Late-Onset Sepsis in a Premature Infant Mediated by Breast Milk: Mother-to-Infant Transmission of Group B Streptococcus Detected by Whole-Genome Sequencing.

Background: Late-onset group B Streptococcus (LOGBS) sepsis is a cause of infection and death in infants. Infected breast milk has been considered a source of neonatal GBS infection and invasive infection. However, mother-to-infant transmission of GBS detected by the high-resolution diagnostic method is rarely reported. Methods: This study describes a low-weight premature infant who developed late-onset GBS septicemia 21 days after birth. GBS strains isolated from the mother's cervical secretion, the mother's milk, and the baby's blood were cultured to identify the source of GBS infection. We further confirmed the GBS isolates through matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS). Finally, we performed whole-genome sequencing (WGS) and phylogenetic analyses on the GBS strains recovered. Results: GBS isolates were cultured from the bloodstream of the premature infant and the mother's milk, respectively. Subsequently, WGS and phylogenetic analyses on three GBS isolates demonstrated that the GBS strain from the infant's bloodstream was 100% homologous to that from the mother's breast milk, which had some different gene fragments from the GBS strain from the mother's cervical secretion. It provided evidence that this infant's late-onset GBS septicemia originated from his mother's breast milk instead of the vertical mother-to-infant transmission. Conclusion: Through WGS and phylogenetic analysis of the GBS strains, we proved in this study that the late-onset GBS sepsis in a premature infant was derived from his mother's breast milk. It indicated that WGS diagnosis is an effective tool for infection tracing. Furthermore, this report provides direction for preventing late-onset GBS infection.

Genomic and Phenotypic Diversity of Listeria monocytogenes Causing Pregnancy-Associated Listeriosis from Zhejiang Province, China, 2016-2018.

INTRODUCTION: There are few investigations describing the pregnancy-associated listeriosis in China, and the molecular characteristics of Listeria monocytogenes causing such infections remain largely unknown. We aim to investigate the phenotypic and genomic profiles of pregnancy-associated L. monocytogenes isolates and their association with isolates recovered from human and non-human in China. MATERIALS AND METHODS: In this study, we conducted a 3-year surveillance of listeriosis in a women's hospital in Zhejiang province, using whole genome sequencing and bioinformatics tools. RESULTS: From 2016 to 2018, we identified 13 clinical L. monocytogenes isolates. Among these pregnancy-associated isolates, we found seven sequence types (STs), with the prevalent STs of ST87 and ST7. Serotyping divided the strains into four serotypes, including serotype 1/2a, 1/2b, 3a, and 4b. Antimicrobial resistance testing showed that all the isolates were susceptible to 10 antibiotics. Comparative genomics analysis clearly classified our genome collection into four distinct evolutionary lineages with most isolates grouping into lineages I and II. Interestingly, we found three pairs of isolates with high identity, although no evident epidemiological association was observed. CONCLUSION: This study reports for the first time the surveillance of pregnancy-associated listeriosis in Zhejiang province, China, which indicates that the infection rate is low in this region. Our findings provide insight into the evolution and genetic diversity of pregnancy-associated L. monocytogenes from Zhejiang province. Additional investigations involving more human and non-human isolates with a "one health" strategy are needed for prediction of the listeriosis risk associated with a typical prevalent clone in Zhejiang province, such as ST87.