Streptococcus pneumoniae Invasive Disease, 2008

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 2008, 712 (13.7 per 100,000 population) cases of invasive pneumococcal disease were reported. By age group, annual incidence rates per 100,000 were 23.7 cases among children aged 0-4 years; 3.9 cases among children and adults aged 5-39 years, 15.5 cases among adults 40-64 years, and 41.1 cases among adults aged 65 years and older.

In 2008, pneumonia accounted for 409 (57%) cases of invasive pneumococcal disease among all cases (ie, 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 221 (31%) cases statewide. Pneumococcal meningitis accounted for 35 (5%) cases. Sixty-three (9%) case-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 per 100,000. Over the years 2000-2002 there was a major downward trend in incidence in this age group (Figure 5). 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, 23.3, 30 and 27.8 cases per 100,000 each year from 2004-2008, respectively) (Figure 5). Based on the distribution of serotypes among isolates from these cases, this increase was limited to disease caused by non-vaccine serotypes (ie, serotypes other than the seven included in PCV-7 [Figure 5]). 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 5, 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 7F, is now most commonly associated with invasive pneumococcal disease in Minnesota. However, this serotype as well as five other serotypes are included in a 13-valent conjugate vaccine now awaiting licensure.

Of the 659 isolates submitted for 2008 cases, 5 (1%) isolates were resistant to penicillin and 32 (5%) exhibited intermediate-level resistance using nonmeningitis breakpoints (Note: CLSI penicillin breakpoints changed in 2008; refer to the MDH antibiogram for details on pp 28-29); 110 isolates (17%) exhibited multi-drug resistance (ie, high-level resistance to two or more antibiotic classes).

Figure 4. Invasive Pneumococcal Disease Incidence Among Children <5 and Adults >65 years of Age, by Year and Serotype, Twin Cities Metropolitan Area, 1999-2008

Updated Friday, 19-Nov-2010 15:16:32 CST