Adaptation of Group A Streptococcus to Human Amniotic Fluid

The American Journal of Pathology, 2020

Infection and Immunity, 2005

Group A Streptococcus (GAS) causes a range of diseases in humans, from mild noninvasive infections to severe invasive infections. The molecular basis for the varying severity of disease remains unclear. We identified genes expressed during invasive disease using in vivo-induced antigen technology (IVIAT), applied for the first time in a gram-positive organism. Convalescent-phase sera from patients with invasive disease were pooled, adsorbed against antigens derived from in vitro-grown GAS, and used to screen a GAS genomic expression library. A murine model of invasive GAS disease was included as an additional source of sera for screening. Sequencing DNA inserts from clones reactive with both human and mouse sera indicated 16 open reading frames with homology to genes involved in metabolic activity to genes of unknown function. Of these, seven genes were assessed for their differential expression by quantitative real-time PCR both in vivo, utilizing a murine model of invasive GAS dis...

American journal of obstetrics and gynecology, 1987

The group B Streptococcus is one of the most virulent organisms causing perinatal infection. Human amniotic fluid from the second and third trimesters was pooled and analyzed for electrolytes, protein, albumin, zinc, inorganic phosphorus, ferritin, lysozyme, and immunoglobulins. We inoculated replicates of specimens with known virulent strains of group B streptococci (893, 891, and 878) and Escherichia coli (C5) with Todd-Hewitt broth and normal saline solution used as controls. Group B streptococci strains 893 and 891 proliferated rapidly at rates similar to their rates in Todd-Hewitt Broth. Strain 878 grew at a rate slower than that of strains 893 and 891. The amniotic fluid specimens were similar with respect to factors reported as inhibitory to bacterial proliferation. Second- and third-trimester amniotic fluid supports the growth of group B streptococci as well as a culture medium optimized for bacterial growth. Strain-specific variance in group B streptococci growth rates in a...

The Journal of clinical investigation, 2020

Group A Streptococcus (GAS), a Gram-positive human-specific pathogen yields 517,000 deaths annually worldwide, including 163,000 due to invasive infections and among them puerperal fever. Before efficient prophylactic measures were introduced, the mortality rate for mothers during childbirth was about 10%; puerperal fever still accounts for over 75,000 maternal deaths annually. Yet little is known regarding the factors and mechanisms of GAS invasion and establishment in postpartum infection. We characterized the early steps of infection in an ex vivo infection model of the human decidua, the puerperal fever portal of entry. Coordinate analysis of GAS behavior and the immune response led us to demonstrate that (i) GAS growth was stimulated by tissue products; (ii) GAS invaded tissue and killed ~50% of host cells within two hours; these processes required SpeB protease and Streptolysin O activities, respectively; (iii) GAS impaired the tissue immune response. Immune impairment occurre...

PLoS Pathogens, 2006

BMC Infectious Diseases

Background In pregnant women Streptococcus agalactiae (GBS) can be transmitted to newborn causing severe infections. It is classified into 10 serotypes (Ia, Ib, II-IX). The severity of neonatal disease is determined by the capsular serotype and virulence factors such as the polysaccharide capsule, encoded by the cps gene, protein C, which includes the Cα surface proteins (bca gene), Rib (rib gene) and Cβ (bac gene); the proteins Lmb (lmb gene), FbsB (fbsB gene), FbsA (fbsA gene), the cyl operon encoding a β-hemolysin (hylB gene), the CAMP factor (cfb gene) and the C5a peptidase (scpB gene). The aim of this work was to determine the degree of GBS colonization in pregnant women, the serotypes distribution and to investigate virulence-associated genes. Methods We worked with 3480 samples of vagino-rectal swabs of women with 35–37 weeks of gestation. The identification of the strains was carried out using conventional biochemical tests and group confirmatory serology using a commercial ...

