Rapid detection of the source of a Listeria monocytogenes outbreak in Switzerland through routine interviewing of patients and whole-genome sequencing.

AIMS OF THE STUDY: Listeriosis is a notifiable disease in Switzerland. In summer 2022, the Swiss Federal Office of Public Health noticed an increase in reports of listeriosis cases, indicating a possible ongoing outbreak. Here we present the approaches applied for rapidly confirming the outbreak, detecting the underlying source of infection and the measures put in place to eliminate it and contain the outbreak. METHODS: For close surveillance and early detection of outbreak situations with their possible sources, listeriosis patients in Switzerland are systematically interviewed about risk behaviours and foods consumed prior to the infection. Listeria monocytogenes isolates derived from patients in medical laboratories are sent to the National Reference Laboratory for Enteropathogenic Bacteria and Listeria, where they routinely undergo whole-genome sequencing. Interview and whole-genome sequencing data are continuously linked for comparison and analysis. RESULTS: In summer 2022, 20 patient-derived L. monocytogenes serotype 4b sequence type 388 strains were found to belong to an outbreak cluster (≤10 different alleles between neighbouring isolates) based on core genome multilocus sequence typing analysis. Geographically, 18 of 20 outbreak cases occurred in northeastern Switzerland. The median age of patients was 77.4 years (range: 58.1-89.7), with both sexes equally affected. Rolling analysis of the interview data revealed smoked trout from a local producer as a suspected infection source, triggering an on-site investigation of the production facility and sampling of the suspected products by the responsible cantonal food inspection team on 15 July 2022. Seven of ten samples tested positive for L. monocytogenes and the respective cantonal authority ordered a ban on production and distribution as well as a product recall. The Federal Food Safety and Veterinary Office released a nationwide public alert covering the smoked fish products concerned. Whole-genome sequencing analysis confirmed the interrelatedness of the L. monocytogenes smoked trout product isolates and the patient-derived isolates. Following the ban on production and distribution and the product recall, reporting of new outbreak-related cases rapidly dropped to zero. CONCLUSIONS: This listeriosis outbreak could be contained within a relatively short time thanks to identification of the source of contamination through the established combined approach of timely interviewing of every listeriosis patient or a representative and continuous molecular analysis of the patient- and food-derived L. monocytogenes isolates. These findings highlight the effectiveness of this well-established, joint approach involving the federal and cantonal authorities and the research institutions mandated to contain listeriosis outbreaks in Switzerland.

Stable iron (58Fe) isotopic measurements in Kenyan toddlers during 3 months of iron supplementation demonstrate that half of the iron absorbed is lost.

Increased iron loss may reduce the effectiveness of iron supplementation. The objective of this study was to determine if daily oral iron supplementation increases iron loss, measured using a stable isotope of iron (58Fe). We enrolled and dewormed 24 iron-depleted Kenyan children, 24-27 months of age, whose body iron was enriched and equilibrated with 58Fe given at least 1 year earlier. Over 3 months of supplementation (6 mg iron/kg body weight [BW]/day), mean (±SD) iron absorption was 1.10 (±0.28) mg/day. During supplementation, 0.55 (±0.36) mg iron/day was lost, equal to half of the amount of absorbed iron. Supplementation did not increase faecal haem/porphyrin or biomarkers of enterocyte damage and gut or systemic inflammation. Using individual patient data, we examined iron dose, absorption and loss among all available long-term iron isotopic studies of supplementation. Expressed in terms of body weight, daily iron loss was correlated significantly with iron absorption (Pearson's r = 0.66 [95% confidence interval 0.48-0.78]) but not with iron dose (r = 0.16 [95% CI -0.10-0.40]). The results of this study indicate that iron loss is increased with daily oral iron supplementation and may blunt the efficacy of iron supplements in children. This study was registered at ClinicalTrials.gov as NCT04721964.

Nutrition transition, double burden of malnutrition, and urbanization patterns in secondary cities of Bangladesh, Kenya and Rwanda.

