Seasons, climate influence age and risk of bacterial infection in CF
MSSA, P. aeruginosa often cause infections in patients
The season and climate influence the age and risk of the first bacterial exposure or infection, that is, initial acquisition, in cystic fibrosis (CF) patients, a study suggests.
Methicillin-sensitive Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa are the primary causes of infections in CF patients. A MSSA infection occurs earlier in life than a P. aeruginosa infection. This pattern was inverted in the Mediterranean zone of France, which features dry, hot summers and mild winters, however.
“Environmental conditions modulate the age at initial acquisitions of both [bacteria],” scientists wrote. “Seasonality influences the risk of these infections, with an increased risk observed in autumn and winter.” The risk of initial acquisition of P. aeruginosa was highest during autumn, with no differences between climate zones. MSSA risk was higher in the oceanic and continental zones in winter, but lower in the Mediterranean zone.
The study, “Seasonal and climatic influence on respiratory infections in children with cystic fibrosis,” was published in Scientific Reports.
In CF, mutations in the CFTR gene causes thick, sticky mucus to build up, particularly the lungs, pancreas, liver, and intestine. In the lungs, it creates an environment where harmful bacteria can easily grow and cause infections.
Recurring respiratory tract infections are a well known complication of CF. Patient-specific or external factors, like pollution or access to healthcare, have been described as risk modifiers of bacterial infections in patients. The influence of the seasons and climate on bacterial infections hasn’t been described in detail, however, particularly in European countries.
Differences in P. aeruginosa, MSSA infections
Here, researchers explored whether the risk of P. aeruginosa and MSSA initial acquisition varies with the seasons or the climate zone where patients live. The study included 1,184 French people with CF born between 2001 and 2019. Their median age was 13.2 and their median follow-up time was 11.2 years.
The first MSSA infection occurred at a younger median age than that of P. aeruginosa , at two versus five years.
Three different climate zones in France were studied. The Mediterranean zone (6% of patients) has hot, dry summers, mild winters, and rainfall in autumn. The oceanic zone (58%) features cool summers, mild winters, and high rainfall. The continental zone (36%) includes mountainous and semi-continental climates with hot summers, cold winters, and low rainfall.
In the oceanic and continental zones, patients were initially infected with MSSA at around age 2 and with P. aeruginosa at around age 5. In the mediterranean zone, P. aeruginosa infection happened earlier than a MSSA infection — median age, 3.3 versus 5.
The risk of initial P. aeruginosa infection varied with the progression of seasons. Compared to spring, autumn had the highest infection risk, an increase of 53%. For MSSA, winter showed the highest risk, with a 30% increase, and summer had the lowest risk.
These findings were consistently seen in the oceanic and continental zones. In contrast, the Mediterranean zone showed a different seasonal pattern for MSSA infection, as risk decreased during summer and winter compared to spring. With P. aeruginosa, the riskiest season was winter, closely followed by autumn.
“We observed a notable increase in [initial MSSA infection] among the most recent cohorts, with initial acquisitions occurring at progressively younger ages, though the reasons for this remain unclear,” wrote the scientists, who said their findings differ from U.S. data that show a sharp increase in first MSSA infections between 1995 and 2005, which then stabilize or decline between 2006 and 2012.
“Moving forward, it will be intriguing to investigate whether the observed trends stabilize or regress in response to future environmental changes, as well as with exposure to antibiotic treatments and CFTR modulator therapies,” wrote the scientists, who noted the increase in global temperature reported over the last decades is expected to be steeper by 2040, which is “anticipated to have significant implications for human health, potentially exacerbating respiratory diseases.”
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