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10/3/2019
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Barbara Robinson‐Dunn, Ph.D., D(ABMM), F(AAM), FIDSA
Microbiology
Beaumont Health
Royal Oak, MI
Barbara.Robinson‐[email protected]
Update on the Group B Streptococcal Guidelines
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Compliance Issues
• I represent the ASM on the Active Bacterial Core Surveillance (ABCs) Committee of the Centers for Disease Control and Prevention.
• I have no other issues to declare.
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Active Bacterial Core Surveillance, (ABCs), CDC
A laboratory‐ and population‐based surveillance system for invasive bacterial pathogens of public health importance, includes 10 states and approx. 44.1 million people. ABCs sites collect isolates for all cases included in surveillance areas.• To determine the incidence/epi. characteristics of invasive
disease due to H. influenzae, N. meningitidis, GAS, GBS, and S. pneumoniae in large diverse U.S. populations
• To determine molecular epidemiologic patterns and microbiologic characteristics of public health relevance for isolates causing the above invasive infections
• To provide an infrastructure for further research, such as studies aimed at identifying risk factors for disease and post‐licensure evaluation of vaccines
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ABCs States Performing GBS Epidemiology
• 1. California (3 county SF Bay area)
• 2. Colorado (5 county Denver area)
• 3. Connecticut
• 4. Georgia (20 counties)
• 5. Maryland
• 6. Minnesota
• 7. New Mexico
• 8. New York (15 county Rochester & Albany areas)
• 9. Oregon (3 county Portland area)
• 10. Tennessee (20 counties)
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Streptococcus agalactiae (group B Streptococcus, GBS) is a leading cause of neonatal sepsis and meningitis
‐ in the 1990’s CDC, AAP and ACOG released a GBS guidance that reduced the incidence from 1.8 cases/1,000 live births to 0.5 cases/1,000 live births (70% decrease!) (NEJM, 2000)‐Schrag et al. (NEJM, 2002) also projected that intrapartum antibiotics prevented nearly 4,500 early‐onset cases of GBS disease and 225 deaths that year‐later in 2002, CDC published revised guidelines for Prevention of Perinatal Group B Streptococcal Disease
History of the Group B Streptococcal Guidelines
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1. Universal prenatal culture‐based screening of all pregnant women for GBS for vaginal/rectal colonization
2. Identify any amount of GBS present in urine from a pregnant woman including detailed recommendations on GBS culture processing
3. Only perform antimicrobial susceptibility testing on GBS isolates from women who were allergic to penicillin
4. Suggested an algorithm for management of patients with threatened or actual preterm delivery
Recommendations from the 2002 GBS Guidelines
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A ClinMicroNet survey was done with 76 responses1. Identification of GBS from urine specimens
a. Yes, all women 38%b. Yes, if 12‐50 years old 46%c. Yes, if informed that the patient is pregnant 8%d. Other (if specimen is not contaminated/depends who submits it) 8%
2. If yes, is the colony count reported?a. Labs reporting counts as low as <10,000 cfu/ml 46%b. Labs reporting counts of 10,000 to 50,000 cfu/ml 23%c. Labs reporting counts of 50,000 to 100,000 cfu/ml 23%
Potential Issues with the 2002 Guidelines
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3. Is your lab performing routine AST on all GBS from urine?
a. No 38%
b. Only if requested 54%
c. Other (a variety of responses were given) 8%
4. If performing AST, what method is used?
a. MIC 73%
b. Disk diffusion 18%
c. Gradient diffusion 1%
Potential Issues with the 2002 Guidelines (cont.)
