Iron fortification adversely affects the gut microbiome, increases pathogen abundance and induces intestinal inflammation in Kenyan infants

BACKGROUND

In-home iron fortification for infants in developing countries is recommended for control of anaemia, but low absorption typically results in >80% of the iron passing into the colon. Iron is essential for growth and virulence of many pathogenic enterobacteria. We determined the effect of high and low dose in-home iron fortification on the infant gut microbiome and intestinal inflammation.

METHODS

We performed two double-blind randomised controlled trials in 6-month-old Kenyan infants (n=115) consuming home-fortified maize porridge daily for 4 months. In the first, infants received a micronutrient powder (MNP) containing 2.5 mg iron as NaFeEDTA or the MNP without iron. In the second, they received a different MNP containing 12.5 mg iron as ferrous fumarate or the MNP without the iron. The primary outcome was gut microbiome composition analysed by 16S pyrosequencing and targeted real-time PCR (qPCR). Secondary outcomes included faecal calprotectin (marker of intestinal inflammation) and incidence of diarrhoea. We analysed the trials separately and combined.

RESULTS

At baseline, 63% of the total microbial 16S rRNA could be assigned to Bifidobacteriaceae but there were high prevalences of pathogens, including Salmonella Clostridium difficile, Clostridium perfringens, and pathogenic Escherichia coli. Using pyrosequencing, +FeMNPs increased enterobacteria, particularly Escherichia/Shigella (p=0.048), the enterobacteria/bifidobacteria ratio (p=0.020), and Clostridium (p=0.030). Most of these effects were confirmed using qPCR; for example, +FeMNPs increased pathogenic E. coli strains (p=0.029). +FeMNPs also increased faecal calprotectin (p=0.002). During the trial, 27.3% of infants in +12.5 mgFeMNP required treatment for diarrhoea versus 8.3% in -12.5 mgFeMNP (p=0.092). There were no study-related serious adverse events in either group.

CONCLUSIONS

In this setting, provision of iron-containing MNPs to weaning infants adversely affects the gut microbiome, increasing pathogen abundance and causing intestinal inflammation.

TRIAL REGISTRATION NUMBER

NCT01111864.

Bifidobacteria strains isolated from stools of iron deficient infants can efficiently sequester iron

BACKGROUND

Bifidobacteria is one of the major gut commensal groups found in infants. Their colonization is commonly associated with beneficial effects to the host through mechanisms like niche occupation and nutrient competition against pathogenic bacteria. Iron is an essential element necessary for most microorganisms, including bifidobacteria and efficient competition for this micronutrient is linked to proliferation and persistence. For this research we hypothesized that bifidobacteria in the gut of iron deficient infants can efficiently sequester iron. The aim of the present study was to isolate bifidobacteria in fecal samples of iron deficient Kenyan infants and to characterize siderophore production and iron internalization capacity.

RESULTS

Fifty-six bifidobacterial strains were isolated by streaking twenty-eight stool samples from Kenyan infants, in enrichment media. To target strains with high iron sequestration mechanisms, a strong iron chelator 2,2-dipyridyl was supplemented to the agar media. Bifidobacterial isolates were first identified to species level by 16S rRNA sequencing, yielding B. bifidum (19 isolates), B. longum (15), B. breve (11), B. kashiwanohense (7), B. pseudolongum (3) and B. pseudocatenulatum (1). While most isolated bifidobacterial species are commonly encountered in the infantile gut, B. kashiwanohense was not frequently reported in infant feces. Thirty strains from culture collections and 56 isolates were characterized for their siderophore production, tested by the CAS assay. Siderophore activity ranged from 3 to 89% siderophore units, with 35 strains (41%) exhibiting high siderophore activity, and 31 (36%) and 20 (23%) showing intermediate or low activity. The amount of internalized iron of 60 bifidobacteria strains selected for their siderophore activity, was in a broad range from 8 to118 μM Fe. Four strains, B. pseudolongum PV8-2, B. kashiwanohense PV20-2, B. bifidum PV28-2a and B. longum PV5-1 isolated from infant stool samples were selected for both high siderophore activity and iron internalization.

