Pulsed-field gel electrophoresis typing on non-O157 Shiga toxin-producing Escherichia coli isolates / 中华流行病学杂志

<p><b>OBJECTIVE</b>To establish a database and to understand the molecular epidemiological features of non-O157 Shiga toxin-producing Escherichia coli (STEC) isolates from different animal reservoirs and patients.</p><p><b>METHODS</b>Pulsed-field gel electrophoresis (PFGE) was performed according to the PulseNet protocol with minor modifications. A dendrogram was constructed using the BioNumerics.</p><p><b>RESULTS</b>Under the PulseNet protocol, 62 PFGE patterns were obtained from 76 non-O157 STEC isolates and then divided into A to M groups. Isolates from different sources were widely distributed in different groups, but were predominant seen in certain groups.</p><p><b>CONCLUSION</b>The non-O157 STEC isolates in China were highly polymorphic. PulseNet protocol seemed to be suitable for the typing of Chinese non-O157 STEC isolates.</p>

Study on the integration site and arrangement of SfII and SfX prophages in Shigella flexneri serotype 2b strains / 中华流行病学杂志

Objective To study the integration site and arrangement of SfII and SfX prophages in Shigella flexneri serotype 2b strains. Methods A series of primers were designed based on potential integration site of SfII and SfX prophages in Shigella flexneri serotype 2b strains, and PCR were performed for 50 serotype 2b strains to amplify special genes located in host and prophages. PCR products were sequenced to identify integration sites and arrangement of SfII and SfX. Results In all the serotype 2b strains, prophage SfII and SfX were adjacent to each other, and integrated into the thrW tRNA gene of the host, which were located between genes proA and yaiC of host. Prophage SfX was located immediately upstream of prophage SfII in all the detected 50 serotype 2b strains exception for strain 51251. Conclusion This was the first report on the integration site and arrangement of serotype-converting prophages SfII and SfX in Shigella flexneri 2b strains.

Development of a protocol on pulsed field gel electrophoresis analysis for Streptococcus suis / 中华流行病学杂志

Objective To develop a PFGE protocol for Streptococcus suis.Methods We developed and optimized a PFGE protocol for S.suis,in terms of plug preparation,choice of restriction endonucleases and optimized electrophoresis parameters.By analyzing the genome sequences of S.suis P1/7 with Mapdraw of DNAStar.we found three restriction enzymes,Swa Ⅰ,Sma Ⅰ and Apa Ⅰ,were more suitable than others.Results Analysis of 100 isolates of S.suis including 34 of 35 serotypes identified,59,53 and 43 patterns were obtained from Swa Ⅰ,Sma Ⅰ and Apa Ⅰ restriction,respectively.The enzyme Swa Ⅰ had the greatest power for discrimination ability.Conclusion By optimization of the protocol at various conditions,a rapid,reproducible,economic and practical PFGE method for S.suis was developed.

Molecular typing of isolates from two dysentery outbreaks in Chengdu, through pulsed field gel electrophoresis technology / 中华流行病学杂志

<p><b>OBJECTIVE</b>Using pulsed field gel electrophoresis (PFGE) and polymerase chain reaction (PCR) typing to analyze strains isolated from two outbreaks caused by Shigella sonnei and to trace the source of infection.</p><p><b>METHODS</b>Virulence genes ipaH and ial were detected by PCR and PFGE was used to subtype the isolates. Patterns were compared, using the software BioNumerics.</p><p><b>RESULTS</b>Within the 54 isolates, all were ipaH positive with 48 as ial positive. Strains from the Chongzhou outbreak were clustered into 4 PFGE patterns, with the predominant pattern accounted for 72% of the analyzed strains. The pattern of strains isolated from the cold pork with sauce was identical to the predominant pattern. The strains from Dayi outbreak were clustered into 8 PFGE patterns and the predominant pattern accounted for 56% of the test strains.</p><p><b>CONCLUSION</b>Strains from the two outbreaks were quite different and the 'cold pork with sauce' seemed to be the major source of infection, causing the outbreak of diarrhea in Chongzhou. The sources of infection of the Dayi outbreak might be complicated whereas PFGE showed a discriminatory and reproducible laboratory tool in the epidemiologic investigation on outbreaks of diarrhea.</p>