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William Bishai, A Testament to Sustained Macrolide Efficacy, Clinical Infectious Diseases, Volume 36, Issue 7, 1 April 2003, Pages 935–936, https://doi.org/10.1086/368208
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Sir—The recent article by Lonks et al. [1] entitled “Failure of Macrolide Antibiotic Treatment in Patients with Bacteremia due to Erythromycin-Resistant Streptococcus pneumoniae” might well have been entitled “Low Rates of Macrolide Failure during Prolonged Surveillance.” Lonks et al. [1] performed a matched case-control study of 86 patients with pneumococcal bacteremia due to S. pneumoniae that was either resistant or intermediately-resistant to macrolides (MRSP and MISP, respectively). Data spanning a 13-year period were collected from medical records of patients at 4 study sites (2 hospitals in Boston, MA, 1 in Providence, RI, and 1 in Terrassa, Spain [near Barcelona]). Lonks et al. [1] found that concurrent receipt of macrolide therapy increased the likelihood of bacteremia due to MISP or MRSP among case patients, compared with age and sex-matched controls.
However, Lonks et al. [1] stated that breakthrough bacteremia during macrolide or azalide therapy is more likely to occur among patients infected with erythromycin-resistant S. pneumoniae (i.e., MISP or MRSP) than among patients infected with MSSP. This conclusion cannot be drawn from the data they presented because not all of the 1071 pneumococcal blood isolates recovered at the 4 centers during the study interval were evaluated. In fact, it appears that, after evaluation of 90 case patients with MISP or MRSP bacteremia and 141 controls with MSSP bacteremia, as many as 840 additional cases of MSSP bacteremia were seen at the 4 hospitals. These additional cases would need to be analyzed in order to state the proper relative rates of breakthrough bacteremia due to MISP or MRSP strains versus MSSP strains among case patients and controls who were receiving macrolide therapy. The observation of treatment failure for severe pneumonia has been studied for ∼40 years and was well documented by Austrian and Gold [2], who observed a significant rate of treatment failure for infections with drug-susceptible pneumococci, even when such infections were appropriately treated with penicillin (a highly active agent). As the prevalence of pneumococcal strains with elevated macrolide MICs increases, one would anticipate observing a proportional number of macrolide-resistant isolates recovered from bacteremic patients, irrespective of whether the patients received concurrent therapy. Indeed, rather than being an indictment of the macrolides, the fact that collection of data for a 13-year interval and from 4 large medical centers was required to identify 19 patients with MISP or MRSP bacteremia who were receiving macrolide therapy is a testament to the effectiveness of macrolides in the management of pneumococcal pneumonia.
