Increasing Prevalence of Multidrug-Resistant<i>Streptococcus pneumoniae</i>in the United States

TLDR

The emergence of drug‑resistant bacterial strains complicates treatment decisions and can lead to failures. This study examined invasive pneumococcal disease data from 1995‑1998 in the CDC’s Active Bacterial Core Surveillance program. Researchers defined resistance per NCCLS criteria, analyzed 3,475 of 4,013 invasive Streptococcus pneumoniae isolates from 1998, and assessed resistance levels. In 1998, 24 % of invasive isolates were penicillin‑resistant, with higher rates in Georgia, Tennessee, children under five, and whites; these resistant strains were more likely to be multidrug‑resistant, serotypes covered by the 7‑valent and 23‑valent vaccines accounted for 78 % and 88 % of penicillin‑resistant isolates, and the proportion of isolates resistant to three or more drug classes rose from 9 % to 14 % between 1995 and 1998, underscoring the growing prevalence of multidrug‑resistant pneumococci and the potential protective benefit of current conjugate vaccines.

Abstract

The emergence of drug-resistant strains of bacteria has complicated treatment decisions and may lead to treatment failures.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.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.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.