Citation: Ayariga, J.A.; Abugri, D.A.; Amrutha, B.; Villafane, R. Capsaicin Potently Blocks Salmonella typhimurium Invasion of Vero Cells. Antibiotics 2022, 11, 666. https:// doi.org/10.3390/antibiotics11050666 Academic Editors: Marina DellaGreca and William N. Setzer Received: 17 April 2022 Accepted: 10 May 2022 Published: 16 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 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/). antibiotics Article Capsaicin Potently Blocks Salmonella typhimurium Invasion of Vero Cells Joseph A. Ayariga 1,2, * , Daniel A. Abugri 2,3,4, *, Balagopal Amrutha 5 and Robert Villafane 2,3 1 The Biomedical Engineering Program, College of Science, Technology, Engineering and Mathematics (C-STEM), Alabama State University, Montgomery, AL 36104, USA 2 Department of Biological Sciences, College of Science, Technology, Engineering and Mathematics (C-STEM), Alabama State University, Montgomery, AL 36104, USA; rvillafane@alasu.edu 3 Microbiology PhD Program, College of Science, Technology, Engineering and Mathematics (C-STEM), Alabama State University, Montgomery, AL 36104, USA 4 Laboratory of Ethnomedicine, Parasitology, and Drug Discovery, College of Science, Technology, Engineering and Mathematics (C-STEM), Alabama State University, Montgomery, AL 36104, USA 5 Division of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada; amrutakikka@gmail.com * Correspondence: ayarigajosephatia@yahoo.co.uk (J.A.A.); dabugri@alasu.edu (D.A.A.) Abstract: Salmonella typhimurium (S. typhimurium) is one of the major food and waterborne bacteria that causes several health outbreaks in the world. Although there are few antibiotics against this bacterium, some of these drugs are challenged with resistance and toxicity. To mitigate this challenge, our group explored the ethnomedicinal/herbalism knowledge about a certain spice used in Northern Ghana in West Africa against bacterial and viral infection. This plant is Capsicum chinense (C. chinense). The plant is one of the commonest food spices consumed across the world. The seed of the plant contains both capsaicin and dihydrocapsaicin. Apart from capsaicin and dihydrocapsaicin, other major capsaicinoids in C. chinense include nordihydrocapsaicin, homodihydrocapsaicin, and homo- capsaicin. In this pilot work, we investigated the antibacterial activity of pure capsaicin and capsaicin extract obtained from C. chinense against S. typhimurium in vitro. Capsaicin extract showed potent inhibition of S. typhimurium growth at concentrations as low as 100 ng/mL, whereas pure capsaicin comparatively showed poorer inhibition of bacteria growth at such a concentration. Interestingly, both capsaicin extract and pure capsaicin were found to potently block a S. typhimurium invasion of the Vero cell in vitro. Taken together, we believed that capsaicin might work synergistically with dihydrocapsaicin or the other capsaicinoids to inhibit S. typhimurium growth, whereas individually, capsaicin or dihydrocapsaicin could potently block the bacteria entry and invasion of Vero cells. Keywords: Capsicum chinense; capsaicin; inhibition; Salmonella typhimurium; growth 1. Introduction Over the last 4 to 5 decades, the infections related to nontyphoidal Salmonella have increased and continues to be a major global burden in health care systems in most coun- tries [1–5]. Most outbreaks of S. typhimurium are facilitated through the acquisition of new traits that enhance their adaptability and virulence [6,7]. For instance, the emergence of multidrug-resistant (MDR) S. typhimurium DT104 has been demonstrated to be caused by the acquisition of the MDR gene via a plasmid-mediated process [8]. For example, the MDR-AmpC phenotypes S. typhimurium and S. newport have been demonstrated to be exclusively plasmid mediated by plasmid transfer MDR genes [9]. S. typhimurium is a Gram-negative bacterium that causes gastroenteritis, bacteremia, and focal infections [4,7]. The symptoms include high fever and diarrhea [1,4–6]. The infection of S. typhimurium is currently treated with trimethoprim and sulfamethoxazole combination, or with ciprofloxacin, azithromycin, or ceftriaxone [9]. However, the potential Antibiotics 2022, 11, 666. https://doi.org/10.3390/antibiotics11050666 https://www.mdpi.com/journal/antibiotics