CHICAGO (FRONTLINE MEDICAL NEWS) – Treating even uncomplicated acute otitis media (AOM) in 2017 may not be as simple as writing an amoxicillin prescription. Changes in pathogens may mean a shift in prescribing practices, Ellen Wald, MD, said at the annual meeting of the American Academy of Pediatrics.

Dr. Wald, speaking to an audience that filled the lecture hall and an overflow room, said that there has long been good reason to turn to amoxicillin for AOM. “The reason that pediatricians and others like to reserve the use of amoxicillin as first-line therapy for children with AOM is that it is generally effective, it’s safe, it’s narrow in spectrum, and it’s relatively inexpensive. Those are all very desirable characteristics.”

When amoxicillin is chosen as first-line therapy for AOM, it’s dosed at 90 mg/kg rather than the standard 45 mg/kg to overcome resistance from penicillin-resistant Streptococcus pneumoniae, said Dr. Wald, chair of the department of pediatrics at the University of Wisconsin–Madison. Resistant S. pneumoniae have altered penicillin-binding proteins on their cell surfaces; in these organisms, the penicillin cannot bind and inhibit cell wall synthesis, so the organisms are penicillin resistant.

However, the high-dose amoxicillin strategy is predicated on S. pneumoniae being the most likely cause of bacterial AOM. Since the seven-valent pneumococcal conjugate vaccine (PCV7), and then its successor PCV13, became part of the standard series of childhood immunizations, said Dr. Wald , the microbiology of AOM has shifted.

In 1990, S. pneumoniae was estimated to cause 35%-45% of AOM cases, with Haemophilus influenzae responsible for 25%-30% of cases. Moraxella catarrhalis was thought to cause 12%-15% of cases, with Streptococcus pyogenes–related AOM falling into the single digits.

In 2017, the balance has shifted, with S. pneumoniae only responsible for about a quarter of cases of AOM, and H. influenzae causing about half. The prevalence of M. catarrhalis and S. pyogenes cases hasn’t changed. This, said Dr. Wald, should prompt a shift in thinking about antibiotic strategy for AOM.

“The real problem with amoxicillin is that it’s not active against beta-lactamase–producing H. influenzae and M. catarrhalis. So my recommendation would be, rather than using amoxicillin, to use amoxicillin potassium clavulanate.”

However, she said, more data are needed before making this a firm guideline. “This is a very dynamic situation, and over the past decade, we’ve seen swings in the prevalence of the two organisms,” so it’s important to keep tracking trends. Also, she said, the 2017 data regarding AOM pathogens are from a single-site tympanocentesis study, and although the data in the past have represented national trends, caution should be used when generalizing from one study.

Dr. Wald said she can’t currently recommend using azithromycin to treat AOM. “Azithromycin and the other macrolides have almost no activity against H. influenzae,” she said. “So given the current situation with the high prevalence of H. influenzae, azithromycin really should be avoided in the management of AOM.”

For children with non–type 1 penicillin hypersensitivity or mild type 1 hypersensitivity, a second- or third-generation cephalosporin, such as cefuroxime, cefpodoxime, or cefdinir, can be considered, she said.

“For life-threatening type 1 hypersensitivity reactions, we like to choose a drug of an entirely different class. For that reason, levofloxacin might be something you’d consider,” in those cases, said Dr. Wald, making clear that this is not a Food and Drug Administration–approved indication. Levofloxacin does have the antimicrobial spectrum to cover AOM pathogens, she said.

When parenteral therapy is indicated, as when a child isn’t tolerating oral medications or when nonadherence is likely, a single dose of ceftriaxone IM or IV, dosed at 50 mg/kg, remains a good option. “It’s a suitable agent because all middle ear pathogens are susceptible to ceftriaxone,” said Dr. Wald.

When oral antibiotics are used, how long should they be given? Some experts, she said, recommend a 5-day course for older children who have had infrequent previous episodes of AOM. In this age group, the shorter course can still yield an excellent response, she said.

However, a 2016 study that tried a shortened course of amoxicillin/clavulanate for children 6-23 months of age found that clinical failure occurred in 34% of the patients who received 5 days of antibiotics, compared with 16% of those who got the full 10-day course. “The recommendation is pretty clear that, for children under 2 years of age, a 10-day course of therapy is best,” said Dr. Wald.

Dr. Wald reported that she had no conflicts of interest.

On Twitter @karioakes


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