Journal List > Korean J Clin Microbiol > v.12(4) > 1038176

Uh, Choi, Jang, Lee, Cho, Kwon, and Yoon: Colonization Rate, Serotypes, and Distributions of Macrolide-Lincosamide-StreptograminB Resistant Types of Group B Streptococci in Pregnant Women

Abstract

Background

The prevalence of neonatal group B streptococcal infection depends mainly on the colonization rate of pregnant women by group B streptococci (GBS). Although the colonization rate of Korean women by GBS is considered lower than in other countries, recent data on the maternal colonization rate of GBS are sparse.

Methods

From August 2008 to June 2009, swab specimens from the anorectus, vagina, and urethral orifice of a sample of 234 pregnant Korean women were placed in new Granada medium (NGM-H), tube medium (NGM-T), commercial NGM (NGM-B), and selective Todd-Hewitt broth (S-THB) for 18∼24 hours in 5% CO2 at 35oC. Agar dilutional antimicrobial susceptibility tests, serotyping, and PCR were performed for GBS isolates.

Results

The colonization rate of GBS in pregnant women was 11.5% (27/234). Of the specimen cultures, 9.8% of anorectal cultures were positive, 8.1% of urethral orifice cultures were positive, and 7.3% of vagina cultures were positive. The detection rate of GBS in the different culture media was S-THB (96.3%), NGM-B (92.6%), NGM-H (88.9%), and NGM-T (85.2%). The distribution of GBS serotypes was as follows: III (29.6%), V and VI (22.2%), Ib and II (11.1%), and Ia (3.7%). 33.3% of GBS isolates were resistant to erythromycin and 44.4% to clindamycin. Among the nine erythromycin-resistant isolates, eight were serotype V and VI, which are erm(B) positive serotypes.

Conclusion

The colonization of pregnant women by GBS, and the incidence of resistance of the GBS isolates to erythromycin and clindamycin were higher than those previously reported. Serotypes V and VI, GBS serotypes that carry the erm(B), are novel serotypes that have not previously been identified in pregnant Korean women.

REFERENCES

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Table 1.
Colonization incidence of 234 pregnant women by GBS according to specimen type and culture method
Specimen type No. (%) of positive samples detected by
NGM-B plates NGM-H plates NGM tubes Selective THB Any method
Vaginal 14 (6.0) 13 (5.6) 14 (6.0) 17 (7.3) 17 (7.3)
Urethral 17 (7.3) 17 (7.3) 16 (6.8) 19 (8.1) 19 (8.1)
Anorectal 21 (9.0) 20 (8.5) 21 (9.0) 22 (9.4) 23 (9.8)
Total 25 (10.7) 24 (10.3) 23 (9.8) 26 (11.1) 27 (11.5)

Abbreviations: NGM, new Granada medium; NGM-B, commercial NGM, NGM-H, housemade NGM, THB, Todd-Hewitt broth.

Table 2.
Activities of antimicrobial agents against 27 isolates of group B streptococci from pregnant women
Antimicrobials MIC (μg/mL) Percent
Range MIC50 MIC90 S I R
Penicillin G 0.03∼0.06 0.03 0.03 100 0 0
Ceftriaxone 0.06∼0.12 0.06 0.06 100 0 0
Clindamycin 0.06∼≥256 0.06 ≥256 55.6 0 44.4
Erythromycin 0.06∼≥256 0.06 ≥256 66.7 0 33.3
Chloramphenicol 2∼4 2 2 100 0 0
Tetracycline 1∼64 32 64 14.8 0 85.2
Vancomycin 0.5 0.5 0.5 100 0 0

Abbreviations: I, intermediate; R, resistant; S, susceptible.

Table 3.
Distribution of MLSB gene and serotypes of GBS isolated from pregnant women
MLSB gene No. (%) of serotype Total
Ia Ib II III V VI
erm(B) 0 (0) 0 (0) 0 (0) 0 (0) 4 (50.0) 4 (50.0) 8
mef(A) 0 (0) 0 (0) 0 (0) 1 (100) 0 (0) 0 (0) 1
ND 1 (5.6) 3 (16.7) 3 (16.7) 7 (38.9) 2 (11.1) 2 (11.1) 18
Total 1 (3.7) 3 (11.1) 3 (11.1) 8 (29.6) 6 (22.2) 6 (22.2) 27

No. of isolates that MLSB resistant gene was not detected.

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