Outbreak of Infections Caused by Shigella flexneri 2a with ESBL-Producing and Quinolone-Resistance in a Mental Healthcare Center in China

An outbreak of bacillary dysentery occurred in the Xiaoshan Mental Healthcare Center from November 8 to 16, 2012. Eight strains of Shigella flexneri 2a (S. flexneri 2a) were isolated from the same ward. The aim of the investigation was to clarify the origin of outbreak. Rectal swabs or fecal specimens from 7 doctors, 15 nurses, 2 nursing workers, 3 canteen workers, as well as 18 swabs from environmental sample in the ward were screened for Shigella. Phenotypic analysis included standard microbiological identification techniques, serotyping and antimicrobial susceptibility testing. PCR and sequencing were used to characterize drug resistance and virulence genes. Pulsed field gel electrophoresis (PFGE) was carried out for all Shigella isolates. S.flexneri 2a with multidrug resistance was isolated from eight patients and one canteen worker, which carried multiple antibiotics resistance genes and virulence determinants. The results of PFGE confirmed that nine strains of S. flexneri 2a belonged to the same clone. It was suggested that the outbreak strain spread directly from person-person or indirectly from person-food-person from the canteen worker. The outbreak was controlled after quarantine of ill residents, replacement of antibiotics and improvement of hygienic condition.