Abstract
BackgroundSalmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) is one of the most prevalent Salmonella serotypes that cause gastroenteritis worldwide and the most prevalent serotype causing Salmonella infections in China. A rapid molecular typing method with high throughput and good epidemiological discrimination is urgently needed for detecting the outbreaks and finding the source for effective control of S. Enteritidis infections.MethodsIn this study, 194 strains which included 47 from six outbreaks that were well-characterized epidemiologically were analyzed with pulse field gel electrophoresis (PFGE) and multilocus variable number tandem repeat analysis (MLVA). Seven VNTR loci published by the US Center for Disease Control and Prevention (CDC) were used to evaluate and develop MLVA scheme for S. Enteritidis molecular subtyping by comparing with PFGE, and then MLVA was applied to the suspected outbreaks detection. All S. Enteritidis isolates were analyzed with MLVA to establish a MLVA database in Shenzhen, Guangdong province, China to facilitate the detection of S. Enteritidis infection clusters.ResultsThere were 33 MLVA types and 29 PFGE patterns among 147 sporadic isolates. These two measures had Simpson indices of 0.7701 and 0.8043, respectively, which did not differ significantly. Epidemiological concordance was evaluated by typing 47 isolates from six epidemiologically well-characterized outbreaks and it did not differ for PFGE and MLVA. We applied the well established MLVA method to detect two S. Enteritidis foodborne outbreaks and find their sources successfully in 2014. A MLVA database of 491 S. Enteritidis strains isolated from 2004 to 2014 was established for the surveillance of clusters in the future.ConclusionsMLVA typing of S. Enteritidis would be an effective tool for early warning and epidemiological surveillance of S. Enteritidis infections.Electronic supplementary materialThe online version of this article (doi:10.1186/s12941-016-0119-3) contains supplementary material, which is available to authorized users.
Highlights
The results demonstrated that multilocus variable number tandem repeat analysis (MLVA) could be used to improve the efficiency of subtyping and the effectiveness of epidemiologically investigating S
Among the seven variable number tandem repeat (VNTR) loci, four of them (SE1, SE2, SE5 and SE9) showed appropriate discriminating abilities that were similar to previous reports [27,28,29]
Diversity of MLVA and pulse field gel electrophoresis (PFGE) among the sporadic isolates There were 33 MLVA types and 29 PFGE patterns among the sporadic isolates (Table 2), with a Simpson index of 0.7701 and 0.8043, respectively. Both the Simpson’s and Shannon’s indices were higher for PFGE than for MLVA, but there was no statistical difference between the two methods in terms of either index (t tests, P > 0.05)
Summary
Enteritidis) is one of the most prevalent Salmonella serotypes that cause gastroenteritis worldwide and the most prevalent serotype causing Salmonella infections in China. The bacterium Salmonella causes acute gastroenteritis and it is one of the most common and widely distributed foodborne pathogens. There are two species of Salmonella: Salmonella bongori and Salmonella enterica. Over 2500 different serotypes of Salmonella enterica species have been identified to date [1]. The global burden of non-typhoidal Salmonella gastroenteritis is heavy—there are 93.8 million cases annually leading to 155,000 deaths, of which 80.3 million cases are foodborne [2]. Despite the great number of serotypes, the most common foodborne pathogens in human Salmonella infections are S. Enteritidis is the most prevalent serotype in China [3]
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