View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Erasmus University Digital Repository REVIEW published: 04 April 2018 doi: 10.3389/fcimb.2018.00102 Organoid and Enteroid Modeling of Salmonella Infection Yuebang Yin 1 and Daoguo Zhou 2,3* 1 Department of Gastroenterology and Hepatology, Erasmus MC-University Medical Center, Rotterdam, Netherlands, 2 Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, China, 3 Department of Biological Sciences, Purdue University, West Lafayette, IN, United States Salmonella are Gram-negative rod-shaped facultative anaerobic bacteria that are comprised of over 2,000 serovars. They cause gastroenteritis (salmonellosis) with headache, abdominal pain and diarrhea clinical symptoms. Salmonellosis brings a heavy burden for the public health in both developing and developed countries. Antibiotics are usually effective in treating the infected patients with severe gastroenteritis, although antibiotic resistance is on the rise. Understanding the molecular mechanisms of Salmonella infection is vital to combat the disease. In vitro immortalized 2-D cell lines, ex vivo tissues/organs and several animal models have been successfully utilized to study Salmonella infections. Although these infection models have contributed to uncovering the molecular virulence mechanisms, some intrinsic shortcomings have limited their wider applications. Notably, cell lines only contain a single cell type, which cannot reproduce some of the hallmarks of natural infections. While ex vivo tissues/organs alleviate some of these concerns, they are more difficult to maintain, in particular for long term experiments. In addition, non-human animal models are known to reflect only part of the human Edited by: Leigh A. Knodler, disease process. Enteroids and induced intestinal organoids are emerging as effective Washington State University, infection models due to their closeness in mimicking the infected tissues/organs. Induced United States intestinal organoids are derived from iPSCs and contain mesenchymal cells whereas Reviewed by: enteroids are derive from intestinal stem cells and are comprised of epithelial cells only. Bruce Vallance, University of British Columbia, Canada Both enteroids and induced intestinal organoids mimic the villus and crypt domains Mikael Erik Sellin, comparable to the architectures of the in vivo intestine. We review here that enteroids Uppsala University, Sweden Alison Ann Weiss, and induced intestinal organoids are emerging as desired infection models to study University of Cincinnati, United States bacterial-host interactions of Salmonella. *Correspondence: Keywords: Salmonella, infection models, enteroids, intestine, organoids Daoguo Zhou [email protected] GENERAL INTRODUCTION OF SALMONELLA Received: 14 July 2017 Accepted: 16 March 2018 Salmonella are Gram-negative rod-shaped and facultative anaerobes belong to the family of Published: 04 April 2018 Enterobacteriaceae (Coburn et al., 2007). According to the recent classification by the International Citation: Code of Nomenclature of Bacteria, the genus Salmonella are classified into two distinct species Yin Y and Zhou D (2018) Organoid and Enteroid Modeling of Salmonella including Salmonella enterica and Salmonella bongori based on their 16S rRNA sequence Infection. relatedness (Popoff et al., 2003). Salmonella bongori (V) is treated as a separate species due to its Front. Cell. Infect. Microbiol. 8:102. unique clinical features (Fierer and Guiney, 2001). Salmonella enterica is further classified into six doi: 10.3389/fcimb.2018.00102 subspecies: enterica (I), salamae (II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV), and indica Frontiers in Cellular and Infection Microbiology | www.frontiersin.org 1 April 2018 | Volume 8 | Article 102 Yin and Zhou Enteroid Infection Models (VI), mainly based on their genomic sequence and biochemical Many assays have been developed to diagnose Salmonella properties (Fierer and Guiney, 2001). Diverse biochemical infections. Widal test is the most commonly used diagnostic properties of the flagellar, carbohydrate and lipopolysaccharide assay based on agglutinating antibodies against Salmonella (LPS) of S. enterica divided them further into over 2,000 serovars LPS (O) and flagella (H). The enzyme-linked immunosorbent (Eng et al., 2015). Over 50% of these serovars belong to S. enterica assays (ELISAs) and sodium dodecyl sulfate-polyacrylamide gel subspecies enterica which are responsible for most infections electrophoresis (SDS-PAGE) immunoblotting assays are useful in human (Itri et al., 2017). Salmonella are also classified in measuring antibodies in patients’ sera. Recently, PCR, real- based on their somatic (O), capsular (K), and flagellar (H) time PCR, and proteomic approaches have been used to analyze antigenic determinants (Brenner et al., 2000). The commonly bacterial genes and proteins (Kumar et al., 2012; Nigro et al., used Salmonella classification in clinical laboratories is based on 2016). Once the infection is diagnosed, antibiotics might be used simple agglutination reactions to antibodies or antisera specific to treat infected patients with severe gastroenteritis, while most to the somatic O antigens containing six serogroups designated milder infections do not require antibiotics treatment (Boyle A,B,C1,C2,D,andE(Eng et al., 2015). et al., 2007; Hurley et al., 2014). Two typhoid vaccines have been Salmonella infections remain a big burden for the public licensed against enteric fever, both are only suitable for endemic health worldwide (Eng et al., 2015). There are three main types of situation (Griffin and McSorley, 2011; Crump et al., 2015; Eng Salmonellosis: (1) localized intestinal infection (gastroenteritis), et al., 2015). Vaccines against NTS infections have been developed (2) systemic infection of otherwise healthy hosts (typhoid), and recently (Griffin and McSorley, 2011; Eng et al., 2015). Currently, (3) systemic infection of immune-compromised hosts (Griffin food safety from farm to fork and treatment of municipal water and McSorley, 2011; Hurley et al., 2014). Salmonella strains that remain the most effective measures to control the transmission of cause these infections are separated into typhoid Salmonella and Salmonella (Crump et al., 2015). non-typhoid Salmonella (NTS) based on the clinical patterns The virulence determinants needed for S. Typhimurium are in human salmonellosis (Crump et al., 2015; Eng et al., 2015). similar to those of many other intestinal pathogens: First, it Typhoid Salmonella infection seems to be more severe, in needs to successfully survive the hostile acidic environment which patients show prodromal symptoms such as headache, in the stomach before making its way to colonize the small abdominal pain and diarrhea (or constipation), followed by the intestine. In the intestine, the bacteria must breach the barrier onset of fever, which might sustain an incubation period of 1 of intestinal epithelial cells and it has to survive inside the host week or more (Eng et al., 2015). Typhoid Salmonella strains cells. Pathogenic Salmonella spp. evolve complex systems, which are normally restricted to humans causing typhoid fever (also enable the organisms to respond and survive in the stomach with called enteric fever), while NTS strains have a broader host-range low-pH (Foster, 1995),andtoreachMcellsandenterocytesinthe and represent zoonotic features (Gordon, 2011). The typhoid small intestine (Takeuchi, 1967; Moulder, 1985; Lindquist et al., Salmonella infections occur mostly in developing countries 1987; Nietfeld et al., 1992; Clark et al., 1994, 1996; Jones et al., including many regions of the African and Asian continent. The 1994; Sansonetti and Phalipon, 1999). Salmonella Typhimurium illness causes 93.8 million foodborne cases and 155,000 deaths has the ability to enter non-phagocytic eukaryotic cells and to annually (Eng et al., 2015). In comparison, gastroenteritis is exist as intracellular parasites inside enclosed vacuoles (Takeuchi, caused mainly by S. enterica Serovar Typhimurium (Salmonella 1967; Moulder, 1985). The intracellular environment provides a Typhimurium) and Serovar Enteritidis, which are common even unique niche for the bacteria to multiply and evade host immune in developed countries (Eng et al., 2015). The clinical signs of responses. In addition, S. Typhimurium is capable of surviving gastroenteritis can be diarrhea, cramping, and most patients and replicating within macrophages (Buchmeier and Heffron, usually recover within 4–7 days without treatment (Griffin and 1989). McSorley, 2011). Salmonellosis is transmitted mainly via food or Several studies have led to the identification of genes water contaminated with human or animal feces (Crump et al., that are required for Salmonella pathogenesis, in particular 2015). NTS have been reported to transmit via contaminated for Salmonella invasion into non-phagocytic cells (Galán and animals and animal products (Crump et al., 2015). The mortality Curtiss, 1989; Ochman et al., 1996; Shea et al., 1996; Blanc- caused by typhoid Salmonella strains can be up to 7% even Potard and Groisman, 1997; Wong et al., 1998; Wood et al., when antibiotics are used (Eng et al., 2015). The incidence of 1998). Many of these virulence genes and operons are located enteric fever in the USA and European countries is normally low, in large genetic elements of the Salmonella chromosome.