Clinical characteristics and molecular epidemiology of invasive Streptococcus agalactiae infections between 2007 and 2016 in Nara, Japan

Nobuyasu Hirai,Sadahiro Ichimura,Masahide Yoshikawa,Yoshihiko Ogawa,Kei Kasahara,Akiyo Nakano,Miho Ogawa,Hisakazu Yano,Naokuni Hishiya,Ryuichi Nakano,Yuki Suzuki,Matthew Payne

doi:10.1371/journal.pone.0240590

Nobuyasu Hirai, Sadahiro Ichimura + Show 10 more

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https://doi.org/10.1371/journal.pone.0240590

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Abstract

Invasive Streptococcus agalactiae (GBS) infections are increasingly common among neonates and the elderly. Therefore, GBS surveillance for better antibiotic treatment and prophylaxis strategies are needed. We retrospectively evaluated the clinical aspects of invasive infections and the phenotypic and genetic diversity of infectious isolates from Nara, Japan, collected between 2007 and 2016, by using information from hospital records. GBS strains collected from the blood and cerebrospinal fluid cultures were evaluated for capsular types, multi-locus sequence typing (MLST), antibiotic susceptibility, antibiotics resistance gene, and pulsed-field gel electrophoresis. Forty GBS isolates (10 from children and 30 from adults) were analyzed, and the distribution of molecular serotype and allelic profiles varied between children and adults. We found the rates of early-onset disease in neonates with birth complications to be higher than that of previous reports, indicating that there could be relevance between complications at birth and early-onset disease. Standard antibiotic prophylaxis strategies may need to be reconsidered in patients with birth complications. In adults, the mean age of the patients was 68 years (male: 63%). Primary bacteremia was the most common source of infection. In the neonates, six had early-onset diseases and four had late-onset diseases. The most frequently identified strains were molecular serotype Ia ST23 (40%) and molecular serotype Ib ST10 (20%) in children and molecular serotype Ib ST10 (17%), molecular serotype VI ST1 (13%), and molecular serotype V ST1 (13%) in adults. Levofloxacin-resistant molecular serotype Ib strains and molecular serotypes V and VI ST1 were common causes of GBS infection in adults but were rarely found in children. Furthermore, pulsed-field gel electrophoresis in our study showed that specific clone isolates, that tend to have antibiotics resistance were widespread horizontally for a decade. Continuous surveillance and molecular investigation are warranted to identify the transmission route and improve antibiotic treatment strategies.

Highlights

Streptococcus agalactiae, known as Lancefield group B Streptococcus (GBS), is a Gram-positive coccus species of the human gastrointestinal and genitourinary flora, and causes severe diseases, such as bacteremia, chorioamnionitis, and pneumonia [1]
Invasive GBS infections were defined as cases, in which GBS was isolated from blood and spinal fluid cultures
The GBS isolates were susceptible to the antibiotics in all the cases

Summary

Introduction

Streptococcus agalactiae, known as Lancefield group B Streptococcus (GBS), is a Gram-positive coccus species of the human gastrointestinal and genitourinary flora, and causes severe diseases, such as bacteremia, chorioamnionitis, and pneumonia [1]. Early- and late-onset GBS infections in infants occur within or after the first week of life, respectively. Most infections occur in the first three months, with high mortality and morbidity rates [2]. The Centers for Disease Control and Prevention recommends a strategy based on intrapartum chemoprophylaxis for pregnant women to lower the risk of GBS infections in infants [3]. The incidence of GBS infections is increasing in elderly patients with underlying medical conditions, such as malignancies, diabetes, and liver diseases [4]. Invasive GBS infection, especially primary bacteremia, has a high mortality rate of more than 10% [6, 7]

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