CONCLUSIONS

A broad diversity of bifidobacteria were isolated in infant stools using iron limited conditions, with some strains exhibiting high iron sequestration properties. The ability of bifidobacteria to efficiently utilize iron sequestration mechanism such as siderophore production and iron internalization may confer an ecological advantage and be the basis for enhanced competition against enteropathogens.

Is dental erosion really a problem?

Dental erosion is the non-carious dental substance loss induced by direct impact of exogenous or endogenous acids. It results in a loss of dental hard tissue, which can be serious in some groups, such as those with eating disorders, in patients with gastroesophageal reflux disease, and also in persons consuming high amounts of acidic drinks and foodstuffs. For these persons, erosion can impair their well-being, due to changes in appearance and/or loss of function of the teeth, e.g., the occurrence of hypersensitivity of teeth if the dentin is exposed. If erosion reaches an advanced stage, time- and money-consuming therapies may be necessary. The therapy, in turn, poses a challenge for the dentist, particularly if the defects are diagnosed at an advanced stage. While initial and moderate defects can mostly be treated non- or minimally invasively, severe defects often require complex therapeutic strategies, which often entail extensive loss of dental hard tissue due to preparatory measures. A major goal should therefore be to diagnose dental erosion at an early stage, to avoid functional and esthetic impairments as well as pain sensations and to ensure longevity of the dentition.

Stakeholders perspectives on perceived needs and priorities for leprosy control and care, Tamil Nadu, India

Although leprosy has been declared as eliminated in India, treated patients with persisting disabilities still require care. With the shift from vertical to integrated services, questions remain about case detection and maintaining the quality of patient care. We conducted a qualitative study to clarify the perceived status of elimination, patient care and other aspects of leprosy control from the perspective of various stakeholders. We interviewed leprosy programme managers, Non-governmental organization directors, healthcare providers, patients and community leaders from Kanchipuram district, Tamil Nadu. Consensus endorsed the current approach to integration of leprosy in primary healthcare, but healthcare personnel acknowledged problems from shortage of medicines and failure to fill key positions. Patients were concerned about limited clinic hours, long waits and delayed treatment. Disabled patients indicated how they were troubled by stigmatization of their condition. Programme managers mentioned limited support for needed research and some emphasized the potential threat of emerging drug resistance. Although consensus supports an integrated approach for leprosy services in primary care, the relative priority of different aspects of leprosy control vary among stakeholders. Perspectivist approaches to methodologically sound operational research could guide planning for effective case detection and patient care during the post-elimination era.

Iron depletion and repletion with ferrous sulfate or electrolytic iron modifies the composition and metabolic activity of the gut microbiota in rats

Iron (Fe) deficiency anemia is a global health concern and Fe fortification and supplementation are common corrective strategies. Fe is essential not only for the human host but also for nearly all gut bacteria. We studied the impact of Fe deficiency and Fe repletion on the gut microbiota in rats. Weanling rats were fed an Fe-deficient diet for 24 d and then repleted for 13 d with FeSO₄ (n = 15) or electrolytic Fe (n = 14) at 10 and 20 mg Fe · kg diet⁻¹. In addition, one group of rats (n = 8) received the Fe-deficient diet and one group (n = 3) received a Fe-sufficient control diet for all 37 d. Fecal samples were collected at baseline and after the depletion and repletion periods, and colonic tissues were examined histologically. Microbial metabolite composition in cecal water was measured and fecal samples were analyzed for microbial composition with temporal temperature gradient gel electrophoresis and qPCR. Compared to Fe-sufficient rats, Fe-deficient rats had significantly lower concentrations of cecal butyrate (-87%) and propionate (-72%) and the abundance of dominant species was strongly modified, including greater numbers of lactobacilli and Enterobacteriaceae and a large significant decrease of the Roseburia spp./E. rectale group, a major butyrate producer. Repletion with 20 mg FeSO₄ · kg diet⁻¹ significantly increased cecal butyrate concentrations and partially restored bacterial populations compared to Fe-deficient rats at endpoint. The effects on the gut microbiota were stronger in rats repleted with FeSO₄ than in rats repleted with electrolytic Fe, suggesting ferrous Fe may be more available for utilization by the gut microbiota than elemental Fe. Repletion with FeSO₄ significantly increased neutrophilic infiltration of the colonic mucosa compared to Fe-deficient rats. In conclusion, Fe depletion and repletion strongly affect the composition and metabolic activity of rat gut microbiota.

