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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

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Group B Streptococcus


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group b streptococcus

Group B Streptococcus

Peter Nguyen MSIII

etiology
Etiology
  • Facultative encapsulated gram-positive diplococcus
  • Produces a narrow zone of -hemolysis on blood agar
  • Most strains are bacitracin resistant
  • Positive CAMP test
etiology3
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
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
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
early onset v late onset7
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
early onset v late onset8
Pneumonia with bacteremia

Pulmonary HTN (COX)

Meningitis

Bacteremia without a focus (55%)

Meningitis (35%)

Osteomyelitis and arthritis

Early Onset v. Late Onset
differential diagnosis
Differential Diagnosis
  • HMD
  • Amniotic fluid aspiration
  • Sepsis from other ascending infections
  • Metabolic and anatomic abnormalities that manifest as sepsis
laboratory findings
Laboratory Findings
  • Isolation and identification from normally sterile sites
    • CSF
    • Gastric or tracheal aspirates
    • Skin or mucous membranes
laboratory findings11
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 findings12
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
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
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 meningitis15
GBS Meningitis
  • Obtain CSF culture within 48 hours of therapy induction
  • If growth is present, add an aminoglycoside to the treatment
treatment duration
Treatment Duration
  • Pneumonia: 10 days
  • Arthritis: 2-3 weeks
  • Osteomyelitis: 3-4 weeks
  • Endocarditis: 3-4 weeks
recurrent infection
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
Supportive Care
  • Hypoxia and shock
  • DIC
  • Seizures
  • Increased ICP
  • SIADH
complications
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
complications20
Complications
  • Neurologic sequelae occur in 20-30% of meningitis cases
    • Mental retardation
    • Quadriplegia/hemiplegia
    • Seizures
    • Hypothalamic dysfunction
    • Cortical blindness
    • Hydrocephalus
    • Bilateral deafness
laboratory findings21
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 findings22
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
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/