Efficacy of a universal screening program for the prevention of neonatal group B streptococcal disease

Universal antepartum vaginal cultures for group B streptococcus (GBS) were initiated in a Spanish hospital in 1994 using Granada medium. Infants born to carriers were monitored closely, and blood, urine and mucocutaneous areas were cultured for GBS. Group B streptococcus was detected in 543 of 4,525 women (12 %). Of these, 454 gave birth vaginally, of whom 201 (44 %) received intrapartum ampicillin. Prophylaxis was not administered to 253 women (56 %). In this group, infants of 120 women were colonized and 1 case of neonatal GBS disease occurred. Using this protocol, most GBS carriers with risk factors received intrapartum prophylaxis. This protocol also led to early identification of colonized newborns.     

Group B streptococcal colonization patterns in mothers and their infants.

Maternity patients and their newborn infants were cultured for group B streptococci (GBS) at Tampa General Hospital, Tampa, Fla., from September 1982 to May 1983. Culture swabs were placed into Lim Group B Strep Broth (GIBCO Laboratories, Madison, Wis.) and quantitated for GBS. A strong correlation was found between the numbers of GBS in the maternal vagina and the infant rectum. Infants symptomatic for early-onset GBS disease were delivered by mothers heavily colonized (greater than or equal to 3 X 10(4) GBS per swab) at the vagina. Such mothers were identified as GBS carriers by slide coagglutination and latex agglutination after their broth cultures had been incubated for 5 h. These data indicate that maternity patients at high risk of delivering infants heavily colonized with GBS and potentially symptomatic for early-onset GBS disease can be rapidly and selectively identified.     

Comparison of a modified DNA hybridization assay with standard culture enrichment for detecting group B streptococci in obstetric patients.

Infection with group B streptococcus (GBS) results in 12,000 to 15,000 cases of neonatal sepsis annually in the United States. GBS is transmitted vertically in up to 70% of infants born to colonized women. Early-onset GBS disease (septicemia, pneumonia, or meningitis occurring within 7 days of life) has a mortality rate of up to 50%, with permanent neurologic sequelae occurring in 15 to 50% of infants surviving meningeal infection. Because of the fulminant nature of neonatal infection, it would be useful to have a rapid assay for determining the GBS status of laboring women. This study illustrated how a commercially available DNA probe-based test was modified to achieve this goal. Modifications included the use of mixed cultures rather than pure isolates for detecting GBS, along with a shorter culture enrichment time and a sample concentration step. To this end, vaginal and rectal swabs from 402 pregnant women during their third trimester were cocultured and tested for GBS rRNA. The 8-h enrichment protocol resulted in an assay with a sensitivity of 95% and specificity of 98%, while the 3-h enrichment protocol revealed a sensitivity of 73% and specificity of 99%. In summary, GBS was detected in the majority of colonized women in less than 4 h. This study illustrated the usefulness of the approach in identifying the most heavily colonized women, who are at the highest risk of transmitting GBS to their neonates. The modified test would have a significant impact on both the medical management and antibiotic therapy for these women and their newborns.     

Lim group B Strep Broth and coagglutination for rapid identification of group B streptococci in preterm pregnant women.

A total of 147 preterm pregnant women at Orlando Regional Medical Center were screened for group B streptococci by using Lim Group B Strep Broth (GIBCO Laboratories, Madison, Wis.) and the Phadebact Strep B Test (Pharmacia Diagnostics, Piscataway, N.J.). Test results were available within 20 h of culture and, in the case of heavily colonized women, within 5 h. This procedure is useful in rapid diagnosis of preterm pregnant women for group B streptococcal colonization.     

