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Perinatal Group B Streptococcal Disease

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Perinatal Group B Streptococcal Disease Objectives Describe the epidemiology of Group B Update: Perinatal Group B Streptococcus, including incidence and Streptococcal Disease risk factors. Discuss the latest treatment & Michele B. Zitzmann, M.H.S., MT(ASCP) prevention guidelines for perinatal LSUHSC Dept. of Clinical Laboratory Sciences Group B streptococcal disease. New Orleans CLPC Spring, 2017 Group B Streptococcus (GBS) Group B Streptococcus (GBS) Leading bacterial infection associated with Currently: Remains the leading illness and death among newborns in the infectious cause of morbidity & mortality U.S. among newborns in the U.S. • Prior to active prevention activities (1996): – CDC estimates 1,200 cases of GBS –8,000 – 12,000 cases of GBS sepsis & sepsis & meningitis in newborns each year meningitis in newborns each year (U.S.) (U.S.) –Approximately 2,000 deaths – Approximately 70% of cases are among –Direct medical costs: $300 million/year babies born at term (>37 weeks gestation) Group B Streptococcus Gram Stain Streptococcus agalactiae Gram positive cocci – Short chains in clinical specimens – Longer chains in culture Blood Agar plate – Gray-white mucoid colonies – Small zone of beta hemolysis 1 S. agalactiae: Blood Agar Plate Beta-Hemolysis Streptococcus agalactiae CAMP test Laboratory Tests: Used to presumptively identify group B – Catalase: Negative streptococci – 6.5% NaCl: No growth Named after the individuals who discovered the reaction – CAMP test: Positive –Christie, Atkins, & Munch-Petersen – Bile Esculin: Negative Staphylococcus aureus is inoculated onto blood – Hippurate hydrolysis: Positive agar plate Unknown streptococcal isolate inoculated perpendicularly to S. aureus inoculum Positive CAMP test Positive & Negative CAMP test 2 Hippurate Hydrolysis Lancefield Classification Differentiates S. agalactiae from other Developed in the 1930’s beta-hemolytic streptococci Rebecca Lancefield Inoculate sodium hippurate with colony; Differentiation of C carbohydrate in cell incubate 2 hours at 35oC; add ninhydrin wall reagent (indicator); incubate 10-15 min Streptococcus agalactiae – Group B Deep purple color = positive Only one organism in Group B category result Names used interchangeably Schematic Representation: Source & Transmission Streptococcal Cell Wall Normal flora of bowel, vagina, or throat Many “carriers” of GBS (asymptomatic) 10 - 30% of all pregnant women carry GBS in the rectum or vagina Fetus may come into contact with GBS before or during birth (vertical transmission) Cesarean section does NOT eliminate risk Maternal to Infant Transmission Clinical Disease If mother carries GBS: Sepsis – most dramatic & devastating – 1 of every 100-200 babies will be affected complication • 1 in 4,000 chance if IAP is administered Pneumonia - early-onset only; 0-5 days – 80% of the cases occur in the first week of Meningitis – can be early-onset or late- life (Early-onset disease – EOD) onset (5-90 days) – Most cases apparent a few hours after birth Neurologic - hearing and/or visual loss; – Premature babies are more susceptible impaired mental abilities 3 Signs & Symptoms – Early Onset Asymptomatic at birth Within first 24 hours of life: – Tachypnea – Mottling of skin – Lethargy – Hypotension – Irritability – Decreased feeding – Jaundice – Cyanosis 60 – 80% of infections occur within 12 hours of life Mechanical ventilation often required GBS Disease in Infants 90 80 70 60 50 40 30 20 Percent of cases of Percent 10 0 < 1 1-3 1234567891011 wk wk Age (months) Early-Onset Risk Factors for Early-Onset Neonatal GBS Disease GBS Disease 90 Maternal GBS colonization – primary risk 80 70 Obstetric: prolonged rupture of 60 50 membranes (>18 hours), preterm labor 40 (<37 weeks), intrapartum fever (100.4o F) 30 20 Percent of cases Previous infant with GBS disease 10 0 Demographic (age < 20 yrs, African- 0123456 American) Age (days) 4 Obstetric Risk Factors Among Women with GBS Infants Prevention Strategies: 1992-96 n = 245 American College of Ob & Gyn (ACOG) – No prenatal screening * no obstetric risk – Prophylaxis for women with OB risk factors factors * obstetric risk American Academy of Pediatrics (AAP) 46% factors – Universal prenatal screening 54% – Prophylaxis for carriers with OB risk factors EITHER approach expected to prevent * premature < 37 wk, ROM > 18 hr, temp > 100.4o F (38o C) 60-75% of early-onset disease Prevention: Intrapartum Antibiotic Impact of Prevention Early-Onset GBS Disease by Year and Prophylaxis (IAP) Percent Hospitals with a GBS Policy -- Atlanta, GA ACOG Tech Bulletin AAP Guidelines Consensus Antibiotics administered IV after onset 2.5 60 Meeting y of labor or membrane rupture, but 2 50 before delivery Provider Practice