[Etiological survey and traceability analysis of five cases of typhoid fever during the same period in Yantai city]

Objective: To analyze the etiological characteristics and molecular epidemiological correlation of five cases of typhoid fever during the same period in yantai city. Methods: Six S. Typhis strains were isolated from 5 typhoid patients and epidemiological samples in Yantai city in 2018. The onset time of the cases were from May 26, 2018 to July 24, 2018, distributed in Shuidao Town of Muping District, Dengzhou Street of Penglai District, Donglai Street of Longkou District, Wenhua Street of Muping District and Fulaishan Street of zhifu District. S. Typhis strains were analyzed by conventional bacterial isolation method and XbaⅠ/BlnⅠ double-enzyme digestion pulse-field gel electrophoresis (PFGE). Meanwhile, ViaB virulence gene detection and 27 common antibiotics sensitivity tests were conducted to study the etiology of S. Typhis. Results: Six strains of S. Typhi were isolated from 5 patients and the domestic egg of one patient, which were divided into 4 PFGE patterns by PFGE-XbaⅠ and PFGE-BlnⅠ and among which 3 strains had the same PFGE patterns.One multi-drug resistant strain (foreign patient), one single-drug resistant strain (patient with a history of provincial retention), and one completely sensitive strain were detected. The three strains of the same PFGE pattern exhibit the same drug-sensitive phenotype which were intermediate against aminoglycosides and quinolones and susceptibility against the other antibiotics.All of the strains carried the ViaB virulence factor except the strain from the foreign patient. Conclusion: Local S. Typhi is susceptibility or intermediate against antibiotics commonly used in clinic.Sporadic cases of typhoid fever and typhoid imported infections still need attention.