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Salmonella Carriage
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
The introduction of public health principles such as sanitary infrastructure, pasteurization of milk and water-supply chlorination has led to the virtual elimination of typhoid fever from most developed countries in the 20th century. Strategies for enteric fever prevention include improving sanitation, ensuring the safety of food and water supplies, identification and treatment of chronic carriers of Salmonella serovar Typhi and the use of typhoid vaccines to reduce the susceptibility of hosts to infection or disease. Reducing the proportion of people without access to safe drinking water is a component of Millennium Development Goal 7. Several vaccines exist: an oral vaccine containing a live, attenuated virus, Salmonella serovar Typhi strain Ty21a, and the parenteral Vi vaccine based on the Salmonella serovar Typhi Vi capsular polysaccharide antigen. For both vaccines, the protective efficacy over 3 years is about 50%. Newer Vi conjugate vaccines which are still in development have shown an efficacy of 90%. However, Vi-based monovalent vaccines do not offer protection against most paratyphoid fever, because only Salmonella serovar Typhi, Paratyphi C and Dublin carry the Vi antigen. Ty21a may provide limited protection against Salmonella serovar Paratyphi B.
The gastrointestinal system
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Sharon J. White, Francis A. Carey
Infection by Salmonella typhi or S. paratyphi causes typhoid and the milder paratyphoid fever. These diseases are seen only rarely in Western countries, largely due to the availability of clean drinking water. However, food poisoning by less virulent salmonellae is becoming increasingly common in the UK. Symptoms usually relate to the upper intestinal tract, with colicky periumbilical pain, vomiting, and watery diarrhoea, but sometimes they relate to the large intestine with frequent bloody stools and tenderness over the sigmoid colon. Sigmoidoscopy in the latter case reveals changes that are very similar, both macroscopically and microscopically, to those of ulcerative colitis (see below).
Salmonella
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
S.I. Smith, A. Ajayi, A. Seriki
Salmonella Paratyphi A, B, or C causes paratyphoid fever, which is a milder enteric fever with low mortality in contrast to Salmonella typhi, which causes typhoid fever. Both serotypes are solely human pathogen. After penetration of the ileal mucosa, the organisms pass through the lymphatics to the mesenteric lymph nodes, when after a period of multiplication they invade the bloodstream via the thoracic duct. The liver, gall bladder, spleen, kidney, and bone marrow become infected during the first 7–10 days of the incubation period. The interval between ingestion of the organisms and the onset of illness varies with the size of the infecting dose. Enteric fever is characterized by abdominal pain, headache, and diarrhea followed by the onset of fever. Apart from fever, patients may develop splenomegaly (enlarged spleen), myalgia, hepatomegaly (enlarged liver), and bradycardia. Roughly 10% of patients may relapse, die, or encounter serious complications such as typhoid encephalopathy, gastrointestinal bleeding, and intestinal perforation. Intestinal perforation may present with abdominal pain, rising pulse, and falling blood pressure in infected persons.1,17,24–26
Progress in the overall understanding of typhoid fever: implications for vaccine development
Published in Expert Review of Vaccines, 2020
Peter J O’Reilly, Dikshya Pant, Mila Shakya, Buddha Basnyat, Andrew J Pollard
A systematic analysis of results from the GBD 2017 study highlighted a lack of reliable data regarding rates of paratyphoid fever. A paucity of national-level reporting of paratyphoid fever rates and the failure of individual studies to differentiate between S. Paratyphi A, B, and C leaves potential gaps in understanding and estimation of paratyphoid fever incidence. There were an estimated 3.4 million (2.7– 4.2) cases of paratyphoid fever and 19,000 deaths attributed to paratyphoid fever in 2017 [6]. Most cases are caused by S. Paratyphi A, and disease caused by S. Paratyphi B or C is rarely reported. Studies published in the past 20 years have shown an increase in paratyphoid fever. Ochiai and colleagues reported a higher incidence of Salmonella Paratyphi A (64%) than Salmonella Typhi in China [15]. An increasing incidence of S. Paratyphi A has also been documented in studies from India [16,17] and Nepal [18]. Salmonella Typhi accounts for an estimated 76.3% (71.8–80.5) of cases of enteric fever and the majority of the remaining cases currently attributed to S. Paratyphi A [6]. Growing rates of paratyphoid fever are of concern. Little is known about the probable cause for this increase. Currently, available vaccines do not protect against infection caused by S. Paratyphi A. With the current drive toward vaccination against S. Typhi, it will be important to monitor the incidence of paratyphoid fever because of the theoretical risk of replacement.
