Objective: To evaluate the positive predictive value (PPV) of group B Streptococcus (GBS)
cultures at 35–37 weeks of gestation relative to GBS colonization status at delivery.
Methods: Rectovaginal swabs from 221 women at labor in four Lisbon hospitals were collected
for GBS screening according to the CDC guidelines.
Results: The PPV was 24.4%. IAP was administered to 100% of prenatally GBS positive women.
There was no case of early onset GBS disease (EOD).
Conclusions: Poor accuracy of prenatal cultures in identifying true candidates for IAP highlights
the need for Portuguese clinical and laboratory guidelines to prevent EOD and antibiotic
overtreatment of pregnant women

Borrego, M.J.

Caetano, P.

Damião, V.

Florindo, C.

Gomes, João Paulo

Lima, J.

Nogueira, I.

Ribeiro, L.

Rocha, I.

Viegas, S.

The Journal of Maternal-Fetal & Neonatal Medicine

Scientific Repository of the National Health Institute Doutor Ricardo Jorge

Accuracy of prenatal culture in predicting intrapartum group B streptococcus colonization status

OBJECTIVE:
To evaluate the positive predictive value (PPV) of group B Streptococcus (GBS) cultures at 35-37 weeks of gestation relative to GBS colonization status at delivery.
METHODS:
Rectovaginal swabs from 221 women at labor in four Lisbon hospitals were collected for GBS screening according to the CDC guidelines.
RESULTS:
The PPV was 24.4%. IAP was administered to 100% of prenatally GBS positive women. There was no case of early onset GBS disease (EOD).
CONCLUSIONS:
Poor accuracy of prenatal cultures in identifying true candidates for IAP highlights the need for Portuguese clinical and laboratory guidelines to prevent EOD and antibiotic overtreatment of pregnant women