Cervical Secretions in Pregnant Women Colonized Rectally with Group B Streptococci have High Levels of Antibodies to Serotype III Polysaccharide Capsular Antigen and Protein R

Group B streptococci (GBS) colonizing the female genital tract will often infect newborn infants during delivery. In 200 pregnant women studied, 14% were colonized with GBS in the cervix, 12% in the rectum, and 9% in both cervix and rectum. We have previously reported that antibody levels to GBS serotypes Ia, II, and III in sera and cervical secretions were increased in women colonized in the rectum and/or cervix, when analyzed by a whole-cell ELISA. Here, we report the levels of antibodies to GBS serotype III capsular polysaccharide antigen (CPS III) and to protein antigen R₄, which are present in most GBS III strains. Compared to culture-negative women, the group of women colonized rectally had markedly elevated levels of immunoglobulin (Ig)A and IgG antibodies in cervical secretions to both CPS III and protein R₄ ( P  < 0.01 and P  < 0.001, respectively). In sera, the corresponding differences between culture-negative and culture-positive women were less pronounced, or not present. In contrast to antibody levels to whole-cell GBS, antibody levels to CPS III and protein R₄ in cervical secretions were not significantly increased in women colonized only in the cervix, except that IgA antibodies to protein R₄ were slightly elevated ( P  < 0.05). These findings suggest that capsular type-specific polysaccharides and protein R₄ in a mucosal vaccine might induce protective antibodies against GBS colonization of the uterine cervix.     

Value of a rapid screening technique for vaginal carriage of group B Streptococcus during hig-risk pregnancies]

Vaginal colonization by Group B streptococci (GBS) during pregnancy is associated with lige-threatening neonatal infections acquired during passage through the birth canal. Factors associated with an increased risk of GBS transmission to the neonate include prematurity, premature spontaneous rupture of the membranes before 37 weeks of gestational age, prolonged (> 12 h) rupture of the membranes at full term, fever in the mother, multiple pregnancy, and a history of GBS infection. A study was conducted to evaluate the performance characteristics of a rapid GBS screening test comparatively with conventional microbiological cultures. The 113 high-risk women admitted for delivery to the obstetrics department of the Charleville-Mézières Hospital from January to May 1998 were included in the study. Vaginal specimens were examined by both the Strep B OIA test (International Microbio) and by conventional culturing. Comparison of the results of these two methods showed that sensitivity and specificity of the Strep B OIA test were satisfactory. The Strep B OIA test is a rapid test suitable for use in emergency situations. A positive result should lead to intrapartum prophylactic antimicrobial therapy.     

MATERNAL AND NEONATAL SCREENING FOR GROUP B STREPTOCOCCI BY SCP B GENE BASED PCR: A PRELIMINARY STUDY

Objective: To detect the magnitude of group B streptococcal (GBS) colonization and disease among a sample of pregnant women and their infants in Egypt. Study Design: Prospective observational study. Participants: The study included 95 pregnant females, 35–37 weeks of gestational age, attending the antenatal outpatient clinic at AlFayom University Hospital between September 2006 and June 2007. All participants were screened with vaginorectal swabs by a conventional GBS PCR assay. Participants were grouped into group A (GBS present, 17 patients) and group B (GBS absent, 78 patients). Details with regard to labor and delivery were recorded and placental pathology was examined to detect histological chorioamnionitis. Ninety-five infant data were also recorded. All neonates of group A (17 out of 95 with known positive maternal GBS) underwent collection of simultaneous specimens from surface sites for PCR before their first bath and within four hours of birth. Results: GBS carriage rate in the study sample was 17.89%. Chorioamnionitis confirmed in three patients by placental pathology (one was in group A and two in group B) was statistically not significant. Twenty-two women had rupture of membranes (<12 hours) before delivery (four from group A and 18 from group B) that was not statistically significant. There were three infants out of 17 in group A who had GBS colonized at one or more sites by PCR which was statistically significant. However, only one infant was admitted to neonatal intensive care unit (NICU) that was not statistically significant. Conclusion: Maternal GBS carriage is associated with a significant increase in neonatal infection rate but is not associated with an increase in neonatal intensive care admission. An accurate evaluation of colonization rate (using a larger sample) is desired to evaluate neonatal invasive disease and determine the cost effectiveness of PCR to select an appropriate preventive strategy in Egypt.     

