The 1997 AAP guidelines for prevention of early-onset group B streptococcal disease. American Academy of Pediatrics

Comparison of selective and nonselective enrichment broth media for the detection of vaginal and anorectal colonization with group B streptococcus

The use of a selective enrichment broth medium has been widely recommended to optimize the recovery of group B streptococci (GBS) from genital and anorectal samples. Because selective antibiotic-containing versions of broth media are significantly more expensive than their nonselective parent formulations, we sought to examine whether the use of the nonselective Todd-Hewitt broth (THB) could accomplish comparable recovery of GBS to the recommended, selective version of this medium (Lim broth). During the study, vaginal and anorectal swab samples submitted to our laboratory for GBS culture were all inoculated onto Columbia colistin-nalidixic acid agar (CNA) and into either THB or Lim broth (alternated on a weekly basis). During the 45-week study period, 1200 samples (600 in each study arm) were evaluated. GBS were recovered from 164 samples (27.3%) in the Lim arm of the study, of which 60 (36.7%) were positive only on subculture of broths. In the THB study arm, 161 samples (26.8%) yielded GBS, of which 58 (36.0%) were positive only in broths. This study conclusively demonstrates that a nonselective enrichment broth media provides comparable sensitivity to the recommended selective broth for detection of GBS colonization during pregnancy.

Group B streptococcal infections in newborns

Group B streptococcus (GBS) is the most common cause of neonatal infection in North America and is associated with morbidity and mortality. Prompt recognition and treatment of the infection is imperative. Diagnostic tests and treatment options vary, without clear research-based recommendations. Future trends should focus on GBS infection as a public health issue, with an emphasis on prevention.

Risk factors for early-onset group B streptococcal sepsis: estimation of odds ratios by critical literature review

OBJECTIVE

To identify and to establish the prevalence of ORs factors associated with increased risk for early-onset group B streptococcal (EOGBS) infection in neonates. streptococcal (EOGBS) infection in neonates.

STUDY DESIGN

Literature review and reanalysis of published data.

RESULTS

Risk factors for EOGBS infection include group B streptococcal (GBS)-positive vaginal culture at delivery (OR: 204), GBS-positive rectovaginal culture at 28 (OR: 9.64) or 36 weeks gestation (OR: 26. 7), vaginal Strep B OIA test positive at delivery (OR: 15.4), birth weight </= 2500 g (OR: 7.37), gestation <37 weeks (OR: 4.83), gestation <28 weeks (OR: 21.7), prolonged rupture of membranes (PROM) >18 hours (OR: 7.28), intrapartum fever >37.5 degrees C (OR: 4.05), intrapartum fever, PROM, or prematurity (OR: 9.74), intrapartum fever or PROM at term (OR: 11.5), chorioamnionitis (OR: 6.43). Chorioamnionitis is reported in most (88%) cases in which neonatal infection occurred despite intrapartum maternal antibiotic therapy. ORs could not be estimated for maternal GBS bacteriuria during pregnancy, with preterm premature rupture of membranes, or with a sibling or twin with invasive GBS disease, but these findings seem to be associated with a very high risk. Multiple gestation is not an independent risk factor for GBS infection.

CONCLUSIONS

h Mothers with GBS bacteriuria during pregnancy, with another child with GBS disease, or with chorioamnionitis should receive empirical intrapartum antibiotic treatment. Their infants should have complete diagnostic evaluations and receive empirical treatment until infection is excluded by observation and negative cultures because of their particularly high risk for EOGBS infection. Either screening with cultures at 28 weeks gestation or identification of clinical risk factors, ie, PROM, intrapartum fever, or prematurity, may identify parturients whose infants include 65% of those with EOGBS infection. Intrapartum screening using the Strep B OIA rapid test identifies more at-risk infants (75%) than any other method. These risk identifiers may permit judicious selection of patients for prophylactic interventions.

Characterization of the triage process in neonatal intensive care

OBJECTIVE

Despite intense interest in allocation of resources to neonatal intensive care, no description exists of resource use by the large numbers of newborns admitted for triage, the process of short-term evaluation and management of infants after delivery. This study characterized the triage phase of neonatal care with respect to infant demographics, risk factors for illness, and the course of the hospital admission. We hypothesized that triage infants were responsible for a significant fraction of total intensive care resource utilization, and that patterns of use were predictable.

DESIGN

Cross-sectional cost analysis of prospectively collected data.

PARTICIPANTS

Data were collected prospectively on 2486 inborn infants admitted to two neonatal intensive care units (NICUs) for <24 hours and subsequently discharged to routine care. Over the 11-month study period, these two hospitals delivered 15 097 live births and admitted a further 1837 infants for nontriage NICU care.

