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Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women

Nabil El Aila (UGent) , Inge Tency (UGent) , Geert Claeys (UGent) , Bart Saerens (UGent) , Piet Cools (UGent) , Hans Verstraelen (UGent) , Marleen Temmerman (UGent) , Rita Verhelst and Mario Vaneechoutte (UGent)
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Abstract
Background: Streptococcus agalactiae (group B streptococcus; GBS) is a significant cause of perinatal and neonatal infections worldwide. To detect GBS colonization in pregnant women, the CDC recommends isolation of the bacterium from vaginal and anorectal swab samples by growth in a selective enrichment medium, such as Lim broth (Todd-Hewitt broth supplemented with selective antibiotics), followed by subculture on sheep blood agar. However, this procedure may require 48 h to complete. We compared different sampling and culture techniques for the detection of GBS. Methods: A total of 300 swabs was taken from 100 pregnant women at 35-37 weeks of gestation. For each subject, one rectovaginal, one vaginal and one rectal ESwab were collected. Plating onto Columbia CNA agar (CNA), group B streptococcus differential agar (GBSDA) (Granada Medium) and chromID Strepto B agar (CA), with and without Lim broth enrichment, were compared. The isolates were confirmed as S. agalactiae using the CAMP test on blood agar and by molecular identification with tDNA-PCR or by 16S rRNA gene sequence determination. Results: The overall GBS colonization rate was 22%. GBS positivity for rectovaginal sampling (100%) was significantly higher than detection on the basis of vaginal sampling (50%), but not significantly higher than for rectal sampling (82%). Direct plating of the rectovaginal swab on CNA, GBSDA and CA resulted in detection of 59, 91 and 95% of the carriers, respectively, whereas subculturing of Lim broth yielded 77, 95 and 100% positivity, respectively. Lim broth enrichment enabled the detection of only one additional GBS positive subject. There was no significant difference between GBSDA and CA, whereas both were more sensitive than CNA. Direct culture onto GBSDA or CA (91 and 95%) detected more carriers than Lim broth enrichment and subculture onto CNA (77%). One false negative isolate was observed on GBSDA, and three false positives on CA. Conclusions: In conclusion, rectovaginal sampling increased the number GBS positive women detected, compared to vaginal and/or rectal sampling. Direct plating on CA and/or GBSDA provided rapid detection of GBS that was at least as sensitive and specific as the CDC recommended method of Lim broth subcultured onto non chromogenic agar.
Keywords
ENRICHMENT, DISEASE, BROTH, MEDIA, COLONIZATION, IDENTIFICATION, RECTAL SWABS, GRANADA MEDIUM, CHROMOGENIC AGAR MEDIUM, AGALACTIAE

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MLA
El Aila, Nabil, et al. “Comparison of Different Sampling Techniques and of Different Culture Methods for Detection of Group B Streptococcus Carriage in Pregnant Women.” BMC INFECTIOUS DISEASES, vol. 10, 2010, doi:10.1186/1471-2334-10-285.
APA
El Aila, N., Tency, I., Claeys, G., Saerens, B., Cools, P., Verstraelen, H., … Vaneechoutte, M. (2010). Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women. BMC INFECTIOUS DISEASES, 10. https://doi.org/10.1186/1471-2334-10-285
Chicago author-date
El Aila, Nabil, Inge Tency, Geert Claeys, Bart Saerens, Piet Cools, Hans Verstraelen, Marleen Temmerman, Rita Verhelst, and Mario Vaneechoutte. 2010. “Comparison of Different Sampling Techniques and of Different Culture Methods for Detection of Group B Streptococcus Carriage in Pregnant Women.” BMC INFECTIOUS DISEASES 10. https://doi.org/10.1186/1471-2334-10-285.
Chicago author-date (all authors)
El Aila, Nabil, Inge Tency, Geert Claeys, Bart Saerens, Piet Cools, Hans Verstraelen, Marleen Temmerman, Rita Verhelst, and Mario Vaneechoutte. 2010. “Comparison of Different Sampling Techniques and of Different Culture Methods for Detection of Group B Streptococcus Carriage in Pregnant Women.” BMC INFECTIOUS DISEASES 10. doi:10.1186/1471-2334-10-285.
Vancouver
1.
El Aila N, Tency I, Claeys G, Saerens B, Cools P, Verstraelen H, et al. Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women. BMC INFECTIOUS DISEASES. 2010;10.
IEEE
[1]
N. El Aila et al., “Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women,” BMC INFECTIOUS DISEASES, vol. 10, 2010.
@article{1071173,
  abstract     = {{Background: Streptococcus agalactiae (group B streptococcus; GBS) is a significant cause of perinatal and neonatal infections worldwide. To detect GBS colonization in pregnant women, the CDC recommends isolation of the bacterium from vaginal and anorectal swab samples by growth in a selective enrichment medium, such as Lim broth (Todd-Hewitt broth supplemented with selective antibiotics), followed by subculture on sheep blood agar. However, this procedure may require 48 h to complete. We compared different sampling and culture techniques for the detection of GBS.
Methods: A total of 300 swabs was taken from 100 pregnant women at 35-37 weeks of gestation. For each subject, one rectovaginal, one vaginal and one rectal ESwab were collected. Plating onto Columbia CNA agar (CNA), group B streptococcus differential agar (GBSDA) (Granada Medium) and chromID Strepto B agar (CA), with and without Lim broth enrichment, were compared. The isolates were confirmed as S. agalactiae using the CAMP test on blood agar and by molecular identification with tDNA-PCR or by 16S rRNA gene sequence determination.
Results: The overall GBS colonization rate was 22%. GBS positivity for rectovaginal sampling (100%) was significantly higher than detection on the basis of vaginal sampling (50%), but not significantly higher than for rectal sampling (82%). Direct plating of the rectovaginal swab on CNA, GBSDA and CA resulted in detection of 59, 91 and 95% of the carriers, respectively, whereas subculturing of Lim broth yielded 77, 95 and 100% positivity, respectively. Lim broth enrichment enabled the detection of only one additional GBS positive subject. There was no significant difference between GBSDA and CA, whereas both were more sensitive than CNA. Direct culture onto GBSDA or CA (91 and 95%) detected more carriers than Lim broth enrichment and subculture onto CNA (77%). One false negative isolate was observed on GBSDA, and three false positives on CA.
Conclusions: In conclusion, rectovaginal sampling increased the number GBS positive women detected, compared to vaginal and/or rectal sampling. Direct plating on CA and/or GBSDA provided rapid detection of GBS that was at least as sensitive and specific as the CDC recommended method of Lim broth subcultured onto non chromogenic agar.}},
  articleno    = {{285}},
  author       = {{El Aila, Nabil and Tency, Inge and Claeys, Geert and Saerens, Bart and Cools, Piet and Verstraelen, Hans and Temmerman, Marleen and Verhelst, Rita and Vaneechoutte, Mario}},
  issn         = {{1471-2334}},
  journal      = {{BMC INFECTIOUS DISEASES}},
  keywords     = {{ENRICHMENT,DISEASE,BROTH,MEDIA,COLONIZATION,IDENTIFICATION,RECTAL SWABS,GRANADA MEDIUM,CHROMOGENIC AGAR MEDIUM,AGALACTIAE}},
  language     = {{eng}},
  pages        = {{8}},
  title        = {{Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women}},
  url          = {{http://dx.doi.org/10.1186/1471-2334-10-285}},
  volume       = {{10}},
  year         = {{2010}},
}

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