Florindo, C

Damião, V

Lima, J

Nogueira, I

Rocha, I

Caetano, P

Ribeiro, L

Viegas, S

Gomes, J

Borrego, MJ

Repositório do Hospital Prof. Doutor Fernando Fonseca

Carlos Florindo

Vera Damião

Jorge Lima

Isabel Nogueira

Isilda Rocha

Paula Caetano

Lurdes Ribeiro

Silvia Viegas

João P. Gomes

Maria J. Borrego

Crossref

Repositório Científico do Instituto Nacional de Saúde

2014http://informahealthcare.com/jmfISSN: 1476-7058 (print), 1476-4954 (electronic)J Matern Fetal Neonatal Med, 2014; 27(6): 640–642! 2014 Informa UK Ltd. DOI: 10.3109/14767058.2013.820700SHORT REPORTAccuracy of prenatal culture in predicting intrapartum group Bstreptococcus colonization statusCarlos Florindo1, Vera Damia˜o1, Jorge Lima2, Isabel Nogueira3, Isilda Rocha2,4, Paula Caetano2,5, Lurdes Ribeiro2,Silvia Viegas1, Joa˜o P. Gomes1, and Maria J. Borrego11National Institute of Health, Lisbon, Portugal, 2CUF Descobertas Hospital, Lisbon, Portugal, 3Maternity Alfredo da Costa, Lisbon, Portugal,4Fernando Fonseca Hospital, Amadora, Portugal, and 5Dona Estefaˆnia Hospital, Lisbon, PortugalAbstractObjective: To evaluate the positive predictive value (PPV) of group B Streptococcus (GBS)cultures at 35–37 weeks of gestation relative to GBS colonization status at delivery.Methods: Rectovaginal swabs from 221 women at labor in four Lisbon hospitals were collectedfor GBS screening according to the CDC guidelines.Results: The PPV was 24.4%. IAP was administered to 100% of prenatally GBS positive women.There was no case of early onset GBS disease (EOD).Conclusions: Poor accuracy of prenatal cultures in identifying true candidates for IAP highlightsthe need for Portuguese clinical and laboratory guidelines to prevent EOD and antibioticovertreatment of pregnant women.KeywordsEarly onset disease, intrapartum antibioticprophylaxis, intrapartum screening,Streptococcus agalactiaeHistoryReceived 13 February 2013Accepted 26 June 2013Published online 7 August 2013IntroductionStreptococcus agalactiae, group B Streptococcus (GBS) hasmultiple serotypes and is an opportunistic human pathogenthat can lead to life-threatening infections in newborns andimmunocompromized adults [1]. Maternal GBS carriage hasbeen recognized as the major risk factor of early onset diseasein newborns (EOD, 57 days of age) [1,2]. Up to 30% ofpregnant women are anogenital colonized, although thecarrier status is considered dynamic during pregnancy [2,3].CDC guidelines [2,4] recommend GBS screening at 35–37weeks of gestation in order to identify women at risk thatshould undergo intrapartum antibiotic prophylaxis (IAP) toavoid transmission to the newborn during labor; IAP becameresponsible for the reduction of EOD in developed countries.Nevertheless, strategies to prevent late onset disease (LOD),which occurs after the first week of life, have yet to emerge,as IAP is unable to avoid LOD. The screening-based approachis challenging, as its efficacy relies on its capacity to predictGBS colonization status at the time of labor. Publishedreports [5,6] showed that both negative (NPV) and positive(PPV) predictive values of prenatal GBS cultures relativelyto the GBS status at delivery are suboptimal, especially thePPV. We aimed to evaluate the PPV of GBS positive cultureat 35–37 weeks of gestation considering the GBS colonizationstatus at delivery.MethodsPatients and study designBetween March 2008 through June 2009, 221 pregnantwomen presenting a positive result for GBS at 35–37 weeksof gestation from 4 hospitals (Dona Estefaˆnia Hospital, n¼ 9;Maternity Alfredo da Costa, n¼ 42; Fernando FonsecaHospital, n¼ 67; and CUF Descobertas Hospital, n¼ 103)were selected for this study. It was not possible to determinethe laboratories (private and/or public) where pregnantwomen performed their GBS prenatal nor the methodologiesthat were used by those laboratories. The unknown coloniza-tion status at delivery was also used as an inclusion criterionin order to verify the intrapartum positivity of GBS in thisgroup of women (n¼ 88). Considering the main focus of thisstudy, and due to budget constraints, women with negativeGBS cultures at 35–37 weeks