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Discovery of infants’ airway microbiomes may help predict lung disease

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Researchers at the University of Alabama of Birmingham have found that the infant airway is already colonized with bacteria or bacterial DNA when a baby is born. This finding hold true for even babies who are born at 24 weeks gestation. These findings are in contrast to the general belief that the airways of an infant are sterile until after birth. It is not known how microbes get into the airways and what is the purpose of  this pre-birth colonization, but the pattern of colonization seem to have an important link to later severe neonatal lung diseases.

A microbial imbalance at such an early age is predictive of the development of bronchopulmonary dysplasia, or BPD, a disease of prematurity. In this study, the researchers observed that the extremely low birth weight (ELBW) infants who went on to develop life-threatening BPD exhibited abnormal microbial colonization patterns at birth, as compared to pre-term infants who did not get BPD.

BPD is the most common lung pathology of ELBW infants and a significant cause of morbidity and mortality. Adults and children who had BPD as infants typically have lungs that failed to develop properly and are more susceptible to worse lung function, asthma, lung infections and pulmonary hypertension.

Charitharth Vivek Lal, M.D., lead investigator of the study and assistant professor in the UAB Pediatrics Division of Neonatology remarked that an infant’s respiratory microbiome at the time of birth can possibly predict his risk for BPD. The findings of the study were published in the journal -Scientific Reports. It says that it seems likely that the early airway microbiome may prime the developing pulmonary immune system, and set the stage for subsequent lung disease. In that case it is important to develop novel therapeutic interventions.

Lal opined this is the first unbiased study of its kind. All the early saline aspirates from the tracheas of the newborns were collected at or within six hours of delivery. The infant airway microbiome analysis was also validated at a second medical center. A group of 23 ELBW infants and 10 full-term infants were studied at the Regional Neonatal Intensive Care Unit, UAB Women & Infants Center. The second group of 14 ELBW infants was studied in collaboration with Vineet Bhandari, M.D., at Drexel University College. It was seen that half of the ELBW infants at both sites, later developed BPD. It was also noted that the differences in the microbiomes between infants who were BPD-resistant and BPD-predisposed were similar for infants in both Birmingham and Philadelphia.

To further the study, the researchers also looked at the airway microbiomes of 18 ELBW infants with established BPD. There was a significant difference in the diversity and pattern from those of ELBW infants shortly after birth or full-term infants at birth. It was noted that the phylum Proteobacteria, which includes E. coli, is involved in BPD pathology, and the genus Lactobaccillus, part of the phylum Firmicutes, seemed to be protective.

The researchers observed that there was a decrease in the abundance of Lactobacillus in the airway microbiomes of 10 infants born to mothers who had chorioamnionitis. Chorioamnionitisn is an infection of the membranes of the placenta and it is an independent risk factor for BPD. In some other research, researchers had suggested a beneficial role for Lactobacillus against airway diseases and for lung development. Lal opined that the use of respiratory probiotics and the role of the gut-lung microbiome axis will be subjects of research in coming days.

Lal and colleagues remarked that it is a common belief that colonization of neonates originates in the birth canal. So, it was a surprise for the researchers to find that the airway microbiome of vaginally delivered and caesarean section-delivered neonates were similar. These findings suggest that it is likely that the microbial DNA in the airways is transplacentally derived. Since, the placenta has a rich micro biome, the transmission of bacteria or bacterial DNA could be via blood or amniotic fluid.