The antimicrobial activity of zinc against group B Streptococcus is strain-dependent across diverse sequence types, capsular serotypes, and invasive versus colonizing isolates.

BACKGROUND: Streptococcus agalactiae or Group B Streptococcus (GBS) is an encapsulated gram-positive bacterial pathobiont that commonly colonizes the lower gastrointestinal tract and reproductive tract of human hosts. This bacterium can infect the gravid reproductive tract and cause invasive infections of pregnant patients and neonates. Upon colonizing the reproductive tract, the bacterial cell is presented with numerous nutritional challenges imposed by the host. One strategy employed by the host innate immune system is intoxication of bacterial invaders with certain transition metals such as zinc. METHODOLOGY: Previous work has demonstrated that GBS must employ elegant strategies to circumnavigate zinc stress in order to survive in the vertebrate host. We assessed 30 strains of GBS from diverse isolation sources, capsular serotypes, and sequence types for susceptibility or resistance to zinc intoxication. RESULTS: Invasive strains, such as those isolated from early onset disease manifestations of GBS infection were significantly less susceptible to zinc toxicity than colonizing strains isolated from rectovaginal swabs of pregnant patients. Additionally, capsular type III (cpsIII) strains and the ST-17 and ST-19 strains exhibited the greatest resilience to zinc stress, whereas ST-1 and ST-12 strains as well as those possessing capsular type Ib (cpsIb) were more sensitive to zinc intoxication. Thus, this study demonstrates that the transition metal zinc possesses antimicrobial properties against a wide range of GBS strains, with isolation source, capsular serotype, and sequence type contributing to susceptibility or resistance to zinc stress.

Functional Insights into the High-Molecular-Mass Penicillin-Binding Proteins of Streptococcus agalactiae Revealed by Gene Deletion and Transposon Mutagenesis Analysis.

High-molecular-mass penicillin-binding proteins (PBPs) are enzymes that catalyze the biosynthesis of bacterial cell wall peptidoglycan. The Gram-positive bacterial pathogen Streptococcus agalactiae (group B streptococcus [GBS]) produces five high-molecular-mass PBPs, namely, PBP1A, PBP1B, PBP2A, PBP2B, and PBP2X. Among these, only PBP2X is essential for cell viability, whereas the other four PBPs are individually dispensable. The biological function of the four nonessential PBPs is poorly characterized in GBS. We deleted the pbp1a, pbp1b, pbp2a, and pbp2b genes individually from a genetically well-characterized serotype V GBS strain and studied the phenotypes of the four isogenic mutant strains. Compared to the wild-type parental strain, (i) none of the pbp isogenic mutant strains had a significant growth defect in Todd-Hewitt broth supplemented with 0.2% yeast extract (THY) rich medium, (ii) isogenic mutant Δpbp1a and Δpbp1b strains had significantly increased susceptibility to penicillin and ampicillin, and (iii) isogenic mutant Δpbp1a and Δpbp2b strains had significantly longer chain lengths. Using saturated transposon mutagenesis and transposon insertion site sequencing, we determined the genes essential for the viability of the wild-type GBS strain and each of the four isogenic pbp deletion mutant strains in THY rich medium. The pbp1a gene is essential for cell viability in the pbp2b deletion background. Reciprocally, pbp2b is essential in the pbp1a deletion background. Moreover, the gene encoding RodA, a peptidoglycan polymerase that works in conjunction with PBP2B, is also essential in the pbp1a deletion background. Together, our results suggest functional overlap between PBP1A and the PBP2B-RodA complex in GBS cell wall peptidoglycan biosynthesis. IMPORTANCE High-molecular-mass penicillin-binding proteins (HMM PBPs) are enzymes required for bacterial cell wall biosynthesis. Bacterial pathogen group B streptococcus (GBS) produces five distinct HMM PBPs. The biological functions of these proteins are not well characterized in GBS. In this study, we performed a comprehensive deletion analysis of genes encoding HMM PBPs in GBS. We found that deleting certain PBP-encoding genes altered bacterial susceptibility to beta-lactam antibiotics, cell morphology, and the essentiality of other enzymes involved in cell wall peptidoglycan synthesis. The results of our study shed new light on the biological functions of PBPs in GBS.

