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Group B Streptococcus Peter Nguyen MSIII. Etiology Facultative encapsulated gram-positive...
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![Page 1: Group B Streptococcus Peter Nguyen MSIII. Etiology Facultative encapsulated gram-positive diplococcus Produces a narrow zone of -hemolysis on blood.](https://reader035.fdocuments.us/reader035/viewer/2022062516/56649dbb5503460f94aac466/html5/thumbnails/1.jpg)
Group B Streptococcus
Peter Nguyen MSIII
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Etiology
Facultative encapsulated gram-positive diplococcus
Produces a narrow zone of -hemolysis on blood agar
Most strains are bacitracin resistant Positive CAMP test
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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
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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
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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
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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
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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
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Early Onset v. Late Onset Pneumonia with
bacteremia Pulmonary HTN
(COX) Meningitis
Bacteremia without a focus (55%)
Meningitis (35%) Osteomyelitis and
arthritis
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Differential Diagnosis
HMD Amniotic fluid aspiration Sepsis from other ascending infections Metabolic and anatomic abnormalities that
manifest as sepsis
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Laboratory Findings
Isolation and identification from normally sterile sites – CSF – Gastric or tracheal aspirates – Skin or mucous membranes
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Laboratory Findings
Latex particle agglutination – Less sensitive than culture – Useful in patient who has had prior antibiotic
therapy, and is in sepsis without bacteremia
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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
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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
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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
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GBS Meningitis
Obtain CSF culture within 48 hours of therapy induction
If growth is present, add an aminoglycoside to the treatment
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Treatment Duration
Pneumonia: 10 days Arthritis: 2-3 weeks Osteomyelitis: 3-4 weeks Endocarditis: 3-4 weeks
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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
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Supportive Care
Hypoxia and shock DIC Seizures Increased ICP SIADH
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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
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Complications Neurologic sequelae occur in 20-30% of
meningitis cases – Mental retardation – Quadriplegia/hemiplegia– Seizures – Hypothalamic dysfunction – Cortical blindness – Hydrocephalus – Bilateral deafness
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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
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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
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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/