Use of GBS Media for Rapid Detection of Group B Streptococci in Vaginal and Rectal Swabs from Women in Labor

 In order to evaluate the differences in efficacy, three methods were used to detect group B streptococci (GBS) in women in labor. The recommended method for detecting GBS carriage in pregnant women is to culture vaginal and anorectal swabs in a selective broth medium and to subculture them onto blood agar. This method was compared with the use of GBS agar and GBS broth, both of which produce an orange pigment in response to GBS strains. A total of 319 women in labor were screened. Among the 638 specimens tested, 134 (21%) were positive in the selective Todd-Hewitt broth subcultured onto sheep blood agar, 133 (20.8%) were positive on the GBS agar and 126 (19.7%) were positive in the GBS broth. Altogether, 89 (27.9%) women in labor were found to be colonized with GBS; 87 (97.8%) of them were identified as carriers using the Todd-Hewitt broth, 87 (97.8%) with the GBS agar and 86 (96.6%) with the GBS broth. These results indicate that both GBS agar and GBS broth are reliable methods that can be used to screen for maternal and neonatal GBS colonization.     

Vaginal colonization of the Streptococcus agalactiae in pregnant woman in Tunisia: risk factors and susceptibility of isolates to antibiotics

Streptococcus agalactiae or Group B Streptococcus (GBS) is one of the main bacterial causes of serious infections in newborns. We have evaluated prospectively GBS vaginal colonization in pregnant women and we have tried to determine the risk factors of the colonization by GBS and the particularities of the different isolated strains. We have screened 300 pregnant women with vaginal and anal sample in a same swab. Thirty nine (13%) pregnant women are colonized by SGB, 0% in the first trimester, 10.2% in the second trimester and 17% in the third trimester. Different factors are associated significantly with GBS colonization: past history of infection in newborns, genital infection during pregnancy and parity The highest rates of resistance are found in tetracycline (97.4%), erythromycin (51.3%) and lincomycin (46.2%). All the strains were susceptible to amoxicilin and pristinamycin.     

Carriage of group B Streptococcus in pregnant women and newborns: a 2-year study at Perugia General Hospital

Objective: To study the prevalence of group B Streptococcus (GBS) colonization in pregnant women and their newborns at Perugia General Hospital.
Method: The number of mother-child pairs examined was 2300. Vaginal swabs were collected from the mothers at delivery, and auricular and pharyngeal swabs and gastric aspirate from the newborns at birth. Maternal risk factors for GBS disease, including premature delivery, intrapartum fever, prolonged rupture of membranes and multiple births, were evaluated.
Results: Maternal and neonatal colonization rates were 11.3% and 4.6%, respectively. GBS was isolated in 41.5% of the neonates born to colonized mothers and in 0.1% of those born to non-colonized mothers. No significant difference was observed in vertical transmission rates in the presence or absence of maternal risk factors. The external auditory canal was the most frequent (93.5%) and heavily colonized body site. Type Ib was the most common serotype among GBS isolates from mothers and babies. C surface protein was not detected in serotype V and VIII isolates, but was frequent in all other serotypes. Early-onset disease was observed in 0.4/1000 live births.
Conclusions: The prevalence of maternal and neonatal colonization at Perugia General Hospital was similar to that obtained in other studies performed in Italy. The external auditory canal was confirmed as the most reliable body site to be sampled for the detection of neonates exposed to maternal GBS colonization.     

Prevention of early-onset neonatal group B streptococcal disease with selective intrapartum chemoprophylaxis

Most cases of neonatal group B streptococcal disease with early onset have an intrapartum pathogenesis. Attack rates are increased substantially in infants born to mothers with prenatal group B streptococcal colonization and various perinatal risk factors (premature labor, prolonged membrane rupture, or intrapartum fever). In a randomized controlled trial, we studied the effect of selective intrapartum prophylaxis with ampicillin in 160 such high-risk women. In infants born to mothers who received intravenous ampicillin during labor, as compared with controls who received no treatment, neonatal colonization with group B streptococci was present in 8 of 85 (9 percent) versus 40 of 79 (51 percent; P less than 0.001), colonization at multiple (greater than or equal to 3) sites was observed in 3 of 85 (4 percent) versus 24 of 79 (30 percent; P less than 0.001), and bacteremia occurred in none of 85 versus 5 of 79 (6 percent; P = 0.024). The side effects of ampicillin were limited to a single episode of urticaria in a mother who had no history of penicillin allergy. We conclude that intrapartum ampicillin prophylaxis in women with positive prenatal cultures for group B streptococci who have certain perinatal risk factors can prevent early-onset neonatal group B streptococcal disease.     