Streptococcus pneumoniae, S. pyogenes and S. agalactiae membrane phospholipid remodelling in response to human serum.

Streptococcus pneumoniae, S. pyogenes (Group A Streptococcus; GAS) and S. agalactiae (Group B Streptococcus; GBS) are major aetiological agents of diseases in humans. The cellular membrane, a crucial site in host-pathogen interactions, is poorly characterized in streptococci. Moreover, little is known about whether or how environmental conditions influence their lipid compositions. Using normal phase liquid chromatography coupled with electrospray ionization MS, we characterized the phospholipids and glycolipids of S. pneumoniae, GAS and GBS in routine undefined laboratory medium, streptococcal defined medium and, in order to mimic the host environment, defined medium supplemented with human serum. In human serum-supplemented medium, all three streptococcal species synthesize phosphatidylcholine (PC), a zwitterionic phospholipid commonly found in eukaryotes but relatively rare in bacteria. We previously reported that S. pneumoniae utilizes the glycerophosphocholine (GPC) biosynthetic pathway to synthesize PC. Through substrate tracing experiments, we confirm that GAS and GBS scavenge lysoPC, a major metabolite in human serum, thereby using an abbreviated GPC pathway for PC biosynthesis. Furthermore, we found that plasmanyl-PC is uniquely present in the GBS membrane during growth with human serum, suggesting GBS possesses unusual membrane biochemical or biophysical properties. In summary, we report cellular lipid remodelling by the major pathogenic streptococci in response to metabolites present in human serum.

Phenotypic changes in group B streptococci grown in the presence of the polyols, erythritol, sorbitol and mannitol.

BACKGROUND: Group B streptococci (GBS) are important neonatal bacterial pathogens that can cause severe invasive disease in the newborn. It is thought that in many cases of invasive neonatal GBS disease, the bacteria ascend the vagina into the uterus and infect the amniotic fluid surrounding the fetus. Important constituents of this environment include the polyols or sugar alcohols of which erythritol, sorbitol and mannitol are examples. The aim of our study was to investigate the effect of polyols on GBS grown in media containing these sugar alcohols. RESULTS: GBS incubated in varying concentrations of polyols (erythritol, sorbitol or mannitol) did not display any significant enhancement or inhibition of bacterial growth. However, growth of GBS in the presence of erythritol significantly increased the surface expression of GBS-PGK (a plasminogen binding protein) 1.25 to 1.5-fold depending on the erythritol concentration and significantly enhanced the survival in human blood 3X to 18X depending on the concentration of polyol used. Interestingly, GBS grown in 1% erythritol significantly increased invasion by the bacteria of HeLa cells (epithelial cell line) (150% vs 100%) however, at higher concentrations (2% or 4% of polyol) the number of CFUs was significantly reduced (55-75% vs 100%) suggesting higher concentrations of polyols may inhibit invasion. Erythritol also increased GBS hemolytic activity as well as enhancing biofilm formation 1.4X to 3.3X depending on the concentration of polyol used. CONCLUSIONS: GBS grown in the presence of polyols alters the bacteria's phenotype resulting in changes associated with GBS virulence. This effect was greatest for the polyol erythritol.

Effects of sodium butyrate and Lippia origanoides essential oil blend on growth, intestinal microbiota, histology, and haemato-immunological response of Nile tilapia.