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GBS isolates from penicillin allergic patients must have AST to erythromycin and clindamycin
•Difficult to determine who was allergic to penicillin
•Mandatory AST and rapid testing increased the cost
•New methods were urgently needed
PROBLEMS! Techniques Maximizing GBS Recovery Were Required
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Many laboratories started using chromogenic media (eg. Granada agar and/or Carrot broth for rapid identification
Some labs used a rapid antigen test to identify isolates directly from the primary isolation plate
It was still necessary to subculture isolates 1‐2x before performing AST
New Culture Methods
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CDC‐GBS Susceptibility Data, 1996 to 2003
Antimicrobial Agent
1996 2003
Erythromycin 84.2% 67.2%
Clindamycin 89.5% 85.0%
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WBH GBS Susceptibility Patterns, 2004
Antimicrobial Agent % Susceptible
Penicillin 100
Erythromycin 61
Clindamycin 65
Vancomycin 100
~2000 isolates tested
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GBS Susceptibility, 2007‐2008
Antimicrobial Agent % Susceptibility
Erythromycin 56.2
Clindamycin 60.9
Erythromycin and Clindamycin
62.1
Penicillin andVancomycin
100
2598 Isolates tested
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WBH GBS Susceptibility Patterns, 2008
Antimicrobial Agent % Susceptible
Penicillin 100
Erythromycin 56
Clindamycin 61
Vancomycin 100
1,996 isolates tested
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Incidence of Early and Late GBS Disease, 1990‐2008
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1. Expanded recommendations on laboratory methods for identification of GBS
2. Clarified the threshold for reporting GBS from urine from pregnant patients
3. Updated the algorithms for screening and intrapartum chemoprophylaxis for women with preterm labor or preterm premature rupture of membranes
2010 Group B Streptococcus Guidelines‐Changes
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4. Changed the recommended dose of penicillin‐G for prophylaxis
5. Updated prophylaxis regimens for women with penicillin allergy
6. Revised the algorithm for management of newborns as to the risk of early‐onset GBS disease
Additional Changes to the Guidelines
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1. Women with GBS isolated from the urine at any time
in the pregnancy or who had a previous child with
invasive GBS disease
2. Screen all other women at 35‐37 weeks’ gestation
3. At the time of labor or rupture of membranes,
antibiotics should be given to all women who tested
positive for GBS or to women whose GBS status was
unknown
2010 Guidelines for Intrapartum Prophylaxis
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1. If NAAT for GBS is available, intrapartum testing can be performed if the woman didn’t have any risk factors
2. Women with positive intrapartum NAAT results for GBS should receive prophylaxis
3. Women admitted with signs of labor or rupture of membranes should be screened upon admission. If GBS colonization status is unknown or if there was a positive GBS test within the previous 5 weeks, antibiotics should be given
Additional Changes in GBS Guidance
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1. Approved GBS identification from chromogenic media and directly from enriched broth. NAAT could also be used after enrichment with appropriate validation
2. Direct plating without enrichment should not be used.
3. Testing for inducible clindamycin resistance should be performed on isolates that are resistant to erythromycin, susceptible to clindamycin and from penicillin‐allergic patients at high risk for anaphylaxis!
4. Report GBS from urine cultures with counts >104
cfu/mL
Changes to Specimen Collection and Processing
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1. Penicillin (or ampicillin) was the agent of choice
2. AST should be ordered for antenatal GBS cultures performed on penicillin‐allergic women at high risk for anaphylaxis
3. The clinician must inform laboratories of the need for AST!
Antibiotic Prophylaxis (2010)
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Yes and No!
1. CDC has decided that they will no longer be responsible for these guidelines
2. ACOG and AAP have written guidelines for their respective population. These were recently published.
3. An updated mini‐review of guidelines for laboratory testing of GBS will be published (??JCM in early 2020).
Are There Newer Versions of the GBS Guidelines?
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1. Is your lab performing antenatal cultures according to the 2010 Guidelines?
a. Yes 31
b. No 24
2. Is your lab performing antenatal screening for GBS using a molecular assay?
a. Yes 20
b. No 22
CMN Survey for More Information
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3. If using a molecular assay, is the specimen enriched in LIM (or other similar) broth?
a. Yes 20
b. No (no one answered this negatively)
4. Is your lab performing intrapartum testing for GBS?
a. Yes 18
b. No 22 (some said they would not know if specimens were intrapartum)
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5. Is your lab performing AST on GBS isolates from…
a. antenatal specimens (vag/rectal)