The Journal of Infectious Diseases, 2010

See the editorial commentary by Bessen and Tengra, on pages 800-802.) Group A streptococci (GAS) may engage different sets of virulence strategies, depending on the site of infection and host context. We previously isolated 2 phenotypic variants of a globally disseminated M1T1 GAS clone: a virulent wild-type (WT) strain, characterized by a SpeB + /SpeA Ϫ /Sda1 low phenotype, and a hypervirulent animal-passaged (AP) strain, better adapted to survive in vivo, with a SpeB Ϫ /SpeA + /Sda1 high phenotype. This AP strain arises in vivo due to the selection of bacteria with mutations in covS, the sensor part of a key 2component regulatory system, CovR/S. To determine whether covS mutations explain the hypervirulence of the AP strain, we deleted covS from WT bacteria (DCovS) and were able to simulate the hypervirulence and gene expression phenotype of naturally selected AP bacteria. Correction of the covS mutation in AP bacteria reverted them back to the WT phenotype. Our data confirm that covS plays a direct role in regulating GAS virulence. The pathogenesis of group A Streptococcus (GAS) infections reflects the complex interplay between bacterial and host factors. GAS diseases vary from uncomplicated pharyngitis to life-threatening streptococcal toxic shock syndrome and necrotizing fasciitis. Multiple virulence factors play important roles in distinct host niches and different stages of GAS infections [1, 2]. Depending on

American journal of obstetrics and gynecology, 2016

Group B streptococcus (GBS) infection in pregnancy is a major cause of maternal and neonatal morbidity. An understanding of the mechanisms responsible for GBS persistence in the genital tract, as well as recognition of host defenses employed to combat its presence, are crucial to our efforts to reduce maternal GBS colonization and prevent the acquisition of neonatal infections. However, alterations in vaginal immunity in response to GBS colonization in pregnant women remain incompletely defined. Whether GBS modulates autophagy, a major host defense mechanism and contributor to the control of intracellular microbial infections, also remains unclear. We sought to identify differences in the extent of autophagy as well as in the concentration of biomarkers previously shown to be involved in vaginal innate immunity between GBS-positive and GBS-negative pregnant women. We performed a prospective cohort study of healthy pregnant women, who had vaginal secretions obtained at 35-37 weeks of...

Science immunology, 2016

Preterm birth is a leading cause of neonatal morbidity and mortality. Although microbial invasion of the amniotic cavity (MIAC) is associated with the majority of early preterm births, the temporal events that occur during MIAC and preterm labor are not known. Group B Streptococci (GBS) are β-hemolytic, gram-positive bacteria, which commonly colonize the vagina but have been recovered from the amniotic fluid in preterm birth cases. To understand temporal events that occur during MIAC, we utilized a unique chronically catheterized nonhuman primate model that closely emulates human pregnancy. This model allows monitoring of uterine contractions, timing of MIAC and immune responses during pregnancy-associated infections. Here, we show that adverse outcomes such as preterm labor, MIAC, and fetal sepsis were observed more frequently during infection with hemolytic GBS when compared to nonhemolytic GBS. Although MIAC was associated with systematic progression in chorioamnionitis beginning...

Streptococcus agalactiae is a leading cause of neonatal infections and an increasing cause of infections in adults with underlying diseases. One of the first S. agalactiae isolates to be subjected to whole genome sequencing was NEM316, a strain responsible for a fatal case of septicemia that has been widely used as reference strain for in vitro assays. Whole transcriptome analyses may provide an essential contribute to the understanding of the molecular mechanisms responsible for bacteria adaptation and pathogenicity, still, so far, very few studies were dedicated to the analysis of global gene expression of S. agalactiae. Here, we applied RNA-sequencing to perform a comparative overview of the global gene expression levels of the S. agalactiae reference strain NEM316 at the exponential growth phase. Genes were ranked by expression level and grouped by functional category and 46% of the top-100 expressed genes encode proteins involved in “Translation, ribosomal structure and biogene...

