NEW YORK (Reuters Health) – Chronic rhinosinusitis may be the result of an overactive immune response to normal microbes, not necessarily bacterial infection, a new study suggests.
Researchers found that patients and healthy controls tended to have qualitatively similar microbiomes. While control lavage samples triggered interleukin (IL)-5 production in peripheral blood leukocytes from patients, this was not the case with leukocytes from controls.
“These results indicate that immune cells from a patient with chronic rhinosinusitis are getting activated by the microbes found in the normal sinus,” said lead author Dr. Rajeev Aurora of Saint Louis University School of Medicine in Missouri.
“These organisms are probably picked up from the air, and therefore antibiotics cannot eliminate them in the sinus as they re-colonize the sinus with each breath,” he told Reuters Health by email. “The constant exposure to these organisms in people whose immune system is aberrantly sensitive to these common organisms leads to a persistent inflammation.”
Dr. Neil Bhattacharyya, a professor or otology and laryngology at Harvard Medical School who was not involved with the study, said that there has been a gradual recognition over the last five to ten years that chronic sinus inflammation is more of an inflammatory state rather than a simple bacterial infection.
The novel finding in the new study, he said, is that this inflammatory state may be driven by exposure to commensal microorganisms, which normally cause no harm.
“This is not something that one would expect,” Dr. Bhattacharyya said. “These bacteria are organisms that help us live and adjust to our environment and the question is why in some patients (they) are all of a sudden being part of the inflammatory cascade that leads to chronic rhinosinusitis.”
For their study, Dr. Aurora and colleagues took samples from thirty patients with chronic rhinosinusitis and 12 controls undergoing nasal surgery for other conditions. They used deep sequencing to characterize the patients’ microbiomes and search for pathogens that may potentially trigger an immune response. They also identified the immune cells and cytokines in the samples.
Nearly all the fungal and bacterial species identified were commensals, the investigators report in JAMA Otolaryngology–Head & Neck Surgery, online October 31. Although there were generally higher numbers of these microorganisms in patients than in controls, the microbiomes in the two groups were qualitatively similar.
When also considering that only leukocytes from patients with chronic rhinosinusitis reacted to nasal samples from controls, this suggests that chronic rhinosinusitis patients have an abnormal immune response to normal microorganisms, Dr. Aurora said.
Dr. Itzhak Brook, a pediatrician at Georgetown University in Washington, D.C., who specializes in infectious diseases, called the study “innovative and provocative.”
But he noted that 16 of 30 patients in the chronic rhinosinusitis group were asthma suffers and prone to allergies.
“They therefore do not represent the average patient with chronic rhinosinusitis, but a subgroup in whom the immune system is hyperactive,” Dr. Brook told Reuters Health by email, adding that the findings shouldn’t change how doctors treat patients.
Dr. Bhattacharyya said doctors are turning more frequently to anti-inflammatory therapies like steroids to treat chronic rhinosinusitis, but that after a period of four to six weeks, patients may also receive a course of antibiotics.
The study, he said, “doesn’t mean these patients don’t get a bacterial infection on top of their inflammation, but treating just the bacterial infection is not the solution for the vast majority of patients.”
JAMA Otolaryngol Head Neck Surg 2013.