Streptococcus pneumoniae Invasive Disease, 2006

Statewide active surveillance for invasive Streptococcus pneumoniae (pneumococcal) disease began in 2002, expanding from the metropolitan area, where active surveillance has been ongoing since 1995. In 2006, 635 cases (12.4 per 100,000) of invasive pneumococcal disease were reported. By age group, annual incidence rates per 100,000 were 22.4 among children aged 0-4 years; 4.0 among children and adults aged 5-39 years; 12.5 among adults 40-64 years; and 40.1 among adults aged 65 years and older.

In 2006, pneumonia accounted for 357 (56%) 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 196 (31%) cases statewide. Pneumococcal meningitis accounted for 32 (5%) cases. Seventy patients (11%) 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 of age 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 4 years were somewhat higher, although there has not been a continuing upward trend (25.8 cases per 100,000 in 2003; 29.0, 27.4, and 23.3 cases per 100,000 in 2004, 2005, and 2006, 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 because further increases due to non-vaccine serotypes are possible. In Figure 4 rates of invasive pneumococcal disease among adults aged >65 years are 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 578 isolates submitted in 2006, 46 (8%) were highly resistant to penicillin and 66 (11%) exhibited intermediate-level resistance; 86 (15%) exhibited multi-drug resistance (i.e., high-level resistance to two or more drug classes). S. pneumoniae is one of several pathogens included in the MDH Antibiogram (see pp. 24-25), which gives detailed antimicrobial susceptibility results of isolates tested at the Public Health Laboratory from 2006 cases, and is available to download on the MDH website at: Antibiogram.

• For up to date information see>> Streptococcus pneumoniae (Pneumococcal Disease)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2006