The Lancet Commission on water, sanitation and hygiene, and health

Environmental fecal contamination is common in many low-income cities, contributing to a high burden of enteric infections and associated negative sequelae. To evaluate the impact of a shared onsite sanitation intervention in Maputo, Mozambique on enteric pathogens in the domestic environment, we collected 179 soil samples at shared latrine entrances from intervention (n = 49) and control (n = 51) compounds during baseline (preintervention) and after 24 months (postintervention) as part of the Maputo Sanitation Trial. We tested soils for the presence of nucleic acids associated with 18 enteric pathogens using a multiplex reverse transcription qPCR platform. We detected at least one pathogen-associated gene target in 91% (163/179) of soils and a median of 3 (IQR = 1, 5) pathogens. Using a difference-in-difference analysis and adjusting for compound population, visibly wet soil, sun exposure, wealth, temperature, animal presence, and visible feces, we estimate the intervention reduced the probability of detecting ≥1 pathogen gene by 15% (adjusted prevalence ratio, aPR = 0.85; 95% CI: 0.70, 1.0) and the total number of pathogens by 35% (aPR = 0.65; 0.44, 0.95) in soil 24 months following the intervention. These results suggest that the intervention reduced the presence of some fecal contamination in the domestic environment, but pathogen detection remained prevalent 24 months following the introduction of new latrines.

Impact of an Urban Sanitation Intervention on Enteric Pathogen Detection in Soils.

Rigorous studies of water, sanitation, and hygiene interventions in low- and middle-income countries (LMICs) suggest that children are exposed to enteric pathogens via multiple interacting pathways, including soil ingestion. In 30 compounds (household clusters) in low-income urban Maputo, Mozambique, we cultured Escherichia coli and quantified gene targets from soils (E. coli: ybbW, Shigella/enteroinvasive E. coli (EIEC): ipaH, Giardia duodenalis: β-giardin) using droplet digital PCR at three compound locations (latrine entrance, solid waste area, dishwashing area). We found that 88% of samples were positive for culturable E. coli (mean = 3.2 log₁₀ CFUs per gram of dry soil), 100% for molecular E. coli (mean = 5.9 log₁₀ gene copies per gram of dry soil), 44% for ipaH (mean = 2.5 log₁₀), and 41% for β-giardin (mean = 2.1 log₁₀). Performing stochastic quantitative microbial risk assessment using soil ingestion parameters from an LMIC setting for children 12–23 months old, we estimated that the median annual infection risk by G. duodenalis was 7100-fold (71% annual infection risk) and by Shigella/EIEC was 4000-fold (40% annual infection risk) greater than the EPA’s standard for drinking water. Compounds in Maputo, and similar settings, require contact and source control strategies to reduce the ingestion of contaminated soil and achieve acceptable levels of risk.

Quantitative Microbial Risk Assessment of Pediatric Infections Attributable to Ingestion of Fecally Contaminated Domestic Soils in Low-Income Urban Maputo, Mozambique

Environmental fecal contamination is common in many low-income cities, contributing to a high burden of enteric infections and associated negative sequelae. To evaluate the impact of a shared onsite sanitation intervention in Maputo, Mozambique on enteric pathogens in the domestic environment, we collected 179 soil samples at shared latrine entrances from intervention (n= 49) and control (n= 51) compounds during baseline (pre-intervention) and after 24 months (post-intervention) as part of the Maputo Sanitation Trial. We tested soils for the presence of nucleic acids associated with 20 enteric pathogens using a multiplex reverse transcription qPCR platform. We detected at least one pathogen-associated target in 91% (163/179) of soils and a median of 3 (IQR=1.5, 5) pathogens. Using a difference-in-difference analysis and adjusting for compound population, visibly wet soil, sun exposure, wealth, temperature, animal presence, and visible feces, we estimate the intervention reduced the probability of ≥1 pathogen detected by 15% (adjusted prevalence ratio, aPR=0.85; 95% CI: 0.70, 1.0) and the total number of pathogens detected by 35% (aPR =0.65; 0.44, 0.95) in soil 24 months following the intervention. These results suggest that the intervention reduced the presence of some fecal contamination in the domestic environment, but pathogen detection remained prevalent 24-months following the introduction of new latrines.

