Common acid blockers tied to gut microbiome damage and worse lung outcomes in CF babies

More than half of infants with cystic fibrosis in a major Australian longitudinal study were receiving acid blocker therapy before their third birthday, even though clinical guidelines offer little direction on whether these drugs actually help. Now, research from the PEARL-CF Study published in the Journal of Cystic Fibrosis suggests that persistent use of these medications, particularly proton pump inhibitors (PPIs), is associated with measurably lower gut microbial diversity and more severe early-onset lung disease. The findings add a cautionary note to a prescribing habit that has become routine in pediatric CF care.

Acid blocker use in young CF patients is strikingly common

M.J. Coffey and colleagues followed 145 infants with CF, all identified through newborn screening by age 3 months and tracked at six CF centers until they turned 36 months old. Across that cohort, 81 children (56%) received acid blocker therapy at some point before age 3. Use was highest among children who were pancreatic insufficient, with 60% of that group receiving the drugs compared to 26% of pancreatic sufficient children. Infants often started on H2 receptor antagonists (H2RAs), a milder class of acid suppressants, before transitioning to the stronger PPIs. PPIs work by blocking proton pumps in gastric cells, substantially reducing stomach acid and altering the digestive environment that gut bacteria depend on.

Persistent PPI use is tied to reduced gut diversity and lung damage

The headline finding is concerning: children who were persistent ABT users showed significantly lower gut microbiome alpha-diversity at 3 years of age compared to nonusers. Alpha-diversity is a measure of the variety of microbial species living in the gut, and lower diversity is broadly associated with worse health outcomes across many conditions. Separate research has already shown that infants with CF exhibit delayed gut microbiome maturation compared to healthy peers, so layering PPI-driven diversity loss on top of an already disrupted baseline is a double hit. Beyond the microbiome signal, persistent ABT users also had more severe early-onset lung disease as assessed by a clinical scoring system. Crucially, that lung disease severity difference appeared even though ABT use was not associated with significantly greater growth improvements, undermining the most common rationale for prescribing these drugs in the first place.

The proposed mechanism is biologically plausible. By neutralizing stomach acid, PPIs allow oral and upper gastrointestinal bacteria, including Streptococcaceae, to survive and colonize the lower gut in greater numbers. At the same time, communities of beneficial bacteria drop off. Prior work in infants treated with PPIs for gastroesophageal reflux found specific genus-level gut microbiome changes whose long-term consequences remain poorly understood, including decreased Lactobacillus and increased Haemophilus, a known respiratory pathogen. In children already burdened by CF, whose gut microbiota may act as a reservoir for airway pathogens, that shift could translate directly into worse lung outcomes. Research on gut dysbiosis in pediatric CF highlights how the gut-lung axis may drive disease progression, lending further plausibility to this connection.

How the PEARL-CF Study captured these patterns

The strength of the PEARL-CF findings rests on its prospective design. Rather than reconstructing drug histories after the fact, the team collected longitudinal data on growth, pancreatic function, pulmonary symptoms, and acid blocker medication use at six specialized CF centers over three years. Gut microbiome composition was characterized using 16S rRNA gene sequencing, the same approach used in an earlier longitudinal CF gut microbiome study that traced microbial development from birth through early childhood. The PEARL-CF cohort also included a separate arm that tested a 15-strain Lactobacillus and Bifidobacterium probiotic given daily for 12 months; that arm found no significant difference in bacterial alpha-diversity between probiotic and placebo groups, though probiotic users did show less Haemophilus influenzae in respiratory swabs during the intervention period.

The key caveat: association, not proof of causation

The PEARL-CF Study is observational. Children who received persistent acid blockers may have been sicker at baseline, and sicker children may naturally develop worse lung disease and more disrupted microbiomes regardless of medication. The authors acknowledge this and call for a systematic risk-benefit analysis of acid blocker therapy specifically in CF children, something that does not yet exist in clinical guidelines. Broader evidence on PPIs and pediatric microbiome risks in the general population has already flagged associations with Clostridium difficile infection, asthma, and small intestinal bacterial overgrowth, but CF introduces a different disease context that makes direct extrapolation unreliable. What the data cannot yet tell us is whether stopping PPIs in CF infants would reverse the microbiome changes or improve lung trajectories.

What comes next for CF acid blocker guidelines

The practical implication is straightforward even if the science is still maturing: clinicians prescribing acid blockers to infants with CF are doing so largely on intuition and habit, in the absence of rigorous trial evidence. The PEARL-CF team calls for further research to guide prescribing practices, including randomized controlled work that would let researchers test whether withdrawing or limiting PPIs in early childhood changes microbiome and lung outcomes over time. Until those trials happen, the new data at minimum justify a harder look at whether each infant's acid blocker prescription is genuinely necessary, and whether the gut costs of long-term suppression are being factored into clinical decisions.

Evidence rating

EMERGING — 75/100

Caveats:

• This is a conference abstract; full peer-reviewed methodology and statistical details are not yet publicly available.
• Observational design: the study shows association, not causation — sicker children may have been more likely to receive acid blockers, which could partly explain the worse outcomes.
• Findings are specific to children with cystic fibrosis and may not apply to the general pediatric population.
• No funding source was disclosed for this study.
• Results have not yet been independently replicated in a separate CF cohort.

Prospective longitudinal observational cohort of 145 infants with cystic fibrosis followed to 36 months across six centers. The study demonstrates association, not causation; children prescribed persistent acid blocker therapy may differ systematically in disease severity from non-users, limiting causal inference. Published as a conference abstract, full peer-reviewed data are not yet available, and findings have not been independently replicated.