Abstract
Typhoid fever is a life-threatening disease caused by Salmonella enterica serovar Typhi (S. Typhi) and remains a significant public health burden in developing countries. In China, typhoid fever is endemic with a limited number of reported outbreaks. Recently, Chinese local Center for Disease Prevention and Control is starting to apply whole genome sequencing for tracking the source of outbreak isolates. In this study, we conducted a retrospective investigation into a community outbreak of typhoid fever in Lanling, China, in 2016. A total of 26 S. Typhi isolates were recovered from the drinking water (n = 1) and patients' blood (n = 24) and stool (n = 1). Phylogenetic analysis indicated the persistence of the outbreak isolates in drinking water for more than 3 months. The genomic comparison demonstrated a high similarity between the isolate from water and isolates from patients in their genomic content, virulence gene profiles, and antimicrobial resistance gene profile, indicating the S. Typhi isolate from drinking water was responsible for the examined outbreak. The result of pulsed-field gel electrophoresis (PFGE) revealed these isolates had identical PFGE pattern, indicating they are clonal variants. Additionally, phylogeographical analysis of global S. Typhi isolates suggested the outbreak isolates are evolutionarily linked to the isolates from the United Kingdom and Vietnam. Taken together, this study highlights the drinking water and international travel as critical control points of mitigating the outbreak, emphasizing the necessity of regular monitoring of this pathogen in China.
Highlights
Salmonella enterica contains >2,600 identified serovars and is commonly related to gastroenteritis in humans, threatening the public health system over the world [1]
Sporadic cases from the same community were reported between February and March (n = 5)
Multidrug-resistant bacterial pathogen causes antimicrobial treatment failure, threatening public health. To understand whether these isolates are multidrug-resistant, we investigated their antimicrobial susceptibility profiles by determining the minimal inhibitory concentration (MIC) of 20 antibiotics belonging to seven antibiotic classes
Summary
Salmonella enterica contains >2,600 identified serovars and is commonly related to gastroenteritis in humans, threatening the public health system over the world [1]. Though typhoid fever is rarely reported in developed countries,. The majority of them are sporadic cases, while the outbreak of typhoid fever is rarely reported [9, 10]. In these sporadic cases, Pulse Field Gel Electrophoresis (PFGE) was widely applied to generate bacterial DNA fingerprints to trace the sources of S. But the PFGE may cause misleading results because of its low resolution in distinguishing strains [11, 12]. Only one study used WGS to track the source of typhoid fever outbreaks in China [9]
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