Effects of intrapartum penicillin prophylaxis on intestinal bacterial colonization in infants

Early-onset group B streptococcal (GBS) infections remain a leading cause of morbidity and mortality in infants. To prevent the vertical transmission of GBS and neonatal GBS infection, guidelines recommend intrapartum penicillin or amoxicillin prophylaxis. This intrapartum antibiotic prophylaxis (IAP) is suspected to favor colonization by antibiotic-resistant bacteria. However, the effects of this prophylaxis on the patterns of acquisition of gastrointestinal bacterial flora in infants have never been studied. We collected stool samples from 3-day-old infants born to mothers who received intrapartum amoxicillin (antibiotic-exposed group; n = 25) and to untreated mothers (non-antibiotic-exposed group; n = 25). The groups were matched for factors known to affect intestinal microbial colonization: gestational age, type of delivery, and type of feeding. Qualitative and quantitative differential analyses of the bacterial flora in stool samples were performed. Similar numbers of infants in the non-antibiotic-exposed and antibiotic-exposed groups were colonized by aerobic bacteria and amoxicillin-resistant enterobacteria (75 and 77%, respectively) (P = 0.79). In contrast, significantly fewer infants in the antibiotic-exposed group than in the non-antibiotic-exposed group were colonized by anaerobic bacteria, especially Clostridium (12 and 40%, respectively) (P < 0.05). Regarding intestinal bacterial colonization, the differences between antibiotic-exposed and non-antibiotic-exposed infants were remarkably few. The only statistically significant effect was the reduced initial bacterial colonization by Clostridium in the antibiotic-exposed group. In our study, the use of IAP did not favor colonization by beta-lactam-resistant bacteria. However, further evaluations are required to highlight the potential risks of the widespread use of antibiotics to prevent early-onset GBS infection.     

Rapid detection of group B streptococcal antigen in human amniotic fluid.

Infants exposed in utero to group B streptococcus (GBS)-infected human amniotic fluid (HAF) are at high risk for serious infection. Latex particle agglutination (LPA) tests are not approved for detection of GBS in HAF. Two LPA systems, Patho-Dx Strep B and Wellcogen Strep B, were used to test unfiltered sterile HAF and filtered HAF containing concentrations of GBS carbohydrate from 0.2 to 100 micrograms/ml. Four different processing techniques were used to prevent nonspecific LPA: EDTA, nitrous acid, enzyme, and nitrous acid-heat. GBS (10(2) CFU/ml) was inoculated into filtered HAF, incubated, sampled serially, processed with enzyme, and tested by LPA. Unprocessed, unfiltered HAF showed 33% nonspecific agglutination when tested by LPA. Processing of HAF removed nonspecific agglutination and improved GBS antigen detection. Without processing, LPA could not detect less than 100 micrograms of GBS carbohydrate per ml. With nitrous acid or enzyme processing, as little as 0.2 microgram/ml could be detected. Results were easier to read after enzyme processing than after nitrous acid processing. Although both LPA systems were equally efficient, testing was easier with the Patho-Dx system. After enzyme processing, LPA could detect as few as 10(4) CFU/ml when agglutination was read with a 4 X hand lens. Substances in HAF induce false-positive reactions during LPA testing. Processing removes the interference and improves the detection of GBS. LPA testing of HAF may allow earlier identification and treatment of infants at risk for serious GBS infection.     