Yes 34 No 7
b. intrapartum specimens
Yes 11 No 20
c. neonatal specimens
Yes 22 No 16
6. Is AST only performed is the woman is at high risk for PCN anaphylaxis?
Yes 35 No 7
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1. 2018 study looked at the sensitivity & specificity of RT‐PCR compared to reference standard culture (15 studies included 6,368 women in labor)
2. Prevalence of maternal colonization was 23.8% by RT‐PCR and 22.1% by culture
3. Sensitivity of RT‐PCR was 93.7% (92.1‐95.3)
4. Specificity was 97.6% (97.0‐98.1)
Detection of GBS by Molecular Methods
Feuerschuette, O.H.M, et al. 2018, DMID, 99:99‐104
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Growth studies may have been affected by minimal amount of GBS colonies, overpopulation of Enterococcus spp., collection, storage or transport errors and problems in the stability of the culture medium
Additional considerations from this study
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Study compared 3 FDA cleared NAATs to culture
1. 314 vaginal‐rectal specimens
2. Broth enrichment tested after 18‐24 h incubation and also after 4‐8 h incubation
a. agreement of NAATS was 97.1% to 98.4%
b. agreement of cultures was less sensitive than all the NAATs (67% to 73%)
c. shortened incubation period resulted in 1 false‐negative culture in 68 (1.5%)
Effect of Shortened Enrichment Period on Cultures
Couturier, B., et al., 2014, JCM, 52(9):3429‐3432
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Comparison of 3 NAATs to culture
1. Study included the Hologic Panther Fusion, Luminex Aries and Cepheid Xpert LB
2. 500 vaginal‐rectal specimens tested after 18‐24 h broth enrichment
3. 108 specimens positive by at least 1 culture (21.6%)
4. At least 1/3 NAATs positive in 155 specimens (31.0%)
5. 61 specimen positive by at least 1 NAAT but negative by culture, of these, 24 (39.3%) were positive by all three NAATs
Additional Comparisons of NAATs to Enriched Cultures
Shin, J.H., D.T. Pride, 2019, JCM, 57(6):1‐9
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The proportion of labs using NAATs varies by state (13.% to 16.7%)
1. Less than 10% of live births occurred at hospitals affiliated with labs offering intrapartum NAATs for GBS (2.9%‐34.1%)
2. Licensed NAATs still require a lengthy enrichment phase to achieve a sensitivity similar to culture
3. Intrapartum screening requires a much faster TAT than 1‐2 hr
4. A NAAT that could detect R to macrolides and GBS would be beneficial!
ABCs Data for Use of NAATs for GBS Detection
Fay, K., et al., 2018, DMID, 94(2):157‐159
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Surveillance was performed to monitor diagnostic test performance
1. 31 isolates of S. agalactiae found to contain deletions in or adjacent to the region of the chromosome that encodes the hemolysin gene cfb
2. Whole genome sequencing of 15 isolates from 11 labs showed 4 unique deletions of chromosomal DNA ranging from 181 bp to 49 kb.
3. Prevalence was <1% in 3 locations but 7% in a 4th
location
Problem: Strains with Chromosomal Deletions
Tickler, I.A., et al., 2019, JCM, 57(4): e02040‐18
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Among the 15 isolates with chromosomal deletions
1. Multiple pulsed‐field gel electrophoresis types were identified
2. One of these appears to be broadly dispersed across the United States
Chromosomal Deletions (cont.)
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Screening cultures performed on 3,276 women
1. Recovered 32 (1%) Strep. pseudoporcinus isolates from female genital sources and 2 additional isolates from urine)
2. 18% of isolates in this study were resistant to clindamycin and erythromycin. Previous studies reported high susceptibility to the beta‐lactams.
3. “The clinical significance of genitourinary S. pseudoporcinus, the patients’ clinical characteristics and their relationship to peripartum neonatal and maternal infections requires further investigation.”
