Streptococcus, Haemophilus Bacteria Dominate Airways of CF Babies for First 2 Years, Study Says

Bacteria species of the genus Streptococcus and Haemophilus are the most common in airways of children with cystic fibrosis (CF) for their first two years of life, a study reveals.

The data suggest these bacteria may play an important role in the early progression of CF, but its clinical significance is still unknown. The bacteria may help prevent the onset of harmful infections and lung damage, or may contribute to airway disease.

The study “Longitudinal development of the airway microbiota in infants with cystic fibrosis” was published in the journal Nature Scientific Reports.

Airway infections begin early in childhood, and young toddlers affected by frequent flares risk poorer lung function later.

However, little is known about the bacterial community, or microbiota, present in the airways of infants with CF and their roles — harmful or protective — in disease progression and the development of more serious lung infections.

To address this question, a team of researchers looked in-depth at the airway microbiota of babies with CF, and how that bacterial community changed during their first two years.

Researchers followed 30 infants, diagnosed with CF through newborn screening, for up to two years. Infants had regular throat swabs as a surrogate sample of the microbiota of their lower airways (trachea, bronchi, bronchioli, and lungs). DNA sequencing and other genetic methods were used to identify the different groups of bacteria present at each sample. In total, 241 throat swabs were collected.

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Results showed that the most common species were those of the genus Streptococcus (55%) and Haemophilus (12.5%). Their presence was inversely related, as Streptococcus species became more abundant in the first nine months of life, while the proportion of Haemophilus bacteria decreased.

Other frequent groups detected were Veillonella and Neisseria species. In contrast, bacteria of the genus Staphylococcus and Pseudomonas were rare. This contrasts with data known for bacteria culture tests (bacteria grown in petri dishes), which has identified these as the most common bacteria in the airways of children with CF.

This apparent contradiction may be explained by the fact that all children studied had received preventive anti-staphylococcal antibiotics. The low amounts of Staphylococcus species seen also may be due to the fact that bacteria of the throat do not fully reflect the microbiota of the lower airways.

Regarding Pseudomonas, these results may be due to a greater sensitivity of bacteria cultures for detecting these bacteria versus others species, and overestimate its relative amounts, compared with DNA sequencing.

The fact that Streptococcus and Haemophilus species were overly common in the airways of CF infants may indicate these bacteria play an important role in early CF, researchers noted.

However, “whether either or both are protective against infection with more typical CF micro-organisms, or pathogenic and thus meriting treatment needs to be determined,” researchers wrote.

A future study comparing the microbiota between infants on antibiotic prophylaxis (prevention) with those not receiving prophylaxis, like the U.K. registry CF START, “would provide real insights into the role of antibiotic prophylaxis in airway infections in CF,” the team added.