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Impact of an Urban Sanitation Intervention on Enteric Pathogen Detection in Soils

How does sanitation influence people's quality of life? Qualitative research in low-income areas of Maputo, Mozambique.

We conducted a controlled before-and-after trial to evaluate the impact of an onsite urban sanitation intervention on the prevalence of enteric infection, soil transmitted helminth re-infection, and diarrhea among children in Maputo, Mozambique A non-governmental organization replaced existing poor-quality latrines with pour-flush toilets with septic tanks serving household clusters We enrolled children aged 1-48 months at baseline and measured outcomes before and 12 and 24 months after the intervention, with concurrent measurement among children in a comparable control arm Despite nearly exclusive use, we found no evidence that intervention affected the prevalence of any measured outcome after 12 or 24 months of exposure Among children born into study sites after intervention, we observed a reduced prevalence of Trichuris and Shigella infection relative to the same age group at baseline (<2 years old) Protection from birth may be important to reduce exposure to and infection with enteric pathogens in this setting

Effects of an urban sanitation intervention on childhood enteric infection and diarrhea in Maputo, Mozambique: A controlled before-and-after trial.

We conducted a controlled before-and-after trial to evaluate the impact of an onsite urban sanitation intervention on the prevalence of enteric infection, soil transmitted helminth re-infection, and diarrhea among children in Maputo, Mozambique. A non-governmental organization replaced existing poor-quality latrines with pour-flush toilets with septic tanks serving household clusters. We enrolled children aged 1-48 months at baseline and measured outcomes before and 12 and 24 months after the intervention, with concurrent measurement among children in a comparable control arm. Despite nearly exclusive use, we found no evidence that intervention affected the prevalence of any measured outcome after 12 or 24 months of exposure. Among children born into study sites after intervention, we observed a reduced prevalence of Trichuris and Shigella infection relative to the same age group at baseline (

/pdf/effects-of-an-urban-sanitation-intervention-on-childhood-12x59zqni0.pdf

Effects of an urban sanitation intervention on childhood enteric infection and diarrhea in Maputo, Mozambique: a controlled before-and-after trial

Quorum sensing (QS) is a mechanism of cell to cell communication that connects gene expression to environmental conditions (e.g. density) in many bacterial species, mediated by diffusible signal molecules. Current functional studies focus on a dichotomy of QS on/off (or, quorate / sub-quorate) states, overlooking the potential for intermediate, graded responses to shifts in the environment. Here, we track QS regulated protease (lasB) expression and show that Pseudomonas aeruginosa can deliver a graded behavioral response to fine-scale variation in population density, on both the population and single-cell scales. On the population scale, we see a graded response to variation in environmental population density. On the single-cell scale, we see significant bimodality at higher densities, with separate OFF and ON sub-populations that respond differentially to changes in density; static OFF cells and increasing intensity of expression among ON cells. While the QS-controlled behavioral output is graded, the underlying multi-signal dynamics display a threshold shift in signal concentration with increasing density, reflecting the onset of positive signal auto-regulation at intermediate densities. Together these results indicate that QS can tune gene expression to graded environmental change, with no critical cell mass or quorum at which behavioral responses are activated on either the individual cell or population scale. In an infection context, our results indicate there is not a hard threshold separating sub-quorate stealth mode and a quorate attack mode.

/pdf/bacterial-quorum-sensing-allows-graded-and-bimodal-cellular-1a1qybxm5e.pdf

Evgeniya Molotkova

Papers

Effects of an urban sanitation intervention on childhood enteric infection and diarrhea in Maputo, Mozambique: A controlled before-and-after trial.

Effects of an urban sanitation intervention on childhood enteric infection and diarrhea in Maputo, Mozambique: a controlled before-and-after trial

Bacterial quorum sensing allows graded and bimodal cellular responses to variations in population density