Benefits of nanotechnology: Dietary supplementation with nerolidol-loaded nanospheres increases survival rates, reduces bacterial loads and prevents oxidative damage in brains of Nile tilapia experimentally infected by Streptococcus agalactiae.

Rampant and uncontrolled use of antibiotics is a major concern for aquaculture; the practice foments the emergence of resistant strains of Streptococcus agalactiae, among other negative impacts. Constituents of plant essential oils such as nerolidol are being considered as replacements for synthetic drugs to support fish nutrition and health. There is evidence to suggest that nanotechnology may enhance the efficacy of natural bioactive compounds; this is a substantial advance for the development and sustainability of aquaculture. Against the backdrop of this evidence, we aimed determine whether dietary supplementation with free nerolidol and nerolidol-loaded nanospheres would exert bactericidal effects against S. agalactiae, as well as prevent S. agalactiae-induced brain oxidative damage. In Experiment I, we measured the antimicrobial properties of dietary supplementation of nerolidol and nerolidol nanosphere in terms of mortality, longevity and relative percent survival. Fish infected with S. agalactiae fed 0.5 and 1.0 mL nerolidol nanospheres kg/diet demonstrated lower mortality and higher relative percent survival than the control group, while longevity was higher in all infected plus supplementation groups. Experiment II showed significantly lower microbial loads in brains of fish infected with S. agalactiae that were fed 1.0 mL nerolidol nanospheres kg/diet than in the control group. Brain nerolidol levels were significantly higher in uninfected as well as infected fish supplemented with nerolidol nanospheres than in fish supplemented with free nerolidol. Finally, brain reactive oxygen species and lipid peroxidation levels were higher in infected fish supplemented with basal diet compared to uninfected fish and supplemented with basal diet, and the supplementation with 1.0 mL/kg nerolidol nanospheres prevented this augmentation caused by infection. These data suggest that dietary supplementation with nerolidol nanospheres (1.0 mL/kg diet) has potent bactericidal effects in terms of augmentation of fish longevity and survival, and reduction of brain microbial loads. Also, S. agalactiae-induced brain oxidative damage that contributed to disease pathogenesis, and the dietary supplementation with nerolidol nanospheres (1.0 mL/kg diet) prevented this alteration. In summary, nanotechnology is a compelling approach to enhancing the efficacy of nerolidol, giving rise to reduction of S. agalactiae loads in fish brains.

The Streptococcus agalactiae Stringent Response Enhances Virulence and Persistence in Human Blood.

Streptococcus agalactiae (group B Streptococcus [GBS]) causes serious infections in neonates. We previously reported a transposon sequencing (Tn-seq) system for performing genomewide assessment of gene fitness in GBS. In order to identify molecular mechanisms required for GBS to transition from a mucosal commensal lifestyle to bloodstream invasion, we performed Tn-seq on GBS strain A909 with human whole blood. Our analysis identified 16 genes conditionally essential for GBS survival in blood, of which 75% were members of the capsular polysaccharide (cps) operon. Among the non-cps genes identified as conditionally essential was relA, which encodes an enzyme whose activity is central to the bacterial stringent response-a conserved adaptation to environmental stress. We used blood coincubation studies of targeted knockout strains to confirm the expected growth defects of GBS deficient in capsule or stringent response activation. Unexpectedly, we found that the relA knockout strains demonstrated decreased expression of ß-hemolysin/cytolysin, an important cytotoxin implicated in facilitating GBS invasion. Furthermore, chemical activation of the stringent response with serine hydroxamate increased ß-hemolysin/cytolysin expression. To establish a mechanism by which the stringent response leads to increased cytotoxicity, we performed transcriptome sequencing (RNA-seq) on two GBS strains grown under stringent response or control conditions. This revealed a conserved decrease in the expression of genes in the arginine deiminase pathway during stringent response activation. Through coincubation with supplemental arginine and the arginine antagonist canavanine, we show that arginine availability is a determinant of GBS cytotoxicity and that the pathway between stringent response activation and increased virulence is arginine dependent.

Group B Streptococcus causes severe sepsis in term neonates: 8 years experience of a major Chinese neonatal unit.

