Application of fluorescent PCR in screening of group B streptococcus in perinatal pregnant women and analysis of molecular characteristics of group B streptococcus with negative CAMP test

ObjectiveTo explore the application value of fluorescent polymerase chain reaction (PCR) in screening of group B streptococcus (GBS) in perinatal pregnant women and the identification and analysis of GBS with negative CAMP test.

MethodsA total of 1 143 vaginal/rectal swabs were collected from pregnant women aged 35-37 weeks in the obstetric clinic.The swabs were placed in a GBS enrichment broth tube to enrich the bacteria, and then GBS chromogenic plate and fluorescent PCR were used to detect GBS.16SrDNA molecular identification technology was used to identify the species of GBS with negative CAMP test, and PCR was used to detect its cfb gene.

ResultsThe chromogenic plate detected 146 positive samples, with a positive rate of 12.77%, and the fluorescent PCR detected 191 positive samples, with a positive rate of 16.71%.The difference between the two methods was statistically significant (P<0.01).Compared with the chromogenic plate culture method, the fluorescent PCR method had a sensitivity of 93.15%, a specificity of 94.48%, and a coincidence rate of 94.31%.Among the 146 GBS strains, 10 strains were negative for CAMP test, with a detection rate of 6.85%, and all strains were cfb gene deletion.

ConclusionsThe fluorescent PCR can effectively increase the positive rate of GBS screening for pregnant women during the perinatal period.The detection rate of GBS with negative CAMP test is relatively high in this area, and CAMP test should not be used as an identification test for GBS.Due to the deletion of cfb gene, GBS molecular detection reagents should not select this gene to design primers.