of gestation were excluded.All pregnant delivering before 35 weeks of gestation aswell as pregnant that had received antibiotic treatment up to3 weeks before admission were excluded.This study was approved by the ethics board of the involvedinstitutions, and a written informed consent was obtained fromall women prior to their enrolment in the study. Informationabout age, obstetric risk factors, and type of delivery werecollected. Later, information on whether newborns developedEOD during the hospital stay was also acquired.Collection and culture of specimensA combined recto-vaginal swab was collected from eachparturient on admission for delivery. Swabs were thenmaintained in a non-nutritive Amies medium (Biome´rieux)Address for correspondence: Maria J. Borrego, Department of InfectiousDiseases, National Institute of Health, Av. Padre Cruz 1649-016 Lisbon,Portugal. E-mail: m.jose.borrego@insa.min-saude.ptJ Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Instituto Nacional de Saúde Dr. Ricardo Jorge on 06/16/14For personal use only.at room temperature until processing at the National Instituteof Health in Lisbon, within 24 h, according to the describedby the CDC guidelines [4]. Briefly, each swab was inoculatedin Todd Hewitt selective media broth at 37C, 5% CO2 for18 h and sub-cultured on Columbia agar supplementedwith 5% sheep blood (COS) (Biome´rieux) at 37C in 5%CO2 for an additional period of 24–48 h.GBS identification and antibiotic susceptibility testingS. agalactiae isolates were identified by standard criteriaon the basis of colony morphology, Gram staining, non-hydrolysis of aesculin on bile-aesculin agar and group Blatex-agglutination test. Antimicrobial susceptibility testing(penicillin G, erythromycin, clindamycin and vancomycin)was performed by Etest according to the Clinical andLaboratory Standards Institute guidelines [7].Capsular typing and screening of ST-17hypervirulent lineageCapsular typing was performed by using specific antiserafor serotypes Ia to V (Essum AB) and cps genotyping [3].The detection of ST-17 lineage was achieved by PCR, asdescribed elsewhere [8].StatisticsPositive predictive value (PPV) of prenatal GBS cultureswas calculated through the following formula: [(Number ofwomen GBSþ/þ)7 (number of women GBSþ/þ andGBSþ/)] 100%, where GBSþ/þ and GBSþ/ correspondto intrapartum positive and negative results, respectively(all samples had been positive positive at prenatal stage) [5].ResultsVaginal-rectal cultures were obtained from 221 GBS positivewomen on admission for delivery, 118 (53.4%) and 103(46.6%) from three public and one private hospitals, respect-ively. Overall, the average maternal age was 30.4 years (range,14–45 years) and the average gestational age at labor was 39.0weeks (range, 35.9–41.4 weeks). The mode of delivery wasvaginal or cesarean in 166 (75.1%) and 55 (24.9%) women,respectively. Among 55 women giving birth by cesareansection, 38 (69.1%) were performed electively and 17 (30.9%)were performed after labor, of whom 38 (69.1%) occurred atthe private hospital. Of 221 prenatally GBS-positive women,only 54 remained positive at delivery, corresponding to a PPVof 24.4%. All these 54 prenatal GBS-positive women receivedIAP (ampicillin was the first choice for IAP in the fourhospitals). However, on a risk-based screening (e.g. pretermdelivery), only 11 (5%) would have justified antibiotictreatment.None of the 88 parturients without prior GBS screeningrevealed intrapartum GBS colonization; however, 9/9 attend-ing to the private hospital and 17/79 attending to publichospitals (the ones presenting risk factors: preterm deliveries[n¼ 14]; GBS bacteriuria during the current pregnancy[n¼ 2]; previous child with EOD [n¼ 1]) received IAP.The serotype distribution showed the predominance ofserotype III (25/54 [46.3%]) followed by serotypes Ia (10/54[18.5%]), II (9/54 [16.7%]), V (7/54 [12.9%]), Ib (2/54[3.7%]) and IV (1/54 [1.9%]), which was quite similar to thatdescribed in Portugal for GBS colonization during the lasttrimester of pregnancy [3]. The lineage ST17 was identifiedin 56% (14/25) of the isolates belonging to