Colonization by Strep. pseudoporcinus
Suwantarat, N., et al., 2015, JCM, 53(12) 3926‐3930
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In a four center comparison between molecular detection and the CDC‐screening cultures for GBS, two labs missed more than 10%
1. The lab changed to GBS Detect Agar for enhanced selectivity and better detection of hemolysis
2. Specimens were received from 2 pen‐allergic women
3. Culture yielded beta‐hemolytic, catalase neg colonies that reacted with Ab to the GBS Ag
4. AST was performed on the BD Phoenix SMIC/ID2 panel but neither isolate was identified
Additional Issues with Testing
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5. Both isolates were PYR + but not S. agalactiae
6. MALDI‐T0F identified both as S. halichoeri (scores of 2.1 and 2.3)
7. Both were inoculated into blood culture bottles and gave a negative result when tested by a molecular blood culture identification panel
Additional Information
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717 screening cultures obtained from pregnant women
1. 260 (36.3%) were beta hemolytic and group B Ag +
2. The positive isolates were tested by MALDI‐ToF and 248 (95.4% of 260; 34.6% of 717) confirmed as S. agalactiae
3. 6 identified as S. halichoeri and 6 were identified as S. pseudoporcinus
Without MALDI‐ToF, 12(14.6%) of screen‐positive organisms would have been falsely identified as S. agalactiae
Confirmation of Results
Salimnia, H., et al., 2019, 57(8) e00446‐19
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WBH GBS Susceptibility Results
Year # Isolates Erythro %S Clinda %S
2008 1996 56 61
2010 1208 53 58
2012 1759 50 58
2014 2035 46 56
2016 2260 42 53
2018 2369 41 51
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Updated Recommendations (ACOG)
1. Perform universal GBS screening between 36 0/7 to 37 6/7 weeks of gestation.
2. Lab requisitions for GBS screening cultures note when a patient has an allergy to penicillin to ensure that susceptibility to clindamycin is determined.
3. Consider penicillin allergy skin testing in patients with a history of penicillin allergy that is a low or unknown risk for anaphylaxis
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ACOG Recommendations (cont.)
• 4. Women who present in labor at 37 0/7 weeks of gestation or greater with unknown culture status in the current pregnancy but with known positive GBS colonization in a prior pregnancy are candidates for intrapartum antibiotic prophylaxis.
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AAP Recommendations
1. All pregnant women should undergo antepartum screening for GBS at 36 0/7 to 37 6/7 weeks gestation, unless intrapartum antibiotic prophylaxis for GBS is indicated due to GBS bacteriuria during the pregnancy or due to a history of a previous GBS‐infected child (includes deliveries that occur up to gestational ages of at least 41 0/7 weeks)
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• 2. Exceptions to universal prenatal GBS screening protocol are women who have GBS bacteriuria identified at any time during the current pregnancy and those who have previously given birth to a neonate with early‐onset GBS disease (risk factors that are overriding indications for intrapartum antibiotic prophylaxis).
• 3. If the prenatal GBS screening culture result is unknown when labor starts, intrapartum antibiotic prophylaxis is indicated for women who have risk factors for GBS EOD.
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• 4. In women who are at risk for anaphylaxis following exposure to penicillin, the laboratory requisitions that accompany antepartum screening GBS cultures shouldbe marked for the laboratory to be aware that they have this allergy, to ensure that appropriate testing of any GBS isolates for clindamycin susceptibility is performed.
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• 5. Intravenous penicillin (or IV ampicillin) remains the agent of choice for intrapartum prophylaxis. For women who are at low risk for anaphylaxis to penicillin, cefazolin should be used for intrapartum GBS prophylaxis. For women with a high risk for anaphylaxis, clindamycin is the recommended alternative to penicillin only if the GBS isolate is known to be susceptible.
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• 6. Intravenous vancomycin remains the only proven effective option for intrapartum antibiotic prophylaxis for women who report a severe penicillin allergy and whose GBS isolate is not susceptible to clindamycin.
• ***It should be noted that two cases of vancomycin‐resistant GBS were reported from New York and New Mexico in 2014.
– Park, C., M. Nichols, S. Schrag, 2014, NEJM, 370(9):885‐886.
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Suggestions for Intrapartum Testing
• Obtain vaginal/rectal specimens for both intrapartum molecular analysis and for routine broth enriched culture with AST
– Specimen collection devices must be compatible with test methods
• This will provide a rapid molecular answer and AST for appropriate antimicrobial therapy
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1. Testing for GBS has greatly advanced but problems still exist due to chromosomal deletions/alterations
2. Intrapartum testing is still limited due to the need to enhance growth in broth
3. Susceptibility to effective antibiotics continues to decrease including isolates that have reduced susceptibility to penicillin and vancomycin in addition to those already described
4. The role of other beta‐hemolytic species of Streptococcus in neonatal disease must be further clarified.
Conclusions
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