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Group B Streptococcus

An overview of risk factors, screening, and treatment for moms and babies

Erin Burnette, FNPFebruary 2011

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What is Group B Strep (GBS)?A bacteria that is often found in the GI

tract that can colonize the vagina in some women

Colonization can be transient.

Gram positive

Also known as Streptococcus agalactiae

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GBS and pregnancyGBS in pregnancy can cause miscarriage,

endometritis, bacteremia, and chorioamnionitis.

GBS infection can also affect the baby leading to still birth, prematurity, or invasive neonatal disease.

Because of these potential consequences, pregnant women are screened prenatally.

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TransmissionInfants can acquire GBS from the mother

through vertical transmission from the vagina during labor.

GBS can be transmitted through intact membranes but this is not common.

The infant can become sick from GBS, or become colonized and remain healthy.

Aspirating GBS into fetal lungs can lead to bacteremia.

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Universal Screening Universal culture based screening has

been shown to be more effective than risk based screening.

Testing is done between 35-37 weeksVaginal and rectal areas are swabbedIf a woman had GBS UTI during

pregnancy, culture may not be done as she automatically would be treated as GBS +.

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Neonatal Early Onset GBS infection

May cause pneumonia, sepsis, meningitisOnset usually within 24 hours (60-70%)32% of cases identified between 24-48h.<8% of cases identified after 48 hours.Rapid clinical decline common

with early onset disease.Incidence: 0.4 per every 1000 live births.

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Signs/Symptoms of sepsisUsually general,

nonspecific, and nonlocalizing:

Temperature instability

Respiratory distressLethargyFeeding problemsJaundice Apnea

Some symptoms can be more severe:

PurpuraSeizures

90% of babies show symptoms within 24 hours of life.

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At Risk?Presence of certain risk factors make

infants at higher risk of GBS infection.Gestational age <37 weeks, ROM >18

hours, intraamniotic infection, young mothers, black race, and previous infant with invasive disease.

Low levels of maternal GBS antibody may also be a risk factor.

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Infants Immature Immune system

Limitations in neutrophil productionImpaired/immature neutrophils don’t

function properlyMore likely to exhaust marrow reserves if

stressed, such as in sepsisPreterm infants have less vernix, which

has been shown to play a role in host defense

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LabsCBC drawn early in life may not always be

helpful in determining risk of sepsis.Blood cultures can be helpful. Studies

have shown median time for a blood culture to become positive with GBS: 9.3 hours. Positive with other organisms: 19.8 hours.

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Late Onset GBS infectionMay present between 1-3 months of life.

Often presents as bacteremia or meningitis.

Not seen in the newborn nursery period due to timing of onset.

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Complications of GBS infectionGBS infection can lead to developmental

delay, blindness, deafness, as well as other neurological impairments.

GBS can also lead to death. Risk of death is generally inversely related to gestational age and birth weight.

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Maternal Treatment Recommendations

Intrapartum antibiotic treatment given intravenously can reduce risk of vertical transmission.

Goal: Reach adequate circulating levels of the antibiotic in maternal and fetal circulation without reaching toxic levels.

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Intrapartum Antibiotic Therapy…Moms in labor should get IV antibiotics if:

1. + GBS culture late in gestation.2. Unknown GBS status delivering before 37 weeks.3. ROM >18 hours4. Previous infant with GBS disease5. GBS bacturia during pregnancy6. Maternal temp of 100.4/38 ̊�

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…Intrapartum Antibiotic TherapyGBS is susceptible to Penicillin and

AmoxicillinIf mom has a mild PCN allergy, may use

CefazolinIf mom has a history of anaphylactic type

reaction to PCN, may use Clindamycin or Vancomycin

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What About??C/S prior to labor onset with intact

membranes?Risk of vertical transmission very

low.Routine screening still indicated in case ROM or labor starts before c/s.If no risk factors, intrapartum

antibiotics not necessarily indicated.