Dynamics of Streptococcus agalactiae colonization in women during and after pregnancy and in their infants

The population dynamics of Streptococcus agalactiae (group B streptococci [GBS]) colonization of the vagina and anorectal area was investigated in a cohort of 77 Danish women during and after their pregnancy by a new sensitive method. The mean carriage rate among individual observations was 36%, and the cumulative carriage rate over the entire observation period was 54%. Examination of more than 1500 GBS isolates by pulsed-field gel electrophoresis demonstrated that the GBS population was remarkably homogeneous and stable in each carrier. Virtually all carriers were colonized by a single GBS clone on all occasions spanning up to 2 years. Repeated detection of the same clone even in women who were recorded as intermittent carriers suggests that the actual carrier rate exceeds 50% but that fluctuations in the GBS proportions of the flora occasionally preclude their detection. Newborns and young infants usually carried the same GBS clone as their mothers. However, only twice were identical clones of GBS detected in different women in contrast to the observed clonal relationships of clinical isolates. These observations strongly suggest differences in the properties and epidemiology of virulent GBS clones compared to clones commonly carried by healthy individuals.     

Seroprevalence of antibodies to group B streptococcal polysaccharides in Gambian mothers and their newborns.

In developing countries, little is known about the relationship between group B streptococcal (GBS) colonization in pregnant women and serum antibody levels to capsular polysaccharide antigens of these organisms. This study examined the prevalence of antibodies to two polysaccharides of GBS, Ia and III, in 124 Gambian women with known GBS colonization at delivery and their newborns. Mean antibody levels in maternal-cord serum pairs were 4.06 +/- 0.25 micrograms/mL and 2.64 +/- 0.20 micrograms/mL for type Ia GBS, and 1.1 +/- 0.52 microgram/mL and 0.78 +/- 0.43 microgram/mL for type III GBS. Women colonized with type V GBS had significantly higher antibody levels to type III GBS than did noncolonized women, but no difference was found when these groups were compared for antibody levels to type Ia GBS. Women > or = 20 years had significantly higher antibody levels to type III GBS compared with younger women and those colonized by other GBS serotypes. Maternal antibodies to types la and III GBS were transferred across the placenta to newborns. The rarity of GBS disease in Gambia and other developing countries may be due to the prevalence of maternally derived GBS antibodies, the low prevalence of colonization with serotype III strains, or other undefined factors.     

Maternal immunoglobulin allotype (Gm and Km) and neonatal group B streptococcal infection

Gm and Km(1) allotypes in 37 mothers of neonates with severe Group B streptococcal (GBS) infection were compared with 115 mothers of non-infected infants, 36 of whom were known to be colonized with GBS. Deficits in G1m(1) and Km(1), and an increased incidence of G2m(23), were found in mothers of infected infants. Km(1) was associated mainly with the phenotype Gm(1, (2), 3, 17; 23; 5, 10, 11, 21) in mothers of infected infants while being uniformly distributed in mothers of non-infected infants. This study would seem, therefore, to support reports of Gm and Km(1) allotype involvement in maternal response to GBS infection and immunity in the new-born.     

Intrapartum Group B streptococcus detection by rapid polymerase chain reaction assay for the prevention of neonatal sepsis

Group B streptococcus (GBS) is a leading cause of infectious neonatal morbidity and mortality. Timely and accurate identification of colonized mothers is imperative so that antibioprophylaxis can be implemented during labour to reduce the risk of neonatal sepsis. We planned our study to analyse the diagnostic accuracy of an intrapartum PCR assay to identify GBS-colonized women and to allow the implementation of correct (i.e. at least 4 h) intrapartum antibiotic prophylaxis based on the PCR results. We included 695 women in labour who were tested for rectovaginal GBS carriage by culture and PCR. Women were also screened at 35–37 weeks of gestation. Intrapartum GBS colonization was 19.3%. Assay sensitivity was 81.0% for antenatal culture and 85.0% for intrapartum PCR; p 0.72. GBS colonization (n = 107) was known at least 4 h before delivery in 68 (64%) and 73 (68%) women based on antenatal culture and intrapartum PCR, respectively. Among 43 women delivering preterm, correct status was known at least 4 h before delivery in 10 (23%) and 32 (74%) women according to antenatal culture and intrapartum PCR, respectively. These results support the concept that GBS screening can be performed routinely during labour in a clinical setting. The intrapartum approach is at least as accurate as the antenatal screening, with the additional advantage of identifying women delivering preterm or not followed during pregnancy.     

Rapid detection of group B streptococci directly from vaginal swabs.

