Microbiological Epidemiology of Invasive Infections Due to Non-Beta-Hemolytic Streptococci, France, 2021.

Non-beta-hemolytic streptococci (NBHS), also referred to as viridans streptococci, represent an underestimated cause of human invasive diseases. Their resistance to antibiotics, including beta-lactam agents, often complicate their therapeutic management. A prospective multicenter study was conducted by the French National Reference Center for Streptococci between March and April 2021 to describe the clinical and microbiological epidemiology of invasive infections due to NBHS, excluding pneumococcus. A total of 522 NBHS invasive cases were collected. Distribution among streptococcal groups was: Streptococcus anginosus (33%), Streptococcus mitis (28%), Streptococcus sanguinis (16%), Streptococcus bovis/equinus (15%), Streptococcus salivarius (8%), and Streptococcus mutans (<1%). Median age of infection was 68 years old (range <1 day to 100 years). Cases were more frequent in male patients (gender ratio M/F 2.1:1) and manifested mainly as bacteremia without focus (46%), intra-abdominal infections (18%) and endocarditis (11%). All isolates were susceptible to glycopeptides and displayed low-level inherent gentamicin resistance. All isolates of the S. bovis/equinus, S. anginosus, and S. mutans groups were susceptible to beta-lactams. Conversely, nonsusceptibility to beta-lactams was found in 31%, 28%, and 52% of S. mitis, S. salivarius, and S. sanguinis isolates, respectively. The screening for beta-lactam resistance using the recommended one unit benzylpenicillin disk screening failed to detect 21% of resistant isolates (21/99). Last, overall resistance rates to the alternative anti-streptococcal molecules clindamycin and moxifloxacin were 29% (149/522) and 1.6% (8/505), respectively. IMPORTANCE NBHS are recognized as opportunistic pathogens particularly involved in infections of the elderly and immunocompromised patients. This study underlines their importance as common causes of severe and difficult-to-treat infections such as endocarditis. Although species of the S. anginosus and S. bovis/equinus groups remain constantly susceptible to beta-lams, resistance in oral streptococci exceeds 30% and screening techniques are not fully reliable. Therefore, accurate species identification and antimicrobial susceptibility testing by MICs determination appears essential for the treatment of NBHS invasive infections, together with continued epidemiological surveillance.

Group B Streptococcus (GBS) Invasive Infections in Women of Childbearing Age, France, 2012-2020: GBS CC-17 Hypervirulence in Intrapartum Infections.

Group B Streptococcus (GBS) is the leading cause of neonatal infections and an important pathogen in pregnancy. However, the features of pregnancy-associated infections are poorly reported. We analyzed 336 cases of GBS invasive infections in women aged 18-50 years, including 242 (72.0%) pregnancy-associated infections. In pregnancy, most cases were intra-amniotic infections (55.8%), occurred preterm (61.3%), and were associated with obstetrical and neonatal complications (81.7%). The GBS clone CC-17 (18.8% of the cases) was overrepresented intrapartum (35.2%; odds ratio, 5.1 [95% confidence interval, 1.6-19.3]). This work highlights the burden of GBS and of the CC-17 clone infections during pregnancy.

Invasive group B Streptococcus infections in non-pregnant adults: a retrospective study, France, 2007-2019.

OBJECTIVES: Group B Streptococcus (GBS) (Streptococcus agalactiae) is a pathogen of growing importance in adults. The objective of this study was to describe the features of invasive infections by GBS in non-pregnant adults. METHODS: GBS infections were reported to the national reference centre for streptococci. Clinical information was abstracted from questionnaires. Capsular typing, identification of the hypervirulent CC-17 clone, and antibiotic susceptibility testing were performed for all GBS isolates. Multi-locus sequence typing and assignment to clonal complexes (CCs) was performed on a representative sample of 324 isolates. RESULTS: In total, 1960 GBS invasive infections were analysed from 2007 to 2019. The median age at onset was 71 years old (range 18-103). The main manifestation was bacteraemia without focus (54.5%). Meningitis was more frequent in patients under 40 (26/180, 14.4% versus 78/1780, 4.4%, p < 0.0001). Capsular types Ia, Ib, II, III and V accounted for 91.0% of the cases (1786/1960). CC-1, -10, -17, -19 and -23 accounted for 96.3% (312/324) of the cases. Capsular type III and CC-17 were overrepresented in meningitis (38/104, 36.5%, p < 0.001 and 22/104, 21.2%, p 0.01, respectively). All isolates were susceptible to ß-lactam antibiotics. Resistance to erythromycin (32.7%) and clindamycin (26.3%) remained stable, whereas decreased susceptibility to fluoroquinolones increased, reaching 2.7% in 2019 (p for trend 0.002). CONCLUSIONS: This work highlights the susceptibility of the elderly to GBS infections and differences in the clinical manifestations according to the patients' age and GBS type. In agreement with worldwide reports on emerging multidrug-resistant GBS, it reinforces the need for a continued surveillance of GBS epidemiology.