This study aimed to verify the effects of dietary supplementation with sodium butyrate and Lippia origanoides, combined and isolated, on the health and zootechnical performance of Nile tilapia juveniles Oreochromis niloticus. A total of 120 fish (5.38 ± 0.65 g) were randomly distributed in 12 experimental units and fed different experimental diets for 30 days, namely: commercial diet without supplementation (Unsupplemented); commercial diet supplemented with 0.5% sodium butyrate (Butyrate); commercial diet supplemented with 0.125% L. origanoides (Lippia) and commercial diet supplemented with a mixture of 0.5% sodium butyrate and 0.125% L. origanoides (Butyrate + Lippia). After preparing the experimental diets there was an increase in the pH of diet Butyrate when compared to the other diets. After 30 days the fish supplemented with Butyrate + Lippia showed reduction significate in the mean corpuscular haemoglobin, concentration of total heterotrophic bacteria in the intestine, and lymphocyte infiltrates in the liver. Besides that, the supplementation with Butyrate + Lippia promoted an increased number of intestinal villi compared to the fish Unsupplemented ones. Additionally, fish fed a diet containing only Lippia presented an increase in the villus perimeter in the posterior region of the gut and in the red blood cell number. Animals supplemented only with sodium butyrate demonstrated increased lactic acid bacterium in the gut and macrosteatosis in the liver, besides decreased melanomacrophages in the spleen. The use of sodium butyrate associated with essential oil had positive effects on the intestinal microbiota, intestinal structure, liver, and spleen integrity, suggesting a greater efficiency of the compounds when used together in the nutrition of Nile tilapia juveniles.

Antitoxin autoregulation of M. tuberculosis toxin-antitoxin expression through negative cooperativity arising from multiple inverted repeat sequences.

Toxin-antitoxin systems play key roles in bacterial adaptation, including protection from antibiotic assault and infection by bacteriophages. The type IV toxin-antitoxin system AbiE encodes a DUF1814 nucleotidyltransferase-like toxin, and a two-domain antitoxin. In Streptococcus agalactiae, the antitoxin AbiEi negatively autoregulates abiE expression through positively co-operative binding to inverted repeats within the promoter. The human pathogen Mycobacterium tuberculosis encodes four DUF1814 putative toxins, two of which have antitoxins homologous to AbiEi. One such M. tuberculosis antitoxin, named Rv2827c, is required for growth and whilst the structure has previously been solved, the mode of regulation is unknown. To complete the gaps in our understanding, we first solved the structure of S. agalactiae AbiEi to 1.83 Šresolution for comparison with M. tuberculosis Rv2827c. AbiEi contains an N-terminal DNA binding domain and C-terminal antitoxicity domain, with bilateral faces of opposing charge. The overall AbiEi fold is similar to Rv2827c, though smaller, and with a 65° difference in C-terminal domain orientation. We further demonstrate that, like AbiEi, Rv2827c can autoregulate toxin-antitoxin operon expression. In contrast with AbiEi, the Prv2827c promoter contains two sets of inverted repeats, which bind Rv2827c with differing affinities depending on the sequence consensus. Surprisingly, Rv2827c bound with negative co-operativity to the full Prv2827c promoter, demonstrating an unexpectedly complex form of transcriptional regulation.

Cyclic di-AMP regulation of osmotic homeostasis is essential in Group B Streptococcus.

Cyclic nucleotides are universally used as secondary messengers to control cellular physiology. Among these signalling molecules, cyclic di-adenosine monophosphate (c-di-AMP) is a specific bacterial second messenger recognized by host cells during infections and its synthesis is assumed to be necessary for bacterial growth by controlling a conserved and essential cellular function. In this study, we sought to identify the main c-di-AMP dependent pathway in Streptococcus agalactiae, the etiological agent of neonatal septicaemia and meningitis. By conditionally inactivating dacA, the only diadenyate cyclase gene, we confirm that c-di-AMP synthesis is essential in standard growth conditions. However, c-di-AMP synthesis becomes rapidly dispensable due to the accumulation of compensatory mutations. We identified several mutations restoring the viability of a ΔdacA mutant, in particular a loss-of-function mutation in the osmoprotectant transporter BusAB. Identification of c-di-AMP binding proteins revealed a conserved set of potassium and osmolyte transporters, as well as the BusR transcriptional factor. We showed that BusR negatively regulates busAB transcription by direct binding to the busAB promoter. Loss of BusR repression leads to a toxic busAB expression in absence of c-di-AMP if osmoprotectants, such as glycine betaine, are present in the medium. In contrast, deletion of the gdpP c-di-AMP phosphodiesterase leads to hyperosmotic susceptibility, a phenotype dependent on a functional BusR. Taken together, we demonstrate that c-di-AMP is essential for osmotic homeostasis and that the predominant mechanism is dependent on the c-di-AMP binding transcriptional factor BusR. The regulation of osmotic homeostasis is likely the conserved and essential function of c-di-AMP, but each species has evolved specific c-di-AMP mechanisms of osmoregulation to adapt to its environment.

