Streptococcal Invasive Disease - Group B, 2001

Two hundred seventy-three cases of Group B streptococcal invasive disease (5.5 per 100,000 population), including 19 deaths, were reported in 2001. These cases included those in which group B Streptococcus (GBS) was isolated from a normally sterile site, in addition to six cases involving a miscarriage or stillbirth in which placenta was the site of disease.

Overall, 118 (43%) cases presented with bacteremia without another focus of infection. The other most common types of infection were cellulitis (12%), arthritis (8%), osteomyelitis (6%), pneumonia (5%), and meningitis (5%). The majority (72%) of cases had GBS isolated from blood only. Fifty-two percent of cases occurred among residents of the seven-county Twin Cities metropolitan area. Forty-five (16%) case-patients were infants less than 1 year of age, and 110 (40%) were 60 years of age or older.

Fifty-three cases of infant (early-onset or late-onset) or maternal GBS disease were reported, compared to 71 cases in 2000. Twenty-two infants developed invasive disease within 6 days following birth (i.e., early-onset disease), and 17 infants became ill at 7 to 89 days of age (i.e., late-onset disease). Eight stillbirths or spontaneous abortions were associated with 14 maternal invasive GBS infections.
From 1997 to 2001, 1,355 cases of GBS invasive disease were reported; 1,034 (76%) were adult non-maternal; 142 (10%) were early-onset; 96 (7%) were late-onset; 69 (5%) were maternal; and 14 (1%) were among children 90 days to 14 years of age. During this time period, 142 women had infants who developed early-onset GBS disease. Sixty-five percent of case-patients were white, 6% were black, 10% were other races, and 25% were of unknown race. Seven infants died. Twenty infants born at less than 37 weeks gestation accounted for 17% of early-onset cases. Bacteremia without focus (80%) was the most common type of infection, followed by pneumonia (15%) and meningitis (7%).

In 1996, CDC, the American Academy of Pediatrics, and the American College of Obstetricians and Gynecologists released consensus guidelines urging prenatal care providers to use risk-based or screening-based approaches to prevent perinatal GBS disease.1 In light of these guidelines, MDH reviewed the maternal charts for 140 (99%) of 142 early-onset cases. Thirty-eight (27%) women had prenatal screening for GBS; of these, 13 (34%) were positive, 23 (61%) were negative, and two (5%) had an unknown result. Among those who were screened, 85% either did not receive screening for vaginal and rectal sites at greater than 34 weeks gestation or did not have documentation of the site or date of screening. Overall, 16% of mothers of infants with invasive GBS disease received intrapartum antimicrobial prophylaxis (IAP). For women with risk factors and positive GBS cultures, regardless of site and date, 67% received IAP. Among women with risk factors and unknown or negative cultures, 30% received IAP, and 56% of women with no risk factor and a GBS-positive culture were given IAP.

In August 2002 the Perinatal Group B Streptococcal (GBS) MMWR: Disease Prevention guidelines were revised. Key changes from the 1996 guidelines include the recommendation for universal prenatal screening for all pregnant women at 35-37 weeks gestation, as well as updated prophylaxis regimens for women with penicillin allergy.2

References:
1. Centers for Disease Control and Prevention. Prevention of perinatal group B streptococcal disease: a public health perspective; MMWR 1996; 45: (RR-7)1-24.
2. Centers for Disease Control and Prevention. Prevention of perinatal group B streptococcal disease, revised guidelines from CDC. MMWR 2002; 51: (RR-11)1-23.

• For up to date information see: Group B Streptococcus (GBS)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2001