Is the pneumococcus the one and only in acute otitis media?

A remarkable feature of medicine is that with tremendous advances in diagnosis and treatment, there may be less agreement, rather than more, about some diseases. For example in the preantibiotic era, when effective therapy was unavailable and acute otitis media (AOM) routinely progressed to rupture of the tympanic membrane, the majority of cases of otitis media in infants were caused by Streptococcus pneumoniae and Haemophilus influenzae and, in older children, by S. pneumoniae and Streptococcus pyogenes. More than one-half century later, with the majority of cases being treated early on and the natural history of disease much less observable, controversy has surfaced. In their editorial entitled “Only the pneumococcus? ” Olson and Jackson argue that S. pneumoniae is the only clinically important cause of otitis media. This suggestion has considerable bearing on therapeutic decisions because, if true, it would justify treatment solely with a beta-lactam antibiotic such as amoxicillin in the majority of cases, removing the need for administering beta-lactamase-stable drugs. However appealing it might be, this suggestion defies the limited data that are now available. Studies done in the antibiotic era do agree that S. pneumoniae is more likely than H. influenzae or Moraxella catarrhalis to cause a more severe and persistent AOM. First, in the absence of therapy pneumococcus tends to persist longer than these other organisms. In a milestone study Howie and Ploussard showed that 3 to 6 days after an initial culture of middle ear fluid (MEF) is positive, the fluid becomes spontaneously sterile in 38 and 48% of cases involving M. catarrhalis and H. influenzae, respectively, compared with only 16% of those with S. pneumoniae. This finding suggests that if infection is inappropriately treated, pneumococcus is more prone to persist and therefore to cause sequelae and complications. Indeed in most reports there appears to be an increased likelihood of finding S. pneumoniae in nonresponsive or recently treated AOM than of finding H. influenzae or M. catarrhalis. 5 Second, although viral infection is implicated as a predisposing factor in most cases of AOM, S. pneumoniae appears to be more likely to cause this condition without a predisposing cause, suggesting its higher virulence. Third, the inflammatory response seems to be greater in pneumococcal AOM both clinically, as expressed by a higher fever and increased redness of the tympanic membranes, or by the presence in serum of inflammatory products associated with severe reaction such as interleukin 6. Recent data from the Beer Sheva group suggest that white blood cell counts are also greater in pneumococcal AOM than in AOM caused by other pathogens (E Leibovitz, unpublished observations). Finally, clinical experience suggests that S. pneumoniae is more often associated with mastoiditis and intratemporal or intracranial complications, although the medical literature does not provide firm support for this statement. The facts that S. pneumoniae is the most virulent organism causing AOM and the most likely to be associated with complications should not be taken as an indication that other organisms are not important. True, the role of M. catarrhalis is not well-defined, and in many series of cases its prevalence is low. With regard to H. influenzae, however, the story is quite different, and the pathogenic role of this organism is now quite clear. Two approaches can be used to examine the role of H. influenzae as a pathogen in AOM. First, as indirect evidence one can study cases of AOM that have failed to respond to antibiotic treatment. The persistence of H. influenzae in the MEF in such cases suggests that the organism is a true pathogen. Although in most studies of nonresponsive AOM S. pneumoniae has been the main pathogen, in one H. influenzae was more frequent in recently treated AOM (presumably representing, at least in part, nonresponsive AOM) than in untreated AOM. Even in the studies in which S. pneumoniae was the most frequent pathogen, H. influenzae was also found. For example in a study from Rochester, NY, nontypable H. influenzae was found in 7% of all cases of persistent AOM, and in a recently published study by the Beer Sheva group it constituted 37% of all isolates. In a recent study Brook Accepted for publication Jan. 26, 2000. From the Infectious Disease Section, Veterans Affairs Medical Center, Houston and the Baylor College of Medicine, Houston, TX (DM); and the Pediatric Infectious Diseases Unit, Soroka University Medical Center and the Faculty of Health, Ben Gurion University, Beer Sheva, Israel (RD).