INTERVENTIONS

On a 50% random subsample, we calculated severity of illness using the Score for Neonatal Acute Physiology (SNAP) and applied a NICU resource checklist. Daily NICU workload was estimated according to the number and labor intensity of NICU admissions using Medicus and SNAP. Charges were obtained from patient-level item charge records and converted to costs using Medicare ratios of costs to charges. Length of stay (LOS) and costs for triage were correlated with diagnoses, perinatal descriptors, severity of illness, and markers of concurrent NICU workload using stepwise regression.

RESULTS

Mean birth weight for triage infants was 3367 g (standard deviation, 600 g) and mean gestational age 39.1 weeks (standard deviation, 1.8 weeks). The predominant reasons for evaluation were exclusion of sepsis (34%), birth complications including meconium aspiration, perinatal depression and trauma (24%), and transitional respiratory distress (23%). Severity illness, as measured by SNAP, was minimal, with 70% having scores of 0, indicating no derangement. Only 6% experienced depressed 5-minute Apgar scores (<7), and 80% required no delivery room resuscitation. The most frequent forms of resource use were antibiotic administration (34%), placement of a peripheral intravenous line (40%), cardiac monitoring (53%) and external warming (26%). Median LOS was 102 minutes, corresponding over the study period to 2% of total NICU hours but 7% of NICU days charged. Median cost was $870, with aggregate costs accounting for a total of 9.5% of total NICU costs. In the multivariate model, LOS was increased by respiratory diagnosis or hypoglycemia, severity of illness, lower gestational age, the need for intravenous placement, daytime shift, hospital, and lower acuity of concurrent NICU admissions (R2 = 0.24).

CONCLUSIONS

Neonatal triage is a low-acuity but time-intensive process that contributes significantly to total resource use by newborns because of the large numbers of infants involved. Both LOS and costs are affected not only by infant medical characteristics but also by nonmedical markers of unit structure, which may be amenable to change. This source of resource consumption should be recognized in future assessments of costs associated with neonatal intensive care.

Epidemiology of group B streptococcal disease in the United States: shifting paradigms

Since its emergence 25 years ago, group B streptococcus has become recognized as a cause of serious illness in newborns, pregnant women, and adults with chronic medical conditions. Heavy colonization of the genital tract with group B streptococcus also increases the risk that a woman will deliver a preterm low-birthweight infant. Early-onset infections (occurring at < 7 days of age) are associated with much lower fatality than when they were first described, and their incidence is finally decreasing as the use of preventive antibiotics during childbirth increases among women at risk. New serotypes of group B streptococcus have emerged as important pathogens in adults and newborns. Clinical and laboratory practices--in obstetrics, pediatrics, and clinical microbiology--have an impact on disease and/or its prevention, and protocols established at the institutional level appear to be critical tools for the reduction of perinatal disease due to group B streptococcus. Since intrapartum antibiotics will prevent at best only a portion of the full burden of group B streptococcal disease, critical developments in vaccine evaluation, including study of polysaccharide-protein conjugate vaccines, offer the potential for enhanced prevention in the relatively near future.

Concepts and controversies in the management of group B streptococcus during pregnancy

BACKGROUND

Group B beta-hemolytic streptococcus colonizes 20 percent of pregnant women. Intrapartum fetal colonization leads to invasive disease in 1 to 2 infants of every 1000 births in the United States, and has a mortality of approximately 6 percent. Several protocols using intrapartum chemoprophylaxis have been devised to improve management of the disease, but confusion continues about details and implementation. This review examined the clinical issues, current management protocols, and advantages and disadvantages of these protocols for group B streptococcus.

METHODS

We reviewed the literature and described the epidemiology, detection methods, risk factors, neonatal disease potential of group B streptococcus, and the historical development of management protocols. Two current alternatives, the American College of Obstetricians and Gynecologists' risk-based protocol and the Centers for Disease Control and Prevention's screening-based protocol, are described and compared.

RESULTS

The risk-based protocol does not entail antepartum screening, but treats women with certain risk factors during labor. The screening-based protocol includes cultures at 35 to 37 weeks' gestation, and offers intrapartum prophylaxis to all women with positive cultures. Uncultured women with risk factors are treated. Both protocols involve high rates of intrapartum antibiotic use and both may significantly lower rates of neonatal group B streptococcus sepsis (screening-based more than risk-based for both). The risk-based approach is simpler than the screening-based approach.

CONCLUSIONS

Practitioners should select one of the two protocols and use it consistently. The differences in efficacy are small; a practitioner may not see a difference in outcomes over the course of his or her career, although more antibiotics will be administered using the screening-based approach.