Genome-Wide Assessment of Streptococcus agalactiae Genes Required for Survival in Human Whole Blood and Plasma.

Streptococcus agalactiae (group B streptococcus, or GBS) is a common cause of bacteremia and sepsis in newborns, pregnant women, and immunocompromised patients. The molecular mechanisms used by GBS to survive and proliferate in blood are not well understood. Here, using a highly virulent GBS strain and transposon-directed insertion site sequencing (TraDIS), we performed genome-wide screens to discover novel GBS genes required for bacterial survival in human whole blood and plasma. The screen identified 85 and 41 genes that are required for GBS growth in whole blood and plasma, respectively. A common set of 29 genes was required in both whole blood and plasma. Targeted gene deletion confirmed that (i) genes encoding methionine transporter (metP) and manganese transporter (mtsA) are crucial for GBS survival in whole blood and plasma, (ii) gene W903_1820, encoding a small multidrug export family protein, contributes significantly to GBS survival in whole blood, (iii) the shikimate pathway gene aroA is essential for GBS growth in whole blood and plasma, and (iv) deletion of srr1, encoding a fibrinogen-binding adhesin, increases GBS survival in whole blood. Our findings provide new insight into the GBS-host interactions in human blood.

Synthetic Ellagic Acid Glycosides Inhibit Early Stage Adhesion of Streptococcus agalactiae Biofilms as Observed by Scanning Electron Microscopy.

Ellagic acid derivatives possess antimicrobial and antibiofilm properties across a wide-range of microbial pathogens. Due to their poor solubility and ambident reactivity it is challenging to synthesize, purify, and characterize the activity of ellagic acid glycosides. In this study, we have synthesized three ellagic acid glycoconjugates and evaluated their antimicrobial and antibiofilm activity in Streptococcus agalactiae (Group B Streptococcus, GBS). Their significant impacts on biofilm formation were examined via SEM to reveal early-stage inhibition of cellular adhesion. Additionally, the synthetic glycosides were evaluated against five of the six ESKAPE pathogens and two fungal pathogens. These studies reveal that the ellagic acid glycosides possess inhibitory effects on the growth of gram-negative pathogens.

Secure application of graphene in medicine.

OBJECTIVE: The objective of our study was to explore the possible graphene impact on microorganism growth as well as on laboratory animal overall condition. Materials and technique: The experiments applied samples of graphene three concentrations and two 15 × 15 mm quartz glasses one of which carrying deposited graphene lattice. We have also used 5% blood agar, thioglycollate broth, bacterial suspensions of standard turbidity containing pure clinical isolate of microorganisms. Three white male 6-month-old laboratory rats were used to estimate the graphene impact on the overall animal condition. RESULTS: Graphene did not contain any microorganisms, does not destroy erythrocytes placed within the artificial nutritional medium, graphene lattice did not add any properties to the quartz glasses which could allow the Proteus spread all over its surface. It was also established that graphene did not show any native antibacterial impact. No significant reaction was noticed in animals after graphene administration to laboratory rats neither at the injection spot nor at the overall level. CONCLUSION: Our data confirm the applicability of graphene both in scientific and practical biomedical purposes.

Glutathione Synthesis Contributes to Virulence of Streptococcus agalactiae in a Murine Model of Sepsis.

