Diarrheal diseases are one of the major causes of mortality among children under five years old and intestinal pathogenic Escherichia coli (InPEC) plays a role as one of the large causative groups of these infections worldwide. InPECs contribute significantly to the burden of intestinal diseases, which are a critical issue in low- and middle-income countries (Asia, Africa and Latin America). Intestinal pathotypes such as enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC) are mainly endemic in developing countries, while ETEC strains are the major cause of diarrhea in travelers to these countries. On the other hand, enterohemorrhagic E. coli (EHEC) are the cause of large outbreaks around the world, mainly affecting developed countries and responsible for not only diarrheal disease but also severe clinical complications like hemorrhagic colitis and hemolytic uremic syndrome (HUS). Overall, the emergence of antibiotic resistant strains, the annual cost increase in the health care system, the high incidence of traveler diarrhea and the increased number of HUS episodes have raised the need for effective preventive treatments. Although the use of antibiotics is still important in treating such infections, non-antibiotic strategies are either a crucial option to limit the increase in antibiotic resistant strains or absolutely necessary for diseases such as those caused by EHEC infections, for which antibiotic therapies are not recommended. Among non-antibiotic therapies, vaccine development is a strategy of choice but, to date, there is no effective licensed vaccine against InPEC infections. For several years, there has been a sustained effort to identify efficacious vaccine candidates able to reduce the burden of diarrheal disease. The aim of this review is to summarize recent milestones and insights in vaccine development against InPECs.

Escherichia coli is primarily known as a commensal colonising the gastrointestinal tract of infants very early in life but some strains being responsible for diarrhoea, which can be especially severe in young children. Intestinal pathogenic E. coli include six pathotypes of diarrhoeagenic E. coli (DEC), namely, the (i) enterotoxigenic E. coli, (ii) enteroaggregative E. coli, (iii) enteropathogenic E. coli, (iv) enterohemorragic E. coli, (v) enteroinvasive E. coli and (vi) diffusely adherent E. coli. Prior to human infection, DEC can be found in natural environments, animal reservoirs, food processing environments and contaminated food matrices. From an ecophysiological point of view, DEC thus deal with very different biotopes and biocoenoses all along the food chain. In this context, this review focuses on the wide range of surface molecular determinants acting as surface colonisation factors (SCFs) in DEC. In the first instance, SCFs can be broadly discriminated into (i) extracellular polysaccharides, (ii) extracellular DNA and (iii) surface proteins. Surface proteins constitute the most diverse group of SCFs broadly discriminated into (i) monomeric SCFs, such as autotransporter (AT) adhesins, inverted ATs, heat-resistant agglutinins or some moonlighting proteins, (ii) oligomeric SCFs, namely, the trimeric ATs and (iii) supramolecular SCFs, including flagella and numerous pili, e.g. the injectisome, type 4 pili, curli chaperone-usher pili or conjugative pili. This review also details the gene regulatory network of these numerous SCFs at the various stages as it occurs from pre-transcriptional to post-translocational levels, which remains to be fully elucidated in many cases.

The aim of this study was to report the antimicrobial resistance, the molecular mechanisms associated and the detection of virulence determinants within faecal Enterococcus spp. and Escherichia coli isolates of Iberian wolf. Enterococci (n = 227) and E. coli (n = 195) isolates were obtained from faecal samples of Iberian wolf (Canis lupus signatus). High rates of resistance were detected for tetracycline and erythromycin among the enterococci isolates, and most of resistant isolates harboured the tet(M) and/or tet(L) and erm(B) genes, respectively. The bla_TEM, tet(A) and/or tet(B), and aadA or strA‐strB genes were detected among most ampicillin‐, tetracycline‐ or streptomycin‐resistant E. coli isolates, respectively. E. coli isolates were ascribed to phylogroups A (n = 56), B1 (91), B2 (13) and D (35). The occurrence of resistant enterococci and E. coli isolates in the faecal flora of Iberian wolf, including the presence of resistant genes in integrons, and virulence determinants was showed in this study. Iberian wolf might act as reservoir of certain resistance genes that could be spread throughout the environment. Significance and Impact of the Study This study shows antimicrobial resistance in commensal bacteria from the free‐range, Portuguese, Iberian wolf population. The results indicate that the Iberian wolf could contribute to the spread of resistant bacteria throughout the environment. Additionally, in case of infection, an increased risk of therapeutic failure due to the presence of multiresistant bacteria may represent a health problem for this endangered species. Future studies must be performed to analyse the possible contamination of these animals through the environment and/or the food chain.

Shiga toxin-encoding E. coli (STEC) regroup strains that carry genes encoding Shiga toxin (Stx). Among intestinal pathogenic Escherichia coli (InPEC), enterohaemorrhagic E. coli (EHEC) constitute the major subgroup of virulent STEC. EHEC cause serious human disease such as haemorrhagic colitis and haemolytic-uremic syndrome (HUS). While EHEC have evolved from enteropathogenic E. coli (EPEC), hybrids with enteroaggregative E. coli (EAEC) have recently emerged. Of note, some enteroinvasive E. coli (EIEC) also belong to the STEC group. While the LEE (locus of enterocyte effacement) is a key and prominent molecular determinant in the pathogenicity, neither all EHEC nor STEC contain the LEE, suggesting that they possess additional virulence and colonisation factors. Currently, nine protein secretion systems have been described in diderm-lipopolysaccharide (LPS) bacteria (archetypal Gram-negative) and can be involved in the secretion of extracellular effectors, cell-surface proteins or assembly of cell-surface organelles, such as flagellum or pili. In this review, we focus on the secretome of STEC and related enteropathotypes, which are relevant to the colonisation of biotic and abiotic surfaces. Considering the wealth of potential protein trafficking mechanisms, the different combination of colonisation factors and modulation of their expression is further emphasised with regards to the ecophysiology of STEC.