serotype III;however, no newborn developed EOD during hospital stay.All clinical isolates were fully susceptible to penicillin Gor vancomycin. We observed a resistance rate of 7.4% toerythromycin and 1.8% to clindamycin, which were low whencompared to our previous data [3].DiscussionIn the present study, public and private hospitals evidenceddifferences regarding both the GBS screening during preg-nancy and the selection of candidates for IAP. As an example,only nine pregnant cases were presented to the privatehospital without GBS screening at 35–37 weeks of gestation,and all received IAP, versus 79 attending to public hospitals,where IAP was provided exclusively to the 17 parturientscomprehending risks. The lack of GBS screening duringpregnancy suggests unawareness, or indifference regardingthe free health care provided under the supervision of low-risk pregnancy in Portugal. Thus, social factors contributingto the exclusion from pregnancy surveillance in Portugal seemto need urgent assessment and adjustment.Although a great heterogeneity of PPVs has been described[5,6,9] ranging (43–100%), our study revealed a considerablylow PPV of 24.4%. This weak concordance between prenataland intrapartum culture results could be attributed to severalvariables, namely (1) timing of prenatal GBS screening;(2) laboratory methodologies; and (3) antibiotic usage.The influence of the timing of prenatal GBS screeningin this study would be neglectable; in fact, all enrolled GBSpositive women were screened at 35–37 weeks of gestation,which has been considered ideal for correlating with GBScolonization status at delivery, by longitudinal studies [9].The observed discrepancy could be explained, in part,by methodological heterogeneity (sampling, swab storageand transport, and culturing procedures) that could not bedetermined in the present study. In fact, in Portugal, the healthsystem allows pregnant women to freely choose thelaboratories where antenatal GBS screening is performed(screening at the same hospital of delivery is rare),implicating that a multitude of laboratories were involved,each one using their particular GBS detection protocols.There is neither Portuguese GBS laboratory screening guide-lines nor recommendations for following scientific guidelinesinternationally accepted, such as the provided by the CDC.In this scenario, an heterogeneity of methodologies appliedto GBS detection are to be expected, comprehending theproposed by the CDC guidelines but also less expensive andtime-consuming procedures, such as direct plating in bothColumbia 5% sheep blood agar and chromogenic medium(such as Strepto B ID or Granada). Each procedure hasinherent limits and drawbacks that can lead to GBSmisidentification.Another technical explanation could hold on the prolifer-ation of non-GBS isolates during storage and transport,such as Enterococcus and Proteus species, impairing theDOI: 10.3109/14767058.2013.820700 Antenatal versus intrapartum group B streptococcus screening 641J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Instituto Nacional de Saúde Dr. Ricardo Jorge on 06/16/14For personal use only.identification and recovery of GBS on blood agar plates.Indeed, and consistent with published data [10], 12.2% of ourintrapartum cultures from prenatally GBS-positive womenevidenced an overgrowth of Gram negative bacteria in bloodagar plates (not supplemented with antibiotics), which mighthave obscured GBS colonies culminating in false-negativeresults. This emphasizes the need to improve the subculturesystem by using selective GBS media (Columbia agar withcolistin and nalidixic acid or a commercial chromogenicagar), as is currently recommended by the 2010 CDCguidelines [2]. Indeed, Van Dyke and colleagues [11] revealedthat 61.4% of EOD cases occurred in term newborns whosemothers were GBS-negative at 35–37 weeks. Whether thosenegative cultures were false-negative results or the parturientsacquired GBS during the interval between pregnancy screen-ing and delivery is unknown, but it surely evidences majorvariations in GBS colonization status during pregnancy.As we excluded pregnant