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  /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 1 st 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, 16 th ed Philadelphia: Saunders W.B. Co. 