Streptococcus agalactiae, a leading cause of sepsis and meningitis in neonates, utilizes multiple virulence factors to survive and thrive within the human host during an infection. Unique among the pathogenic streptococci, S. agalactiae uses a bifunctional enzyme encoded by a single gene (gshAB) to synthesize glutathione (GSH), a major antioxidant in most aerobic organisms. Since S. agalactiae can also import GSH, similar to all other pathogenic streptococcal species, the contribution of GSH synthesis to the pathogenesis of S. agalactiae disease is not known. In the present study, gshAB deletion mutants were generated in strains representing three of the most prevalent clinical serotypes of S. agalactiae and were compared against isogenic wild-type and gshAB knock-in strains. When cultured in vitro in a chemically defined medium under nonstress conditions, each mutant and its corresponding wild type had comparable growth rates, generation times, and growth yields. However, gshAB deletion mutants were found to be more sensitive than wild-type or gshAB knock-in strains to killing and growth inhibition by several different reactive oxygen species. Furthermore, deletion of gshAB in S. agalactiae strain COH1 significantly attenuated virulence compared to the wild-type or gshAB knock-in strains in a mouse model of sepsis. Taken together, these data establish that GSH is a virulence factor important for resistance to oxidative stress and that de novo GSH synthesis plays a crucial role in S. agalactiae pathogenesis and further suggest that the inhibition of GSH synthesis may provide an opportunity for the development of novel therapies targeting S. agalactiae disease.IMPORTANCE Approximately 10 to 30% of women are naturally and asymptomatically colonized by Streptococcus agalactiae However, transmission of S. agalactiae from mother to newborn during vaginal birth is a leading cause of neonatal meningitis. Although colonized mothers who are at risk for transmission to the newborn are treated with antibiotics prior to delivery, S. agalactiae is becoming increasingly resistant to current antibiotic therapies, and new treatments are needed. This research reveals a critical stress resistance pathway, glutathione synthesis, that is utilized by S. agalactiae and contributes to its pathogenesis. Understanding the role of this unique bifunctional glutathione synthesis enzyme in S. agalactiae during sepsis may help elucidate why S. agalactiae produces such an abundance of glutathione compared to other bacteria.

Molecular Evolution of Clinical Pathogenic Streptococci.

The genus Streptococcus comprises a wide variety of pathogenic and commensal gram-positive bacteria, many of which the pathogenic species cause severe, invasive infections that account for a high burden of morbidity and mortality. Here, we reviewed the evolution of representative virulence factors, capsule in Streptococcus pneumoniae, M protein in Streptococcus pyogenes (GAS), biofilm in Streptococcus agalactiae (GBS) and some oral Streptococcus, as well as the effect caused by evolution, antibiotic resistance and vaccine escape. Thanks to the rapid development of whole genome sequence (WGS) data, the impact of genetic recombination to the Streptococcus evolution has been proved. As to adaptive evolution caused by antibiotics, vaccine and so on, continuous surveillance is an essential to monitor evolution of Streptococcus causing disease. This knowledge is invaluable to the development of preventative and control strategies against this important pathogen.

In-vitro effect of vaginal lactobacilli against group B Streptococcus.