Multidrug-Resistant Hypervirulent Group B Streptococcus in Neonatal Invasive Infections, France, 2007-2019.

We analyzed group B Streptococcus (GBS) neonatal invasive infections reported during 2007-2019 in France. The hypervirulent clonal complex (CC) 17 GBS was responsible for 66% (827/1,262) of cases. The role of CC17 GBS increased over time (p for trend = 0.0001), together with the emergence of a multidrug-resistant CC17 GBS sublineage.

Molecular epidemiology of invasive and non-invasive group B Streptococcus circulating in Serbia.

Streptococcus agalactiae (group B Streptococcus, GBS) remains the leading cause of invasive diseases in neonates and an important cause of infections in the elderly. The aim of this study was to access the prevalence of GBS genito-rectal colonisation of pregnant women and to evaluate the genetic characteristics of invasive and non-invasive GBS isolates recovered throughout Serbia. A total of 432 GBS isolates were tested for antimicrobial susceptibility, capsular polysaccharide (CPS) types and the presence of the hvgA gene. One hundred one randomly selected isolates were further characterized by clustered regularly interspaced short palindromic repeats (CRISPRs) analysis and/or multilocus sequence typing (MLST). The prevalence of GBS colonization in pregnant women was 15%. Overall, six capsular types (Ia, Ib, II to V) were identified, the most common being III (32.2%) and V (25.2%). The hiper-virulent clone type III/ST17 was present in 43.1% and 6.3% (p < 0.05) of paediatric and adults isolates, respectively. Comparative sequence analysis of the CRISPR1 spacers content indicated that a few clones comprised the vast majority of the tested GBS isolates. Thus, it was estimated that dominant clones recovered from infants were CPS III/ST17 in late-onset infections (19/23; 82.6%), and Ia/ST23 in early-onset disease (44.4%). Conversely, genotype CPS V/ST1 was the most prevalent in adults (4/9; 25.4%). All isolates were susceptible to penicillin. Macrolide resistance (23.1%) was strongly associated with the ermB gene and constitutive resistance to clindamycin (63.9%). The majority of strains was resistant to tetracycline (86.6%), mostly mediated by the tetM gene (87.7%). GBS isolates of CPS V/ST1 and CPS III/ST23 were significantly associated with macrolide and tetracycline resistance, respectively. In conclusion, hyper-virulent CPS III/ST17 and V/ST1 were recognized as dominant GBS clones in this study.

A clone of the emergent Streptococcus pyogenes emm89 clade responsible for a large outbreak in a post-surgery oncology unit in France.

An outbreak of nosocomial infections due to Streptococcus pyogenes (Group A Streptococcus; GAS) occurred in a post-surgery oncology unit and concerned more than 60 patients and lasted 20 months despite enhanced infection control and prophylaxis measures. All GAS strains were characterized (emm genotype, toxin gene profile and pulse-field gel electrophoresis subtype). Selected strains were sequenced and phylogenetic relationship established. Capacity to form biofilm and interaction with human pulmonary epithelial cells and macrophages were determined. Twenty-six GAS strains responsible for invasive infections (II) and 57 for non-II or colonization were isolated from patients (n = 66) or healthcare workers (n = 13). Seventy strains shared the same molecular markers and 69 the same PFGE pattern; 56 were sequenced. They all belonged to the emerging emm89 clade 3; all but 1 were clonal. Whole genome sequencing identified 43 genetic profiles with sporadic mutations in regulatory genes and acquired mutations in 2 structural genes. Except for two regulatory gene mutants, all strains tested had the same biofilm formation capacity and displayed similar adherence and invasion of pulmonary epithelial cells and phagocytosis and survival in human macrophages. This large outbreak of GAS infection in a post-surgery oncology unit, a setting that contains highly susceptible patients, arose from a strain of the emergent emm89 clade. No relationship between punctual or acquired mutations, invasive status, and strain phenotypic characteristics was found. Noteworthy, the phenotypic characteristics of this clone account for its emergence and its remarkable capacity to elicit outbreaks.

Changing Epidemiology of Group B Streptococcus Susceptibility to Fluoroquinolones and Aminoglycosides in France.

