ID Consult

Outpatient antibiotics ABRS vs. AOM


 

Acute bacterial rhinosinusitis (ABRS) has been suggested as a parallel pyogenic infection to acute otitis media (AOM). Like AOM, ABRS is due to obstruction of the normal drainage system into the nasopharynx from a normally aerated pouch(es) within the bone of the skull. Potential pathogens from the nasopharynx, having refluxed into the aerated spaces, begin to replicate and induce inflammation, at least in part due to the obstruction and the inflammation-induced deficiency of the normal cleansing system. For the middle ear, this system is the eustachian tube complex. For the sinuses, it is the osteomeatal complex. The similarities have led some to designate ABRS as "AOM in the middle of the face."

Other parallels are striking, including the microbiology, although 21st century data are less available for the microbiology of ABRS compared with AOM. The table lists some comparisons between the 2013 American Academy of Pediatrics (AAP) guidelines on managing AOM (Pediatrics 2013;131;e964-e999) and the 2012 Infectious Diseases Society of America (IDSA) ABRS guidelines (Clin. Infect. Dis. 2012;54:e72-e112).

Dr. Christopher J. Harrison

So the question arises: Why was high-dose amoxicillin reaffirmed as the drug of choice for uncomplicated AOM in normal hosts in the 2013 AAP AOM guidelines, whereas the most recent guidelines for ABRS (2012 from IDSA) recommend standard-dose amoxicillin plus clavulanate? Amoxicillin is an inexpensive and reasonably palatable drug with a low adverse effect (AE) profile. Amoxicillin-clavulanate is a broader-spectrum, more expensive, somewhat bitter-tasting drug with a moderate AE profile. When the extra spectrum is needed, the added expense and AEs are acceptable. But they seem excessive for a first-line drug.

Do differences in diagnostic criteria lessen the impact on antimicrobial resistance from use of a broader-spectrum first-line drug for ABRS compared to AOM?

Compared with the 2013 AAP otitis media guidelines, which provide objective, clear, and simple criteria, the 2012 IDSA ABRS Guidelines have less objective and less precise criteria. For an AOM diagnosis, the tympanic membrane (TM) must be bulging or be perforated with purulent drainage. Both result from an expanding inflammatory process that stretches the TM. Using this single criterion in the presence of an effusion, clinicians have a clear understanding of what constitutes AOM. No more need to rely on history of acute onset, or a particular color or opacity, or lack of mobility on pneumatic otoscopy. One need only see a bulging TM and note that there is an inflammatory effusion. Bingo – this is AOM.

So, diagnosis of AOM is easier and can be more precise, eliminating "uncertain AOM" from the options. With these firm diagnostic criteria, the question then is whether the AOM episode requires antibiotics. That question is also addressed in the 2013 guidelines and will not be discussed here. The end result is that the 2013 AOM guidelines should decrease the number of AOM diagnoses and thereby antibiotic overuse.

Based on the 2012 IDSA Guideline for ABRS, in contrast, there are three sets of circumstances whereby an ABRS diagnosis can be made. For the most part these involve historical data about duration and intensity of symptoms reported by patients or parents. Thus these are varied, mostly subjective, and more complex with multiple nuances. There is more art and no real reliance on objective physical findings in diagnosing ABRS. This is due to there being no reliable physical findings to diagnose uncomplicated ABRS. There also is no reliable, inexpensive, and safe laboratory or radiological modality for ABRS diagnosis. This results in considerable wiggle room and subjective clinical judgment about the diagnosis.

And the 2012 IDSA ABRS guidelines state that antibiotic treatment should begin whenever an ABRS diagnosis is made. There is some verbiage that one could consider observation without antibiotics if the symptoms are mild, but there are no specifics about what constitutes "mild." This seems like the perfect storm for potential overdiagnosis and overuse of antibiotics, so a broader-spectrum drug would be less desirable from an antibiotic stewardship perspective.

Are pathogens in routine uncomplicated ABRS more resistant to amoxicillin than in AOM so that addition of clavulanate to neutralize beta-lactamase is warranted?

The 2012 ABRS guidelines indicate that the basis for recommending amoxicillin-clavulanate was the microbiology of AOM. There has been little pediatric ABRS microbiology in the past 25 years because sinus punctures are needed to have the best data. Such punctures have not been used in controlled trials in decades. So it is logical to use AOM data, given that pneumococcal conjugate vaccines (PCVs) have produced shifts in pneumococcal serotypes, and there continues to be an evolving distribution of serotypes and their accompanying antibiotic resistance patterns since the 2010 shift to PCV13.

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