Donor screening for fecal microbiota transplantation with a direct stool testing-based strategy: a prospective cohort study

Fecal microbiota transplantation (FMT) is effective against recurrent Clostridioides difficile infection (rCDI), but its safety is jeopardized by the potential transmission of pathogens, so international guidelines recommend either a quarantine or a direct stool testing. Whereas reports of the quarantine-based approach are emerging, data on the direct testing-based approach are not available. Our aim is to report outcomes of a donor screening framework for FMT including direct stool testing. In this prospective cohort study, all donor candidates recruited at our FMT centre underwent a four-step screening process to be enrolled as actual donors. Each collected stool donation was then evaluated with a direct stool testing including a molecular assay for gut pathogens and a culture assay for multi-drug resistant organisms (MDRO). From January 2019 to June 2023, 72 of 227 candidates (32%) were considered eligible and provided 277 stool donations. Ninety-nine donations (36%) were discarded for positivity to intestinal pathogens, most commonly enteropathogenic Escherichia coli (n = 37) and Blastocystis hominis (n = 20). Overall, 337 stool aliquots were obtained from 165 approved donations. All suspensions were used for patients with rCDI, and no serious adverse events or clinically evident infections were observed at 12 weeks after procedures. In our study, screening of donor faeces including direct stool testing led to the discard of a considerable rate of stool donations but was also extremely safe. This approach may represent a reliable strategy to guarantee the safety of FMT programs, especially in countries with high prevalence of MDRO.

The positive effect of malaria IPTp-SP on birthweight is mediated by gestational weight gain but modifiable by maternal carriage of enteric pathogens

BACKGROUND

Poor pregnancy and birth outcomes are common in sub-Saharan Africa and have complex aetiologies. Sulfadoxine-pyrimethamine (SP), given for intermittent preventive therapy of malaria in pregnancy (IPTp), is one of few existing interventions that improves outcomes of both mother and baby despite widespread SP-resistant malaria. Compelling evidence exists that malaria-independent pathways contribute to this protective effect, but the exact sources of non anti-malarial protection remained unknown. We hypothesized that the beneficial effect of SP on birthweight is mediated by SP activity on maternal factors, including increased gestational weight gain and antibiotic activity on pathogens in the maternal gut.

METHODS

Expectant mothers from a larger randomized control trial comparing the efficacy of IPTp-SP to IPTp with dihydroartemisinin-piperaquine (DP) were also enrolled in this sub-study study at their first antenatal care visit before commencement of IPTp (n = 105). Participants were followed monthly until delivery. Weights and mid-to-upper-arm circumferences (MUAC) were recorded. Monthly stool samples were collected and screened for five Escherichia coli pathotypes, Shigella spp., Vibrio cholerae, Salmonella, Campylobacter coli/jejuni, and three protozoa (Giardia spp., Entameba histolytica, and Cryptosporidium spp.) using previously validated molecular assays.

FINDINGS

IPTp-SP vs. IPTP-DP was associated with higher maternal gestational weight gain (GWG) and nutritional indicators (MUAC and body-mass index, BMI). GWG was found to be a mediator of the birthweight and IPTp-SP relationship, as the birthweight of SP infants, but not DP infants, varied according to maternal GWG. The burden of maternal enteric infections was high. The three most commonly observed pathogens were enteroaggregative E. coli (EAEC), atypical enteropathogenic E.coli/enterohaemorrhagic E. coli (aEPEC/EHEC), and typical enteropathogenic E.coli (tEPEC). We found that SP reduced the prevalence of EAEC in a dose-dependent manner. After 3 or more doses, SP-recipients were 90% less likely to be infected with EAEC compared to DP-recipients (ORadj = 0.07, CI95 = 0.12, 0.39, p = 0.002). Compared to DP, this coincided with higher maternal gestational weight gain (GWG) and nutritional indicators (MUAC and body-mass index, BMI). The beneficial effect of SP on maternal GWG, MUAC and BMI, was lower if SP mothers had detectable EAEC, aEPEC/EHEC, tEPEC, and LT-ETEC at baseline. Maternal EAEC and tEPEC at baseline associated with lower birthweight for babies of both SP mothers and DP mothers. When comparing IPTp regimens, the positive effect of SP on birthweight compared to DP was only observed for infants of women who did not test positive for EAEC at baseline (adjusted mean birthweight difference SP vs. DP = 156.0 g, CI95 = -18.0 g, 336.9 g, p = 0.087), though confidence intervals crossed the null.

