Molecular detection of all 34 distinct O-antigen forms of Shigella

1 Tianjin Biochip Corporation, 23 Hongda Street, TEDA, Tianjin 300457, PR China 2 Tianjin University of Science and Technology, Tianjin 300457, PR China 3 TEDA School of Biological Sciences and Biotechnology, Nankai University, 23 Hongda Street, TEDA, Tianjin 300457, PR China 4 Tianjin Research Center for Functional Genomics and Biochips, 23 Hongda Street, TEDA, Tianjin 300457, PR China 5 Tianjin Key Laboratory of Microbial Functional Genomics, 23 Hongda Street, TEDA, Tianjin 300457, PR China 6 The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, PR China 7 Tianjin Entry-Exit Inspection and Quarantine Bureau, Tianjin 300457, PR China Correspondence Lei Wang wanglei{at}nankai.edu.cn Received January 29, 2008 Accepted August 28, 2008 Shigella is the cause of shigellosis or bacillary dysentery, the occurrence of which is estimated to be 165 million cases per year worldwide, resulting in 1.1 million deaths. Rapid and reliable assays for detecting and identifying Shigella in food, environmental and clinical samples are therefore necessary. Shigella species are traditionally identified by their O antigens. This study developed a DNA microarray targeting O-serotype-specific genes to detect all 34 distinct O-antigen forms of Shigella , including Shigella boydii types 1–18, Shigella dysenteriae types 1–13, Shigella flexneri types 1–5 and 6, and Shigella sonnei . A total of 282 strains were used to test the specificity of the microarray, including 186 Shigella and Escherichia coli representative strains, 86 Shigella clinical isolates and ten strains of other bacterial species that are commonly isolated from food or clinical stool specimens. The oligonucleotide probes were printed on the microarray in concentrations from 1 to 100 µM, and 10 µM proved to be the optimal probe concentration. The detection sensitivity for each serotype was 50 ng genomic DNA or 1 c.f.u. in 25 g milk powder sample following a 6 h enrichment in broth. The microarray is specific, sensitive and reproducible, and, to our knowledge, is the first report of a microarray for serotyping all O-antigen forms of Shigella . Abbreviations: EIEC, enteroinvasive E. coli . These authors contributed equally to this work. Present address: Division of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University, PO Box 334, Canberra, ACT 2601, Australia.