Citation: Shaji, S.; Selvaraj, R.K.; Shanmugasundaram, R. Salmonella Infection in Poultry: A Review on the Pathogen and Control Strategies. Microorganisms 2023, 11, 2814. https://doi.org/10.3390/ microorganisms11112814 Academic Editors: Mónica Oleastro and Ana Botelho Received: 20 October 2023 Revised: 8 November 2023 Accepted: 11 November 2023 Published: 20 November 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). microorganisms Review Salmonella Infection in Poultry: A Review on the Pathogen and Control Strategies Syamily Shaji 1 , Ramesh K. Selvaraj 1 and Revathi Shanmugasundaram 2, * 1 Department of Poultry Science, The University of Georgia, Athens, GA 30602, USA; syamily.shaji@uga.edu (S.S.); selvaraj@uga.edu (R.K.S.) 2 Toxicology and Mycotoxin Research Unit, US National Poultry Research Center, Athens, GA 30605, USA * Correspondence: revathi.shan@usda.gov Abstract: Salmonella is the leading cause of food-borne zoonotic disease worldwide. Non-typhoidal Salmonella serotypes are the primary etiological agents associated with salmonellosis in poultry. Contaminated poultry eggs and meat products are the major sources of human Salmonella infection. Horizontal and vertical transmission are the primary routes of infection in chickens. The principal virulence genes linked to Salmonella pathogenesis in poultry are located in Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2). Cell-mediated and humoral immune responses are involved in the defense against Salmonella invasion in poultry. Vaccination of chickens and supplementation of feed additives like prebiotics, probiotics, postbiotics, synbiotics, and bacteriophages are currently being used to mitigate the Salmonella load in poultry. Despite the existence of various control measures, there is still a need for a broad, safe, and well-defined strategy that can confer long-term protection from Salmonella in poultry flocks. This review examines the current knowledge on the etiology, transmission, cell wall structure, nomenclature, pathogenesis, immune response, and efficacy of preventative approaches to Salmonella. Keywords: Salmonella; vaccines; poultry 1. Introduction Salmonella is the leading cause of foodborne diseases worldwide that infects the gas- trointestinal tract and causes diarrhea, nausea, and cramps in humans [1]. The Center for Disease Control and Prevention (CDC) estimates that approximately 1.35 million infec- tions and 420 deaths are reported annually in the United States. Salmonella enterica ser. Enteritidis (S. Enteritidis), and Salmonella enterica ser. Typhimurium (S. Typhimurium), belonging to the non-typhoidal Salmonella group (NTS), is responsible for the majority of human salmonellosis. Globally, non-typhoidal Salmonella is responsible for approximately 93 million cases of gastroenteritis and 155,000 fatalities annually. The severity of human salmonellosis varies depending on factors such as the specific strain causing the infection, health conditions, and host age. It has been reported that the infective dose in a human infant is reported to be 100 bacterial cells, and even fewer cells are required to cause an infection in an immunocompromised individual [2–4]. Poultry serves as the main reservoir for various non-typhoidal Salmonella (NTS) serotypes among food-producing animals. Epidemiologically significant NTS serotypes include S. Typhimurium, S. Enteritidis, S. Heidelberg, and S. Newport. In North America and Europe, S. Enteritidis dominates the egg-borne transmission of infection to humans, whereas S. Typhimurium was the primary serovar associated with external egg contamina- tion in Australia [5–7]. Between 1998 and 2008, poultry accounted for 17.9% of foodborne illnesses in the United States, with Salmonella ser. Enteritidis and Typhimurium are re- sponsible for 17.4% and 34% of poultry-related foodborne illnesses, respectively [8]. In 2016, a national outbreak of multidrug-resistant S. Heidelberg linked to chicken products Microorganisms 2023, 11, 2814. https://doi.org/10.3390/microorganisms11112814 https://www.mdpi.com/journal/microorganisms