| Objective To investigate the colonization prevalence,and to master antimicrobial susceptibility,drug-resistant phenotypes,drug-resistant genes,virulence genes,capsular serotypes and molecular types of group B streptococcus(GBS)in perinatal women in Qingdao,which provides molecular epidemiological data for effective treatment and prophylaxis of maternal and neonatal GBS infection.Methods Vaginal-rectal swabs were collected from pregnant women at 35 to 37 weeks' gestation from Dec 2017 to Dec 2018 in Qingdao municipal hospital affiliated Qingdao University.The identification and antimicrobial susceptibility testing of isolates were carried out by CAMP testing and VITEK 2 Compact automatic bacterial identification and antimicrobial sensitivity analysis system after culturing,and the drug-resistant phenotypes were completed by D testing.Capsular serotypes were identified by the agglutination method.Erythromycin resistance genes(erm A,erm B,erm C and mef A/E),clindamycin resistance genes(lin B),and virulence genes(lmb,bac,scp B,rib and hyl B)were amplified by polymerase chain reaction(PCR).The seven housekeeping genes were amplified by PCR,and multilocus sequence typing(MLST)was carried out after sequencing.The sequences of the seven loci obtained were concatenated and used to build a phylogenetic tree by Geneious 10.0 software with the UPGMA method.Statistical analysis of the results were used by SPSS 24.0 software.Results(1)54 isolates of GBS were detected in 1265 specimens from the late pregnant women,and the colonization rate with GBS was 4.3%.(2)Five serotypes were detected of 54 isolates(3.7% Ia,31.5% Ib,3.7% II,44.4% III and 9.3% V).(3)All isolates were sensitive to penicillin,ampicillin,linazolamine and vancomycin,whereas the resistance of isolates to erythromycin,clindamycin,levofloxacin and tetracycline was 66.7%,70.4%,74.1% and 53.7%,respectively.Results of macrolide antibiotic resistance phenotypes were c MLSB(77.8%),i MLSB(19.4%)and M phenotype(2.8%).36 isolates of GBS were resistant to erythromycin,and 11.1% isolates possessed erm A genes,75.0% isolates possessed erm B genes,66.7% isolates possessed erm C genes and 22.2% isolates possessed mef A/E genes,but lin B genes were not found.(4)The virulence genes were detected in 54 GBS strains,the most frequent virulence gene was lmb(90.7%),followed by the scp B(88.9%),hyl B(81.5%),rib(42.6%)and bac(31.5%)genes.(5)MLST data from 54 GBS isolates resulted in 13 STs including one new ST(37.0% ST10,29.6% ST19,11.1% ST27,3.7% ST12 and ST862,1.9% ST1,ST17,ST26,ST171,ST485,ST676,ST921 and ST1519).13 STs were grouped into five major clonal complexes(CCs): CC19(44.4%),CC10(40.7%),CC17(3.7%),CC485(5.6%)and CC1(9.4%),and the remaining one was singleton.Significant association between MLST,serotypes and resistance genes or virulence genes were found,such as ST10/?b and bac,carrying both erm B and erm C,ST19/? and rib.Conclusion(1)The prevalence of GBS in parturients in Qingdao was 4.3%.(2)Serotypes ?,?b and ? were the most frequent among 54 GBS isolates evaluated.(3)Resistance to macrolides,lincomycins and quinolones were high,and beta-lactam antibiotics remain appropriate for first line treatment and prophylaxis against GBS infection.The predominant resistance genes to erythromycin were erm B,erm C and mef A/E.(4)The main virulence genes carried by GBS were lmb,scp B and hyl B.(5)Multilocus sequence typing(MLST)were mainly ST10,ST19 and ST27,and clonal complexes(CCs)were mainly comprised of CC19 and CC10.Significant association between MLST,serotypes and resistance genes or virulence genes were found,and the mechanism of erythromycin resistance was complicated in this area,resulting in the widespread prevalence of specific GBS isolates.Medical institutions at all levels should further strengthen GBS routine screening and antimicrobial surveillance. |
PDF Full Text Request