BACKGROUND: By 2050, approximately 68% of the global population will live in cities, but nutrition data on urban populations of low- and middle-income countries are scarce. Fast growing secondary cities, combining characteristics and hurdles of urban and rural settings, are hotspots for the double burden of malnutrition. The Nutrition in City Ecosystems (NICE) project focuses on 6 secondary cities in Bangladesh, Kenya and Rwanda, to improve health and nutrition, and reduce poverty. To assess the baseline situation and guide future interventions, food insecurity, dietary diversity, nutrition status, and food production and purchasing patterns were explored. METHODS: In a cross-sectional study design, data were collected from urban and peri-urban households of Dinajpur and Rangpur in Bangladesh, Bungoma and Busia in Kenya, and Rubavu and Rusizi in Rwanda. Approximately 1200 households, in neighborhoods prone to malnutrition, were involved from April to June 2021. We assessed Household Food Insecurity Access Score (HFIAS), both current and before COVID-19, Household Dietary Diversity Score (HDDS), Minimum Dietary Diversity for Women (MDD-W), anthropometric measurements, household and socioeconomic information, and questions related to food production and consumer behavior. Further we collected secondary data on low birthweight and anemia during pregnancy. RESULTS: All cities experienced a substantial increase in food insecurity during the COVID-19 pandemic. Stunting rates in children under 5 years varied among the cities and ranged from 7.8% in Busia to 46.6% in Rubavu, while half of adult women were overweight (between 42.1% in Rusizi and 55.8% in Bungoma). Furthermore, many women did not consume an adequately diverse diet (MDD-W < 5 for 29.3% in Bangladesh, 47.5% in Kenya, and 67.0% in Rwanda), however many of the urban and peri-urban households were engaged in farming (58-78%). CONCLUSIONS: The double burden of malnutrition is high in secondary cities and the COVID-19 pandemic has exacerbated levels of food insecurity. Demand for, and access to, an affordable healthy diverse diet that comprises local, nutritious, and agroecologically produced foods present a pathway for overcoming the complex challenges of malnutrition.

Nutrition in City Ecosystems (NICE): Protocol of a multi-sectoral development project to improve food and nutrition security of secondary city populations in Bangladesh, Kenya and Rwanda.

Background: Secondary cities tend to be better linked with local food systems than primate cities, acting as important platforms to trade agricultural produce with rural surrounding. COVID-19, conflicts and climate change continue to expose inefficiencies in food systems and have further exacerbated malnutrition, calling for substantial food systems transformations. However, tackling current food systems' challenges requires new approaches to ensure food and nutrition security. Nutritious and agroecologically produced food offer the potential to transform food systems by improving diets and alleviating pressure on the environment, as well as by creating jobs and reducing poverty. This paper describes the design of a project by a Swiss public-private consortium to improve food and nutrition security and to reduce poverty in city ecosystems in six secondary cities in Bangladesh, Kenya and Rwanda through governance/policy and supply and demand side interventions. Methods: The Nutrition in City Ecosystems (NICE) project promotes well-balanced nutrition for city populations through interdisciplinary agricultural, food, and health sector collaborations along city-specific value chains. Adopting a transdiciplinary systems approach, the main interventions of NICE are (i) advocacy and policy dialogue, (ii) building of decentralized institutional capacity in multi-sectoral collaborations, (iii) support of data-driven planning, coordination and resource mobilization, (iv) anchoring of innovations and new approaches in city-level partnerships, (v) capacity building in the agricultural, retail, health and education sectors, as well as (vi) evidence generation from putting policies into practice at the local level. NICE is coordinated by in-country partners and local offices of the Swiss public-private consortium partners. Discussion: The NICE project seeks to contribute to urban food system resilience and enhanced sustainable nutrition for city populations by (A) strengthening urban governance structures involving key stakeholders including women and youth, (B) generating income for producers along the supply chain, (C) triggering change in producers' and consumers' behavior such that nutritious and agroecologically produced foods are both in demand as well as available and affordable in urban markets, and (D) allowing a scale up of successful approaches to other national and international cities and city networks.

Isotopic measurement of iron requirements in sub-Saharan African children.

BACKGROUND: Prevention of iron deficiency in African children is a public health priority. Current WHO/FAO estimations of iron requirements are derived from factorial estimates based on healthy, iron-sufficient "model" children using data derived mainly from adults. OBJECTIVES: In this study, we aimed to quantify iron absorption, loss, and balance in apparently healthy 5- to 7-y-old children living in rural Africa. METHODS: We directly measured long-term iron absorption and iron loss in a 2-y observational study in Malawian children (n = 48) using a novel stable iron isotope method. RESULTS: Of the 36 children with height-for-age and weight-for-age z scores ≥-2, 13 (36%) were iron deficient (soluble transferrin receptor >8.3 mg/L) and 23 were iron sufficient. Iron-deficient children weighed more than iron-sufficient children [mean difference (95% CI): +2.1 (1.4, 2.7) kg; P = 0.01]. Mean iron losses did not differ significantly between iron-deficient and iron-sufficient children and were comparable to WHO/FAO median estimates of 19 µg/(d × kg). In iron-sufficient children, median (95% CI) dietary iron absorption was 32 (28, 34) µg/(d × kg), comparable to WHO/FAO-estimated median requirements of 32 µg/(d × kg). In iron-deficient children, absorption of 28 (25, 30) µg/(d × kg) was not increased to correct their iron deficit, likely because of a lack of bioavailable dietary iron. Twelve children (25%) were undernourished (underweight, stunted, or both). CONCLUSIONS: Our results suggest that WHO/FAO iron requirements are adequate for healthy iron-sufficient children in this rural area of Malawi, but iron-deficient children require additional bioavailable iron to correct their iron deficit.

