Epidemiology of Invasive Group B Streptococcal Disease in the United States
Abstract & Commentary
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine, Section Editor, HIV, is Associate Editor for Infectious Disease Alert.
Synopsis: In an active population-based surveillance study conducted between 1999 and 2005 in 10 states, 14,573 cases of invasive group B streptococcal (GBS) disease were identified. The incidence of invasive GBS among infants from birth through 6 days of age decreased; incidence remained stable in infants aged 7-89 days and in pregnant women. Among persons 15 years of age or older, the incidence of invasive GBS also increased during the period of the study. All 4882 isolates for which antimicrobial susceptibility test results were available, remained susceptible to penicillin, ampicillin, and vancomycin, though some were resistant to erythromycin and clindamycin respectively.
Source: Phares CR, et al. Epidemiology of invasive group B streptococcal disease in the United States, 1999-2005. JAMA. 2008;299:2056-2065.
This active, population-based, surveillance study was conducted by the CDC, in collaboration with state health departments and universities in 10 states participating in the Active Bacterial Core Surveillance (ABCs)/Emerging Infections Program Network. Neonatal cases were categorized as early onset if GBS was isolated from infants younger than 1 week and as late onset if infants were 7-89 days old.
From 1999-2005, surveillance identified 14,573 cases of invasive GBS disease. Age groups included: early-onset neonatal (1232 with 83 deaths), late-onset neonatal (1036 with 48 deaths), children 90 days-12 months (143 with 4 deaths), 1-14-years-old (90 with 11 deaths), 15-64-years-old (6496 with 472 deaths), ≥ 65-years-old (5576 with 730 deaths).
Among 2056 case individuals identified in 2005, 54% were white, 28% were black, 2% were Asian/Pacific Islander, < 2% were Native American, and 14% were of unknown race. Incidence of invasive GBS was 12.8/100,000 among blacks, 6.5/100,000 for whites, and 5.1/100,000 for other races combined. Overall incidence among blacks was two times higher than among whites. Also, the proportion of patients who died, among individuals with early onset neonatal infection and in patients > 45-years-old, was significantly higher for blacks than whites.
In this study, 1232 cases of early-onset disease were identified. After the 2002 release of early-onset GBS disease prevention guidelines (which utilize antepartum screening of the mother and intrapartum administration of parenteral penicillin), disease incidence decreased 27%, from 0.47/1000 live births to 0.34/1000. Interestingly, small increases in the incidence of early-onset GBS disease occurred in 2004 and 2005, with the incidence being 0.52/1000 in 2003 to 0.89/1000 in 2005. This increase was driven primarily by black infants. The most common syndromes seen in early-onset disease were non-focal bacteremia (83%), pneumonia (9%), and meningitis (7%). Of the 1036 cases of late-onset disease, median age at first positive culture was 37 days. Meningitis was more common (27%) than in the early-onset disease group. The risk of death for pre-term infants was more than three times that of term infants. Only 233 cases of invasive GBS infection were identified in children (90 days-14 years). Of children > 1 year of age, underlying conditions (including neurologic disorders, immunosuppression, cancer, asthma, and renal disease) were present in 44%.
There were 6087 cases of invasive GBS infection identified in adults 15-64-years-old and 5576 among those older than 65. Among adults aged 15-64, the incidence increased from 3.4/100,000 population in 1999 to 5.0/100,000 in 2005. Among patients older than 65, the incidence increased from 21.5 to 26.0/100,000. The most common clinical syndromes among all 11,663 adults were bacteremia without focus (48%), bacteremic cellulitis (22%), pneumonia (11%), osteomyelitis (9%), arthritis (9%), peritonitis (3%), and abscess (3%). Underlying conditions included diabetes (41%), heart disease (36%), and malignancy (17%).
Serotype distribution for early-onset neonatal disease revealed a predominance of serotypes Ia, III, V, and II. In late-onset disease serotype III accounted for half the cases followed by Ia and V. In non-pregnant pediatric and adult cases, serotype V predominated, followed by Ia, II, and III. All 4882 isolates submitted for susceptibility testing were susceptible to penicillin, ampicillin, and vancomycin; 32% were resistant to erythromycin and 15% were resistant to clindamycin.
Commentary
This is an important review of a major clinical problem. Some insights from this study include the demonstration that black Americans of all ages bear a disproportionate burden of cases of invasive GBS infection. The reasons for this are unclear. While intrapartum prophylaxis appears to have reduced the incidence of early-onset infection, this strategy will have little effect in preventing infection in children of women who go into pre-term labor. Further development and use of a pentavalent conjugate vaccine, including the most common serotypes, could potentially prevent up to 96% of neonatal disease and 88% of pediatric and adult disease. The large number of cases in adults was surprising to me, and seems largely reflective of the increased numbers of aging adults with diabetes and other underlying conditions. Despite increased use of prophylactic penicillin, it was reassuring that isolates have retained susceptibility to penicillin over time. However, the identification of the large proportion of isolates with reduced susceptibility to erythromycin and clindamycin highlight the importance of susceptibility testing of isolates obtained from pregnant women who are at risk for penicillin anaphylaxis before administration of erythromycin or clindamycin for intrapartum prophylaxis.
This active, population-based, surveillance study was conducted by the CDC, in collaboration with state health departments and universities in 10 states participating in the Active Bacterial Core Surveillance (ABCs)/Emerging Infections Program Network.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content