Infections in pregnant women caused by Streptococcus agalactiae and problems with growing MLSB-type resistance

Abstract number: 1733_6

Strus M., Brzychczy-Wloch M., Gosiewski T., Drzewiecki A., Kochan P., Pawlik D., Heczko P.

Objectives: Over the recent years in Poland one could observe the growing numbers of pregnant women colonised with group B streptococci (GBS). Epidemiologically speaking it raises concern, because of severe consequences, i.e. higher number of infections and deaths in newborns. Therefore, the main aims of this study were to:

- compare the effectiveness of GBS detection in pregnant women using the classical culture method and a modified culture method recommended by the CDC;

- show the frequency of GBS carriage among the populations of healthy pregnant women versus women with high-risk pregnancy;

- examine the frequency of resistance markers to macrolides and lincosamides (MLSB) among the GBS strains isolated from Polish women.

Methods: The study was performed on a group of 629 women between the II and III trimester of pregnancy. 156 women were classified as high-risk pregnancy. The materials collected for microbiological tests were vaginal and anal swabs. The materials were cultured on selective media and evaluated for GBS growth. The bacteria were identified by phenotypic methods and their identification was confirmed by genotyping, using the fluorescent in situ hybridisation (FISH) with the Saga 67 a/b probe selective for Streptococcus agalactiae species. MLSB-type resistance markers were also determined, their presence was verified by looking for the erm a, b, c genes with multiplex PCR.

Results: Carriage of GBS was confirmed in 13.5% of pregnant women by using the classical culture method. Using the CDC recommended method improved the detection to 20.8%. When using the CDC method, it was observed that the high-risk pregnancy had higher rates of carriage of GBS, up to 22.4%. MLSB-type resistance markers were detected in strains isolated with the CDC recommended method.

Conclusion:

1. When comparing the effectiveness of GBS detection in pregnant women using the classical culture method versus the CDC recommend method, we showed improved detection (~5%) using the CDC method.

2. We showed that the frequency of GBS carriage among women with high-risk pregnancy is 3% higher than that for healthy pregnant women.

3. When analysing the phenotypic resistance of GBS strains to macrolides and lincosamides, we showed an 8% more frequent presence of the MLSB-type resistance among S. agalactiae in women with high-risk pregnancy (n = 156), than in women with normal pregnancy (n = 250).