Nature-Identical Compounds and Organic Acids Reduce E. coli K88 Growth and Virulence Gene Expression In Vitro

Abstract

Post-weaning diarrhoea (PWD) is one of the long-standing challenges in pig husbandry. Due to the risks of resistance caused by antibiotics (AB) misuse, conventional treatments against Escherichia coli K88 (E. coli K88), the PWD etiological agent, urgently need to be replaced. Organic acids (OA) and nature-identical compounds (NIC) are currently finding a central role in infection management thanks to their recognized antimicrobial activity. This study investigated the susceptibility of an E. coli K88 field strain to a wide panel of AB, NIC, and OA. Secondly, we evaluated the ability of sub-lethal doses of the most active compounds to modulate the expression of E. coli K88 virulence genes. Results showed that the bacterial strain was resistant to many of the tested antibiotics, but an antimicrobial action was registered for selected NIC and OA. The quantitative PCR analysis revealed that thymol, carvacrol, eugenol, and benzoic acid were able to downregulate (p < 0.05) the expression of bacterial genes related to motility, adhesion to enterocytes, heat-labile (LT) and heat-stable (ST) toxin secretion, quorum sensing, and biofilm formation. Therefore, this study demonstrated that selected OA and NIC not only control E. coli K88 growth but also modulate the expression of many virulence genes at sub-lethal doses, thus offering new insights on their mechanism of action and suggesting a powerful tool to manage PWD.

Antimicrobial Power of Organic Acids and Nature-Identical Compounds against Two Vibrio spp.: An In Vitro Study

“…to the same classes of molecules. Furthermore, we reported sensitivities that are comparable to what was observed in other Gram-negative pathogens, namely S. typhimurium and E. coli [21,23]. In fact, the most effective molecules in inhibiting Vibrio spp.…”

“…The aim of this study was to perform a screening of the in vitro antimicrobial activity of a wide panel of NIC and OA against 2 Vibrio species characteristic of the Mediterranean area, Vibrio harveyi ( V. harveyi ) and Vibrio anguillarum ( V. anguillarum ). Ten OA and eleven NIC were selected among different chemical classes and according to their efficacy, previously detected against other terrestrial livestock pathogens [ 21 ]. More precisely, OA were selected among different classes such as short-chain fatty acids (SCFA—formic, propionic and butyric acid), medium-chain fatty acids (MCFA—hexanoic, octanoic, decanoic and dodecanoic acid), tricarboxylic acids (TCA—citric acid) and other OA widely used in the food and feed preservation (sorbic and benzoic acid).…”

Chemistry, Safety, and Challenges of the Use of Organic Acids and Their Derivative Salts in Meat Preservation

“…Nature, Composition, and Production. Organic acids are chemical compounds widely present in nature as normal constituents of plants or animal tissues [10]. For instance, citric acid can be extracted from the juice of citrus and other acidic fruits such as limes, lemons, oranges, pineapples, and gooseberries [11][12][13], while benzoic acid exists naturally in cinnamon, cloudberries, cranberries, and lingonberries [3].…”

“…For instance, citric acid can be extracted from the juice of citrus and other acidic fruits such as limes, lemons, oranges, pineapples, and gooseberries [11][12][13], while benzoic acid exists naturally in cinnamon, cloudberries, cranberries, and lingonberries [3]. Ubiquitous microorganisms such as bacteria, fungi, and yeasts can also produce organic acids [10]. Nevertheless, lactic acid bacteria (LAB) are the most popular bacteria regarding the production of organic acids as their metabolic end-products of carbohydrate fermentation [3,14].…”

“…On the other hand, it is important to note that organic acids exist in two basic forms: (i) pure organic acids (e.g., lactic, acetic, citric, and benzoic acids) and (ii) buffered organic acids such as the calcium and sodium salts of the already mentioned acids [3]. Organic acids differ in structure basing on the involvement of their constituent elements of carbon, hydrogen, and oxygen [10]. Chemical properties and physical characteristics of the most used organic acids and their salts that are commonly used in food industry are presented in Table 1.…”