Screening And Serotyping Value Of Streptococcus Lactis-free Colonization In Late Pregnancy

Objective :Rectal genital tract colonization and mother-to-child transmission of Streptococcus agalactis,or Group B streptococci(GBS),is one of the important causes of maternal puerperal infection and neonatal infection or death.The overall colonization rate is 18% globally and 11.3% in China.The incidence of vertical infection due to GBS colonization is 1-2%,resulting in miscarriage,low birth weight infants,neonatal infections,and in severe cases,neonatal death,while 30% of survivors will have neurological sequelae.Thus,group B streptococcus is a considerable threat to the health of newborns.In this study,we used a prospective study to screen 6259 pregnant women with rectal and vaginal swabs,and collected maternal and fetal-related data from 35 weeks of gestation until discharge by follow-up,and performed risk factors for GBS colonization in pregnant women and analysis of maternal and fetal adverse outcomes and analysis of the prevalence of serotypes and virulence genes to investigate the risk factors for GBS colonization and the impact of colonization on maternal and fetal adverse outcomes,with the aim of reducing maternal and neonatal The aim was to reduce the incidence of maternal and neonatal adverse outcomes and improve the quality of maternal and child survival.Methods: 1.A prospective cohort study of pregnant women in the First Affiliated Hospital of Kunming Medical University hospital from November 2021 to October2022,vaginal secretions and rectal swabs were collected for GBS culture,identification and drug sensitivity test,and 298 GBS positive were included in the observation group and 298 GBS negative were randomly selected for the control group during the same period of maternity examination according to the culture results.Maternal and neonatal data were followed from 35 weeks of gestation until discharge,and the risk factors for GBS colonization were analyzed by univariate analysis of adverse outcomes between the two groups and multifactorial regression.2.200 GBS strains obtained by isolation were serotyped by multiplex PCR,and 9virulence genes bac,bca,rib,chyl B,Imb,scp B,cyl B,fbs A and fbs B were detected by PCR,and the correlation between serotyping,prevalence characteristics of virulence genes and the two was analyzed.Results:1.Detection: rectal and vaginal swabs from 6259 pregnant women were isolated from a total of 512 pregnant women without Streptococcus lactis,with a positive colonization rate of 7.6%,of which only rectal swabs were positive at a rate of 4.2%(263/6259),accounting for 51.4%(263/512),vaginal swabs were positive at a rate of0.88%(55/6259),accounting for 10.7%(55/512),and 3.1%(194/6259)or 37.9%(194/512)for both swabs were positive.2.Drug resistance: No strains of GBS resistant to penicillin and vancomycin were found among 512 strains of GBS,but the resistance rates to clindamycin and erythromycin were high,76.6% and 72.3%,respectively.In the test for clindamycin resistance induction,81 strains of GBS showed positive results,with a positive rate of15.8%.3.Univariate analysis of pregnant women revealed that the differences in maternal age,number of pregnant women ≥35 years,gestational diabetes,gestational hypothyroidism,intrapartum antibiotic prophylaxis(IAP),postpartum hemorrhage,and chorioamnionitis were higher in the observation group than in the control group,and the differences were statistically significant(P < 0.05).There was no statistically significant difference between the two groups in terms of education,albumin level at delivery,pre-pregnancy body mass index(BMI),maternal weight gain,hypertensive disorders during pregnancy,maternal fever at delivery,history of miscarriage,primiparity or menstruation,number of children born,puerperal infection,and endometritis(P > 0.05).4.Univariate analysis of neonatal aspects revealed that the proportions of fetal distress,low birth weight infants,high risk infants,and neonatal infections were significantly higher in the observation group than in the control group,and the difference was statistically significant(P < 0.05).There were no statistically significant differences between the two groups in terms of neonatal sex,delivery via the birth canal or cesarean section,premature rupture of membranes,amniotic fluid properties,preterm delivery,amniotic fluid index,neonatal weight,full-term small sample,neonatal respiratory disease,neonatal hyperbilirubinemia,blue light treatment,and number of neonatal deaths((P > 0.05)).5.Multi-factor logistic regression analysis showed that gestational combined diabetes,gestational combined hypothyroidism and maternal age ≥35 years were independent risk factors for GBS rectovaginal colonization.6.For the 200 GBS colonized strains,a total of 7 serotypes were detected by multiplex PCR typing: III(31.0%)and V(30.5%)ranked the top two,accounting for61.5%,followed by Ib(27.0%),Ia(7.0%),II(3.0%),and VI(1.0%),respectively,and1 case was not typed,while types IV,VII,VIII,and IX were not detected.7.Among the 200 GBS colonized strains,the detection rate of 9 virulence genes:30.0% for bac gene,55.5% for bca gene,40.5% for rib gene,92.0% for chyl B gene,92.0% for Imb gene,91.5% for scp B gene,100% for cyl B gene,fbs A gene and fbs B gene,91.0% GBS all contained 6 virulence genes of chyl B-Imb-scp B-cyl B-fbs A-fbs B.8.Serotype and virulence gene correlation: the highest proportion of serotype Ⅲ strains carried the rib gene,and the difference was statistically significant(P < 0.05);the proportion of serotype Ib strains carrying the bac gene and bca gene was much higher than the proportion carried in serotype Ia,type Ⅲ,type Ⅱ and type Ⅴ,and the difference was statistically significant(P < 0.05).Conclusion: The rate of GBS rectal and vaginal positivity in our region was 7.6%;gestational combined diabetes mellitus,gestational combined hypothyroidism,and maternal age ≥35 years(all P < 0.05)were independent risk factors for GBS rectovaginal colonization in late pregnancy;GBS rectovaginal colonization in pregnant women leads to postpartum hemorrhage and chorioamnionitis,resulting in fetal distress,low birth weight infants,high risk infants,and neonatal infections in the newborns born.It can lead to fetal distress,low birth weight babies,high risk babies,neonatal infections and other adverse outcomes.Penicillin is still the drug of choice for the prevention and treatment of GBS infection,so we should pay great attention to the screening and detection of GBS in women in late pregnancy,and actively work on early prevention and treatment to reduce adverse outcomes.The occurrence of adverse pregnancy outcomes should be reduced.