Streptococcal Invasive Disease - Group B, 2000

Two hundred ninety-four cases (6.0 per 100,000 population) of Group B streptococcal invasive disease (including 17 deaths) were reported in 2000. These cases included only those in which group B Streptococcus (GBS) was isolated from a normally sterile site, in addition to nine cases involving a miscarriage or stillbirth in which placenta was the site of disease. Sixty percent of cases occurred among residents of the Twin Cities metropolitan area. Fifty-seven (19%) cases were infants less than 1 year of age, and 126 (43%) cases were 60 years of age or older.

Overall, 156 (53%) cases presented with bacteremia without another focus of infection. The other most common types of infection were cellulitis (11%), pneumonia (6%), osteomyelitis (4%), arthritis (4%), and meningitis (4%). A majority (68%) of cases had GBS isolated from blood only.

There were 71 cases of infant (early-onset or late-onset) or maternal GBS disease, compared to 53 such cases in 1999. Thirty-three infants developed invasive disease within the first 6 days following birth (i.e., early-onset disease), and 23 infants became ill at 7 to 89 days of age (i.e., late-onset disease). Ten stillbirths and spontaneous abortions were associated with 15 maternal invasive GBS infections.

In May 1996, the CDC, the American College of Obstetricians and Gynecologists, and the American Academy of Pediatrics published guidelines which urged providers to take either a screening-based or risk-based approach to determine use of intrapartum antibiotic prophylaxis (IAP) for the prevention of perinatal GBS disease (MMWR; vol. 45, May 31, 1996;). If a screening-based approach is used, vaginal/rectal cultures should be obtained at 35-37 weeks gestation and cultured using a selective broth medium.

From 1997 to 2000, 1,082 cases of GBS invasive disease were reported; 825 (76%) were adult non-maternal, 120 (11%) were early-onset, 79 (7%) were late-onset, 54 (5%) were maternal, and 4 (< 1%) were among children 90 days to 14 years of age. Medical charts were reviewed for all 120 women in Minnesota whose infant developed early-onset GBS disease. These included 34 women in 1997, 28 in 1998, 25 in 1999, and 33 in 2000. The infants included 61 females and 59 males. Sixty-five percent of cases were white, 6% were black, 5% were other races, and 24% were of unknown race. Four (3%) 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 (14%) and meningitis (5%).

Thirty-three (28%) of these 120 women were screened prenatally for GBS; 12 were positive (and seven of these women received IAP), 19 were GBS negative, and two had unknown results. Among women who were GBS negative, up to 89% may have been screened inappropriately with either documentation of the wrong site or wrong time in gestation, or no documentation of site and time. Twenty-seven (23%) of these 120 women had at least one documented GBS risk factor (gestation <37 weeks - 20; intrapartum fever - 7; rupture of membranes at ≥18 hours - 7; GBS bacteriuria - 5). Overall, 18 (15%) of the 120 women received IAP. Only 15 (48%) of 31 women who had a positive screening results or were not screened and had at least one GBS risk factor received IAP (50% in 1997, 33% in 1998, 50% in 1999, and 55% in 2000).

Providers are urged to review consensus guidelines for the prevention of perinatal GBS disease. Additional information, including a laboratory protocol on the prevention of perinatal GBS disease, can be found on the following website: MMWR: Prevention of Perinatal Group B Streptococcal Disease: A Public Health Perspective.

• For up to date information see: Group B Streptococcus (GBS)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2000