| ObjectiveTo investigate prevalence rate of maternal(vagin)and neonatal(oral,eyes,ears and umbilicus)Staphylococcus aureus(S.aureus)colonization,phenotypes and molecular characteristics of S.aureus,relationship of S.aureus between mothers and infants and the relative risk(RR),in order to provide the theory for preventing and controlling S.aureus infection effectively.MethodsProspective cohort study and molecular epidemiology were conducted in our study.Convenience sampling method was performed to enroll expectant mothers who were in hospitals of Shenzhen Longhua and vaginal swabs were collected.Pregnant women were distributed to exposure group which the vaginal samples were S.aureus positive and the control group which the vaginal samples were S.aureus negative.The main outcome was the result of S.aureus colonization of babies.We compared the neonatal prevalence rate of S.aureus between the two groups and computed the relative risk(RR).The relationships between influencing factors and S.aureus and MRSA carriage were examined using Generalized Linear Models(GLM),including variables with P < 0.05 in the univariate analysis.Kirby-Bauer test was conducted to test the antimicrobial drug resistance of S.aureus.Cefoxitin disk diffusion test and mecA gene PCR assay were conducted to identify methicillin-resistant Staphylococcus aureus(MRSA).Then t-test,?2 test and fisher exact probability test were conducted to investigate the influencing factors of S.aureus and MRSA colonization,the drug resistance between MRSA isolates and methicillin-susceptible Staphylococcus aureus(MSSA)isolates.Kappa test was used to analyze phenotypes and toxin-encoding genes characteristics consistency of S.aureus isolates from mothers and infants.PCR assay was performed to test PVL gene,TST gene,ETA gene,ETB gene and SCCmec typing of MRSA isolates.Multilocus sequencing typing(MLST)was conducted to identify the molecular typing of S.aureus homology.ResultsDemographics characteristic: The cohort study totally enrolled 1834 pregnant women,including 133 pregnant women in exposure group(S.aureus positive)and 1701 pregnant women in control group(S.aureus negative).1834 samples of infants were obtained after follow-up.Colonization rate of S.aureus and MRSA: Among 1834 pregnant women,7.25%(133/1834)of them were S.aureus positive,with 1.69%(31/1834)were MRSA positive.Among 1834 infants,3.27%(60/1834)of them were S.aureus positive,with 0.82%(15/1834)were MRSA positive.S.aureus colonization rate of infants from exposure group and control group was 15.79% and 2.29%,respectively and rate of MRSA was 2.26% and 0.71%,respectively.Significant difference of S.aureus colonization in infants between the two cohorts was observed.Maternal S.aureus colonization was a risk factor for neonatal S.aureus colonization(RR=6.89,95% CI: 4.18-11.36).After adjusted gender,delivery way,premature rupture of fetal membranes and pregnancy days,the value of aRR was 6.90(95% CI: 4.22-11.27)of S.aureus colonization.There were 21 mother-newborn pairs who were S.aureus positive in both mothers and infants.Antimicrobial susceptibility test: The resistance rates of S.aureus isolates sampled from pregnant women were especially high in clindamycin(41.35%),erythromycin(50.38%),teicoplanin(81.20%)and Penicillin(92.48%).Compared with MSSA isolates,MRSA was a risk factor for multidrug-resistance(OR=3.64,95% CI: 1.23-13.02).While resistance rates of S.aureus isolates sampled from infants were especially high in clindamycin(28.33%),erythromycin(46.67%)and Penicillin(93.33%).MRSA was a risk factor for multidrug-resistance(OR=12.36,95% CI: 2.56-76.77),too.Statistical significance was not appeared between the resistance rates of neonatal S.aureus isolates of these two cohorts.The phenotypes characteristics of the 21 mother-newborn pairs were significantly consistent(P<0.01),with a moderate consistency(Kappa=0.523).Virulence genes detection: Detection rate of PVL,ETA,ETB and TST genes in maternal S.aureus isolates was 2.26%,3.01%,0.00% and 2.26%,respectively and 5.00%,3.33%,11.67% and 0.00% of neonatal S.aureus isolates.The detection rate of virulence genes was not statistical significant between MRSA and MSSA isolates from both mothers and newborns.PVL gene and ETB gene were not detected in the 21 mother-newborn pairs.Consistency of detection of TST gene and ETA gene in mother-newborn pairs was statistical significantly,with an optimum consistency(Kappa=1.000)and a moderate consistency(Kappa=0.462),respectively.SCCmec typing: Among 31 maternal MRSA isolates,45.16%(14/31)belonged to hospital-associated MRSA(HA-MRSA)and 29.03%(9/31)belonged to community-associated MRSA(CA-MRSA),with predominant isolates of type?(11/31)and type ?a(7/31).Among 15 neonatal MRSA isolates,20.00%(3/15)belonged to HA-MRSA and 26.67%(4/15)belonged to CA-MRSA,with predominant isolates of type ?a(4/7)and type ?(2/7).The resistance rates of both maternal and neonatal MRSA isolates were especially high in clindamycin,erythromycin and Penicillin.There were no significant differences of antimicrobial resistance in HA-MRSA and CA-MRSA isolates.One pair of MRSA isolates was found in the 21 mother-newborn pairs and they both belonged to type ?.MLST: The most prevalent ST types in both maternal and neonatal S.aureus isolates were ST188(37/133,15/60),ST7(18/133,7/60)and ST6(14/133,5/60),while the most common ST types in both maternal and neonatal MRSA isolates were ST59(8/31,4/15),ST6(6/31,2/15)and ST188(5/31,3/15).In clustering analysis,clonal complexes which represented high homology,doublets and singletons were found.The most predominant clonal complexes in maternal and neonatal S.aureus isolates were CC5(71/133,28/60),followed by CC7(18/133,7/60).In tree diagram analysis,19 of 21 mother-newborn pairs were respectively clustered,which were similar to eBURST V3.ConclusionsMaternal and neonatal S.aureus colonization rate was relatively low.But prevalence rate of MRSA colonization increased in pregnant women.About 65% of maternal and 38% of neonatal S.aureus was multidrug-resistance,with a low detection rate of virulence genes.The prevalent maternal MRSA isolates were HA-MRSA and the prevalent neonatal MRSA isolates were CA-MRSA.The predominant ST types of maternal and neonatal S.aureus isolates were ST188,ST7 and ST6 and they were ST59,ST6 and ST188 of MRSA isolates.The ST types of S.aureus isolates were similar to the predominant types in China,and they were relative to international prevalent clones.Infants born to mothers with S.aureus colonization were more likely to be colonized(aRR=6.90). |
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