Fluoroquinolone-resistant Salmonella typhi infection: a report of two cases in South Africa
Published in Southern African Journal of Infectious Diseases, 2018
N Schellack, E Bronkhorst, C Maluleka, L Hunt, P Srinivas, W Grootboom, D Goff, P Naicker, T Modau, O Babarinde
Typhoid and paratyphoid are important global public health concerns as they are major causes of morbidity in the developing world.1 Typhoid and paratyphoid fever are acute and often life-threatening febrile illnesses caused by the enteric Gram-negative bacillus, Salmonella enterica, serotype typhi and paratyphi. The species S. enterica contains more than 2 500 serotypes. However, less than 100 serotypes are responsible for human infections, particularly S. typhi, and S. paratyphi A and B.2,3
Reverse engineering approach: a step towards a new era of vaccinology with special reference to Salmonella
Published in Expert Review of Vaccines, 2022
Shania Vij, Reena Thakur, Praveen Rishi
Vaccines containing multiple epitopes have emerged as a fascinating option in the RV field wherein multiple immunodominant epitopes can be constructed as a single molecule which, in addition to being highly immunogenic, can confer broad-spectrum protection. For instance, a single vaccine against S. Paratyphi A strains along with S. Typhi strains can be developed using the conserved epitopes in the proteome or genome of these pathovars. Although paratyphoid fever cases have been observed to be at par with typhoid cases, the absence of vaccines against Paratyphi strains is a matter of concern. Thus, using multi-epitopes-based vaccine can solve this problem. Also, it is likely that infection by pathogens may also trigger responses of the nervous and endocrine systems along with those of the immune system. There are some studies that describe the possible neuroendocrine regulation of immune responses through the release of neurotransmitters [188,189]. In a study carried out in our lab, it was observed that post-typhoidal neurological manifestations are caused by Salmonella, which are strain specific [190], and the probiotic intervention at the gut-brain axis can alleviate the host health by the release of certain neurotransmitters [191]. However, the molecular and cellular mechanisms involved in this regulation are still unresolved. Reverse engineering approach of vaccine designing may prove to be an important gambit to unravel the underlying cellular and molecular mechanisms involved. Using the information available in the literature, a database may be generated to develop algorithms which can also take care of this aspect. Further, in the case of epitopes-based vaccines, carrier proteins to increase their size and ultimately immunogenicity are required. Mostly Bovine serum albumin (BSA) or Keyhole Limpet Hemocyanin (KLH) have been employed as carriers in many studies. However, BSA is not recommended for human use as it causes allergic reactions in humans. Because of this, World Health Organization (WHO) has set a guidance of 50 ng or less residual BSA per vaccine dose. KLH, on the other hand, is well tolerated in humans [192,193]. Also, the use of immunogenic proteins should be encouraged as carrier molecules to come up with a vaccine candidate which has multipronged action against the pathogen. The final entity thus developed may induce broad-spectrum protection by targeting the pathogen at different levels. It has been observed that conjugating the peptide-epitopes to carrier protein(s) has sometimes resulted in the loss of immunogenicity. Conjugating chemistries mostly employ a linker molecule to avoid the steric hindrance between the carrier and peptide moieties. Therefore, the selection of linker molecules is also a crucial factor while designing such vaccines.