The Study Of Serotypes Distrbution And Related Resistance Genes For Group B Strepotoccus Isolated From Infant With Invasive Disease

Objectives:To understand the clinical manifestation,perinatal risk factors,laboratory examination and clinical outcome of invasive infection of group B streptococcus in infant.To explore the characteristics of serotypes distribution,antibiotics resistance,antibiotics resistance phenotype and the carrying of related antibiotics resistance genes of GBS strains in infants with invasive infection,so as to provide reliable epidemiological data for the prevention and treatment of GBS infection in infants in the local region.Methods:1.Clinical data of infant who were diagnosed as invasive GBS infection in Jiangxi Children’s Hospital from January 2017 to December 2021 were Collected,and relevant clinical data and laboratory examination results were counted.2.From June 2017 to June 2021,62 GBS strains isolated from sterile parts of children were identified by Phoneix-100 automatic bacterial analysis system,and the antibiotics resistance phenotypes of GBS strains resistant to erythromycin and clindamycin were detected by double-disk diffusion method.3.ermA,ermB and mefA/E of erythromycin resistance genes;linB of Clindamycin resistance gene;tetO,tetM,tetL,tetK of tetracycline resistance genes and capsular serotype cps genes were amplificated by common PCR.Results:1.A total of 77 children with invasive GBS infection were admitted to Jiangxi Children’s Hospital from 2017 to 2021.During the 5 years,the number of children with GBS infection showed a downward trend,and the number of early-onset infection showed a more obvious downward trend than that of late-onset infection.Children with early-onset infection were prone to respiratory symptoms,mostly manifested as moaning,shortness of breath and spitting.Late-onset infections were often hospitalized with fever as the first symptom.The incidence of meningitis in children with invasive GBS infection was 50.7%.There were significant differences in WBC,CRP,SAA and PCT between sepsis group and meningitis group.The mortality rate of children with GBS invasive infection was 6.5%,and the mortality rate of early onset was higher than that of late onset,2.Serotype Ⅰ a,Ⅰ b,Ⅲ,Ⅴ were detected in 62 strains of group B streptococcus.Serotype Ⅲ was the most common serotype(51.6%),followed by type Ⅰ b(33.6%),type Ⅰ a(12.9%)and type Ⅴ(1.6%).There was no significant difference between early-onset and late-onset GBS infection iyn serological distribution.63.6%of GBS strains isolated from CSF were serotypeⅢ.3.The resistance rate of the isolates to erythromycin,clindamycin,tetracyline and levofloxacin were 83.9%,80.6%,69.4%,17.7%.No resistance strains to penicillin,cefotaxime,linezolid and vancomycin were found.There were significant differences in resistance rates of erythromycin,clindamycin and tetracycline among different serotypes of GBS.Type Ⅰ b and type Ⅲ showed higher resistance than type I a.4.49 cMLSB and 3 M-type strains were found from 54 erythromycin and(or)clindamycin resistant strains;2 strains showed L phenotype and no iMLSB was found by antibiotics resistance phenotype.The most prevalent of erythromycin resistance gene was ermB(86.5%),followed by mefA/E(44.2%).ermB and mefA/E could exist alone or coexist,and all three M phenotype strains carried mefA/E gene alone.ermA gene was not detected,and linB gene was detected in 32.0%of strains.TetO and tetM genes of Tetracycline resistance were prevalent,and tetL and tetK were not found.The Ⅰb serotype strains of GBS showed cMLSB resistance phenotype and all of them carried ermB and tetO genes.Conclusions:1.In recent years,the number of children with GBS invasive infection had been declining,mainly in early onset.The decline of WBC and the greatly increase of CRP,SAA and PCT on infant with GBS infected indicated the occurrence of suppurative meningitis.2.Serotypes of invasive GBS strains in infants were concentrated in this region,the most prevalent of Serotypes were Ⅲ and Ⅰ b,The resistance rate to erythromycin and clindamycin were high,cMLSB was the most prevalent resistance phenotype,Bacterial antibiotics susceptibility test should be performed before clinical antibiotics use.The high resistance produced by strains with highly prevalent serotypes of GBS should be concerned.