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Adequacy of TreatmentIn order to be deemed “adequate

treatment”:1. IV administration of a beta

lactam antibiotic (such as PCN 5mu) at least 4 hours prior to delivery.

2. Continue maintenance dosing q4 hours until delivery (such as PCN

3mu)3. Antibiotic given was PCN,

ampicillin, or cefazolin

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What do we do in the nursery?Suggestions from the new 2010 CDC guidelines

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New CDC algorithms, click link for: Indications for intrapartum antibiotics and Treatment of the infant

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Newborn Nursery GBS Algorithm

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Treatment of the infant: signs of sepsis present

These infants need a full diagnostic workup (CBC & blood culture, and a CXR if respiratory distress is significant, and LP if condition warrants).

Antibiotics should be started and continued until results of evaluation are complete.

IV ampicillin and gram – coverage, often gentamicin.

These infants most often go to NICU.

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Treatment of the Infant: maternal diagnosis of chorioamnionitis:

S/Sx of “chorio”: maternal fever, uterine tenderness, maternal or fetal tachycardia, foul/purulent amniotic fluid.

These infants should undergo a limited diagnostic evaluation (CBC and blood culture).

Give antibiotics pending results of the culture.

Observe for 48 hours.

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Treatment of the Infant: well appearing w/ inadequate maternal abxIt can be appropriate to monitor the

infant clinically for signs of sepsis. Well appearing infant >37 weeks with

ROM <18 hours: monitor for 48 hours.Well appearing infant <37 weeks &/or

ROM >18 hours: limited evaluation and monitor for 48 hours.

Use clinical judgment!

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Treatment of the Infant: Well appearing infant (any GA) w/ adequate maternal abxObserve clinically for 24-48 hoursUsually do not need a workupIf ALL discharge criteria are met at 24

hours, can consider discharge.Be sure to educate family on home

observation and ensure adequate medical follow up.

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Treatment of the Infant: Maternal GBS status unknown

GBS status can be unknown due to lack of prenatal care, lack of prenatal records, premature delivery, etc.

Obstetrically, these moms should be managed according to risk factors (gestational age, length of ROM, etc) and treated as appropriate.

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When GBS is negativeGBS negative means LOW risk but not NO

risk. Why?False negative rates have been reported

from 4-8%. Why?Transient nature of GBS, errors in

specimen collection/lab processing.

FYI: 60% of infants with GBS disease were born to GBS negative mothers.

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Other bugs causing neonatal sepsis

While GBS is the most common organism causing early onset sepsis, it isn’t the only one.

Others include E. Coli, H. influenzae, and coagulase negative staphyloccus.

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Future ResearchMaternal Vaccine against GBS!

This has been difficult due to ethical issues with pregnant women in clinical trials.

Also, EOS GBS is not extremely common, so it can be a difficult outcome to measure.

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References Centers for Disease Control and Prevention. (2010). Prevention of

Perinatal Group B Streptococcal Disease MMWR. CDC. Illuzzi, J., & Bracken, M. (2006). Duration of Intrapartum Prophylaxis for

Neonatal Group B Streptococcal Disease. Obstetrics and Gynecology , 108 (5), 1254-1267.

Jardine, L., Davies, M., & Faoagali, J. (2006). Incubation Time Required for Neonatal Blood Cultures to Become Positive. Journal of Paediatrics and Child Health , 797-802.

Koenig, J., & Keenan, W. (2009). Group B Streptococcus and Early-Onset Sepsis in the Era of Maternal Prophylaxis. Pediatric Clinics of North America , 56 (3).

Merenstein, G., & Gardner, S. (2002). Handbook of Neonatal Intensive Care (Fifth ed.). St. Louis: Mosby.

Verani, J., & Schrag, S. (2010). Group B Streptococcal Disease in Infants: Progress in Prevention and Continued Challenges. Clinics in Perinatology , 37, 375-392.