserum agglutination methods and is promising for applications in basic microbiological research, clinical diagnosis, food safety, and epidemiological surveillance.