Group B Streptococcus (GBS) is the leading cause of neonatal invasive infections and an emerging pathogen in the elderly. Our objectives were to describe the evolution of GBS resistance to antibiotics in France and to investigate the emergence of fluoroquinolone (FQ)-resistant isolates. A total of 8,757 unrelated GBS isolates were collected and tested for antibiotic susceptibility from 2007 to 2014 according to EUCAST recommendations. All isolates were susceptible to penicillin G, amoxicillin, and vancomycin. Resistance to macrolides decreased from 47.0% to 30.0%, whereas high-level resistance to aminoglycosides, especially amikacin, increased from 6.4% to 8.8% and 24 isolates (0.3%) were highly resistant to gentamicin. FQ resistance gradually increased from 0.2% in 2007 (n = 1) to 1.5% in 2014 (n = 18, P < 0.01). Capsular polysaccharide (CPS) genotyping, multilocus sequence typing, and sequencing of the quinolone resistance-determining region (QRDR) showed that GBS isolates of sequence type 19 (ST-19) CPS type V were largely overrepresented in FQ-resistant isolates (n = 30, 45.5%). All 30 strains displayed the same QRDR mutations and were often associated with cross-resistance to macrolides (93.3%) and gentamicin (30%). In conclusion, we report the rise of FQ- and aminoglycoside-resistant GBS in France over an 8-year study period, an evolution likely linked to the clonal expansion of ST-19 CPS V-resistant isolates. This study emphasizes the need for a continuous surveillance of GBS epidemiology and antibiotic susceptibility.

Characterization of Streptococcus pyogenes isolates responsible for adult meningitis in France from 2003 to 2013.

Sixty-three cases of Streptococcus pyogenes meningitis in adults were studied. Three predominant emm types were associated with meningitis: emm1 (44%), emm3 (11%), and emm6 (11%). Streptococcal toxic shock syndrome and mortality rates were 40% and 38%, respectively.

Molecular Characterization of Nonhemolytic and Nonpigmented Group B Streptococci Responsible for Human Invasive Infections.

Group B Streptococcus (GBS) is a common commensal bacterium in adults, but is also the leading cause of invasive bacterial infections in neonates in developed countries. The ß-hemolysin/cytolysin (ß-h/c), which is always associated with the production of an orange-to-red pigment, is a major virulence factor that is also used for GBS diagnosis. A collection of 1,776 independent clinical GBS strains isolated in France between 2006 and 2013 was evaluated on specific medium for ß-h/c activity and pigment production. The genomic sequences of nonhemolytic and nonpigmented (NH/NP) strains were analyzed to identify the molecular basis of this phenotype. Gene deletions or complementations were carried out to confirm the genotype-phenotype association. Sixty-three GBS strains (3.5%) were NH/NP, and 47 of these (74.6%) originated from invasive infections, including bacteremia and meningitis, in neonates or adults. The mutations are localized predominantly in the cyl operon, encoding the ß-h/c pigment biosynthetic pathway and, in the abx1 gene, encoding a CovSR regulator partner. In conclusion, although usually associated with GBS virulence, ß-h/c pigment production is not absolutely required to cause human invasive infections. Caution should therefore be taken in the use of hemolysis and pigmentation as criteria for GBS diagnosis in routine clinical laboratory settings.

In vitro evaluation and comparison of 5 rapid antigen detection tests for the diagnosis of beta-hemolytic group A streptococcal pharyngitis.

Streptococcus pyogenes (group A Streptococcus [GAS]) is the leading cause of bacterial pharyngitis. To perform a rapid diagnosis of GAS pharyngitis, rapid antigen detection tests (RADTs) have been developed. In this study, we evaluated and compared the sensitivity and specificity of 5 RADTs (bioNexia Strep A plus™, bioNexia Strep A dipstick™, Clearview Strep A™, QuickVue Strep A plus™, and Streptatest™), using analytical approaches combining dilutions in NaCl 0.9% or in pharyngeal flora. The practicability of each RADT was also determined. Among the 630 RADTs performed in this work, all were specific, as no false positive was found resulting in a specificity of 100%. The 5 RADTs detected GAS at 10(6)CFU/mL in NaCl 0.9% or pooled pharyngeal flora. Regarding the practicability analysis, bioNexia Strep A plus, bioNexia Strep A dipstick and Streptatest RADTs obtained the highest scores for secondary items including kit content and instructions for use information. We concluded that these 5 easy-to-use RADTs are suitable for diagnosis of GAS pharyngitis, as they all detect GAS at a concentration commonly found during pharyngitis.

Comparative evaluation of 5 different selective media for Group B Streptococcus screening in pregnant women.

We compared the performances and the cost-effectiveness of 5 selective media for Group B Streptococcus (GBS) screening in vaginal samples from pregnant women. The usefulness of these media is unquestionable for GBS screening; the choice will depend largely on the laboratory organization.

Streptococcus agalactiae clones infecting humans were selected and fixed through the extensive use of tetracycline.

Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones. The parallel expansion of the clones is preceded by the insertion of integrative and conjugative elements conferring tetracycline resistance (TcR). Thus, we propose that the use of tetracycline from 1948 onwards led in humans to the complete replacement of a diverse GBS population by only few TcR clones particularly well adapted to their host, causing the observed emergence of GBS diseases in neonates.

