Community-Acquired Pneumonia Drug Resistance Patterns Prove Puzzling

A ntibiotic resistance skyrocketed during the 1990s. In general, treatment failures and mortality rose in tandem with resistance. But not so in the case of macrolide resistance among isolates of Streptococcus pneumoniae and other bacterial agents that cause community-acquired pneumonia (CAP). This phenomenon can be called the in vitro-in vivo paradox, according to William Bishai of the Johns Hopkins University School of Public Health in Baltimore, Md. By this he means that drug resistance is measured in clinical isolates yet is not accompanied by an epidemic of treatment failures or a rise in mortality among those who are infected. Nonetheless, to some observers, the rising resistance in CAP portends disastrous levels of treatment failures to come if macrolides are not replaced in common clinical practice. The issue, which has taken up many journal pages of late, is critical. For one thing, macrolides are usually the best choice for treating CAP, being effective against the major culprits and the rarer etiologic agents, but sparing just about everything else. The second-choice alternative, the fluoroquinolones, are broad-spectrum agents that act less discriminately against bacterial pathogens, potentially generating resistance among many of their scattershot targets. Certainly fluoroquinolones are powerful but also resistance to these drugs remains relatively uncommon. Thus, they are highly valued, among other reasons because they sometimes serve as the antibiotics of last resort. Lately resistance to fluoroquinolones also is edging up, worrying clinicians. Antibiotics are hard-to-replace resources, not to be squandered. “When do we say we have to switch to the newest agents?” wonders infectious disease specialist Victor Yu of the University of Pittsburgh in Pittsburgh, Pa.