Streptococcus agalactiae(GBS) is a leading cause of infection during pregnancy, preterm birth and neonatal infection, with a significant clinical and socio-economic impact. To prevent maternal GBS vaginal colonization, new antibiotic-free approaches, based on lactobacilli probiotics, are advisable. The aim of this study was to assess the anti-GBS activity of 14 vaginal Lactobacillus strains, belonging to different species (L. crispatus, L. gasseri, L. vaginalis), isolated from healthy pre-menopausal women. In particular, we performed 'inhibition' experiments, evaluating the ability of both Lactobacillus cells and culture supernatants in reducing Streptococcus viability, after 60 min contact time. First, we demonstrated that the acidic milieu, produced by vaginal lactobacilli metabolism, is crucial in counteracting GBS growth in a pH-dependent manner. Experiments with organic/inorganic acid solutions confirmed the strict correlation between pH levels and the anti-GBS activity. GBS was more sensitive to lactic acid than to hydrochloric acid, indicating that the presence of H+ ions is necessary but not sufficient for the inhibitory activity. Moreover, experiments with Lactobacillus pH-adjusted supernatants led to exclude a direct role in the anti-GBS activity by other bioactive molecules. Second, we found that only a few Lactobacillus strains were able to reduce Streptococcus viability by means of cell pellets. The anti-GBS effect displayed by Lactobacillus cells was related to the their ability to interact and aggregate with Streptococcus cells. We found that the anti-GBS activity was retained after methanol/proteinase K treatment, but lost after lysozyme exposure of Lactobacillus cells. Therefore, we supposed that non-proteinaceous components of Lactobacillus cell wall could be responsible for the anti-GBS activity. In conclusion, we identified specific Lactobacillus strains able to interfere with GBS viability by multiple strategies and we elucidated some of the mechanisms of action. These strains could serve as probiotic formulations for the prevention of GBS vaginal colonization.

Potential effect of selective pressure with different ß-lactam molecules on the emergence of reduced susceptibility to ß-lactams in group B Streptococci.

In this study, the selective potential of group B Streptococcus isolates with reduced penicillin susceptibility (PRGBS) in a neonate-hypervirulent sequence type (ST)17 lineage was investigated by in vitro exposure to ß-lactams. After 19 passages of stepwise penicillin exposure, PRGBS with a high penicillin minimum inhibitory concentration MIC (0.5 mg/L), greatly augmented ceftibuten MIC (>512 mg/L), and acquisition of G406D predicted to provide destabilizing effect (ΔΔG 0.099 kcal/mol) on PBP2X structure were identified. In early passages of stepwise cefotaxime exposure, PRGBS possessing G398E predicted to stabilize PBP2X (ΔΔG -0.038 kcal/mol) emerged with high MICs for cefotaxime (0.5 mg/L), ceftibuten (>512 mg/L) and penicillin (0.25 mg/L). Additionally, G398E + G329V + H438Y predicted to provide more stabilizing effect (ΔΔG -0.415 kcal/mol) were detected in mutants with higher MICs to cefotaxime (1 mg/L) and penicillin (0.5 mg/L). PRGBS mutants selected by penicillin and cefotaxime had a marked growth disadvantage compared with the parent strain. After two passages of stepwise ceftibuten exposure, the mutants exhibited increased MICs toward ceftibuten and acquisition of T555S predicted to provide stabilizing effect (ΔΔG -0.111 kcal/mol) in PBP 2X. In subsequent passages, gradual increases in ceftibuten MICs from 128 mg/L to 512 mg/L were found among selected mutants with accompanying stabilizing T555S+A354V (ΔΔG -0.257 kcal/mol) followed by stabilizing T555S + A354V + A536V (ΔΔG -0.322 kcal/mol), resulting in selection of a penicillin-susceptible group B Streptococcus lineage with reduced ceftibuten susceptibility (CTBr PSGBS). Notably, growth ability of CTBr PSGBS mutants was comparable to that of the parent strain. These findings may predict future failure of treatment for neonatal invasive infections caused by the neonate-hypervirulent PRGBS ST17 lineage.

Vaginal progesterone is associated with decreased group B streptococcus colonisation at term: a retrospective cohort study.

