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Group B Streptococcus
Peter Nguyen MSIII
Etiology
Facultative encapsulated gram-positive diplococcus
Produces a narrow zone of -hemolysis on blood agar
Most strains are bacitracin resistant Positive CAMP test
Etiology
Serologic Strains– Type Ia, Ib, Ia/c, II, III, IV, V, VI, VII, and VIII– Early onset disease can be due to any strain – Late onset disease is due to Type III in >90% of
cases
Epidemiology Colonizes ~20% of pregnant women
– Usually asymptomatic but can have UTIs, chorioamnionitis, or endometritis
40-70% of infants born to colonized mothers are colonized
Nearly 50% of sexually partners of colonized women are colonized themselves
0.2-3.7/1000 live births – Rates are diminishing with prophylaxis
0.5-2% of newborn infants born to colonized mothers
Risk Factors for Colonization Heavily colonized mothers Mothers younger than 20 African Americans Lower socioeconomic groups PROM Prolonged labor Maternal Chorioamnionitis Previous delivery with GBS disease
Early Onset v. Late Onset Occurs within the 1st
week of life (usually <72 hours)
Attack rate 1/birth weight
Accounts for 20% Cases appearing up to
6 months of age Cases after 1 month of
age occur primarily in premature and immunodeficient infants
Early Onset v. Late Onset Vertical transmission Ascending infection
(duration of ROM incidence of infection)
During passage through a colonized birth canal
Maternal transmission Nonmaternal sites:
– Nursery
– Personnel
– Community
Pathophysiology due to weakened host defense
Early Onset v. Late Onset Pneumonia with
bacteremia Pulmonary HTN
(COX) Meningitis
Bacteremia without a focus (55%)
Meningitis (35%) Osteomyelitis and
arthritis
Differential Diagnosis
HMD Amniotic fluid aspiration Sepsis from other ascending infections Metabolic and anatomic abnormalities that
manifest as sepsis
Laboratory Findings
Isolation and identification from normally sterile sites – CSF – Gastric or tracheal aspirates – Skin or mucous membranes
Laboratory Findings
Latex particle agglutination – Less sensitive than culture – Useful in patient who has had prior antibiotic
therapy, and is in sepsis without bacteremia
Laboratory Findings
Urine culture – Yields false positives due to colonization of
healthy neonates in the perineum and rectum
Urine latex test– Do not perform on an asymptomatic patient
Treatment DOC: penicillin G Empirical ABX treatment with ampicillin and an
aminoglycoside until GBS has been cultured Also susceptible to:
– Vancomycin
– Semi-synthetic penicillins
– Cefotaxime
– Ceftriaxone
– Impipnem
GBS Meningitis
Penicillin should be used in high doses (300mg/kg/day) for the treatment of GBS meningitis because of: – A high CSF inoculum – Relapse in patients treated with 200 mg/kg/day – The Relative safety of penicillin in neonates
GBS Meningitis
Obtain CSF culture within 48 hours of therapy induction
If growth is present, add an aminoglycoside to the treatment
Treatment Duration
Pneumonia: 10 days Arthritis: 2-3 weeks Osteomyelitis: 3-4 weeks Endocarditis: 3-4 weeks
Recurrent Infection
Due to persistent mucosal colonization rather than a sequestered focus
Full course of penicillin and aminoglycoside followed by rifampin
Mother’s breast milk may be a source– Culture milk – Treat mother with rifampin
Supportive Care
Hypoxia and shock DIC Seizures Increased ICP SIADH
Complications
Mortality rate ranges from 5-15% – Highest in VLBW infants, those in septic shock
or those who had a delay in therapy– Decreasing due to earlier dx and tx, increased
intrapartum prophylaxis, and ECMO
Complications Neurologic sequelae occur in 20-30% of
meningitis cases – Mental retardation – Quadriplegia/hemiplegia– Seizures – Hypothalamic dysfunction – Cortical blindness – Hydrocephalus – Bilateral deafness
Laboratory Findings Selective intrapartum chemoprophylaxis
(SIC)– IV penicillin G or ampicillin at onset of labor or
when PROM is anticipated (clindamycin for penicillin allergic patients)
– Should be implemented in communities and hospitals where GBS perinatal disease is prevalent
– Decreases the incidence of early-onset but not late-onset disease
Laboratory Findings
All infants whose mother received SIC should be observed for 48 hours for signs of infection – Neonatal infection: treatment continued for 5-7
days– Antibiotic resistance
Bibliography
Behrman, Richard E.; Kliegman, Robert; Jenson, Hal B. (1999) Nelson Textbook of Pediatrics, 16th ed Philadelphia: Saunders W.B. Co.
http://www.groupbstrep.org/
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