Swine pathogenic infection caused by Escherichia coli, known as swine colibacillosis, represents an epidemiological challenge not only for animal husbandry but also for health authorities. To note, virulent E. coli strains might be transmitted, and also cause disease, in humans. In the last decades, diverse successful multidrug-resistant strains have been detected, mainly due to the growing selective pressure of antibiotic use, in which animal practices have played a relevant role. In fact, according to the different features and particular virulence factor combination, there are four different pathotypes of E. coli that can cause illness in swine: enterotoxigenic E. coli (ETEC), Shiga toxin-producing E. coli (STEC) that comprises edema disease E. coli (EDEC) and enterohemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and extraintestinal pathogenic E. coli (ExPEC). Nevertheless, the most relevant pathotype in a colibacillosis scenario is ETEC, responsible for neonatal and postweaning diarrhea (PWD), in which some ETEC strains present enhanced fitness and pathogenicity. To explore the distribution of pathogenic ETEC in swine farms and their diversity, resistance, and virulence profiles, this review summarizes the most relevant works on these subjects over the past 10 years and discusses the importance of these bacteria as zoonotic agents.

Enteric colibacillosis is a common disease in nursing and weanling pigs. It is caused by the colonization of the small intestine by enterotoxigenic strains ofEscherichia coli(ETEC) that make use of specific fimbria or pili to adhere to the absorptive epithelial cells of the jejunum and ileum. Once attached, and when both the immunological systems and the gut microbiota are poorly developed, ETEC produce one or more enterotoxins that can have local and, further on, systemic effects. These enterotoxins cause fluid and electrolytes to be secreted into the intestinal lumen of animals, which results in diarrhea, dehydration, and acidosis. From the diversity of control strategies, antibiotics and zinc oxide are the ones that have contributed more significantly to mitigating post-weaning diarrhea (PWD) economic losses. However, concerns about antibiotic resistance determined the restriction on the use of critically important antimicrobials in food-producing animals and the prohibition of their use as growth promoters. As such, it is important now to begin the transition from these preventive/control measures to other, more sustainable, approaches. This review provides a quick synopsis of the currently approved and available therapies for PWD treatment while presenting an overview of novel antimicrobial strategies that are being explored for the control and treatment of this infection, including, prebiotics, probiotics, synbiotics, organic acids, bacteriophages, spray-dried plasma, antibodies, phytogenic substances, antisense oligonucleotides, and aptamers.

Staphylococcal enterotoxin A (SEA) is the most frequently reported in staphylococcal food poisoning (SFP) outbreaks. Aptamers are single-stranded nucleic acids that are seen as promising alternatives to antibodies in several areas, including diagnostics. In this work, systematic evolution of ligands by exponential enrichment (SELEX) was used to select DNA aptamers against SEA. The SELEX protocol employed magnetic beads as an immobilization matrix for the target molecule and real-time quantitative PCR (qPCR) for monitoring and optimizing sequence enrichment. After 10 selection cycles, the ssDNA pool with the highest affinity was sequenced by next generation sequencing (NGS). Approximately 3 million aptamer candidates were identified, and the most representative cluster sequences were selected for further characterization. The aptamer with the highest affinity showed an experimental dissociation constant (K_D) of 13.36 ± 18.62 nM. Increased temperature negatively affected the affinity of the aptamer for the target. Application of the selected aptamers in a lateral flow assay demonstrated their functionality in detecting samples containing 100 ng SEA, the minimum amount capable of causing food poisoning. Overall, the applicability of DNA aptamers in SEA recognition was demonstrated and characterized under different conditions, paving the way for the development of diagnostic tools.