subjected to antibiotic treatmentwithin 3 weeks before delivery, we would expect no influenceof this factor for the low PPV; however, we cannot excludethat some pregnant women during their hospital admissionquestionnaire omitted (by unidentified reasons) taking medi-cation, namely antibiotics. In fact, although in Portugala medical prescription is required for antibiotic purchase,irregularities to this rule exist, allowing self-medication.In conclusion, the reasons underlying a low PPV ofprenatal culture in predicting GBS colonization duringlabor in Portugal are hard to determine due to the lack ofnational clinical and laboratory guidelines for GBS preventionthat would contribute to the uniformity and quality of GBSscreening. This requisite would surely contribute to a higherPPV that would prevent EOD while avoiding overtreatmentof pregnant women.Also, and until the availability of an effective GBSvaccine, new reliable and fast intrapartum diagnostic toolsshould be developed to supplement antenatal GBS screening.AcknowledgementsThe authors thank Albertina Louro (National Institute ofHealth); Conceic¸a˜o Telhado, Mariana Loureiro, Glo´riaCarvalhosa, Mafalda Lucas, Maria Joa˜o Santos, Maria doCe´u Ramalho, Rosa Portela, Luı´s Mo´s, Anaı´lde Arau´jo,and Cristina Castel Branco (CUF Descobertas Hospital);Ana Lima, and Patrı´cia Silva (Maternity Alfredo da Costa);Graciete Novais, Elsa Guerreiro, Cecı´lia Artilheiro, PedroMendes, Anto´nio Fatia, and Lilita Miranda (FernandoFonseca Hospital) for collecting/processing clinical samples.Declaration of interestThe authors report no conflicts of interest. This work wassupported by Fundac¸a˜o para a Cieˆncia e Tecnologia grantPTDC/SAU-MII/105114/2008 from Ministe´rio da Cieˆncia,Tecnologia e Ensino Superior, Portugal and, PhD grantSFRH/BD/48231/2008 awarded to C.F.References1. Edwards MS, Nizet V. Group B streptococcal infections.In: Remington JS, Klein JO, Wilson CB, et al, eds. Diseases ofthe fetus and newborn infant, 7th ed. Philadelphia, PA: Elsevier;2011:419–69.2. Centers for Disease Control and Prevention (CDC). Prevention ofperinatal group B streptococcal disease. Revised guidelines fromCDC, 2010. MMWR Recomm Rep 2010;59:1–36.3. Florindo C, Viegas S, Paulino A, et al. Molecular characterizationand antimicrobial susceptibility profiles in Streptococcus agalactiaecolonizing strains: association of erythromycin resistance withsubtype III-1 genetic clone family. Clin Microbiol Infect 2010;16:1458–63.4. Centers for Disease Control and Prevention (CDC). Prevention ofperinatal group B streptococcal disease. Revised guidelines fromCDC. MMWR Recomm Rep 2002;51:1–22.5. Lin FY, Weisman LE, Azimi P, et al. Assessment of intrapartumantibiotic prophylaxis for the prevention of early-onset group BStreptococcal disease. Pediatr Infect Dis J 2011;30:759–63.6. El Helali N, Nguyen JC, Ly A, et al. Diagnostic accuracy of a rapidreal-time polymerase chain reaction assay for universal intrapartumgroup B streptococcus screening. Clin Infect Dis 2009;49:417–23.7. Clinical and Laboratory Standard Institute (CLSI). PerformanceStandards for Antimicrobial Susceptibility Testing M100-S19;19th Informational Supplement. Wayne: CLSI; 2009.8. Lamy MC, Dramsi S, Billoe¨t A, et al. Rapid detection of the highlyvirulent group B Streptococcus ST-17 clone. Microbes Infect 2006;8:1714–22.9. Valkenburg-van den Berg AW, Houtman-Roelofsen RL, OostvogelPM, et al. Timing of group B streptococcus screening in pregnancy:a systematic review. Gynecol Obstet Invest 2010;69:174–83.10. Tazi A, Re´glier-Poupet H, Dautezac F, et al. Comparativeevaluation of Strepto B ID chromogenic medium and Granadamedia for the detection of Group B streptococcus from vaginalsamples of pregnant women. J Microbiol Methods 2008;73:263–65.11. Van Dyke MK, Phares CR, Lynfield R, et al. Evaluation ofuniversal antenatal screening for group B streptococcus. N Engl JMed 2009;360:2626–36.642 C. Florindo et al. J Matern Fetal Neonatal Med, 2014; 27(6): 640–642J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Instituto Nacional de Saúde Dr. Ricardo Jorge on 06/16/14For personal use only.

