We examined data on invasive
pneumococcal disease in patients identified from 1995 to 1998 in the Active Bacterial Core Surveillance program of the Centers for Disease Control and Prevention. Pneumococci that had a high level of resistance or had intermediate resistance according to the definitions of the National Committee for Clinical Laboratory Standards were defined as "resistant" for this analysis.
RESULTS: During 1998, 4013 cases of invasive Streptococcus pneumoniae disease were reported (23 cases per 100,000 population); isolates were available for 3475 (87 percent). Overall, 24 percent of isolates from 1998 were resistant to
penicillin. The proportion of isolates that were resistant to
penicillin was highest in Georgia (33 percent) and Tennessee (35 percent), in children under five years of age (32 percent, vs. 21 percent for persons five or more years of age), and in whites (26 percent, vs. 22 percent for blacks).
Penicillin-resistant isolates were more likely than susceptible isolates to have a high level of resistance to other
antimicrobial agents. Serotypes included in the 7-valent conjugate and 23-valent pneumococcal
polysaccharide vaccines accounted for 78 percent and 88 percent of
penicillin-resistant strains, respectively. Between 1995 and 1998 (during which period 12,045 isolates were collected), the proportion of isolates that were resistant to three or more classes of drugs increased from 9 percent to 14 percent; there also were increases in the proportions of isolates that were resistant to
penicillin (from 21 percent to 25 percent),
cefotaxime (from 10 percent to 15 percent),
meropenem (from 10 percent to 16 percent),
erythromycin (from 11 percent to 16 percent), and
trimethoprim-sulfamethoxazole (from 25 percent to 29 percent). The increases in the frequency of resistance to other
antimicrobial agents occurred exclusively among
penicillin-resistant isolates.
CONCLUSIONS: Multidrug-resistant pneumococci are common and are increasing. Because a limited number of serotypes account for most
infections with
drug-resistant strains, the new
conjugate vaccines offer protection against most
drug-resistant strains of S. pneumoniae.