REPLY
We thank S. Di Bella et al. for their comments regarding the potential of tetracyclines to improve the treatment of community-acquired pneumonia (CAP) in elderly patients at risk of Clostridium difficile infection (CDI) (1). Prescribing for CAP is a major driver of seasonal trends in antibiotic use in temperate countries, where wintertime antibiotic prescribing increases by almost one-third relative to summer levels (2). These differences in antibiotic prescribing in elderly patients may be at least partially responsible for the increased wintertime risk of CDI in North America (3, 4).
As S. Di Bella et al. note, the low risk profile of the use of tetracyclines for treatment of CDI in observational epidemiologic studies of hospital- and community-acquired CDI suggests that they may have advantages as a class of agents for patients with CAP at risk of CDI. Doxycycline, for example, which has activity against susceptible pneumococci and atypical pneumonic pathogens, has been shown to have only a moderate effect on total counts of gut anaerobic bacteria (5).
We caution that increased prescribing of tetracyclines for CAP could help select antimicrobial-resistant Clostridium difficile pathogens, and so tetracycline-associated CDI risks have the potential to change over time (6), such that ongoing monitoring of this relationship is necessary (7). It is also important to note other drawbacks of this class of antimicrobials, including their contraindication in children and pregnant women.
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