Gomes, JP

Repositório Comum

2014http://informahealthcare.com/jmfISSN: 1476-7058 (print), 1476-4954 (electronic)J Matern Fetal Neonatal Med, 2014; 27(6): 640–642! 2014 Informa UK Ltd. DOI: 10.3109/14767058.2013.820700SHORT REPORTAccuracy of prenatal culture in predicting intrapartum group Bstreptococcus colonization statusCarlos Florindo1, Vera Damia˜o1, Jorge Lima2, Isabel Nogueira3, Isilda Rocha2,4, Paula Caetano2,5, Lurdes Ribeiro2,Silvia Viegas1, Joa˜o P. Gomes1, and Maria J. Borrego11National Institute of Health, Lisbon, Portugal, 2CUF Descobertas Hospital, Lisbon, Portugal, 3Maternity Alfredo da Costa, Lisbon, Portugal,4Fernando Fonseca Hospital, Amadora, Portugal, and 5Dona Estefaˆnia Hospital, Lisbon, PortugalAbstractObjective: To evaluate the positive predictive value (PPV) of group B Streptococcus (GBS)cultures at 35–37 weeks of gestation relative to GBS colonization status at delivery.Methods: Rectovaginal swabs from 221 women at labor in four Lisbon hospitals were collectedfor GBS screening according to the CDC guidelines.Results: The PPV was 24.4%. IAP was administered to 100% of prenatally GBS positive women.There was no case of early onset GBS disease (EOD).Conclusions: Poor accuracy of prenatal cultures in identifying true candidates for IAP highlightsthe need for Portuguese clinical and laboratory guidelines to prevent EOD and antibioticovertreatment of pregnant women.KeywordsEarly onset disease, intrapartum antibioticprophylaxis, intrapartum screening,Streptococcus agalactiaeHistoryReceived 13 February 2013Accepted 26 June 2013Published online 7 August 2013IntroductionStreptococcus agalactiae, group B Streptococcus (GBS) hasmultiple serotypes and is an opportunistic human pathogenthat can lead to life-threatening infections in newborns andimmunocompromized adults [1]. Maternal GBS carriage hasbeen recognized as the major risk factor of early onset diseasein newborns (EOD, 57 days of age) [1,2]. Up to 30% ofpregnant women are anogenital colonized, although thecarrier status is considered dynamic during pregnancy [2,3].CDC guidelines [2,4] recommend GBS screening at 35–37weeks of gestation in order to identify women at risk thatshould undergo intrapartum antibiotic prophylaxis (IAP) toavoid transmission to the newborn during labor; IAP becameresponsible for the reduction of EOD in developed countries.Nevertheless, strategies to prevent late onset disease (LOD),which occurs after the first week of life, have yet to emerge,as IAP is unable to avoid LOD. The screening-based approachis challenging, as its efficacy relies on its capacity to predictGBS colonization status at the time of labor. Publishedreports [5,6] showed that both negative (NPV) and positive(PPV) predictive values of prenatal GBS cultures relativelyto the GBS status at delivery are suboptimal, especially thePPV. We aimed to evaluate the PPV of GBS positive cultureat 35–37 weeks of gestation considering the GBS colonizationstatus at delivery.MethodsPatients and study designBetween March 2008 through June 2009, 221 pregnantwomen presenting a positive result for GBS at 35–37 weeksof gestation from 4 hospitals (Dona Estefaˆnia Hospital, n¼ 9;Maternity Alfredo da Costa, n¼ 42; Fernando FonsecaHospital, n¼ 67; and CUF Descobertas Hospital, n¼ 103)were selected for this study. It was not possible to determinethe laboratories (private and/or public) where pregnantwomen performed their GBS prenatal nor the methodologiesthat were used by those laboratories. The unknown coloniza-tion status at delivery was also used as an inclusion criterionin order to verify the intrapartum positivity of GBS in thisgroup of women (n¼ 88). Considering the main focus of thisstudy, and due to budget constraints, women with negativeGBS cultures at 35–37 weeks of gestation were excluded.All pregnant delivering before 35 weeks of gestation aswell as pregnant that had received antibiotic treatment up to3 weeks before admission were excluded.This study was approved by the ethics board of the involvedinstitutions, and a written informed consent was obtained fromall women prior to their enrolment in the study. Informationabout age, obstetric risk factors, and type of delivery werecollected. Later, information on whether newborns developedEOD during the hospital stay was also acquired.Collection and culture of specimensA combined recto-vaginal swab was collected from eachparturient on admission for delivery. Swabs were thenmaintained in a non-nutritive Amies medium (Biome´rieux)Address for correspondence: Maria J. Borrego, Department of InfectiousDiseases, National Institute of Health, Av. Padre Cruz 1649-016 Lisbon,Portugal. E-mail: m.jose.borrego@insa.min-saude.ptJ Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Jorge Lima on 06/07/14For personal use only.at room temperature until processing at the National Instituteof Health in Lisbon, within 24 h, according to the describedby the CDC guidelines [4]. Briefly, each swab was inoculatedin Todd Hewitt selective media broth at 37C, 5% CO2 for18 h and sub-cultured on Columbia agar supplementedwith 5% sheep blood (COS) (Biome´rieux) at 37C in 5%CO2 for an additional period of 24–48 h.GBS identification and antibiotic susceptibility testingS. agalactiae isolates were identified by standard criteriaon the basis of colony morphology, Gram staining, non-hydrolysis of aesculin on bile-aesculin agar and group Blatex-agglutination test. Antimicrobial