Direct assessment of body iron balance in women with and without iron supplementation using a long-term isotope dilution method in Benin and Switzerland.

BACKGROUND: Long-term isotopic dilution measurements of body iron may allow quantification of basal body iron balance and iron gains during an iron intervention with higher precision and accuracy than conventional iron indices. OBJECTIVES: We compared body iron balance before, during, and after oral iron supplementation in women in Benin and in Switzerland. METHODS: In prospective studies, Beninese (n = 11) and Swiss (n = 10) women previously labeled with stable iron isotopes were followed preintervention for 90-120 d, then received 50-mg iron daily for 90-120 d and were followed postintervention for 90-120 d. We used changes in blood isotopic composition to calculate iron absorption (Feabs), iron loss (Feloss), and net iron balance (Fegain). RESULTS: Compliance with supplementation was >90%. In Benin, during the preintervention, intervention, and postintervention periods, Fe means ± SDs were as follows: 1) Feabs: 0.92 ± 1.05, 3.75 ± 2.07, and 0.90 ± 0.93 mg/d; 2) Feloss: 1.46 ± 1.95, 1.58 ± 1.57, and 1.84 ± 1.61 mg/d; and 3) Fegain: -0.55 ± 1.56 mg/d, 2.17 ± 1.81 mg/d, and -0.94 ± 1.13 mg/d. In Switzerland, the corresponding values were: 1) 1.51 ± 0.37, 4.09 ± 1.52, and 0.97 ± 0.41 mg/d; 2) 0.76 ± 1.37, 2.54 ± 1.43, and 2.08 ± 1.05 mg/d; and 3) 0.75 ± 1.37, 1.55 ± 1.75, and -1.11 ± 1.06 mg/d. Inflammation was low in both settings, and isotopically calculated iron balance was comparable to that calculated from changes in conventional iron indices. CONCLUSION: Without iron supplementation, Beninese women had lower long-term dietary iron absorption and higher iron losses in the preintervention period than Swiss women. During iron supplementation, both groups had high iron absorption and similar iron gains. However, there was a 3-fold increase in iron losses in the Swiss women during the supplementation and postintervention period compared with the preintervention period. Body iron isotope dilution is a promising new method for quantifying long-term body iron balance and for assessing the impact of iron interventions. The studies were registered at clinicaltrials.gov as NCT02979080 and NCT02979132, respectively.

Measurement of long-term iron absorption and loss during iron supplementation using a stable isotope of iron (57 Fe).

We report the first measurements of long-term iron absorption and loss during iron supplementation in African children using a stable isotope of iron (57 Fe). After uniform labelling of body iron with 57 Fe, iron absorption is proportional to the rate of decrease in the 57 Fe tracer concentration, while iron loss is proportional to the rate of decrease in the 57 Fe tracer amount. Anaemic Gambian toddlers were given 2 mg 57 Fe orally to equilibrate with total body iron over 8-11 months. After assignment to the positive control arm of the HIGH study, 22 toddlers consumed a micronutrient powder containing 12 mg iron for 12 weeks followed by 12 weeks without iron supplementation. Their daily iron absorption increased 3·8-fold during the iron supplementation period compared to the control period [median (interquartile range, IQR): 1·00 (0·82; 1·28) mg/day vs. 0·26 (0·22; 0·35) mg/day; P = 0·001]. Unexpectedly, during the supplementation period, daily iron loss also increased by 3·4-fold [0·75 (0·55; 0·87) mg/day vs. 0·22 (0·19; 0·29) mg/day; P = 0·005]. Consequently, most (~72%) of the absorbed iron was lost during supplementation. Long-term studies of iron absorption and loss are a promising and accurate method for assessing and quantifying long-term iron balance and may provide a reference method for evaluating iron intervention programs in vulnerable population groups. This study was registered as ISRCTN 0720906.