OBJECTIVE: To investigate whether women using intravaginal progesterone suppositories for preterm birth prevention during pregnancy will have lower rates of group B streptococcus (GBS) colonisation at term, compared with women receiving intramuscular 17-alpha-hydroxyprogesterone caproate. DESIGN: This was a retrospective observational cohort study of women who were prescribed a progestogen during their pregnancy for preterm birth prevention, and who delivered at term. SETTING: A tertiary referral hospital in central Ohio. POPULATION: Patients who were prescribed a progestogen during their pregnancy for preterm birth prevention between 2004 and 2017 were included in the study. Patients who delivered at <37 weeks of pregnancy, switched progestogen type during the pregnancy, or had a pessary or cerclage placed were excluded. METHODS: Baseline characteristics were compared using Mann-Whitney U-test or Chi-square test as appropriate. The association between type of progestogen and GBS colonisation was assessed using bivariate and multivariable analyses. MAIN OUTCOME MEASURES: The primary outcome was GBS colonisation. RESULTS: In all, 565 patients were included in the study, of whom 173 received intravaginal progesterone, and 392 17-alpha-hydroxyprogesterone caproate. Patients receiving intravaginal progesterone were less likely to be colonised with GBS (19.7 versus 28.1%). After adjustments for potential confounders were made in a multivariable logistic regression analysis, receiving intravaginal progesterone suppositories (adjusted odds ratio [OR] 0.61, 95% CI 0.39-0.95) was associated with reduced GBS colonisation. CONCLUSIONS: Intravaginal progesterone is associated with a decreased prevalence of rectovaginal GBS colonisation at term. TWEETABLE ABSTRACT: Vaginal progesterone is associated with a lower incidence of rectovaginal GBS colonisation, compared with 17α-hydroxyprogesterone caproate.

In vitro synergistic activity of erythromycin and nisin against clinical Group B Streptococcus isolates.

AIMS: This study investigated the potential synergy between erythromycin and nisin against clinical Group B Streptococcus (GBS) strains. METHODS AND RESULTS: The combination of erythromycin and nisin was examined for synergistic activity using checkerboard and time-kill assays against invasive and colonizing GBS strains. Additionally, the immunological effect of the antibiotic combination was investigated in vitro using human U937 cells and ELISA analysis. Checkerboard assays confirmed an additive effect when the antimicrobials were combined, while time-kill assays demonstrated a synergistic effect when antimicrobials were combined for invasive GBS isolates. Furthermore, a significantly lower TNF-alpha response (P < 0·05) was observed in U937 cells challenged with GBS when erythromycin and nisin were used in combination. CONCLUSIONS: The results suggest that erythromycin and nisin can act synergistically to inhibit the growth of GBS. SIGNIFICANCE AND IMPACT OF THE STUDY: Group B Streptococcus is the leading cause of invasive neonatal disease worldwide and is becoming increasingly more prevalent in adults. Resistance to some conventionally used antibiotics, such as erythromycin and clindamycin, continue to rise among GBS, indicating a need for alternative treatments. This study demonstrates the potential of an erythromycin-nisin combination for treatment of GBS infections and encourages further investigation of this treatment option.

Biofilm production and distribution of pilus variants among Streptococcus agalactiae isolated from human and animal sources.

Streptococcus agalactiae (group B Streptococcus, GBS) is a major pathogen in humans and animals. Pili and biofilm may be important virulence factors in this bacterial species. Here, biofilm production and the distribution of pilus variants among 134 GBS isolates from human and animal sources were evaluated. Biofilm production was significantly enhanced in 1% glucose-supplemented medium (p < 0.05). Using this medium, most GBS strains were strong biofilm producers. Biomass was mainly composed of proteins, followed by extracellular DNA, while polysaccharides represented a minor portion. All GBS strains presented at least one pilus variant. PI-2a was the most common among human GBS while PI-2b was the most common among animal isolates. Human GBS harboring PI-2b and animal GBS harboring PI-2a presented significantly reduced biofilm production (p = 0.0033). In conclusion, strong biofilm production seems to be a common characteristic in GBS, and association of the clinical source with the pilus variant may be crucial for this.

Prevalence and risk factors of group B Streptococcus colonisation in intrapartum women: a cross-sectional study.