susceptibility testing(penicillin G, erythromycin, clindamycin and vancomycin)was performed by Etest according to the Clinical andLaboratory Standards Institute guidelines [7].Capsular typing and screening of ST-17hypervirulent lineageCapsular typing was performed by using specific antiserafor serotypes Ia to V (Essum AB) and cps genotyping [3].The detection of ST-17 lineage was achieved by PCR, asdescribed elsewhere [8].StatisticsPositive predictive value (PPV) of prenatal GBS cultureswas calculated through the following formula: [(Number ofwomen GBSþ/þ)7 (number of women GBSþ/þ andGBSþ/)] 100%, where GBSþ/þ and GBSþ/ correspondto intrapartum positive and negative results, respectively(all samples had been positive positive at prenatal stage) [5].ResultsVaginal-rectal cultures were obtained from 221 GBS positivewomen on admission for delivery, 118 (53.4%) and 103(46.6%) from three public and one private hospitals, respect-ively. Overall, the average maternal age was 30.4 years (range,14–45 years) and the average gestational age at labor was 39.0weeks (range, 35.9–41.4 weeks). The mode of delivery wasvaginal or cesarean in 166 (75.1%) and 55 (24.9%) women,respectively. Among 55 women giving birth by cesareansection, 38 (69.1%) were performed electively and 17 (30.9%)were performed after labor, of whom 38 (69.1%) occurred atthe private hospital. Of 221 prenatally GBS-positive women,only 54 remained positive at delivery, corresponding to a PPVof 24.4%. All these 54 prenatal GBS-positive women receivedIAP (ampicillin was the first choice for IAP in the fourhospitals). However, on a risk-based screening (e.g. pretermdelivery), only 11 (5%) would have justified antibiotictreatment.None of the 88 parturients without prior GBS screeningrevealed intrapartum GBS colonization; however, 9/9 attend-ing to the private hospital and 17/79 attending to publichospitals (the ones presenting risk factors: preterm deliveries[n¼ 14]; GBS bacteriuria during the current pregnancy[n¼ 2]; previous child with EOD [n¼ 1]) received IAP.The serotype distribution showed the predominance ofserotype III (25/54 [46.3%]) followed by serotypes Ia (10/54[18.5%]), II (9/54 [16.7%]), V (7/54 [12.9%]), Ib (2/54[3.7%]) and IV (1/54 [1.9%]), which was quite similar to thatdescribed in Portugal for GBS colonization during the lasttrimester of pregnancy [3]. The lineage ST17 was identifiedin 56% (14/25) of the isolates belonging to serotype III;however, no newborn developed EOD during hospital stay.All clinical isolates were fully susceptible to penicillin Gor vancomycin. We observed a resistance rate of 7.4% toerythromycin and 1.8% to clindamycin, which were low whencompared to our previous data [3].DiscussionIn the present study, public and private hospitals evidenceddifferences regarding both the GBS screening during preg-nancy and the selection of candidates for IAP. As an example,only nine pregnant cases were presented to the privatehospital without GBS screening at 35–37 weeks of gestation,and all received IAP, versus 79 attending to public hospitals,where IAP was provided exclusively to the 17 parturientscomprehending risks. The lack of GBS screening duringpregnancy suggests unawareness, or indifference regardingthe free health care provided under the supervision of low-risk pregnancy in Portugal. Thus, social factors contributingto the exclusion from pregnancy surveillance in Portugal seemto need urgent assessment and adjustment.Although a great heterogeneity of PPVs has been described[5,6,9] ranging (43–100%), our study revealed a considerablylow PPV of 24.4%. This weak concordance between prenataland intrapartum culture results could be attributed to severalvariables, namely (1) timing of prenatal GBS screening;(2) laboratory methodologies; and (3) antibiotic usage.The influence of the timing of prenatal GBS screeningin this study would be neglectable; in fact, all enrolled GBSpositive women were screened at 35–37 weeks of gestation,which has been considered ideal for correlating with GBScolonization status at delivery, by longitudinal studies [9].The observed discrepancy could be explained, in part,by methodological heterogeneity (sampling, swab storageand transport, and culturing procedures) that could not bedetermined in the present study. In fact, in Portugal, the healthsystem allows pregnant women to freely choose thelaboratories where antenatal GBS screening is performed(screening at the same hospital of delivery is rare),implicating that a multitude of laboratories were involved,each one using their particular GBS detection protocols.There is neither Portuguese GBS laboratory screening guide-lines nor recommendations for following scientific guidelinesinternationally accepted, such as the provided by the CDC.In this scenario, an heterogeneity of methodologies appliedto GBS detection are to be expected, comprehending theproposed by the CDC guidelines but also less expensive andtime-consuming procedures, such as direct plating in bothColumbia 5% sheep blood agar and chromogenic medium(such as Strepto B ID or Granada). Each procedure hasinherent limits and drawbacks that can lead to GBSmisidentification.Another technical explanation could hold on the prolifer-ation of non-GBS isolates during storage and transport,such as Enterococcus and Proteus species, impairing theDOI: 10.3109/14767058.2013.820700 Antenatal versus intrapartum group B streptococcus