Antibiotic-Resistance Increasing Problem In Treating Otitis Media; Study Shows 3 Bacteria Resisting Drugs

BUFFALO, N.Y. -- Three types of bacteria responsible for up to 90 percent of middle-ear infections in children have developed significant resistance to commonly prescribed antibiotics, a study by researchers at the University at Buffalo and the University of Massachusetts has shown.

The data, reported recently in Pediatric Infectious Disease Journal, provide a clear warning that antibiotic resistance is becoming a significant problem in treating the ailment, said Howard Faden, M.D., UB professor of pediatrics, a specialist in childhood infectious diseases and lead researcher on the study.

Otitis media -- middle-ear infection -- is one of the most common infections of early childhood, accounting for approximately 30 percent of visits to pediatricians. Infectious-disease researchers have identified three bacteria types -- Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis -- as the pathogens that cause 50-90 percent of these infections. Various studies over the past four years have reported that standard antibiotics used to defeat these organisms were becoming less effective, because the bacteria were developing resistance to the medicines.

To assess the extent of bacterial resistance, the researchers collected nasal mucus specimens from 216 infants who had not received any prior antibiotic therapy. Research has shown a direct connection between nasal colonization by the organisms and development of otitis media.

The researchers identified the pathogens and subjected them to eight antimicrobial agents commonly used to fight middle-ear infections -- amoxicillin-clavulanate, ampicillin, cefaclor, cefpodoxime, cefprozil, cefuorxime, penicillin, and trimethoprim-sulfamethoxazole (TMP/SMX.)

• 96 percent of M. catarrhalis strains were resistant to penicillin, 90 percent to ampicillin, and 19 percent to TMP/SMX.

• 32 percent of nontypeable H. influenzae strains were resistant to ampicillin and 17 percent did not respond to cefaclor.

• In contrast to some reports of strong resistance of pneumococci bacteria to penicillin -- more than 30 percent in Kentucky and 26 percent among Native Americans in Alaska -- this study showed penicillin and its derivatives remain highly effective against this pathogen. Only 1.2 percent of S. pneumoniae were resistant and another 4.7 percent were somewhat resistant. However, 20 percent of the strains were resistant to TMP/SMX.

Faden said rates of bacterial resistance to antibiotics vary widely geographically, and are related to patterns of antibiotic use in any given region.

"We learned from this study that there are some commonly used drugs that are no longer valuable," he said. "For example, it is clear from this study that trimethoprim - sulfamethoxazole should not be prescribed for otitis media, and that in our community, amoxicillin is still very effective for simple ear infections.

"Surveys of resistance should be done on a regular basis to keep up with changes in susceptibility patterns," Faden said.

Gary Doern, Ph.D., from the University of Massachusetts at Worcester, an expert in bacterial resistance, conducted the resistance testing. Judy Wolf from UB, and Michael Blocker, from the University of Massachusetts, also assisted in the research.

The study was supported by a grant from the National Institute of Child Health and Human Development.