Dental Erosion

There is some evidence that dental erosion is steadily spreading. To diagnose erosion, dental professionals have to rely on clinical appearance, as there is no device available to detect it. Adequate preventive measures can only be initiated if the different risk factors and potential interactions between them are known. When substance loss, caused by erosive tooth wear, reaches a certain degree, oral rehabilitation becomes necessary. Prior to the most recent decade, the severely eroded dentition could only be rehabilitated by the provision of extensive crown and bridgework or removable dentures. As a result of the improvements in composite restorative materials and in adhesive techniques, it has become possible to rehabilitate eroded dentitions in a less invasive manner.

Controlled toothbrush abrasion of softened human enamel

The aim of this in vitro study was to compare toothbrush abrasion of softened enamel after brushing with two (soft and hard) toothbrushes. One hundred and fifty-six human enamel specimens were indented with a Knoop diamond. Salivary pellicle was formed in vitro over a period of 3 h. Erosive lesions were produced by means of 1% citric acid. A force-measuring device allowed a controlled toothbrushing force of 1.5 N. The specimens were brushed either in toothpaste slurry or with toothpaste in artificial saliva for 15 s. Enamel loss was calculated from the change in indentation depth of the same indent before and after abrasion. Mean surface losses (95% CI) were recorded in ten treatment groups: (1) soft toothbrush only [28 (17-39) nm]; (2) hard toothbrush only [25 (16-34) nm]; (3) soft toothbrush in Sensodyne MultiCare slurry [46 (27-65) nm]; (4) hard toothbrush in Sensodyne MultiCare slurry [45 (24-66) nm]; (5) soft toothbrush in Colgate sensation white slurry [71 (55-87) nm]; (6) hard toothbrush in Colgate sensation white slurry [85 (60-110) nm]; (7) soft toothbrush with Sensodyne MultiCare [48 (39-57) nm]; (8) hard toothbrush with Sensodyne MultiCare [40 (29-51) nm]; (9) soft toothbrush with Colgate sensation white [51 (37-65) nm]; (10) hard toothbrush with Colgate sensation white [52 (36-68) nm]. Neither soft nor hard toothbrushes produced significantly different toothbrush abrasion of softened human enamel in this model (p > 0.05).

Erosion--diagnosis and risk factors

Dental erosion is a multifactorial condition: The interplay of chemical, biological and behavioural factors is crucial and helps explain why some individuals exhibit more erosion than others. The erosive potential of erosive agents like acidic drinks or foodstuffs depends on chemical factors, e.g. pH, titratable acidity, mineral content, clearance on tooth surface and on its calcium-chelation properties. Biological factors such as saliva, acquired pellicle, tooth structure and positioning in relation to soft tissues and tongue are related to the pathogenesis of dental erosion. Furthermore, behavioural factors like eating and drinking habits, regular exercise with dehydration and decrease of salivary flow, excessive oral hygiene and, on the other side, an unhealthy lifestyle, e.g. chronic alcoholism, are predisposing factors for dental erosion. There is some evidence that dental erosion is growing steadily. To prevent further progression, it is important to detect this condition as early as possible. Dentists have to know the clinical appearance and possible signs of progression of erosive lesions and their causes such that adequate preventive and, if necessary, therapeutic measures can be initiated. The clinical examination has to be done systematically, and a comprehensive case history should be undertaken such that all risk factors will be revealed.

