1. Group B Streptococcus Peter Nguyen MSIII

2. Etiology  Facultative encapsulated gram-positive diplococcus  Produces a narrow zone of  -hemolysis on blood agar  Most strains are bacitracin resistant  Positive CAMP test

3. 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

4. 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

5. 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

6. 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

7. 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

8. Early Onset v. Late Onset  Pneumonia with bacteremia  Pulmonary HTN (COX)  Meningitis  Bacteremia without a focus (55%)  Meningitis (35%)  Osteomyelitis and arthritis

9. Differential Diagnosis  HMD  Amniotic fluid aspiration  Sepsis from other ascending infections  Metabolic and anatomic abnormalities that manifest as sepsis

10. Laboratory Findings  Isolation and identification from normally sterile sites –CSF –Gastric or tracheal aspirates –Skin or mucous membranes

11. Laboratory Findings  Latex particle agglutination –Less sensitive than culture –Useful in patient who has had prior antibiotic therapy, and is in sepsis without bacteremia

12. 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

13. 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

14. 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

15. GBS Meningitis  Obtain CSF culture within 48 hours of therapy induction  If growth is present, add an aminoglycoside to the treatment

16. Treatment Duration  Pneumonia: 10 days  Arthritis: 2-3 weeks  Osteomyelitis: 3-4 weeks  Endocarditis: 3-4 weeks

17. 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

18. Supportive Care  Hypoxia and shock  DIC  Seizures  Increased ICP  SIADH

19. 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

20. Complications  Neurologic sequelae occur in 20-30% of meningitis cases –Mental retardation –Quadriplegia/hemiplegia –Seizures –Hypothalamic dysfunction –Cortical blindness –Hydrocephalus –Bilateral deafness

21. 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

22. 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

23. Bibliography  Behrman, Richard E.; Kliegman, Robert; Jenson, Hal B. (1999) Nelson Textbook of Pediatrics, 16 th ed Philadelphia: Saunders W.B. Co.  http://www.groupbstrep.org/