Abstract
The rapid emergence of multidrug resistant Salmonella is a global public-health concern as outbreaks in recent years have mostly been caused by multidrug resistant strains. Here, we evaluated an outbreak in China caused by multidrug resistant Salmonella enterica serovar Typhimurium (S. Typhimurium) by employing an epidemiological and laboratory investigation using conventional methods and whole genome sequencing (WGS). Eleven of the 12 people who participated in a banquet showed gastrointestinal symptoms, and 8S. Typhimurium strains were recovered. Isolated outbreak strains showed multidrug resistance (MDR), and decreased susceptibility to ciprofloxacin, a first-line drug recommended by WHO for clinical treatment of intestinal infections. Antimicrobial resistance (AMR) gene analysis indicated that the MDR phenotype of these outbreak strains may be due to the presence of a number of AMR genes, including the blaOXA-1 and blaTEM-1 β-lactamase genes, which are often plasmid-borne and easily transferred. Further virulence gene analysis indicated that these outbreak strains also carried a large number of virulence genes, including 2 types of Salmonella pathogenicity islands (SPI-1 and SPI-2) and many adhesion-related virulence genes. Cluster analysis based on pulse-field gel electrophoresis data and phylogenetic analysis based on WGS revealed that the outbreak clone was closely related to and thus probably derived from local strains. This outbreak caused by multidrug resistant S. Typhimurium highlights the need for government improved strategies for the prevention and control of Salmonella infections.
Highlights
Salmonella is one of the common pathogens causing sporadic cases or outbreaks of gastroenteritis (Hawker et al, 2019; Jain et al, 2020)
Virulence gene analysis on 119 strains in Figure 2, we found that these virulence genes were exactly the same in all outbreak strains (Figure 5)
Epidemiological surveys showed that all 11 people exhibiting gastrointestinal symptoms attended the same banquet and presented with symptoms within 3 days of attending the banquet
Summary
Salmonella is one of the common pathogens causing sporadic cases or outbreaks of gastroenteritis (Hawker et al, 2019; Jain et al, 2020). We Evaluated an Outbreak by the foodborne disease surveillance system of China from 2006 to 2010, suggested that Salmonella was the second most common bacteria causing foodborne outbreaks (Pang et al, 2011). Typhimurium) is one of the predominant serotypes in many countries (PieterJan et al, 2015; Simpson et al, 2018) and it has held the first or second place in China for many years (Ran et al, 2011; Wang Y. et al, 2017). Some studies have shown that the proportion of multidrug resistant bacteria in S. Typhimurium has brought difficulties to clinical treatment resulting in increased morbidity and mortality
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