INTERPRETATION

Our findings indicate that in pregnant Malawian women, IPTp-SP vs. IPTp-DP is consistently associated with higher MUAC, BMI, and GWG following the WHO-recommended regimen of at least 3 doses, but carriage of maternal gut pathogens before initiation of IPTp lessens this effect. Because GWG was a mediator of the association between birthweight and SP, we show that SP's previously proven positive effect on birthweight is by promoting maternal weight gain. Overall, our results present one plausible pathway SP exerts malaria-independent protection against poor birth outcomes in the context of its waning antimalarial activity and warrants further investigation.

FUNDING

A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.

Investigating host-bacterial interactions among enteric pathogens

Background

In 2017, World Health Organization (WHO) published a catalogue of 12 families of antibiotic-resistant “priority pathogens” that are posing the greatest threats to human health. Six of these dreaded pathogens are known to infect the human gastrointestinal system. In addition to causing gastrointestinal and systemic infections, these pathogens can also affect the composition of other microbes constituting the healthy gut microbiome. Such aberrations in gut microbiome can significantly affect human physiology and immunity. Identifying the virulence mechanisms of these enteric pathogens are likely to help in developing newer therapeutic strategies to counter them.

Results

Using our previously published in silico approach, we have evaluated (and compared) Host-Pathogen Protein-Protein Interaction (HPI) profiles of four groups of enteric pathogens, namely, different species of Escherichia, Shigella, Salmonella and Vibrio. Results indicate that in spite of genus/ species specific variations, most enteric pathogens possess a common repertoire of HPIs. This core set of HPIs are probably responsible for the survival of these pathogen in the harsh nutrient-limiting environment within the gut. Certain genus/ species specific HPIs were also observed.

Conslusions

The identified bacterial proteins involved in the core set of HPIs are expected to be helpful in understanding the pathogenesis of these dreaded gut pathogens in greater detail. Possible role of genus/ species specific variations in the HPI profiles in the virulence of these pathogens are also discussed. The obtained results are likely to provide an opportunity for development of novel therapeutic strategies against the most dreaded gut pathogens.

Strain-specific probiotic properties of lactic acid bacteria and their interference with human intestinal pathogens invasion

BACKGROUND

One of the working mechanisms of probiotic bacteria is their ability to compete with pathogens. To define the probiotic properties of seven Lactic Acid Bacteria (LAB) strains, we tested them for survival in simulated gastro-intestinal conditions, antimicrobial activities, co-aggregative abilities, and interferences studies against five human intestinal pathogens (Salmonella enteritidis ATCC 13076, Listeria monocytogenes ATCC 7644, Escherichia coli O157: H7 ATCC 35150, Cronobacter sakazakii ATCC 29544 and Campylobacter jejuni ATCC 33291).

RESULTS

The LAB strains were able to survive the stomach simulated conditions, and varied in their abilities to survive the small intestinal-simulated conditions. The strains showed antibiotic susceptibility profiles with values equal or below the breakpoints set by the European Food and Safety Authority. The LAB cell-free cultures supernatants showed antimicrobial activities, with inhibition zones ranging from 10.0 to 17.2 mm. All the LAB strains showed moderate auto-aggregation abilities while the greatest co-aggregation abilities were observed for Bifidobacterium bifidum W23, Lactobacillus plantarum W21 and Lactobacillus rhamnosus W71. The individual LAB strains showed strain-specific abilities to reduce the invasion of intestinal pathogens in an interference model with Caco-2 cells. Increased invasion inhibition was found when different combinations of LAB strains were used in the interference tests.

CONCLUSION

The LAB strains examined in this study may protect the intestinal epithelium through a series of barriers (antimicrobial activity, co-aggregation with pathogens, adherence) and interference mechanisms. Consequently, these LAB strains may be considered candidates for prophylactic use to prevent intestinal infections.