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From September 1 to October 27, 2015, an outbreak of bacillary dysentery occurred in the Shenzhen Children Welfare Institute (SCWI). The shigellosis was uncommon in Shenzhen and no related outbreak was reported during the last 5 years. An epidemiological investigation was conducted and the children and nursing workers in SCWI were surveyed for gastrointestinal symptoms; 28 of children reported having a diarrheal illness. Rectal swabs or fecal specimens from 14 case patients and 24 nursing workers or cook, as well as 17 swabs from implicated items were collected and examined for Shigella , Vibrio parahaemolyticus , and Salmonella. Susceptibility testing and pulse-field gel electrophoresis (PFGE) were performed on the Shigella isolates. The multiple-antibiotic-resistant Shigella flexneri 2a was isolated from 10 ill children aged less than 5 years. The source of the outbreak was most likely a new welfare child transferred from an institute in another county and the secondary transmission of the illness was facilitated by the limited activity space and the cohabiting of ill and well residents. The outbreak was controlled after quarantine of ill residents, introduction of new antibiotics and the improvements of hygienic condition. This was the first time that shigellosis outbreak was reported at such settings in Shenzhen and the results of this investigation underscored the need for adequate precautions to prevent secondary transmission of multiple-antibiotic-resistant strain in the welfare setting. [ABSTRACT FROM AUTHOR]

Shiga toxin (Stx) is the key virulence factor in Shiga toxin producing Escherichia coli (STEC), which can cause diarrhea and hemorrhagic colitis with life-threatening complications. Stx comprises two toxin types, Stx1 and Stx2. Several Stx1/Stx2 subtypes have been identified in E. coli , which are variable in sequences, toxicity and host specificity. Here, we report the identification of a novel Stx2 subtype, designated Stx2k, in E. coli strains widely detected from diarrheal patients, animals, and raw meats in China over time. Stx2k exhibits varied cytotoxicity in vitro among individual strains. The Stx2k converting prophages displayed considerable heterogeneity in terms of insertion site, genetic content and structure. Whole genome analysis revealed that the stx 2k -containing strains were genetically heterogeneous with diverse serotypes, sequence types, and virulence gene profiles. The nine stx 2k -containing strains formed two major phylogenetic clusters closely with strains belonging to STEC, enterotoxigenic E. coli (ETEC), and STEC/ETEC hybrid. One stx 2k -containing strain harbored one plasmid-encoded heat-stable enterotoxin sta gene and two identical copies of chromosome-encoded stb gene, exhibiting STEC/ETEC hybrid pathotype. Our finding enlarges the pool of Stx2 subtypes and highlights the extraordinary genomic plasticity of STEC strains. Given the wide distribution of the Stx2k-producing strains in diverse sources and their pathogenic potential, Stx2k should be taken into account in epidemiological surveillance of STEC infections and clinical diagnosis. [ABSTRACT FROM AUTHOR]