Streptococcus pneumoniae Invasive Disease, 2007

Statewide active surveillance for invasive Streptococcus pneumoniae (pneumococcal) disease began in 2002, expanded from the metropolitan area, where active surveillance has been ongoing since 1995. In 2007, 664 (12.9 per 100,000 population) cases of invasive pneumococcal disease were reported. By age group, annual incidence rates per 100,000 were 30.3 cases among children aged 0-4 years; 3.7 cases among children and adults aged 5-39 years, 12.9 cases among adults 40-64 years, and 40.0 cases among adults aged 65 years and older.

In 2007, pneumonia accounted for 381 (57%) cases of invasive pneumococcal disease among all cases (i.e., those infections accompanied by bacteremia or isolation of pneumococci from another sterile site such as pleural fluid). Bacteremia without another focus of infection accounted for 206 (31%) cases statewide. Pneumococcal meningitis accounted for 38 (6%) cases. Sixty-one (9%) patients with invasive pneumococcal disease died.

In 1999, the year before the pediatric pneumococcal conjugate vaccine (Prevnar, Wyeth-Lederle [PCV-7]) was licensed, the rate of invasive pneumococcal disease among children < 5 years in the metropolitan area was 111.7 cases/100,000. Over the years 2000-02 there was a major downward trend in incidence in this age group (Figure 4). Rates in each of the subsequent four years were somewhat higher, although there has not been a continuing upward trend (25.8 cases/100,000 in 2003; 29.0, 27.4, and 23.3, and 30 cases/100,000 in 2004, 2005, 2006, and 2007, respectively (Figure 4). Based on the distribution of serotypes among isolates from these cases, this increase was limited to disease caused by non-vaccine serotypes (i.e. serotypes other than the seven included in PCV-7) [Figure 4]). This small degree of replacement disease due to non-PCV-7 serotypes, similar to that seen in other parts of the country, has been far outweighed by the declines in disease caused by PCV-7 serotypes. This trend supports the need for ongoing monitoring, however, because further increases due to non-vaccine serotypes are possible. In Figure 4 rates of invasive pneumococcal disease among adults aged > 65 years are also shown by serotypes included and not included in PCV-7. Declines in incidence in this age group, particularly in disease due to PCV-7 serotypes, have been observed elsewhere in the United States and are likely attributable to herd immunity from use of PCV-7 among children. Among cases overall, a serotype not included in the PCV-7 vaccine, serotype 19A, is now most commonly associated with invasive pneumococcal disease in Minnesota.

Of the 615 isolates submitted for 2007 cases, one (<1%) isolate was resistant to penicillin and 40 (6%) exhibited intermediate-level resistance using nonmeningitis breakpoints (Note: CLSI penicillin breakpoints changed in 2008; refer to the MDH antibiogram on pp. 25-26); 96 isolates (16%) exhibited multi-drug resistance (i.e., high-level resistance to two or more antibiotic classes).

• For up to date information see>> Streptococcus pneumoniae (Pneumococcal Disease)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2007