Updates By Carol A. Kemper, MD, FACP

Levofloxacin-Resistant Pneumococci

Source: Wortmann GW, Bennett SP. Clin Infect Dis 1999;29:1599-1600.

A 58-year-old man with a history of splenectomy was hospitalized in Washington, DC, with fever and sinusitis. He received levofloxacin, but became increasingly lethargic and died. Cultures of CSF yielded Streptococcus pneumoniae susceptible to penicillin but no zone of inhibition to levofloxacin was seen on Etest. This unfortunate case serves as a harsh reminder that a small percentage of S. pneumoniae are resistant to levofloxacin.

While resistance to the macrolides, clindamycin, trimethoprim-sulfamethoxazole, and tetracycline, is significantly increased in penicillin-resistant strains, it is important to recognize that the likelihood of quinolone resistance is independent of penicillin resistance. Therefore, no inference can be made regarding the susceptibility of a penicillin-sensitive strain of S. pneumoniae to the quinolones. Recent susceptibility data for the United States of 2752 clinical isolates collected between 1996 and 1997 found that, on the basis of MIC data, grepafloxacin was the most active agent against S. pneumoniae, followed by sparfloxacin, levofloxacin, ciprofloxacin, and ofloxacin in descending order of activity (Thornsberry C, et al. Antimicrob Agents Chemother 1999;43:2612-2623). Nonetheless, ~0.2% of strains were resistant to levofloxacin or grepafloxacin with an MIC more than 2.0 mcg/mL. However, a recent report from Hong Kong identified a 5.5% resistance rate to levofloxacin among multiple drug-resistant strains of pneumococci (Ho PL, et al. Antimicrob Agents Chemother 1999;43: 1310-1313). The newer quinolones should therefore not be used for cases of invasive or life-threatening streptococcal disease, irrespective of penicillin susceptibility data, unless their susceptibility to these agents has been predetermined.