Molecular characterization of Streptococcus agalactiae isolates harboring small erm(T)-carrying plasmids.

Among 1,827 group B Streptococcus (GBS) strains collected between 2006 and 2013 by the French National Reference Center for Streptococci, 490 (26.8%) strains were erythromycin resistant. The erm(T) resistance gene was found in six strains belonging to capsular polysaccharides Ia, III, and V and was carried by the same mobilizable plasmid, which could be efficiently transferred by mobilization to GBS and Enterococcus faecalis recipients, thus promoting a broad dissemination of erm(T).

Molecular epidemiology of sil locus in clinical Streptococcus pyogenes strains.

Streptococcus pyogenes (group A Streptococcus [GAS]) causes a wide variety of diseases, ranging from mild noninvasive to severe invasive infections. Mutations in regulatory components have been implicated in the switch from colonization to invasive phenotypes. The inactivation of the sil locus, composed of six genes encoding a quorum-sensing complex, gives rise to a highly invasive strain. However, studies conducted on limited collections of GAS strains suggested that sil prevalence is around 15%; furthermore, whereas a correlation between the presence of sil and the genetic background was suggested, no link between the presence of a functional sil locus and the invasive status was assessed. We established a collection of 637 nonredundant strains covering all emm genotypes present in France and of known clinical history; 68%, 22%, and 10% were from invasive infections, noninvasive infections, and asymptomatic carriage, respectively. Among the 637 strains, 206 were sil positive. The prevalence of the sil locus varied according to the emm genotype, being present in >85% of the emm4, emm18, emm32, emm60, emm87, and emm90 strains and absent from all emm1, emm28, and emm89 strains. A random selection based on 2009 French epidemiological data indicated that 16% of GAS strains are sil positive. Moreover, due to mutations leading to truncated proteins, only 9% of GAS strains harbor a predicted functional sil system. No correlation was observed between the presence or absence of a functional sil locus and the strain invasiveness status.

Capsular switching in group B Streptococcus CC17 hypervirulent clone: a future challenge for polysaccharide vaccine development.

BACKGROUND: The capsular polysaccharide (CPS) is an important virulence factor and a vaccine target of the major neonatal pathogen group B Streptococcus (GBS). Population studies revealed no strong correlation between CPS type and multilocus sequence typing (MLST) cluster, with the remarkable exception of the worldwide spread of hypervirulent GBS CC17, which were all until recently CPS type III. METHODS: A total of 965 GBS strains from invasive infection isolated in France were CPS typed and the presence of the CC17-specific surface protein encoding gene hvgA gene was investigated. Three hvgA-positive GBS strains screened were surprisingly CPS type IV and thus further characterized by MLST typing, pulsed-field gel electrophoresis (PFGE), and whole genome sequencing. RESULTS: MLST and PFGE demonstrated a capsular switching from CPS type III to IV within the highly homogeneous GBS CC17. Sequence analysis revealed that this capsular switch was due to the exchange of a 35.5-kb DNA fragment containing the entire cps operon. CONCLUSIONS: This work shows that GBS CC17 hypervirulent strains have switched one of their main vaccine targets. Thus, continued surveillance of GBS population remains of the utmost importance during clinical trials of conjugate GBS vaccines.

The surface protein HvgA mediates group B streptococcus hypervirulence and meningeal tropism in neonates.

Streptococcus agalactiae (group B streptococcus; GBS) is a normal constituent of the intestinal microflora and the major cause of human neonatal meningitis. A single clone, GBS ST-17, is strongly associated with a deadly form of the infection called late-onset disease (LOD), which is characterized by meningitis in infants after the first week of life. The pathophysiology of LOD remains poorly understood, but our epidemiological and histopathological results point to an oral route of infection. Here, we identify a novel ST-17-specific surface-anchored protein that we call hypervirulent GBS adhesin (HvgA), and demonstrate that its expression is required for GBS hypervirulence. GBS strains that express HvgA adhered more efficiently to intestinal epithelial cells, choroid plexus epithelial cells, and microvascular endothelial cells that constitute the blood-brain barrier (BBB), than did strains that do not express HvgA. Heterologous expression of HvgA in nonadhesive bacteria conferred the ability to adhere to intestinal barrier and BBB-constituting cells. In orally inoculated mice, HvgA was required for intestinal colonization and translocation across the intestinal barrier and the BBB, leading to meningitis. In conclusion, HvgA is a critical virulence trait of GBS in the neonatal context and stands as a promising target for the development of novel diagnostic and antibacterial strategies.

Invasive group B streptococcal infections in infants, France.

Clinical features and molecular characterization of 109 group B streptococci causing neonatal invasive infections were determined over an 18-month period in France. Sixty-four percent of the strains were from late-onset infections, and 75% were capsular type III. The hypervirulent clone ST-17 was recovered in 80% of meningitis cases.