Influence of the condition of the adjacent tooth surface on fluorescence measurements for the detection of approximal caries

The aim of this study was to test whether the status of the adjacent tooth surface has an influence on the signal of a new laser fluorescence (LF) device for the detection of approximal caries. Seventy-eight teeth were selected from a pool of extracted permanent human molars, frozen at -20 degrees C until use. Before being measured the teeth were defrosted, cleaned, and any calculus removed. As a control, a defined approximal surface of each tooth was measured with the LF device holding the tip with the detecting- and the reverse-side on it, but without a neighboring tooth contacting the surface. The proximal site under examination was then placed adjacent to a tooth, which had deep dentinal caries, a composite restoration, a provisional ZnO-Eugenol restoration, or a ceramic restoration. The adjacent tooth with the ZnO-Eugenol restoration, the composite restoration, and the dentinal caries all demonstrated a statistically significant increase of LF readings on sound tooth surfaces. Teeth with enamel or dentinal caries were only slightly (and not statistically significantly) influenced by the different types of neighboring surfaces compared with the control LF readings. It can be concluded that caries detection of approximal tooth surfaces with the new LF system might be influenced by the condition of the adjacent tooth surface.

Dental erosion in children

Erosive tooth wear in children is a common condition. The overlapping of erosion with mechanical forces like attrition or abrasion is probably in deciduous teeth more pronounced than in permanent teeth. Early erosive damage to the permanent teeth may compromise the dentition for the entire lifetime and require extensive restorative procedures. Therefore, early diagnosis of the condition and adequate preventive measures are of importance. Knowledge of the etiological factors for erosive tooth wear is a prerequisite for such measures. In children and adolescents (like in adults) extrinsic and intrinsic factors or a combination of them are possible reasons for the condition. Such factors are frequent and extensive consumption of erosive foodstuffs and drinks, the intake of medicaments (asthma), gastro-esophageal reflux (a case history is discussed) or vomiting. But also behavioral factors like unusual eating and drinking habits, the consumption of designer drugs and socio-economic aspects are of importance.

Effect of Amine/Sodium Fluoride Rinsing on Toothbrush Abrasion of Softened Enamel in situ

The aim of this study was to test the effect of fluoride rinsing on the prevention of toothbrush abrasion of softened enamel in situ. For softening, the samples were immersed in 0.1 M citric acid (pH 3.5) for 3 min. Eight test subjects had to make 5 runs in which 4 slabs per run were attached to intraoral appliances. They were as follows: (1) no softening, no fluoride rinsing (control 1); (2) softening, no fluoride rinsing (control 2); (3) softening, rinsing in situ with a sodium/amine fluoride rinsing solution (250 ppm F) for 30 s; (4) rinsing in situ with the sodium/amine fluoride rinsing solution (250 ppm F) for 30 s, softening; (5) softening, rinsing in situ with an experimental amine fluoride-containing rinsing solution (250 ppm F) for 30 s. After exposure for 60 min to the oral milieu, the volunteers brushed the samples for 30 s with toothpaste and the loss of tooth substance was determined. For each test person, the secretion rate of resting and paraffin-stimulated saliva, buffering capacity and pH were measured. Toothbrush abrasion in situ was not significantly lower using the fluoride rinsing solutions before or after softening the enamel compared to no rinsing (p > 0.05). Multiple linear regression analyses revealed that 57% of the variation in toothbrush abrasion could be attributed to the severity of softening (p < 0.001) and the pH of stimulated saliva (p < 0.001). It was concluded that a single rinse for 30 s had no statistically significant effect on the prevention of toothbrush abrasion of softened enamel.

The Role of Diet in the Aetiology of Dental Erosion

Acids of intrinsic and extrinsic origin are thought to be the main etiologic factors for dental erosion. There is evidence that acidic foodstuffs and beverages play a role in the development of erosion. However, the pH of a dietary substance alone is not predictive of its potential to cause erosion as other factors modify the erosive process. These factors are chemical (pKa values, adhesion and chelating properties, calcium, phosphate and fluoride content), behavioural (eating and drinking habits, life style, excessive consumption of acids) and biological (flow rate, buffering capacity, composition of saliva, pellicle formation, tooth composition, dental and soft tissue anatomy). The interplay between erosion and abrasion (specially oral hygiene practices) may be the main driver leading to the clinical manifestation of this disorder. Recommendations for patients at risk for dental erosion such as reducing acid exposure by reducing the frequency and contact of acids will be discussed.

