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Although brought to the forefront in the 1980s with the AIDS pandemic, microsporidia infecting humans are still little known. Enterocytozoon bieneusi, by far the most frequent microsporidia species causing diseases in humans, is responsible for intestinal illness in both non- and immunocompromised patients. This species presents an astonishing genetic diversity with more than 500 genotypes described, some of which have a strong zoonotic potential. Indeed, E. bieneusi infects a broad array of hosts, from wild to domestic animals. This emerging eukaryotic pathogen has thus been associated with foodborne/waterborne outbreaks. Several molecular assays have been developed to enhance its diagnosis or for epidemiological purposes, providing valuable new data. Here, we propose an overview of the current knowledge on this major species among the microsporidia, so far rather neglected in human medicine.

Lawsonia (L.) intracellularis is a widespread, economically important bacterium causing the porcine proliferative enteropathy (PPE). In this study, we evaluated intestinal microbiota of naturally exposed L. intracellularis-positive pigs under standardized conditions. To obtain three independent repetitions, 27 L. intracellularis-infected pigs (19.0 ± 1.50 kg body weight) from one farm were divided into three groups at an age of 7 to 8 weeks (nine pigs/group). Pigs were either vaccinated against L. intracellularis via oral drenching on their 21st day of life (attenuated live vaccine) or non-vaccinated and selected according to clinical findings (pigs without deviating fecal consistency or with moderate to soft fecal consistency). Comparison of the clinically inconspicuous piglets that differed regarding their vaccination status showed fewer significant differences in fecal microbiota composition. The vaccination led to an overall enrichment of bacterial species belonging to the order Clostridiales, while species of the genus Collinsella and Prevotella were decreased. Several bacterial species belonging to the order Bacteroidales, mainly of the family Prevotellacecae, often closely matching Prevotella copri differed significantly between non-vaccinated clinically inconspicuous and conspicuous piglets. Whether those bacterial species play a role in mitigating the severity of an L. intracellularis infection remains to be defined.

Enterohaemorrhagic Escherichia coli (EHEC) are food-borne pathogens responsible for bloody diarrhoea and renal failure in humans. While Shiga toxin (Stx) is the cardinal virulence factor of EHEC, its production by E. coli is not sufficient to cause disease and many Shiga-toxin producing E. coli (STEC) strains have never been implicated in human infection. So far, the pathophysiology of EHEC infection is not fully understood and more knowledge is needed to characterize the “auxiliary” factors that enable a STEC strain to cause disease in humans. In this study, we applied a recombinase-based in vivo expression technology (RIVET) to the EHEC reference strain EDL933 in order to identify genes specifically induced during the infectious process, using mouse as an infection model. We identified 31 in vivo-induced (ivi) genes having functions related to metabolism, stress adaptive response and bacterial virulence or fitness. Eight of the 31 ivi genes were found to be heterogeneously distributed in EHEC strains circulating in France these last years. In addition, they are more prevalent in strains from the TOP seven priority serotypes and particularly strains carrying significant virulence determinants such as Stx2 and intimin adhesin. This work sheds further light on bacterial determinants over-expressed in vivo during infection that may contribute to the potential of STEC strains to cause disease in humans.

Bacterial isolates from raw camel milk were screened for antibacterial activity using the agar diffusion assay. Ten isolates selected for their inhibition of Gram-positive bacteria were identified by 16S sequencing as Enterococcus faecium or durans. An isolate named E. faecium LCW 44 exhibited the broadest antibacterial spectrum with an inhibitory activity against several Gram-positive strains belonging to the genera Clostridium, Listeria, Staphylococcus, and Lactobacillus. E. faecium LCW 44 was shown to produce N-formylated enterocins L50A and L50B, as revealed by mass spectrometry and PCR analyses. This isolate did not harbor any of the virulence factors tested and was shown to be sensitive to all tested antibiotics. It showed high resistance to gastric and intestinal conditions (78 ± 4% survival). Its adhesion index was evaluated at 176 ± 86 and 24 ± 86 on Caco-2 cells and HT-29 cells, respectively, and it significantly reduced adhesion of Listeria monocytogenes by 65 and 49%, respectively. In Macfarlane broth (simulating the nutrient content of the colon), counts of L. monocytogenes were reduced by 2 log10 cycles after 24 h in co-culture with E. faecium LCW 44, compared to the increase of 4 log10 cycles when cultured alone. Comparison with a bacteriocin-non-producing mutant of E. faecium LCW 44 strongly suggests that inhibition of L. monocytogenes was due to bacteriocin production. Altogether, E. faecium LCW 44 thus has potential for use as a probiotic for humans and veterinary medicine.