RESUMEN
The gastrointestinal tract (GIT) microbiota has been identified as an important reservoir of antibiotic resistance genes (ARGs) that can be horizontally transferred to pathogenic species. Maternal GIT microbes can be transmitted to the offspring, and recent work indicates that such transfer starts before birth. We have used culture-independent genetic screenings to explore whether ARGs are already present in the meconium accumulated in the GIT during fetal life and in feces of 1-week-old infants. We have analyzed resistance to ß-lactam antibiotics (BLr) and tetracycline (Tcr), screening for a variety of genes conferring each. To evaluate whether ARGs could have been inherited by maternal transmission, we have screened perinatal fecal samples of the 1-week-old babies' mothers, as well as a mother-infant series including meconium, fecal samples collected through the infant's 1st year, maternal fecal samples and colostrum. Our results reveal a high prevalence of BLr and Tcr in both meconium and early fecal samples, implying that the GIT resistance reservoir starts to accumulate even before birth. We show that ARGs present in the mother may reach the meconium and colostrum and establish in the infant GIT, but also that some ARGs were likely acquired from other sources. Alarmingly, we identified in both meconium and 1-week-olds' samples a particularly elevated prevalence of mecA (>45%), six-fold higher than that detected in the mothers. The mecA gene confers BLr to methicillin-resistant Staphylococcus aureus, and although its detection does not imply the presence of this pathogen, it does implicate the young infant's GIT as a noteworthy reservoir of this gene.
Asunto(s)
Microbioma Gastrointestinal , Meconio/química , Resistencia a la Tetraciclina/genética , Resistencia betalactámica/genética , Estudios de Cohortes , Femenino , Humanos , Lactante , Recién Nacido , Meconio/microbiología , EmbarazoRESUMEN
BACKGROUND: Culture-dependent methods have shown that meconium, the newborn's first intestinal discharge, is not sterile, but the diversity of bacteria present in this material needs to be further characterized by means of more sensitive molecular techniques. OBJECTIVE: Our aims were to characterize molecularly the meconium microbiota in term infants, to assess whether it contributes to the future microbiota of the infants' gastrointestinal tract, and to evaluate how it relates to lifestyle variables and atopy-related conditions. METHODS: We applied high-throughput pyrosequencing of the 16S rRNA gene to study the meconium microbiota in twenty term newborns from a Spanish birth cohort. For comparison, we characterized the microbiota in fecal samples from seven pregnant women days before delivery and in two series of infant samples spanning the first seven months of life. We also compared our data with vaginal and skin microbiota characterized in independent studies. Different types of meconium microbiota were defined based on taxonomic composition and abundance and their associations with different factors were statistically evaluated. RESULTS: The meconium microbiota differs from those in adult feces, vagina and skin, but resembles that of fecal samples from young infants. Meconium samples clustered into two types with different bacterial diversity, richness and composition. One of the types was less diverse, dominated by enteric bacteria and associated with a history of atopic eczema in the mother (P = 0.038), whereas the second type was dominated by lactic acid bacteria and associated with respiratory problems in the infant (P = 0.040). CONCLUSIONS & CLINICAL RELEVANCE: Our findings suggest that the meconium microbiota has an intrauterine origin and participates in gut colonization. Although based on a small population sample, our association analyses also suggest that the type of bacteria detected in meconium is influenced by maternal factors and may have consequences for childhood health.
Asunto(s)
Eccema/microbiología , Enterobacteriaceae/clasificación , Hipersensibilidad Inmediata/microbiología , Intestinos/microbiología , Lactobacillales/clasificación , Meconio/microbiología , Metagenoma , Adulto , ADN Bacteriano , Enterobacteriaceae/genética , Femenino , Humanos , Recién Nacido , Lactobacillales/genética , Estilo de Vida , Filogenia , Embarazo , ARN Ribosómico 16S , Factores de RiesgoRESUMEN
BACKGROUND: Mercury is a ubiquitous heavy metal that may negatively affect human health. It is desirable to investigate mercury exposure in vulnerable populations. OBJECTIVE: To determine the concentrations of total mercury (T-Hg) in cord blood and to evaluate the role of maternal fish consumption in a Spanish mother and child cohort. METHODS: A total of 1883 mother and child pairs from a population-based cohort were included between 2004 and 2008. T-Hg concentrations were measured in whole cord blood and maternal seafood consumption was ascertained by means of a food-frequency questionnaire. Linear regression was used in stratified analyses, while a joint model was adjusted using a mixed-effects linear model. RESULTS: Maternal daily seafood consumption was 78g/d and the geometric mean for T-Hg was 8.2µg/L. Maternal fish intake during pregnancy, mother's age, country of origin, educational level, employment status and parity, as well as area of study and season of delivery, were associated with cord blood T-Hg levels. A doubling in consumption of large oily fish was associated with an increase of 11.4% (95%CI: 3.8 to 19.6%) in cord blood T-Hg levels, followed by an increase of 8.4% (95%CI: 5.7 to 11.2%) in the case of canned tuna and 8.3% (95%CI: 5.5 to 11.1%) in that of lean fish. CONCLUSION: A high proportion of newborns had elevated concentrations of cord blood T-Hg according to the current US-EPA reference dose (5.8µg/L for methylmercury). Mercury concentrations were related to maternal fish consumption, with large oily fish being the main contributor.
Asunto(s)
Contaminantes Ambientales/sangre , Exposición Materna/estadística & datos numéricos , Mercurio/sangre , Lesiones Prenatales/epidemiología , Adulto , Estudios de Cohortes , Demografía , Dieta/estadística & datos numéricos , Femenino , Sangre Fetal/metabolismo , Humanos , Embarazo , Lesiones Prenatales/inducido químicamente , Alimentos Marinos/estadística & datos numéricos , Factores Socioeconómicos , EspañaRESUMEN
UNLABELLED: Nitrogen dioxide (NO2) is produced from the exhausts of vehicles and gas appliances and is known to pose certain health risks. In this study, we characterize the exposure to this substance during the first year of life, which is an important period of development. To this end, we used passive samplers to measure indoor and outdoor NO2 levels for 2 weeks in the homes of 352 children. To compensate for the fact that NO2 levels were measured only once in each home, a correction factor was calculated to assign each child an outdoor NO2 exposure value for the first year of life. The outdoor NO2 concentrations were 26.1 microg/m(3) while those measured indoors averaged 18.0 microg/m(3). A multivariate linear regression analysis showed that the main determinants of outdoor NO2 levels were the degree of urbanization and the frequency of vehicle traffic at the location of the residence while for indoor NO2 levels the principal determinants were the type of cooking range and water heater present in the home, the season of the year, and both the country of origin and educational level of the mother. PRACTICAL IMPLICATIONS: Exposure to NO2 has been related to respiratory and other health problems among children. Precise identification of the main sources of both indoor and outdoor NO2 should shed light on appropriate intervention periods and methods. Our results indicate that while population density and traffic-related variables are the main determinants of outdoor NO2 levels, the use of gas appliances have the greatest impact on indoor levels. Strategies should thus be developed to reduce such exposure, especially with regard to reducing emissions from vehicle traffic.