Group A Streptococcus (GAS; Streptococcus pyogenes) is a bacterial pathogen for which a commercial vaccine for humans is not available. Employing the advantages of high-throughput DNA sequencing technology to vaccine design, we have analysed 2,083 globally sampled GAS genomes. The global GAS population structure reveals extensive genomic heterogeneity driven by homologous recombination and overlaid with high levels of accessory gene plasticity. We identified the existence of more than 290 clinically associated genomic phylogroups across 22 countries, highlighting challenges in designing vaccines of global utility. To determine vaccine candidate coverage, we investigated all previously described GAS candidate antigens for gene carriage and gene sequence heterogeneity. Only 15 of 28 vaccine antigen candidates were found to have both low naturally occurring sequence variation and high (>99%) coverage across this diverse GAS population. This technological platform for vaccine coverage determination is equally applicable to prospective GAS vaccine antigens identified in future studies.

One-hundred sixty-eight group B streptococcal (GBS) isolates from a Brazilian hospital were phenotypically and genotypically characterized. Isolates were recovered from human sources from April 2006 to May 2008 and classified as either invasive, noninvasive, or colonizing isolates. Classical methods for serotyping and antibiotic resistance profiling were employed. Clonal groups were also defined by pulsed-field gel electrophoresis (PFGE). Results showed that susceptibility to beta-lactam antimicrobials was predominant among the isolates. Only 4.7% were resistant to erythromycin and clindamycin. The erm(B) gene was widely detected in our GBS isolates, according to our phenotypic results (constitutive macrolide-lincosamide-streptogramin B [cMLS B ] resistance phenotype), and the erm(A) gene was also detected in some isolates. MLS B resistance was restricted to strains isolated from patients with noninvasive infections and carriers. Serotype Ia was predominant (38.1%), serotype IV isolates were found at a high frequency (13.1%), and few isolates of serotype III were identified (3%). Pulsed-field gel electrophoresis results revealed a variety of types, reflecting the substantial genetic diversity among GBS strains, although a great number of isolates could be clustered into two major groups with a high degree of genetic relatedness. Three main PFGE clonal groups were found, and isolates sharing the same PFGE type were grouped into different serotypes. Furthermore, in a few cases, isolates from the same patients and possessing the same PFGE type were of different serotypes. These findings could be related to the occurrence of capsular switching by horizontal transfer of capsular genes.In the last 40 years, Streptococcus agalactiae (group B streptococcus [GBS]) has been described as an important pathogen in neonates and pregnant women. Vaginal colonization with GBS during pregnancy is significantly associated with infections in newborns and requires investigation (40,46,48). Despite the reduction in the incidence of early-onset neonatal disease by using antimicrobial intrapartum prophylaxis, mortality and permanent disability rates caused by GBS continue to be significant. However, GBS has also emerged as an important pathogen in other patient groups, such as children, young adults with underlying medical conditions, and elderly individuals (40). Penicillin is the drug of choice for prevention and treatment of GBS infections, which remain universally susceptible. Erythromycin and clindamycin are recommended when risks of anaphylaxis or therapeutic failure are present. However, resistance to erythromycin and clindamycin has increased in many countries in North America (2,6,16,40), Europe (21,22,42,45), and Asia (24) but not in Brazil (18,50) and other Latin American countries (23,35,36). Such a resistance profile is mainly due to two mechanisms: a methylasemediated target site modification and an active efflux pump (53). In GBS, coresistance to macrolide, lincosamide, and streptogramin B (MLS B ) is due to methylases e...

GAS meningitis is associated with high mortality and with a high diversity of GAS emm-types and virulence determinants in Brazil.

BackgroundStreptococcus agalactiae or Group B Streptococcus (GBS) remains the leading cause of infections in newborns worldwilde. Prenatal GBS screening of pregnant women for vaginal-rectal colonization is recommended in many countries to manage appropriate intrapartum antimicrobial prophylaxis for those identified as carriers. In this study, a novel melting-curve based multiplex real-time PCR assay for the simultaneous detection of GBS and macrolide and lincosamide resistance markers was developed. The usefulness of the assay was evaluated for rapid and accurate prenatal GBS screening.MethodsOne hundred two pregnant women who were at 35–37 weeks of gestation were enrolled in this study. The analytical performance of the multiplex real-time PCR was first tested using a panel of reference and clinical bacterial and fungal strains. To test the clinical performance, vaginal-rectal swabs were obtained from pregnant women who were seen at the teaching hospital for regular prenatal care. The results of real-time were compared with those obtained from microbiological analyses.ResultsThe real-time PCR assay showed 100% specificity and a limit of detection of 104 colony forming units equivalent per reaction. The prevalence of GBS colonization among the population studied was 15.7% (16/102) based on a positive culture and the real-time PCR results. Agreement between the two assays was found for 11 (68.75%) GBS colonized women. Using the culture-based results as a reference, the multiplex real-time PCR had a sensitivity of 91.7% (11/12, CI 59.7–99.6%), a specificity of 95.5% (86/90, CI 89.8–98.7%), a positive predictive value of 73.3% (11/15, CI 44.8–91.1%) and a negative predictive value of 98.9% (86/87, CI 92.9–99.9%).ConclusionThe multiplex real-time PCR is a rapid, affordable and sensitive assay for direct detection of GBS in vaginal-rectal swabs.Electronic supplementary materialThe online version of this article (10.1186/s12884-018-1774-5) contains supplementary material, which is available to authorized users.

This polyclonal spreading of cMLS(B) macrolide resistance has not been previously observed in South America and should stimulate further epidemiological surveillance in this part of the world.