Dietary Iron Bioavailability: A Simple Model That Can Be Used to Derive Country-Specific Values for Adult Men and Women.

BACKGROUND: Reference intakes for iron are derived from physiological requirements, with an assumed value for dietary iron absorption. A new approach to estimate iron bioavailability, calculated from iron intake, status, and requirements was used to set European dietary reference values, but the values obtained cannot be used for low- and middle-income countries where diets are very different. OBJECTIVE: We aimed to test the feasibility of using the model developed from United Kingdom and Irish data to derive a value for dietary iron bioavailability in an African country, using data collected from women of child-bearing age in Benin. We also compared the effect of using estimates of iron losses made in the 1960s with more recent data for whole body iron losses. METHODS: Dietary iron intake and serum ferritin (SF), together with physiological requirements of iron, were entered into the predictive model to estimate percentage iron absorption from the diet at different levels of iron status. RESULTS: The results obtained from the 2 different methods for calculating physiological iron requirements were similar, except at low SF concentrations. At a SF value of 30 µg/L predicted iron absorption from the African maize-based diet was 6%, compared with 18% from a Western diet, and it remained low until the SF fell below 25 µg/L. CONCLUSIONS: We used the model to estimate percentage dietary iron absorption in 30 Beninese women. The predicted values agreed with results from earlier single meal isotope studies; therefore, we conclude that the model has potential for estimating dietary iron bioavailability in men and nonpregnant women consuming different diets in other countries.

Cold Extrusion but Not Coating Affects Iron Bioavailability from Fortified Rice in Young Women and Is Associated with Modifications in Starch Microstructure and Mineral Retention during Cooking.

Background: Rice can be fortified with the use of hot or cold extrusion or coating, but the nutritional qualities of the resulting rice grains have never been directly compared.Objective: Using fortified rice produced by coating or hot or cold extrusion, we compared 1) iron and zinc absorption with the use of stable isotopes, 2) iron and zinc retention during cooking, and 3) starch microstructure.Methods: We conducted 2 studies in young women: in study 1 [n = 19; mean ± SD age: 26.2 ± 3.4 y; body mass index (BMI; in kg/m2): 21.3 ± 1.6], we compared the fractional iron absorption (FAFe) from rice meals containing isotopically labeled ferric prophosphate (57FePP), zinc oxide (ZnO), citric acid, and micronutrients fortified through hot extrusion (HER1) with rice meals fortified through cold extrusion containing 57FePP, ZnO, citric acid, and micronutrients (CER); in study 2 (n = 22; age: 24 ± 4 y; BMI: 21.2 ± 1.3), we compared FAFe and fractional zinc absorption (FAZn) from rice meals fortified through hot extrusion (HER2) compared with rice meals fortified through coating containing 57FePP, ZnO, a citric acid and trisodium cirate mixture (CA/TSC), and micronutrients (COR) relative to rice meals extrinsically fortified with ferrous sulfate (reference). Rice types HER1 and CER contained citric acid, whereas types HER2 and COR contained CA/TSC. We assessed retention during standardized cooking experiments and characterized the rice starch microstructure.Results: FAFe (95% CI) was greater from CER [2.2% (1.4%, 3.4%)] than from HER1 [1.2% (0.7%, 2.0%)] (P = 0.036). There was no difference in FAFe between HER2 [5.1% (3.7%, 7.1%)] and COR [4.0% (2.9%, 5.4%)] (P = 0.14), but FAFe from COR was lower than that from the reference meal [6.6% (4.9%, 9.0%)] (P = 0.003), and the geometric mean FAZn (95% CI) did not differ between HER2 [9.5% (7.9%, 11.6%)] and COR [9.6% (8.7%, 10.7%)] (P = 0.92). Cooking in a rice-to-water ratio of 1:2 resulted in iron and zinc retentions >80%, and cooking in excess water did not affect iron retention from hot-extruded rice but caused iron losses of 25% from CER and COR. Distinct variations in starch microstructure were found in CER and HER1.Conclusions: Iron absorption was 64% higher from CER than from hot-extruded rice, with no difference between COR compared with hot-extruded rice. Lower extrusion temperatures may generate a more readily digestible starch structure, allowing for greater iron release in vivo but lower mineral retention during cooking. This trial was registered at clinicaltrials.gov as NCT02176759.