screening 641J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Jorge Lima on 06/07/14For personal use only.identification and recovery of GBS on blood agar plates.Indeed, and consistent with published data [10], 12.2% of ourintrapartum cultures from prenatally GBS-positive womenevidenced an overgrowth of Gram negative bacteria in bloodagar plates (not supplemented with antibiotics), which mighthave obscured GBS colonies culminating in false-negativeresults. This emphasizes the need to improve the subculturesystem by using selective GBS media (Columbia agar withcolistin and nalidixic acid or a commercial chromogenicagar), as is currently recommended by the 2010 CDCguidelines [2]. Indeed, Van Dyke and colleagues [11] revealedthat 61.4% of EOD cases occurred in term newborns whosemothers were GBS-negative at 35–37 weeks. Whether thosenegative cultures were false-negative results or the parturientsacquired GBS during the interval between pregnancy screen-ing and delivery is unknown, but it surely evidences majorvariations in GBS colonization status during pregnancy.As we excluded pregnant subjected to antibiotic treatmentwithin 3 weeks before delivery, we would expect no influenceof this factor for the low PPV; however, we cannot excludethat some pregnant women during their hospital admissionquestionnaire omitted (by unidentified reasons) taking medi-cation, namely antibiotics. In fact, although in Portugala medical prescription is required for antibiotic purchase,irregularities to this rule exist, allowing self-medication.In conclusion, the reasons underlying a low PPV ofprenatal culture in predicting GBS colonization duringlabor in Portugal are hard to determine due to the lack ofnational clinical and laboratory guidelines for GBS preventionthat would contribute to the uniformity and quality of GBSscreening. This requisite would surely contribute to a higherPPV that would prevent EOD while avoiding overtreatmentof pregnant women.Also, and until the availability of an effective GBSvaccine, new reliable and fast intrapartum diagnostic toolsshould be developed to supplement antenatal GBS screening.AcknowledgementsThe authors thank Albertina Louro (National Institute ofHealth); Conceic¸a˜o Telhado, Mariana Loureiro, Glo´riaCarvalhosa, Mafalda Lucas, Maria Joa˜o Santos, Maria doCe´u Ramalho, Rosa Portela, Luı´s Mo´s, Anaı´lde Arau´jo,and Cristina Castel Branco (CUF Descobertas Hospital);Ana Lima, and Patrı´cia Silva (Maternity Alfredo da Costa);Graciete Novais, Elsa Guerreiro, Cecı´lia Artilheiro, PedroMendes, Anto´nio Fatia, and Lilita Miranda (FernandoFonseca Hospital) for collecting/processing clinical samples.Declaration of interestThe authors report no conflicts of interest. This work wassupported by Fundac¸a˜o para a Cieˆncia e Tecnologia grantPTDC/SAU-MII/105114/2008 from Ministe´rio da Cieˆncia,Tecnologia e Ensino Superior, Portugal and, PhD grantSFRH/BD/48231/2008 awarded to C.F.References1. Edwards MS, Nizet V. Group B streptococcal infections.In: Remington JS, Klein JO, Wilson CB, et al, eds. Diseases ofthe fetus and newborn infant, 7th ed. Philadelphia, PA: Elsevier;2011:419–69.2. Centers for Disease Control and Prevention (CDC). Prevention ofperinatal group B streptococcal disease. Revised guidelines fromCDC, 2010. MMWR Recomm Rep 2010;59:1–36.3. Florindo C, Viegas S, Paulino A, et al. Molecular characterizationand antimicrobial susceptibility profiles in Streptococcus agalactiaecolonizing strains: association of erythromycin resistance withsubtype III-1 genetic clone family. Clin Microbiol Infect 2010;16:1458–63.4. Centers for Disease Control and Prevention (CDC). Prevention ofperinatal group B streptococcal disease. Revised guidelines fromCDC. MMWR Recomm Rep 2002;51:1–22.5. Lin FY, Weisman LE, Azimi P, et al. Assessment of intrapartumantibiotic prophylaxis for the prevention of early-onset group BStreptococcal disease. Pediatr Infect Dis J 2011;30:759–63.6. El Helali N, Nguyen JC, Ly A, et al. Diagnostic accuracy of a rapidreal-time polymerase chain reaction assay for universal intrapartumgroup B streptococcus screening. Clin Infect Dis 2009;49:417–23.7. Clinical and Laboratory Standard Institute (CLSI). PerformanceStandards for Antimicrobial Susceptibility Testing M100-S19;19th Informational Supplement. Wayne: CLSI; 2009.8. Lamy MC, Dramsi S, Billoe¨t A, et al. Rapid detection of the highlyvirulent group B Streptococcus ST-17 clone. Microbes Infect 2006;8:1714–22.9. Valkenburg-van den Berg AW, Houtman-Roelofsen RL, OostvogelPM, et al. Timing of group B streptococcus screening in pregnancy:a systematic review. Gynecol Obstet Invest 2010;69:174–83.10. Tazi A, Re´glier-Poupet H, Dautezac F, et al. Comparativeevaluation of Strepto B ID chromogenic medium and Granadamedia for the detection of Group B streptococcus from vaginalsamples of pregnant women. J Microbiol Methods 2008;73:263–65.11. Van Dyke MK, Phares CR, Lynfield R, et al. Evaluation ofuniversal antenatal screening for group B streptococcus. N Engl JMed 2009;360:2626–36.642 C. Florindo et al. J Matern Fetal Neonatal Med, 2014; 27(6): 640–642J Matern Fetal Neonatal Med Downloaded from informahealthcare.com by Jorge Lima on 06/07/14For personal use only.

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Accuracy of prenatal culture in predicting intrapartum group B streptococcus colonization status

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