Group B Streptococcus

Peter Nguyen MSIII

Etiology

Facultative encapsulated gram-positivediplococcus

Produces a narrow zone of -hemolysis onblood 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% ofcases

Epidemiology

Colonizes ~20% of pregnant women

–Usually asymptomatic but can have UTIs,chorioamnionitis, or endometritis

40-70% of infants born to colonized mothers arecolonized

Nearly 50% of sexually partners of colonizedwomen are colonized themselves

0.2-3.7/1000 live births

–Rates are diminishing with prophylaxis

0.5-2% of newborn infants born to colonizedmothers

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 1stweek of life (usually<72 hours)

Attack rate  1/birthweight

Accounts for 20%

Cases appearing up to6 months of age

Cases after 1 month ofage occur primarily inpremature andimmunodeficientinfants

Early Onset v. Late Onset

Vertical transmission

Ascending infection(duration of ROM incidence of infection)

During passagethrough a colonizedbirth canal

Maternal transmission

Nonmaternal sites:

–Nursery

–Personnel

–Community

Pathophysiology dueto weakened hostdefense

Early Onset v. Late Onset

Pneumonia withbacteremia

Pulmonary HTN(COX)

Meningitis

Bacteremia without afocus (55%)

Meningitis (35%)

Osteomyelitis andarthritis

Differential Diagnosis

HMD

Amniotic fluid aspiration

Sepsis from other ascending infections

Metabolic and anatomic abnormalities thatmanifest as sepsis

Laboratory Findings

Isolation and identification from normallysterile 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 antibiotictherapy, and is in sepsis without bacteremia

Laboratory Findings

Urine culture

–Yields false positives due to colonization ofhealthy 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 anaminoglycoside 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 GBSmeningitis 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 oftherapy induction

If growth is present, add an aminoglycosideto 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 colonizationrather than a sequestered focus

Full course of penicillin andaminoglycoside 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 shockor those who had a delay in therapy

–Decreasing due to earlier dx and tx, increasedintrapartum prophylaxis, and ECMO

Complications

Neurologic sequelae occur in 20-30% ofmeningitis 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 orwhen PROM is anticipated (clindamycin forpenicillin allergic patients)

–Should be implemented in communities andhospitals where GBS perinatal disease isprevalent

–Decreases the incidence of early-onset but notlate-onset disease

Laboratory Findings

All infants whose mother received SICshould be observed for 48 hours for signs ofinfection

–Neonatal infection: treatment continued for 5-7days

–Antibiotic resistance

Bibliography

Behrman, Richard E.; Kliegman, Robert;Jenson, Hal B. (1999) Nelson Textbook ofPediatrics, 16th ed Philadelphia: SaundersW.B. Co.

http://www.groupbstrep.org/