Enterotoxigenic Escherichia coli (ETEC) is the major bacterial cause of diarrheal diseases in pigs, particularly at young ages, resulting in significant costs to swine farming. The pathogenicity of ETEC is largely dependent on the presence of fimbriae and the ability to produce toxins. Fimbriae are responsible for their initial adhesion to the intestinal epithelial cells, leading to the onset of infection. In particular, the F4 type (K88) fimbriae are often attributed to neonatal infections and have also been associated with post-weaning diarrheal infections. This disease is traditionally prevented or treated with antibiotics, but their use is being severely restricted due to the emergence of resistant bacteria and their impact on human health. Emerging approaches such as aptamers that target the F4-type fimbriae and block the initial ETEC adhesion are a promising alternative. The aim of this study is to assess the effectiveness of two aptamers, Apt31 and Apt37, in controlling ETEC infection in the G. mellonella in vivo model. Initially, the dissociation constant (K_D) of each aptamer against ETEC was established using real-time quantitative PCR methodology. Subsequently, different concentrations of the aptamers were injected into Galleria mellonella to study their toxicity. Afterwards, the anti-ETEC potential of Apt31 and Apt37 was assessed in the larvae model. The determined K_D was 81.79 nM (95% CI: 31.21–199.4 nM) and 50.71 nM (95% CI: 26.52–96.15 nM) for the Apt31 and Apt37, respectively, showing no statistical difference. No toxicity was observed in G. mellonella following injection with both aptamers at any concentration. However, the administration of Apt31 together with ETEC-F4+ in G. mellonella resulted in a significant improvement of approximately 30% in both larvae survival and health index compared to ETEC-F4+ alone. These findings suggest that aptamers have promising inhibitory effect against ETEC infections and pave the way for additional in vivo studies.

Foodborne pathogens represent a significant public health risk in both developed and developing countries. Among these pathogens, enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in humans and one of the leading causes of mortality in newly weaned pigs. The main sources of ETEC contamination include environments with poor hygiene and contaminated water, meat, cereals, and vegetables. Therefore, this review manuscript focuses on the pathogenesis of ETEC in humans and pigs. The main virulence factors responsible for ETEC-associated infections, such as colonization factors and toxins, will be described for both species, with particular emphasis on the toxins as well as, their classification and structural characterization. More specifically, this study will outline the main physiological alterations and adaptive mechanisms induced by these enterotoxins, namely heat-stable toxin (ST) and heat-labile toxin (LT), in the three most affected systems: the gastrointestinal system, the enteric nervous system (ENS), and the immune system. This set of findings provides a deeper insight into the pathogenesis of this relevant foodborne pathogen, which is crucial for empowering food scientists and stakeholders to more effectively mitigate associated risks. As such, it provides valuable understanding of toxin activity, serving as a means to raise awareness of food safety practices and strengthening risk communication, surveillance and intervention strategies, thereby ensuring consumer protection. Additionally, this knowledge enables the development of preventive strategies to reduce ETEC infections, thereby decreasing the need for clinical management among consumers exposed to this bacterium. Ultimately, it contributes to the preservation of public health, the reduction of antimicrobial use, and the lowering of antimicrobial resistance gene prevalence.

Biofilms, complex microbial communities adhering to surfaces, represent a significant challenge in clinical contexts. This chapter explores the multifaceted nature of biofilms using the oral microbiota as a model system. The composition of microbial communities in the oral cavity is influenced by complex interactions and a high degree of diversity, which are critical for maintaining oral health and preventing disease. Biofilm formation begins with microbial adhesion, a process influenced by both intrinsic microbial properties and environmental conditions. Following adhesion, quorum sensing facilitates communication between microbes to regulate biofilm development and maintenance. This interspecies communication system contributes to biofilm resilience and resistance to external threats, including antimicrobial agents. The inherent complexity of biofilms, characterized by diverse microbial interactions and structural robustness, poses significant challenges for eradication and control. Current strategies often fall short and novel approaches are needed to address biofilm-related problems. Future perspectives in biofilm research focus on elucidating the molecular mechanisms underlying biofilm formation and maintenance to develop more effective strategies for managing biofilm-related problems. Understanding these complex microbial communities is key to improving interventions and advancing our ability to control biofilms in different settings. <!----> <!----> <!----> <!---->