Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States.

Background: The emergence of drug-resistant strains of bacteria has complic ated treatment decisions and may lead to treatment failures. Methods: We examined data on invasive pneumococcal disease in patients iden tified from 1995 to 1998 in the Active Bacterial Core Surveillance program of the Centers for Disease Control and Prevention. Pneumococci that had a h igh level of resistance or had intermediate resistance according to the def initions of the National Committee for Clinical Laboratory Standards were d efined as "resistant'' for this analysis. Results: During 1998, 4013 cases of invasive Streptococcus pneumoniae disea se were reported (23 cases per 100,000 population); isolates were available for 3475 (87 percent). Overall, 24 percent of isolates from 1998 were resi stant to penicillin. The proportion of isolates that were resistant to peni cillin was highest in Georgia (33 percent) and Tennessee (35 percent), in c hildren under five years of age (32 percent, vs. 21 percent for persons fiv e or more years of age), and in whites (26 percent, vs. 22 percent for blac ks). Penicillin-resistant isolates were more likely than susceptible isolat es to have a high level of resistance to other antimicrobial agents. Seroty pes included in the 7-valent conjugate and 23-valent pneumococcal polysacch aride vaccines accounted for 78 percent and 88 percent of penicillin-resist ant strains, respectively. Between 1995 and 1998 (during which period 12,04 5 isolates were collected), the proportion of isolates that were resistant to three or more classes of drugs increased from 9 percent to 14 percent; t here also were increases in the proportions of isolates that were resistant to penicillin (from 21 percent to 25 percent), cefotaxime (from 10 percent to 14 percent), meropenem (from 10 percent to 16 percent), erythromycin (f rom 11 percent to 15 percent), and trimethoprim-sulfamethoxazole (from 25 p ercent to 29 percent). The increases in the frequency of resistance to othe r antimicrobial agents occurred exclusively among penicillin-resistant isol ates. Conclusions: Multidrug-resistant pneumococci are common and are increasing. Because a limited number of serotypes account for most infections with dru g-resistant strains, the new conjugate vaccines offer protection against mo st drug-resistant strains of S. pneumoniae. (N Engl J Med 2000;343:1917-24. ) (C) 2000, Massachusetts Medical Society.