Streptococcal Invasive Disease Group B, 2009

Four hundred fifty-four cases of invasive group B streptococcal disease (8.7 per 100,000 population), including 25 deaths, were reported in 2009. These cases were those in which group B Streptococcus (GBS) was isolated from a normally sterile site. This represents the largest number of GBS cases reported since surveillance was initiated in 1995.

By age group, annual incidence was highest among infants <1 year of age (53.0 per 100,000 population) and those aged 70 years or older (33.7 per 100,000). Twenty-one (84%) of the 25 case-deaths were among those age 65 years and older. Fifty-five percent of cases were residents of the metropolitan area. Bacteremia without a focus of infection occurred most frequently (45% of cases), followed by cellulitis (15%), osteomyelitis (9%), pneumonia (8%), septic arthritis (5%), and meningitis (2%). The majority (76%) of cases had GBS isolated from blood; other isolate sites included joint fluid (9%) and bone (9%).

Forty-three cases were infants or pregnant women (maternal cases), compared to 45 cases in 2008. Sixteen infants developed early-onset disease (occurred within 6 days of birth [0.22 cases per 1,000 live births]), and 21 infants developed late-onset disease (occurred at 7 to 89 days of age [0.29 cases per 1,000 live births]). One stillbirth/spontaneous abortion was associated with six 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, MDH reviewed the maternal charts for all 16 early-onset cases reported during 2009. Overall, 12 (75%) of 16 women who delivered GBS-positive infants underwent prenatal screening for GBS. Of these, 6 (50%) were positive, 5 (42%) negative, and 1 (8%) had an unknown result. Two of the four women who did not receive prenatal screening were screened upon admission to the hospital and prior to delivery. Among the 16 women who delivered GBS-positive infants, five (32%) received intrapartum antimicrobial prophylaxis (IAP). Of the six women with a positive GBS screen, three (50%) received IAP. Of the three women with a positive GBS screen who did not receive IAP, two (67%) refused 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, 2009