Bacteria and Viruses Cohabitate in Ears of Kids With Otitis Media

TURKU, Finland, Nov. 7 -- Most children with acute otitis media have infections caused by both bacteria and viruses, suggesting that antibiotics may not be enough to control the infections, researchers here have found.

When the investigators drew middle ear fluid through tympanostomy tubes in children with new-onset acute otitis media with effusion, they found that 96% of the samples contained at least one respiratory pathogen, and two-thirds contained both bacteria and viruses, reported Aino Ruohola, M.D., Ph.D., of Turku University Hospital, and colleagues.

"The clinical impact of coinfections of the middle ear is based on observations that bacterial eradication and clinical outcomes are poorer in coinfections than in solely bacterial infections," the investigators wrote in the Dec. 1 issue of Clinical Infectious Diseases.

Viral coinfections may exacerbate the inflammation that is a hallmark of acute otitis media, and may also interfere with the efficacy of antimicrobial therapies, the authors suggested.

The findings suggest that the strategy of observation alone for mild and select stubborn cases of acute otitis media, endorsed by the American Academy of Pediatrics, may be appropriate in children with bacterial and viral infections, noted an otitis media researcher who was not involved in the study.

"For severe acute otitis media cases for which antibiotic is indicated, viral coinfection could lead to clinical failure even when appropriate antibiotic has sterilized the middle ear fluid," wrote Tansee Chonmaitree, M.D., of the University of Texas Medical Branch in Galveston, in an accompanying editorial.

"When one keeps in mind the possibility of combined bacterial and viral infections in acute otitis media," she continued, "expectations for antibiotic treatment of acute otitis media will be more realistic, and a failed course of antibiotic treatment may not be promptly blamed on antibiotic-resistant bacteria, leading to continuous changes in antibiotic regimens. Watchful waiting after a treatment course may also become an alternative."

At least 15% of patients with acute otitis media have an infection of unknown origin, Dr. Ruohola and colleagues noted. To get a better sense of the etiology of acute otitis media, they performed microbiological studies on middle ear effusions collected from 79 young children with otitis media infections that were less than 48 hours old.

The children had a median age of 21 months (range seven to 71 months), and all had tympanostomy tubes through which the investigators could aspirate middle ear fluid following sterilization of the tubes.

The authors used culture and polymerase chain reaction to characterize bacterial isolates, and culture, antigen detection, and PCR to identify viral isolates.

They found that 76 of the 79 children (96%) had a least one respiratory tract pathogen.

Bacteria were found in samples from 73 children (92%), and included the usual suspects, such as Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis.

Viruses were found in 55 of the 79 children (70%). The list included, but was not limited to, rhinovirus, NT picornavirus, respiratory syncytial virus, and human metapneumovirus, plus parainfluenza, enterovirus, and coronavirus species.

Bacteria and viruses were found concomitantly in 52 patients (66%). Viral co-travelers were found in 77% of samples positive for S. pneumoniae, 65% of those positive for H. influenzae, and 73% of those positive M. catarrhalis, but the authors did not find associations of any bacteria with any specific virus.

The authors pointed out that "viruses strengthen the bacteria-induced inflammation in the middle ear, which is evident by the higher concentrations of inflammatory mediators in coinfections than in cases of acute otitis media due solely to bacteria. Thus, viruses do not seem to be 'innocent bystanders' in the middle ear."

Concomitant viral and bacterial infections are associated with more severe symptoms and poorer treatment responses in respiratory tract infections, they noted.

"Our findings suggest that coinfection with bacteria and viruses in the middle ear may be a more common cause for a poor treatment response in acute otitis media than previously thought," they wrote.

The finding that combined bacterial and viral infections are common in children with acute middle ear implications has important clinical implications, Dr. Chonmaitree suggested in her editorial.

"Results of antibiotic treatment of acute otitis media may not be as expected when the disease is not a pure bacterial infection, and the concept may also apply to other respiratory diseases, such as sinusitis and pneumonia, in both adults and children," she wrote.