New Evidence of Bacteria in Otitis Media

A frequent childhood ear infection called otitis media has been found to be an ideal model for studying the role of certain bacteria in recurrent infectious diseases, according to a study supported by the National Institute on Deafness and Other Communication Disorders (NIDCD). The research, published in the January 28, 1998, issue of the Journal of American Medical Association, was conducted at the Center for Genomic Sciences, University of Pittsburgh School of Medicine. This is the first report detecting a slow dividing, but active or viable bacterial organism in middle ear fluid thought to be sterile when analyzed using standard bacterial culture assays.

Until now, it was thought that the fluid in the middle ear was sterile in chronic cases of otitis media because samples of the fluid taken from this area did not contain bacteria. Using a molecular biological technique, the research team, lead by J. Christopher Post, M.D., and Garth D. Ehrlich, Ph.D., found evidence of active bacteria in many of the fluids. These investigators speculate that this may indicate an infection of longer duration that is undetectable by current testing techniques.

"These findings provide the foundation that will allow us to understand this elusive infection leading to better treatment strategies," said James F. Battey, Jr., M.D., Ph.D., Director, NIDCD.

Otitis media (OM) is an infection of the middle ear. Although it affects primarily infants and young children, it also affects some adults, and costs an estimated $5 billion a year in lost wages and medical costs. OM usually begins with a sore throat, cold or other upper respiratory tract infection that spreads to the middle ear. When OM becomes persistent, fluid may remain in the normally air-filled middle ear space. Referred to as chronic otitis media with effusion (OME), this condition can lead to hearing loss and, in young children, may lead to developmental speech, language and socialization difficulties. Otitis media is the most frequent reason for children to be taken to the emergency room or physicians' offices.

The investigators suggest that the results of this study have implications beyond understanding otitis media or H. influenzae, one of the major bacteria known to cause otitis media. H. influenzae causes many other upper respiratory tract diseases, and there now appear to be strains of H. influenzae which go undetected using standard laboratory culture techniques. Most importantly, H. influenzae may serve as a model for similar bacteria that also have a reduced growth rate making them difficult to detect by the current methods of testing and difficult to treat with available antibiotics. In addition, slow dividing bacteria are known to infect implantable medical devices, such as catheters and artificial joints.

The tip-off to the presence of active bacteria consisted of the mRNA, a part of the genetic material of H. influenzae. "In previous studies we identified the DNA of H. influenzae in the sterile middle ear fluid using molecular biological techniques but its presence did not signify active bacteria," stated Dr. Ehrlich. "The DNA could have been residue from the previous infection." He further explained that mRNA, which is made from DNA in the process of producing the proteins necessary for H. influenzae, only exists for a short time. Its presence indicates that the bacteria DNA was actively in the process of producing H. influenzae proteins, thus indicating an active organism.

Dr. Ehrlich stressed that unfortunately, currently available antibiotics are not designed to attack this type of bacteria, which are slow dividing organisms. Their use will most likely have no effect on the middle ear fluid which needs to be absent from the ear for hearing to be restored. It is likely that a new arsenal of antibiotics, tailored to attack the slower dividing bacteria, will need to be designed to effectively treat OME.

As the nation's focal point for research in human communication, the NIDCD conducts and supports biomedical and behavioral research and research training on normal mechanisms as well as diseases and disorders of hearing, balance, smell, taste, voice, speech and language that affects 46 million Americans.

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