MLST Application in Analysis of Relationship between Group B Streptococcus Resistance Gene and Induction Resistance in Shanghai, China

Abstract

Background With the gradual severe bacterial resistance and slow development of antibiotics, drug-resistant bacterial strains are widely distributed and have become a serious public health problem. Group B Streptococcus (GBS) which cause Group B strep-related disease is the major cause of severe infection in newborns. However, Clindamycin resistance of GBS induced by Erythromycin is emerging and become important clinical concerns today. Methods A retrospective study was conducted on the drug resistance analysis of GBS strains isolated from Obstetrics and Gynecology Hospital from Jan 2016 to Dec 2017. The clinical and microbiological data including patient demographics, antimicrobial susceptibility testing, relative distribution drug resistance-associated genes mefA & ermB to Erythromycin, and multilocus sequence typing (MLST typing) were collected and analyzed. The Kirby-Bauer and VITEK2-compact were used to perform the susceptibility testing. The double disk diffusion method (D-test) was used for the detection of inducible clindamycin resistance. MLST was employed to identify sequence types of these strains. Polymerase Chain Reaction (PCR) was conducted to detect the drug resistance genes mefA & ermB to Erythromycin. Results A total of 1021 strains were cultured and isolated from 31894 specimens. Erythromycin and clindamycin resistance was 53.6%（547/1021）and 50.1 % (512/1021), respectively, in which 74.4%（407/547）had harbored constitutive macrolide, lincosamide and streptogramin B resistance (cMLS B ), 45.0%（63/140）were inducible MLS B (iMLS B ). Additionally, MLST identified 12 different ST types including a new ST type ST1072 in 63 iMLS B GBS strains and the dominant STs were ST12 (30.1%) and ST19 (25.4%). The resistance ratio of ST19 to Levofloxacin (75.0%) was higher than that of other ST types. The relevance resistance ratio of mefA and ermB was respectively 27.0% and 41.3% among 63 GBS isolates. Conclusion Our study not only demonstrated a genetic diversity in iMLS B GBS in Shanghai through the analysis of MLST typing and resistance genes, but also found that there exist different distribution patterns of resistance and related resistance genes between different ST types. These findings would provide theoretical support for clinical prevention and treatment of resistant iMLS B GBS infection.