Mounting Evidence Supports Role of Bacterial Biofilms in Chronic Infections of Middle Ear and Sinuses

Mounting evidence suggests that bacterial biofilms play a role in chronic inflammatory infections of the middle ear and sinuses. Whether these biofilms actually cause chronic ear and sinus infections remains unproven, but it is increasingly shown from a number of animal studies and a recently published human study that biofilms are present in these chronic otolaryngologic conditions.

Hassan H. Ramadan, MD

Biofilms are a relatively novel way of looking at bacteria, said Martin Desrosiers, MD, Department of Otolaryngology, Head and Neck Surgery at McGill University in Montreal, who, along with his colleagues, has examined the role of biofilms in chronic sinusitis. A number of people [studying] chronic sinusitis have found that there are biofilms that are present, he said. So this is quite a revelation that gives us a new therapeutic target.

Although much of the published data showing the presence of biofilms in chronic sinusitis and chronic otitis media have been in animal studies, a recently published study in humans now adds weight to the evidence of the presence of biofilms in these chronic conditions.

Conducted by researchers at the Allegheny-Singer Research Institute in Pittsburgh, the study examined the presence of biofilms in children with chronic otitis media. Investigators used confocal laser scanning microscope images to evaluate the presence of biofilms in the middle-ear muscosa of biopsy specimens taken from 26 children undergoing tympanostomy tube placement for treatment of otitis media with effusion and recurrent otitis media. They compared these images to specimens biopsied in 8 patients undergoing cochlear implantation, who served as the control group.

Mucosal biofilms were detected in 92% of the biopsied specimens of the 26 children undergoing tympanostomy tube placement, whereas no biofilms were found in the 8 control patients.

The key finding [of the study] is that chronic otitis media is associated with a bacterial biofilm, said J. Christopher Post, MD, PhD, Professor of Otolaryngology at Drexel University College of Medicine in Pittsburgh, one of the coauthors of the study. The conventional wisdom is that while acute otitis media is a bacterial process, chronic otitis media is a sterile, inflammatory process. Investigators came to this erroneous conclusion because cultures of chronic middle-ear effusions are generally sterile. But the mistake was that ‘no growth of bacteria’ was interpreted to mean ‘bacteria are not there.’

The study highlighted the importance of accurate detection of bacterial biofilms by using a combination of microbiological culture, polymerase chain reaction (PCR)-based diagnostics, direct microscopic examination, fluorescence in situ hybridization, and immunostaining. According to Dr. Post, relying upon culture techniques to claim that bacteria are not present is clinging to old-fashioned technology.