European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, 2016

Invasive group A streptococcal (GAS) infections constitute an important epidemiological problem. Many cases occur in women during the postnatal period. The objective of this study was to evaluate the presence of the genes responsible for production of iron-chelating protein (perR) and superantigens (speA, speB, speC, speF, speG, speH, speI, speJ, speK, speL, speM, smeZ, and ssa) in S. pyogenes strains isolated from invasive infections in women after delivery. Furthermore, this study sought to verify whether S. pyogenes strains show special phenotypic and genotypic (sla, spy1325) characteristics that may play a decisive role in adherence to the genital tract epithelium. Moreover, the emm-types and antibiotic susceptibility were determined. We tested 30 invasive S. pyogenes strains isolated from postpartum invasive infection and 37 GAS control strains isolated from the genital tracts of asymptomatic multiparous women. The majority of the tested strains were shown to express two types ...

The FASEB Journal, 2013

In Western countries, invasive infections caused by M1T1 serotype group A Streptococcus (GAS) are epidemiologically linked to mutations in the control of virulence regulatory 2-component operon (covRS). In indigenous communities and developing countries, severe GAS disease is associated with genetically diverse non-M1T1 GAS serotypes. Hypervirulent M1T1 covRS mutant strains arise through selection by human polymorphonuclear cells for increased expression of GAS virulence factors such as the DNase Sda1, which promotes neutrophil resistance. The GAS bacteremia isolate NS88.2 (emm 98.1) is a covS mutant that exhibits a hypervirulent phenotype and neutrophil resistance yet lacks the phage-encoded Sda1. Here, we have employed a comprehensive systems biology (genomic, transcriptomic, and proteomic) approach to identify NS88.2 virulence determinants that enhance neutrophil resistance in the non-M1T1 GAS genetic background. Using this approach, we have identified streptococcal collagen-like protein A and general stress protein 24 proteins as NS88.2 determinants that contribute to survival in whole blood and neutrophil resistance in non-M1T1

Infection and Immunity, 2013

The group A streptococcus (GAS) is a strict human pathogen responsible for a wide spectrum of diseases. Although GAS genome sequences are available, functional genomic analyses have been limited. We developed a mariner -based transposon, osKaR , designed to perform Transposon-Site Hybridization (TraSH) in GAS and successfully tested its use in several invasive serotypes. A complex osKaR mutant library in M1T1 GAS strain 5448 was subjected to negative selection in human blood to identify genes important for GAS fitness in this clinically relevant environment. Mutants underrepresented after growth in blood (output pool) compared to growth in rich media (input pool) were identified using DNA microarray hybridization of transposon-specific tags en masse . Using blood from three different donors, we identified 81 genes that met our criteria for reduced fitness in blood from at least two individuals. Genes known to play a role in survival of GAS in blood were found, including those encodi...

Proceedings of the …, 2002

Two-component gene regulatory systems composed of a membrane-bound sensor and cytoplasmic response regulator are important mechanisms used by bacteria to sense and respond to environmental stimuli. Group A Streptococcus, the causative agent of mild infections and life-threatening invasive diseases, produces many virulence factors that promote survival in humans. A twocomponent regulatory system, designated covRS (cov, control of virulence; csrRS), negatively controls expression of five proven or putative virulence factors (capsule, cysteine protease, streptokinase, streptolysin S, and streptodornase). Inactivation of covRS results in enhanced virulence in mouse models of invasive disease.

2017

Genotyping Multiplex PCR Pregnant women Streptococcus agalactiae Background and Aims: Group B streptococcus (GBS) may cause neonatal infection during and or after the delivery, and is the leading cause of sepsis, bacteremia, pneumonia and meningitis. The virulence factors are carried by both capsule and surface proteins by which serotypes and genotypes are determined. However, some genotypes are believed to be related in severity of neonatal diseases, therefor this investigation was aimed to determine the surface proteins genotype of detected GBS from both vagina and urine of pregnant women. Materials and Methods: In the present study, a total of 346 vaginal and urine samples were obtained from the same pregnant women. Following culturing the samples on sheep blood agar medium and related tests (CAMP, Hiporate hydrolysis) the suspected colonies were further confirmed by polymerase chain reaction (PCR) technique. The detected GBS species were then genotyped using multiplex PCR assay....