Streptococcal Invasive Disease Group B, 2011

Five hundred thirty-five cases of invasive group B streptococcal disease (10.1 per 100,000 population), including 25 deaths, were reported in 2011. These cases were those in which group B Streptococcus (GBS) was isolated from a normally sterile site. The largest number of GBS cases reported since surveillance was initiated in 1995 was 454, reported in 2009.

By age group, annual incidence was highest among infants <1 year of age (52.2 per 100,000 population) and those aged 70 years or older (39.1 per 100,000). Sixteen (64%) of the 25 deaths were among those age 65 years and older. Fifty-four percent of cases were residents of the metropolitan area. Bacteremia without a focus of infection occurred most frequently (25% of infections), followed by cellulitis (23%), osteomyelitis (13%), septic arthritis (7%), pneumonia (7%), and meningitis (2%). The majority (70%) of cases had GBS isolated from blood; other isolate sites included bone (14%) and joint fluid (11%).

Thirty-five cases were infants or pregnant women (maternal cases), compared to 52 cases in 2010. Twentyone infants developed early-onset disease (occurred within 6 days of birth [0.31 cases per 1,000 live births]), and 11 infants developed late-onset disease (occurred at 7 to 89 days of age [0.16 cases per 1,000 live births]). One stillbirth/spontaneous abortion was associated with 1 of 3 maternal GBS infections.

Since 2002, there has been a recommendation for universal prenatal screening of all pregnant women at 35 to 37 weeks gestation. In light of this, we reviewed the maternal charts for all early-onset cases reported in 2011. Overall, 12 (57%) of 21 women who delivered GBS-positive infants underwent prenatal screening for GBS. Of these, 5 (42%) were positive, 6 (50%) negative, and 1 (8%) had an unknown result. Two of the seven women who did not receive prenatal screening were screened upon admission to the hospital and prior to delivery. Of the two women for whom it was unknown if they received prenatal screening, one was screened upon admission to the hospital and prior to delivery. Among the 21 women who delivered GBS-positive infants, 11 (52%) received intrapartum antimicrobial prophylaxis (IAP). Of the five women with a positive GBS screen, four (80%) received IAP.

• For up to date information see: Group B Streptococcus (GBS)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2011