Target Audience and Goal Statement: Allergists, pediatricians, dermatologists, nutritionists, emergency department physicians, family medicine physicians
The goal was to explore the association of Staphylococcus aureus colonization with specific immunoglobulin E (sIgE) production to common food allergens and allergies in early childhood independent of eczema severity.
Questions Addressed:
- What was the association between S. aureus and food allergy?
- Was any association of S. aureus colonization with sIgE production to common food allergens and food allergy in early childhood independent of eczema severity?
Synopsis and Perspective:
Nearly
one in twenty five school-age children have food allergies. Some common foods — including peanuts, eggs, milk, tree nuts, fish, shellfish, soy, and wheat — trigger over
90% of the allergic reactions in affected individuals.
Parent-reported childhood food allergies are on the rise, according to a U.S. household
surveyconducted from 2015 through 2016. About 42% reported at least one or more lifetime food-allergy related emergency department visits.
IgE-mediated food allergy is a prime reason for anaphylaxis warranting such a visit. Many survey respondents (40.7%) had a current epinephrine auto-injector prescription.
Lead researcher, Olympia Tsilochristou, MD, of Kings College London, and colleagues recently reported in the
Journal of Allergy and Clinical Immunology that
S. aureus bacteria on the skin of young children with severe eczema may be one of the factors contributing to the chance of developing food allergies.
S. aureus is found in the
nose and on the skin of healthy individuals. However, it tends to be more common in eczema sufferers.
Most of the study participants with skin S. aureus had concurrent moderate and severe eczema at all time points. Evaluations at the 12- to 30- and 60- to 72-month intervals showed that eczema significantly worsened in participants with immediately preceding skin S. aureuscolonization compared to uninfected counterparts. Study participants with skin S. aureuspositivity at any time during the study period also produced sIgE to hen’s egg white, peanut, and cow’s milk. This indicated that the participants were allergic to those foods.
“Participants with S. aureus were more likely to have persistent egg allergy and peanut allergy at 60 and 72 months of age independent of eczema severity,” the researchers wrote.
Results were derived from a secondary analysis of the Learning Early About Peanut Allergy (
LEAP) study and a 12-month extension of the LEAP study, known as the Persistence of Oral Tolerance to Peanut (
LEAP-On) trial. The LEAP study enrolled infants ages 4-11 months with severe eczema, egg allergy, or both. The babies were randomized to therapeutic peanut consumption or peanut avoidance, and all had eczema clinical evaluation and culture of skin and nasal swabs at baseline.
The follow-up LEAP-On study assessed the children at age 72 months, after 12 months of peanut avoidance in both groups.
Skin and nasal swabs were obtained at baseline and at ages 12, 30, and 60 months. A total of 48.8% of the participants had some form of S. aureus colonization (32.2% skin and 32.3% nasal) on at least one LEAP study visit, with most having just one positive test result. The greatest rates of colonization were recorded at 4-11 months of age.
Early
introduction of peanuts in infants at high risk for allergy was shown to prevent peanut allergy. Reduction in the prevalence of peanut allergy following eating peanuts until the age of five years, persisted at the age of six years (after 12 months of not eating peanuts).
However, this related study showed that, even if they ate peanuts at a young age, infants whose skin and noses were colonized with
S. aureus were
more likely to develop a food allergy.
“These findings indicate that
S. aureus may have reduced the chance of young infants gaining tolerance to peanut, even if peanut was eaten in early childhood,”
said co-author, Dr. George Du Toit, a King’s College professor.
While the team used bacteriological culture techniques and not DNA-based testing, they pointed out that they were able to enumerate live microorganisms and did not have to rely on possibly identifying remnant non-viable genetic material from a prior infection. They acknowledged that they did not genotype the isolated strains and that it was not possible to match organisms over time and between skin and nasal swabs. Other study limitations cited by the team were only collecting swabs on four occasions in the LEAP study and none in the LEAP-ON study. Diagnostic food challenges were only undertaken for peanuts and they also cautioned that associations were based on “small numbers of LEAP study consumers with peanut allergy as it is reflected in the wide CIs [confidence intervals] around the ORs [odds ratios].” Tsilochristou’s group could also not rule out the possibility of confounders.
Study Highlights: Explanation of Findings
This secondary analysis of the LEAP and LEAP-on studies was conducted to better understand the relationship between S.aureus and food sensitization/allergy by correcting the analyses for eczema severity. About half of the LEAP participants were colonized with S. aureus. Eczema severity, persistence, and deterioration could be correlated to skin colonization with S. aureus. Interestingly, hen’s egg white and peanut sIgE levels at each visit in the LEAP and LEAP-On studies were significantly linked with skin S. aureus positivity at any LEAP study time point, even after correcting for eczema severity. High-level hen’s egg white and peanut sIgE production reflected a stronger relationship. Similarly, a high-level sIgE response to milk at 30, 60, and 72 months of age was related to any skin S. aureus colonization. Tsilochristou’s group interpreted the collective results as meaning that S. aureus was associated with allergies to a hen’s egg, peanuts, and cow’s milk.
It is worth noting that 42.7% and 38.1% of baseline participants with an egg allergy had persistent egg allergy at 60 and 72 months of age, respectively. This finding contrasted with previous literature evidence suggesting that allergy to a
hen’s egg typically resolves during early childhood. Researchers concluded that
S. aureus can prevent the acquisition of natural tolerance to a hen’s egg.
“Our study reveals that aside from eczema severity, this bacterium that patients with eczema commonly become colonized with could be an added risk factor for food sensitization and allergy,” Tsilochristou said in a related
report.
“S aureus has been associated with more severe forms of atopic diseases, and our data extend these observations in patients with food allergy,” Tsilochristou’s group concluded.
Primary Source
Journal of Allergy and Clinical Immunology
Secondary Source
MedPage Today