[The erosive potential of various oral care products compared to foodstuffs and beverages]

The purpose of the present study was to investigate the erosive potential of various oral care products and to compare the results with those of various foodstuffs and beverages. Furthermore, the chosen method of surface hardness measurements was compared with scanning electron microscopy. Seven oral care products (toothpastes and mouth rinses), three foodstuffs and one beverage (as positive control) were tested for their erosive potential. After initial hardness testing 110 enamel specimens were distributed into 11 groups of 10 specimens each in such a way as to have a homogenous hardness distribution per group. The erosive potential of the products was tested by immersing the enamel specimens into solutions of the various products for 10 and 20 minutes. After the experimental period Knoop hardness was measured on the enamel specimens and the differences between before and after were calculated. The micromorphology of native enamel surfaces before and after immersion was determined by SEM on further enamel specimens treated identically for 20 minutes. Apple puree and orange juice produced the most marked losses of hardness after 10 and 20 minutes, respectively. Among the dental hygiene products only the fluoride-free Weleda toothpaste produced a significant reduction of hardness after 10 as well as after 20 minutes. With the exception of Elmex-Gel, all tested dental hygiene products led to a significant (p<0.05) increase of enamel hardness. The results of the hardness measurements corresponded with the micromorphological findings. It may, therefore, be concluded that the tested fluoride-containing oral care products do not exhibit any erosive potential which could be measured with the methodology used in this investigation.

Toothbrush abrasion of erosively altered enamel after intraoral exposure to saliva: an in situ study

The aim of this in situ study was to test the effect of toothbrush abrasion on enamel previously exposed to a standardized artificial erosive agent. To generate moderate erosive lesions, slabs of the buccal surface of human premolars were immersed in a solution of citric acid for 3 min. Then they were attached to intraoral appliances and each one was exposed for 0 min (= toothbrushing immediately after intraoral exposure), 30 or 60 min to the oral milieu of 1 of 7 female subjects with a mean age of 22 years. Immediately thereafter the volunteers brushed the slabs for 30 s with toothpaste using their preferred brushing technique. For each test person the secretion rate of resting and paraffin-stimulated saliva, buffering capacity and pH were measured. The following mean losses of substance at the surface were registered: 0.258+/-0.141 microm (toothbrushing immediately after intraoral exposure), 0. 224+/-0.087 microm (toothbrushing after intraoral exposure of 30 min) and 0.195+/-0.075 microm (toothbrushing after intraoral exposure of 60 min). Toothbrush abrasion in situ was significantly lower after 60-min exposure to the oral environment than after 0-min (p<0.001). Also, the 30- and 60-min values were significantly different from each other (p<0.001). Multiple linear regression analyses revealed that in this model toothbrush abrasion was associated with the intraoral exposure to saliva (p = 0.026), the severity of the erosive attack (p<0.001) and the secretion rate of resting saliva (p = 0.029). If no other preventive measures are taken we suggest that individuals at risk for erosive tooth wear wait at least 1 h before brushing their teeth after consuming erosive foodstuffs or beverages.

Prediction of the erosive potential of some beverages

The aim of this study was to investigate whether the erosive potential of a beverage on human enamel can be predicted by examining the composition of the beverage. The buccal surfaces of 84 caries-free premolars were embedded in resin and polished flat. Two hundred micrometers of the enamel surface were removed. Then the slabs were divided into 14 groups and immersed for 20 min in commercially available beverages. Surface microhardness was measured before and after immersion. Further, the phosphate concentration, the fluoride concentration, the baseline pH as well as the titrated amount of base to raise the pH to 7.0 of each beverage were determined. Surface microhardness values after immersion were calculated with an equation derived in a recent study and compared with the values measured in this investigation. Apple juice showed the greatest significant decrease (p < 0.05) in surface microhardness, followed by Schweppes, Orangina and Grapefruit soft drink. The smallest decrease in surface microhardness that was significant resulted from Fendant and Isostar orange. The mean absolute deviation of the calculated to the effective erosion was 7.1%, it ranged between 14.6% (apple juice) and 1.6% (Fendant). The data suggest the possibility of predicting erosion caused by a beverage with an accuracy of 7%. This information can be of value in the prevention of dental erosion.