ABSTRACT
Objective:
To investigate the
phenotypes, molecular types and
drug-resistance
genes of
erythromycin (ERY)-resistant group B
Streptococcus (GBS) in
pregnant women in late
pregnancy in Zhengzhou and provide basic data for the prevention, control and
treatment of GBS
infection.
Methods:
This study retrospectively collected 86 GBS
strains isolated from the vaginal
secretions of
pregnant women in late
pregnancy at
Maternal and Child Health Hospital of Henan Province from 2021 to 2022. ERY-resistant GBS
strains were selected using the ERY disk
diffusion method, and their susceptibility to 10 different
antibiotics was tested. Whole-
genome sequencing was performed to analyze their molecular features including molecular types, clonal complex groups and
drug-resistance
genes.
Drug-resistance
genes carried by GBS
strains belonging to different clonal complex groups were compared.
Results:
There were 70 ERY-resistant GBS
strains. Among them, 7.14%(5/70) exhibited an inducible resistance
phenotype to
macrolide-lincosamide-
streptogramin B (MLSB)
antibiotics; 84.29%(59/70) showed constitutive resistance to MLSB
antibiotics; 8.57%(6/70) were resistant to
macrolides but susceptible to
lincosamides. The resistance rates of these
strains to
clindamycin (CLI),
tetracycline (TE) and
levofloxacin (LEV) were 91.43%(64/70), 54.29%(38/70) and 60.00%(42/70), respectively. These ERY-resistant
strains exhibited
multidrug resistance patterns with 40.00%(28/70) showing ERY-CLI-LEV resistance
phenotype and 30.00%(21/70) showing ERY-CLI-TE resistance
phenotype. The major
drug-resistance
genes carried by the 70 GBS
strains were
macrolide/lincosamide resistance
genes mreA (100.00%) and ermB (53/70, 75.71%),
aminoglycoside resistance
genes ant (6)-Ⅰ a (22/70, 31.43%) and aph(3′)-Ⅲ (18/70, 25.71%), and
tetracycline resistance genes tetM (22/70, 31.43%) and tetO (13/70, 18.57%). These
strains belonged to 12 sequence types derived from seven clonal complexes (CCs) and 48.57%(34/70) of them were clustered into CC12. All CC12
strains harbored ermB, but none carried ermA. The positive rates of lsaE, lunB, and aac (6′)- aph(2" ) in CC19 and CC651
strains,
ant (6)-Ⅰ a in CC651 and CC452
strains, and mefA and msrD in CC19 and CC23
strains were significantly higher than those in CC12
strains ( P<0.001).
Conclusions:
ERY-resistant GBS in Zhengzhou exhibited diverse
drug resistance phenotypes and molecular types. CC12 was the most prevalent clonal complex in this region. The constitutive MLSB resistance
phenotype and ermB
gene were the most common ERY resistance
phenotype and
genotype, respectively, and tetM
gene was related to
tetracycline resistance. Furthermore, the
drug-resistance
genes varied in GBS
strains of different clonal complexes. This study suggested that close
attention should be paid to the epidemiological situation of GBS in this region and the
effectiveness of
antibiotics used for clinical prevention and
treatment of GBS
infection should be carefully evaluated.