Duplicate vaginal swabs were obtained from patients who attended obstetric or gynecologic clinics affiliated with the Magee Womens Hospital in Pittsburgh. One swab was cultured semiquantitatively on 5% sheep blood agar to detect group B streptococci (GBS). The other swab was subjected to a rapid method (25 min) for antigen detection and micronitrous acid exposure to extract the GBS antigen, followed by latex particle agglutination. A total of 464 swabs were evaluated by direct plating. Fifty-two swabs (11.2%) were found to contain GBS. Overall, the rapid method detected 21 of 52, or 40.4%, positive specimens. The sensitivity of the rapid method for identifying the most heavily colonized samples was 85.7%. This method can be used to identify maternity patients who are heavily colonized with GBS and are at high risk of delivering septic infants.     

Colonization in the rectum and uterine cervix with group B streptococci may induce specific antibody responses in cervical secretions of pregnant women.

We have studied the relationships between genital or rectal carriage of group B streptococci (GBS) with the levels of systemic and mucosal antibodies to GBS in 200 women at about week 17 of pregnancy. Secretions from the uterine cervix were collected with absorbent cylindrical wicks for quantification of antibody levels with whole cell enzyme-linked immunosorbent assay. GBS were cultured from the cervix (with or without concomitant rectal colonization) of 13.5%, from the rectum (with or without concomitant cervical colonization) of 12%, and from both culture sites of 8.5% of the women. Serotypes Ia, II, and III were predominant. Compared with culture-negative women, the group of women colonized rectally had markedly elevated levels of both immunoglobulin A (IgA) and IgG antibodies to GBS in cervical secretions and also had a moderate but significant elevation of IgA antibodies in sera. Women colonized only in the cervix had increases of specific IgA and IgG antibodies in cervical secretions, but their serum antibody levels were not elevated. In cervical secretions, the increase in antibody levels in the groups of colonized women was most pronounced for the IgG isotype, indicating a mucosal immune response involving IgG as well as IgA. A close correlation was found among the levels of antibodies to each of the three GBS serotypes tested. Evidence for such cross-reacting antibodies to different serotypes of GBS, as well as to group A streptococci, was also obtained from absorption experiments. Altogether, our results show that undiluted secretions for antibody determination can be easily collected from the uterine cervix with absorbent wicks and demonstrate that colonization of GBS in the rectum and the uterine cervix may induce a systemic as well as a pronounced local immune response in the female genital tract. The findings may have implications for the development of a mucosal vaccine against GBS disease.     

Role of cellular lipoteichoic acids in mediating adherence of serotype III strains of group B streptococci to human embryonic, fetal, and adult epithelial cells.

Lipoteichoic acids (LTA) of serotype III strains of group B streptococci (GBS) were shown to mediate adherence of these organisms to human embryonic (HEC), fetal (HFC), and adult buccal (HBEC) epithelial cells. The binding of GBS was temperature dependent, and maximum attachment occurred at 37 degrees C. HEC, HFC, and HBEC preincubated with purified LTA significantly inhibited attachment of GBS, whereas the group B and type III antigens had no effect. Under phosphate-limiting conditions in which cell-associated LTA could not be detected in these organisms, bacterial adherence did not take place. GBS (virulent) that were isolated from infected infants and previously shown to have significantly higher quantities of cell-associated LTA in comparison to GBS strains from asymptomatically colonized infants adhered with greater binding avidity to HEC and HFC and in greater numbers than to HBEC. It was determined that the mechanism of LTA-mediated adherence of GBS to HBEC differed from adherence to embryonic and fetal cells for both virulent and asymptomatic GBS strains bound to HBEC in a similar manner, enhanced by the lipid portion of the LTA. In contrast, the binding of GBS to HEC and HFC was mediated by hydrophobic as well as specific interactions due to the glycerolphosphate polymer of LTA. These results indicate that possible receptor sites for LTA present on cells in prenatal stages of development may differ from those of adult cells, which may result in increased susceptibility of newborn infants to group B streptococcal disease. The implications of LTA-mediated adherence of GBS and their possible role as virulence factors are discussed.