Abstract
Streptococcus agalactiae [also known as group B Streptococcus (GBS)] is a tremendous threat to young infants. Eighty pediatric GBS infection cases were enrolled from a teaching hospital in Shanghai between 2009 and 2020; among them, 72.5% (58/80) were diagnosed with bloodstream infection (BSI). Sequence types (STs) and serotypes of associated GBS strains were identified, and most of the Ib/clonal complex (CC)12 (86.7%, 13/15) strains caused BSIs, which was significantly higher than that of the genetically related clone Ib/CC10 (20%, 2/10; p < 0.05). Ib/CC12 BSI (30.8%) mortality was significantly higher than that of non-Ib/CC12 BSI (2.2%; p < 0.05). Virulence genes associated with adhesion, invasion, and immune evasion were detected using polymerase chain reaction. The fbsA and gbsPC1 positive rates of Ib/CC12 strains was higher than that of non-Ib/CC12 strains, whereas cpsIaJ, cpsJ, cpsI, and cpsG positive rates were lower than those of non-Ib/CC12 (p < 0.05). In in vitro studies, the Ib/CC12 strains had strong invasiveness in RAW264.7 cells, but less invasiveness in human umbilical vein endothelial cells, human brain microvascular endothelial cells, and human mammary epithelial cells when compared to other two clones. In the in vivo model, the Ib/CC12 GBS invaded the circulation system more rapidly after intraperitoneal injection, was more difficult to eradicate by phagocytes, and caused significantly higher mortality than Ib/CC10 and III/ST17 (p < 0.05). Genome analysis showed that the Ib/CC12 strains had two clustered regularly interspaced short palindromic repeat-Cas systems and carried more antibiotic resistant genes, which conferred resistance to macrolides, clindamycin, aminoglycosides, and tetracycline. The Ib/CC12 strains had 45 unique annotated genes compared to that of Ib/CC10, including the pathogen-related toxin/antitoxin system, PezA/T. In conclusion, Ib/CC12 is an emerging hypervirulent multiresistant GBS clone that causes invasive and fatal infections in pediatric patients. The prevention and control of Ib/CC12 GBS infection should be emphasized.
Highlights
Streptococcus agalactiae is a leading cause of invasive disease in neonatal and young infant patients, intrapartum antimicrobial prophylaxis (IAP) has significantly reduced the incidence of early onset group B Streptococcus (GBS) infection (Tan et al, 2021; Vatne et al, 2021; Wong et al, 2021)
Among the 80 patients, 72.5% (58/80) had bloodstream infection (BSI) or BSI complicated with other site infections, such as meningitis, pneumonia, or urinary tract infection, whereas 27.5% (22/80) had a single-site infection that did not progress into a BSI or other severe invasive infections
III/CC17 GBS was considered a highly virulent clone, since it is a major cause of invasive neonatal disease (Poyart et al, 2008)
Summary
Streptococcus agalactiae ( termed as group B Streptococcus, GBS) is a leading cause of invasive disease in neonatal and young infant patients, intrapartum antimicrobial prophylaxis (IAP) has significantly reduced the incidence of early onset GBS infection (Tan et al, 2021; Vatne et al, 2021; Wong et al, 2021). Invasive infection in young infant patients caused by GBS is often very serious, and the overall case fatality rates range from 1–8.4% in term infants to 5–20% in preterm infants (Raabe and Shane, 2019). GBS epidemiology in pediatric patients is changing in the post-IAP era; the number of other GBS clones isolated from pediatric invasive disease cases are increasing (Zhang et al, 2021). As antibiotic resistance increases (Hayes et al, 2020; Mudzana et al, 2021) and a vaccine is clinically unavailable (Berner, 2021), prevention of prenatal GBS remains a significant challenge. It is necessary to determine the clinical and molecular features of GBS isolated from clinical samples to optimize GBS prevention and treatment strategies
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