A cross-sectional study was conducted at a Thai university hospital between November 2016 and March 2017 to evaluate the prevalence and risk factors of group B Streptococcus (GBS) colonisation in pregnant women who were admitted to the labour room for delivery. Rectovaginal specimens were collected and processed for the identification of GBS. Univariate and multiple logistic regression analyses were conducted to evaluate factors associated with GBS colonisation. Statistical significance was set at p < .05. Fifty-seven of 505 pregnant women (11.3%, 95% confidence interval [CI] 9.0-15.0%) were found to have GBS colonisation. Teenage pregnancy (odds ratio [OR] 3.83, 95% CI 1.13-13.02, p < .05), multi-parity (OR 3.59, 95% CI 1.69-7.60, p < .01) and non-Buddhist religions (OR 1.87, 95% CI 1.01-3.48, p < .05) were significantly associated with GBS colonisation. Intrapartum risk factors were not associated with GBS colonisation. Impact statement What is already known on this subject? The prevalence of GBS colonisation in pregnant women varies by geographic areas and ethnicities, ranging from 2.3 to 32.9%. Risk factors for GBS colonisation have been studied but the results were inconsistent. What do the results of this study add? This study reports the prevalence of GBS colonisation in intrapartum women in Southern Thailand to be 11.3%. We also identified some independent risk factors for GBS colonisation which were teenage pregnancy, multi-parity and non-Buddhist religions. To our knowledge, the relationship between religious belief and identification of GBS has never been reported before. We also found that intrapartum risk factors that have been used as the indication for intrapartum antibiotics administration have no correlation with GBS colonisation. What are the implications of these findings for clinical practice and/or further research? This study adds to the literature the prevalence and risk factors of GBS colonisation in the setting of a developing country. It also shows that intrapartum risk identification alone is not an optimal strategy to reduce infection associated with GBS. Instead, prenatal GBS screening should be encouraged to identify women with GBS colonisation to reduce the risk of infection and unnecessary antibiotics exposure.

Maternal obesity and the risk of group B streptococcal colonisation in pregnant women.

The aim of the study was to test if maternal obesity and being overweight are independent risk factors for rectovaginal Group B Streptococcus (GBS) colonisation in pregnancy and for early onset GBS disease in the neonate. A case-control study of 9877 deliveries was conducted. The obese gravidas were significantly more likely to be colonised by GBS when compared with non-obese gravidas (22.7% versus 17.5%, P < .001). Obese gravidas were still 33% more likely than non-obese women to test positive for GBS after adjusting for the perinatal factors (adjusted OR 1.33 [95% CI 1.12-1.56]). The risk of early onset GBS disease was not calculated due to its very low incidence. The conclusion is that maternal obesity is a significant risk factor for GBS colonisation at term. Impact statement What is already known on this subject? Group B Streptococcus (GBS) is as an important cause of perinatal mortality and morbidity if prophylaxis is not performed. Intrapartum antibiotics are given if the carrier status is positive or unknown, provided that the risk factors are present. What do the results of this study add? Maternal obesity is a significant and independent risk factor for GBS colonisation at term. What are the implications of these findings for clinical practice and/or further research? Maternal obesity may be considered as a risk factor that should be taken into account in strategies for reducing GBS disease in neonates.

Human milk oligosaccharides inhibit growth of group B Streptococcus.

Streptococcus agalactiae (group B Streptococcus, GBS) is a leading cause of invasive bacterial infections in newborns, typically acquired vertically during childbirth secondary to maternal vaginal colonization. Human milk oligosaccharides (HMOs) have important nutritional and biological activities that guide the development of the immune system of the infant and shape the composition of normal gut microbiota. In this manner, HMOs help protect against pathogen colonization and reduce the risk of infection. In the course of our studies of HMO-microbial interactions, we unexpectedly uncovered a novel HMO property to directly inhibit the growth of GBS independent of host immunity. By separating different HMO fractions through multidimensional chromatography, we found the bacteriostatic activity to be confined to specific non-sialylated HMOs and synergistic with a number of conventional antibiotic agents. Phenotypic screening of a GBS transposon insertion library identified a mutation within a GBS-specific gene encoding a putative glycosyltransferase that confers resistance to HMOs, suggesting that HMOs may function as an alternative substrate to modify a GBS component in a manner that impairs growth kinetics. Our study uncovers a unique antibacterial role for HMOs against a leading neonatal pathogen and expands the potential therapeutic utility of these versatile molecules.