AAP issues revised guidelines for the prevention of early-onset group B streptococcal infection – American Academy of Pediatrics
Verna L. Rose
Group B streptococcus (Streptococcus agalactiae) has been a significant cause of perinatal morbidity and mortality for more than two decades. The American Academy of Pediatrics (AAP) has issued new, revised guidelines for the prevention of early-onset group B streptococcal infection. These guidelines appear in the March 1997 issue of Pediatrics. The first AAP guidelines on the prevention of early-onset group B streptococcal infection came out in 1992.
The AAP supports the recently published consensus guidelines from the Centers for Disease Control and Prevention on the prevention of group B streptococcal disease. The AAP statement reviews the selection of pregnant women for intrapartum chemoprophylaxis and the management of their newborns. The statement also covers the rationale for the reassessment of the 1992 AAP guidelines, the epidemiology of the disease, the benefits and adverse effects of chemoprophylaxis, identification of carriers of group B streptococcus, management of newborns and future developments.
According to the AAP policy statement, between 15 and 30 percent of women are vaginal or anorectal carriers of group B streptococcus. Neonatal sepsis caused by the disease is significant, and in 1990, 7,600 cases of infant sepsis caused by group B streptococcus were estimated to occur, resulting in 310 deaths. The AAP reports that early-onset disease (invasive disease with onset during the first week of life) occurs in about 80 percent of cases. In early-onset disease, transmission is from mother to child, either in utero or during birth. Several obstetric factors are listed that are associated with increased risk for early-onset group B streptococcal disease, including giving birth before 37 weeks of gestation, rupture of membranes 18 hours or more before delivery and intrapartum fever.
Rapid diagnosis and treatment are necessary to reduce the morbidity and mortality associated with this disease. Culture is the usual method of diagnosing group B streptococcal infection. Studies have shown that intrapartum chemoprophylaxis provides a significant reduction in vertical transmission group B streptococcus and early-onset neonatal sepsis. The AAP statement notes that the three general methods that have been advocated to select women for intrapartum chemoprophylaxis are: (1) all carriers of group B streptococcus are identified by prenatal culture and given intrapartum prophylaxis; (2) only those carriers with an identifiable risk factor are treated, and (3) all women with an obstetric factor associated with increased risk for neonatal septicemia (without prenatal cultures receive intrapartum prophylaxis. The three approaches are discussed in the statement.
The following recommendations have been excerpted from the AAP statement:
* Physicians should adopt a strategy for the prevention of early-onset group B streptococcal infection in neonates. Patients should be told the available strategies for its prevention. Individual patient requests regarding cultures for group B streptococcus should be honored. Insurance coverage for care should include payment for cultures and nursery observation.
Women found to have symptomatic or asymptomatic group B streptococcal bacteriuria -during pregnancy should be treated at the time of diagnosis. Because such women usually have heavy colonization of group B streptococcus, they also should receive intrapartum chemoprophylaxis.
* Intrapartum chemoprophylaxis should be administered to women who have previously given birth to an infant with invasive group B streptococcal disease. Prenatal culture screening is not necessary.
Prevention Strategy for Early-onset Disease Using Prenatal Culture Screening at 35 to 37 Weeks of Gestation. The AAP recommends that all pregnant women at 35 to 37 weeks of gestation should be routinely screened for anogenital group B streptococcal colonization. All women identified as carriers by culture should be offered intrapartum chemoprophylaxis even if a risk factor is not present.
If the results of group B streptococcal cultures are not known at the onset of labor or rupture of membranes, intrapartum antimicrobial prophylaxis should be administered if gestation is 37 weeks or less, if the membranes have been ruptured 18 hours or longer or if the mother has a temperature of 38 [degrees] C (100.4 [degrees] F) or greater. Oral antimicrobial agents should not be used to treat women who are found to have group B streptococcal colonization during prenatal screening.
Prevention strategy for Early-onset Group B Streptococcal Disease Using Risk Factors Without Prenatal Culture Screening. According to the AAP, a prevention strategy based on the presence of intrapartum risk factors without culture screening (e.g., gestation of 37 weeks or less, duration of membrane rupture of 18 hours or more, or temperature of 38 [degrees] C or more) is an acceptable alternative.
* For intrapartum chemoprophylaxis, the AAP recommends that intravenous penicillin G (5 million units initial and then 2.5 million units every four hours) should be given until delivery. Intravenous ampicillin (2 g initially and then 1 g every four hours until delivery) is an acceptable alternative. Penicillin G is preferred, because it has a narrow spectrum and is therefore less likely to select for antibiotic-resistant organisms. If a woman is allergic to penicillin, intravenous clindamycin or erythromycin may be used.
* Routine use of prophylactic antimicrobial agents for infants born to mothers who have received intrapartum chemoprophylaxis is not recommended by the AAP. However, therapeutic use of these agents is appropriate for infants with clinically suspects sepsis.
* The AAP emphasizes that guidelines regarding management of asymptomatic infants born to women given intrapartum chemoprophylaxis are empiric, and their approach should not be considered an exclusive course of management. Other treatments that take into account individual circumstances and individual physician or institutional preferences may be appropriate.
For asymptomatic infants whose mothers have received intrapartum prophylaxis, those with gestations of less than 35 weeks should have a limited diagnostic evaluation and be observed without antimicrobial therapy in the hospital for at least 48 hours. If during hospital observation signs of systemic infection develop, a complete diagnostic evaluation should be performed, and antimicrobial therapy should be initiated.
In asymptomatic infants with a gestational age of 35 weeks or more, the duration of intrapartum prophylaxis before delivery determines subsequent management. If two or more doses of maternal prophylaxis were given before delivery, no laboratory evaluation or antimicrobial therapy is recommended. These infants should be observed in the hospital for at least 48 hours. If only one dose of maternal prophylaxis was given before delivery, infants should have a limited evaluation and at least 48 hours of observation before they are discharged from the hospital.
The AAP also recommends that further investigations be performed to evaluate and compare the outcomes of these and other strategies.
REFERENCES[1.] American Academy of Pediatrics Committee on Infectious Diseases and Committee on Fetus and Newborn. Guidelines for prevention of group B streptococcal (GBS) infection by chemoprophylaxis. Pediatrics 1992,90:775-8.[2.] Centers for Disease Control and Prevention. Prevention of perinatal group B streptococcal disease: a public health perspective. MMWR 1996;45(RR-7):1-24.
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