Contents



Preface

*Salmonella* spp. is a global pathogen responsible for millions of deaths each year. *Salmonella* is a complex genus comprising two species, S. enterica and S. bongori, and more than 2600 different serotypes. S. enterica is composed of six different subspecies: enterica (I), salamae (II), arizonae (IIIa), diarizonae (IIIb), houtenae (IV), and indica (VI). Serotypes of S. enterica subsp. enterica are responsible for more than 99% of human infections. Another way to classify *Salmonella* is according to the type of disease it causes. In general terms, there is typhoid fever

Typhoid fever is caused by the ingestion of water or food contaminated with fecal material carrying S. Typhi. As described by Al-Khafaji et al. in Chapter 1, a tool of mechanisms is responsible for the virulence of S. Typhi. The Vi capsule antigen can inhibit phagocytosis and complement C3. This capsule decreases the recognition of somatic antigens by antibodies. Flagella also contribute to virulence by interacting with host epithelial cells, macrophages, and immune evasion. S. Typhi also encodes in its genome some pathogenic island with the genes necessary to invade the host and effectively evade the immune system. Although typhoid fever is distributed worldwide, improvements in water supply and sewerage systems have resulted in a

In low- and middle-income countries where sanitary conditions continue to be a problem, typhoid fever is still highly prevalent. In developed countries, typhoid fever is a travel-related disease. It is estimated that there are 26.9 million S. Typhi infections annually. However, these data are misleading. The fact that this disease presents non-specific symptoms along with the lack of diagnostic tests and underreporting of cases in some regions of the world suggests that the real prevalence of this disease is much greater. In Chapter 2, Sado and Sado describe the importance of enteric fever diagnosis in primary care. The development of nonspecific symptoms complicates disease diagnosis. It is therefore important to follow a series of criteria

Prevention is undoubtedly the key and vaccines can certainly play a key role in this regard. Although there are some vaccines commercially available, their efficacy can still be improved. In Chapter 3, Rachmawati et al. provide an overview of the in silico approach for the S. Typhi epitope vaccine. There are three types of S. Typhi vaccines: live-attenuated, inactivated, and sub-unit vaccines. The authors further elaborate on the steps to be followed for developing a new type of vaccine using only the part of the subunit that is recognized by B and T cells of the immune system, the epitope area. The development of bioinformatic tools, omic technologies, and recombinant DNA technologies give these types of vaccines enormous potential. In Chapter 4, Mishra et al. describe how computational tools can help in the development of effective vaccines against multidrug-resistant S. enterica strains.

Nontyphoidal *Salmonella* primarily causes gastroenteritis, bacteremia, and focal infection, mainly related to the consumption of food contaminated with this pathogen. Livestock, especially poultry, can carry *Salmonella* in their gut without symptoms. Therefore, *Salmonella* can contaminate products produced from these

established by health authorities to facilitate diagnosis.

caused by S. Typhi and infections caused by non-typhoidal *Salmonella*.

decreased incidence.