Hospital 40 1.5 Survey Site Visits Most likely method for preventing GBS 30 1 CDC Draft Penicillin is drug of choice; ampicillin Guidelines (Dec) 20 Consensus 0.5 10 also used Guidelines (May) % Hospitals with GBS Polic % Hospitals GBS with Cases per 1000 live per births Cases 0 0 1989 1990 1991 1992 1993 1994 1995 1996 1997 Year Barriers to Effective GBS Prevention Statistics Disease Prevention - Initially CDC and Prevention’s surveillance data 63% of clinicians collected prenatal indicate that early-onset GBS disease cultures for GBS declined by 65% between 1993 and 1998 BUT: (in areas with continuous data) 91% used suboptimal sites (not vag/rectal) In 1998, an estimated 3,900 neonatal Few clinicians knew what media their labs infections and 200 deaths were prevented used <10% of 200 labs surveyed were using optimal media (selective broth) Jafari et al., Pediatr Infect Dis J 1995;14:662-7. Whitney et al., OB GYN 1997;89:28-32. 5 Women Screened for GBS Prevention Strategies: 2002 (1998-9) vs. (2003-4) Universal culture screening for all pregnant women at 35-37 weeks gestation Implementation was rapid & widespread However, only 50.3% of women delivering preterm had known GBS status Only 63.4% received prophylaxis Women Who Received IAP Prevention Strategy: 2010 (1998-9) vs. (2003-4) Risk factors: Give • Previous infant w/GBS disease YES intrapartum • GBS bacteriuria this pregnancy penicillin • Delivery < 37 wks gestation NO GBS+ Give Collect rectal & vaginal swab at 35-37 wks intrapartum Not done, incomplete, or penicillin results unknown GBS- Risk factors: • Intrapartum fever > 100.4oF YES Give • ROM > 18 hrs intrapartum penicillin NO No intrapartum prophylaxis needed CDC’s Recommendations for Advantages of Prevention Strategy Prenatal GBS Cultures Optimizes prenatal screening Optimize cultures: – Fewer false negatives Site: vagina and rectum – Less pressure on physicians to treat – Single swab or two swabs Antibiotics to all GBS carriers – Through anal sphincter – Antibiotics start earlier before development Cervical, perianal, & perineal – NOT of risk factors acceptable – Adequate time for antibiotic effectiveness Timing: 35 to 37 weeks Processing: selective broth medium 6 Specimen Transport Inoculate swabs into non-nutritive transport medium – Commercially available (Stuart’s or Amie’s) Specimens in media may remain viable at RT for up to 4 days, however… – Results most sensitive when processed within 24 hours & refrigerated Specimens should be properly labeled – GBS specimen, penicillin allergy status Laboratory Testing Laboratory Testing Inoculate swabs into selective broth Pigmented enrichment broth – Todd-Hewitt broth with nalidixic acid – StrepB Carrot Broth (15 µg/ml) and EITHER colistin (10 µg/ml) or gentamicin (8 µg/ml) – Commercially: SBM or LIM broth Incubate broth 18-24 h. Subculture to sheep blood agar plate Laboratory Testing continued Slide Agglutination Tests Inspect and ID suggestive organisms – B-hemolytic or nonhemolytic, Gram+, catalase- If GBS not identified after 18-24h on sheep BAP, reincubate and inspect at 48h Various GBS Ag detection tests (slide agglutination, genetic probes, fluorescent antibodies) may be used for specific identification or CAMP test for presumptive identification 7 Results: Agglutination Commercial Tests PCR (Nucleic acid amplification tests – NAAT) Can be used for GBS screening at 35-37 weeks if performed from an enrichment broth (incubated for 18-24 hours) Cannot be performed directly from vaginal-rectal swab unless woman with unknown GBS status presents in active labor & has no risk factors A positive agglutination A negative agglutination GBS is present GBS is not present Photo courtesy of Dr. Richard Facklam, CDC Laboratory Testing - Urine GBS bacteriuria – A marker for heavy colonization – A risk factor for having an infant with early- onset GBS disease – Colony count cutoff of 104 cfu/mL or higher • New guidelines • Prevents burden of reporting all colony counts GBS Carriage by Culture Site Women in Vagina (%) Anorectum Both study (#) (%) (%) 789 10 18 21 94 18 28 31 301 11 14 18 8 GBS Carriage by Culture Method Intrapartum Prophylaxis Women in Selective Blood agar Penicillin study (#) broth (%) plate (%) – 5 million units IV load, then 2.5 million units IV every 4h until delivery 166 34 14 Ampicillin – 2 g IV load, then 1g IV every 4h until delivery 952 17 9 – Acceptable alternative, but broader spectrum may select for resistant organisms Penicillin allergy 383 20 13 – Clindamycin or Erythromycin (increase in resistance) – Vancomycin - if resistant Timing of Intrapartum Ampicillin Diagnostic Evaluation of Infants and Transmission of GBS Born to Mothers with IAP Interval between No. of GBS No. (%) GBS Full Evaluation Ampicillin and carrier mothers colonized babies – CBC & Differential
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