BACKGROUND: In contrast to industrialized countries, the clinical characteristics of neonatal sepsis caused by Group B Streptococcus (GBS) are largely unexplored in China. METHODS: A retrospective case series study was performed at a high-capacity neonatal unit in Shanghai, China from January 2008 to December 2015. Clinical characteristics of neonates with culture-proven GBS sepsis and antibiotic susceptibility of isolated strains were analyzed. RESULTS: Forty-three term neonates were included during the study period. The majority (74.4%) had early-onset sepsis with symptoms of respiratory distress. Meningitis was significantly more common in lateonset sepsis than in early-onset sepsis (81.5% vs. 18.8%, P<0.0001). Approximately one third of all patients (n=16) developed severe sepsis, defined as sepsis with organ dysfunctions, and respiratory dysfunction/failure was the most common (32.6%). The in-hospital mortality rate of GBS sepsis was 4.7%. Neonates who progressed to severe sepsis had significantly lower pH level at the onset of symptoms than those who did not (7.26±0.12 vs. 7.39±0.05, P=0.006). Treatment of severe GBS sepsis required lots of medical resources including extracorporeal membrane oxygenation. All tested GBS strains were susceptible to penicillin, but the rate of resistance to clindamycin (84.0%) and erythromycin (88.0%) was high. CONCLUSIONS: GBS as a pathogen for neonatal sepsis has been receiving little attention in China. Our data demonstrated that GBS sepsis was likely to be fulminant. Early recognition followed by antibiotics and adequate supportive therapies was critical for successful treatment. Chinese clinicians should be aware of GBS infection when treating neonatal sepsis, especially in the absence of universal maternal GBS screening.

Perinatal group B streptococcal disease prevention, Minnesota.

In 2002, revised guidelines for preventing perinatal group B streptococcal disease were published. In 2002, all Minnesota providers surveyed reported using a prevention policy. Most screen vaginal and rectal specimens at 34-37 weeks of gestation. The use of screening-based methods has increased dramatically since 1998.

Meningitis por Streptococcus agalactiae en el anciano / Streptococcus agalactiae meningitis in the elderly

La meningitis bacteriana continúa siendo una enfermedad con una alta mortalidad en ancianos, a pesar de la moderna antibioterapia. En los últimos años, la meningitis bacteriana ha cambiado y es frecuente en adultos, especialmente en ancianos. El déficit de la función inmunológica relacionada con el envejecimiento y la mayor propensión a padecer enfermedades agudas o crónicas comórbidas pueden predisponer a la infección por estreptococos del grupo B en el anciano. Las manifestaciones clínicas pueden ser atípicas en la población geriátrica. La fiebre, la cefalea y la rigidez de nuca pueden estar ausentes. Presentamos un caso de meningitis por Streptococcus agalactiae en una mujer anciana sin factores comórbidos. Debemos tener presente esta enfermedad como posible diagnóstico ante un paciente anciano con confusión o bajo nivel de conciencia. (AU)

Capsular type-specific polysaccharide partially inhibits group B Streptococcus-induced pulmonary hypertension.

Capsular type-specific polysaccharide is thought to be an important pathogenetic factor in Group B streptococcus (GBS) sepsis. To determine the effects of capsular type-specific polysaccharide on GBS-induced hemodynamic responses, anesthetized infant piglets were infused for 3 h with three related GBS Type lb strains that express different amounts of capsular type-specific polysaccharide. A larger capsule strain and a smaller capsule strain were isolated from an infected infant and its mother, respectively. A capsule-deficient mutant was then made from the larger capsule strain by transposon insertion mutagenesis. The smaller capsule strain and capsule-deficient mutant caused similar elevations in mean pulmonary artery pressure and pulmonary vascular resistance index and reductions in cardiac index. The larger capsule strain caused moderate pulmonary hypertension, but this response was smaller than for the other two GBS strains. Further comparisons in responses between the large capsule strain and its capsule-deficient mutant were then performed using unanesthetized piglets. The mutant caused significantly greater pulmonary hypertension and arterial plasma thromboxane B2 levels than the large capsule strain. The pulmonary hypertension induced by both strains was reversed by dazmegrel, a thromboxane A2 synthase inhibitor. These results suggest that (1) capsular type-specific polysaccharide is not an essential component in the generation of acute hemodynamic responses; (2) expression of large amounts of capsular type-specific polysaccharide on the organism surface partially inhibits GBS-induced pulmonary hypertension; and (3) the inhibition of the pulmonary responses is due to reduced thromboxane A2 release.(ABSTRACT TRUNCATED AT 250 WORDS)