Parvovirus B19 in Pregnancy.

Importance: Although the risk of parvovirus B19 infection during pregnancy and subsequent risk of adverse fetal outcome are low, understanding management practices is essential for proper treatment of fetuses with nonimmune hydrops fetalis. In addition, continued investigation into delivery management, breastfeeding recommendations, and congenital abnormalities associated with pregnancies complicated by parvovirus B19 infection is needed. Objective: This review describes the risks associated with parvovirus B19 infection during pregnancy and the management strategies for fetuses with vertically transmitted infections. Evidence Acquisition: Original articles were obtained from literature search in PubMed, Medline, and OVID; pertinent articles were reviewed. Results: Parvovirus B19 is a viral infection associated with negative pregnancy outcomes. Up to 50% of people of reproductive age are susceptible to the virus. The incidence of B19 in pregnancy is between 0.61% and 1.24%, and, overall, there is 30% risk of vertical transmission when infection is acquired during pregnancy. Although most pregnancies progress without negative outcomes, viral infection of the fetus may result in severe anemia, congestive heart failure, and hydrops fetalis. In addition, vertical transmission carries a 5% to 10% chance of fetal loss. In pregnancies affected by fetal B19 infection, Doppler examination of the middle cerebral artery peak systolic velocity should be initiated to surveil for fetal anemia. In the case of severe fetal anemia, standard fetal therapy involves an intrauterine transfusion of red blood cells with the goal of raising hematocrit levels to approximately 40% to 50% of total blood volume. One transfusion is usually sufficient, although continued surveillance may indicate the need for subsequent transfusions. There are fewer epidemiologic data concerning neonatal risks of congenital parvovirus, although case reports have shown that fetuses with severe anemia in utero may have persistent anemia, thrombocytopenia, and edema in the neonatal period. Conclusions and Relevance: Parvovirus B19 is a common virus; seropositivity in the geriatric population reportedly reaches 85%. Within the pregnant population, up to 50% of patients have not previously been exposed to the virus and consequently lack protective immunity. Concern for parvovirus B19 infection in pregnancy largely surrounds the consequences of vertical transmission of the virus to the fetus. Should vertical transmission occur, the overall risk of fetal loss is between 5% and 10%. Thus, understanding the incidence, risks, and management strategies of pregnancies complicated by parvovirus B19 is essential to optimizing care and outcomes. Further, there is currently a gap in evidence regarding delivery management, breastfeeding recommendations, and the risks of congenital abnormalities in pregnancies complicated by parvovirus B19. Additional investigations into optimal delivery management, feeding plans, and recommended neonatal surveillance are needed in this cohort of patients.

Fecal metabolite profiling identifies liver transplant recipients at risk for postoperative infection.

Metabolites produced by the intestinal microbiome modulate mucosal immune defenses and optimize epithelial barrier function. Intestinal dysbiosis, including loss of intestinal microbiome diversity and expansion of antibiotic-resistant pathobionts, is accompanied by changes in fecal metabolite concentrations and increased incidence of systemic infection. Laboratory tests that quantify intestinal dysbiosis, however, have yet to be incorporated into clinical practice. We quantified fecal metabolites in 107 patients undergoing liver transplantation (LT) and correlated these with fecal microbiome compositions, pathobiont expansion, and postoperative infections. Consistent with experimental studies implicating microbiome-derived metabolites with host-mediated antimicrobial defenses, reduced fecal concentrations of short- and branched-chain fatty acids, secondary bile acids, and tryptophan metabolites correlate with compositional microbiome dysbiosis in LT patients and the relative risk of postoperative infection. Our findings demonstrate that fecal metabolite profiling can identify LT patients at increased risk of postoperative infection and may provide guideposts for microbiome-targeted therapies.

Bifidobacteria metabolize lactulose to optimize gut metabolites and prevent systemic infection in patients with liver disease.

Progression of chronic liver disease is precipitated by hepatocyte loss, inflammation and fibrosis. This process results in the loss of critical hepatic functions, increasing morbidity and the risk of infection. Medical interventions that treat complications of hepatic failure, including antibiotic administration for systemic infections and lactulose treatment for hepatic encephalopathy, can impact gut microbiome composition and metabolite production. Here, using shotgun metagenomic sequencing and targeted metabolomic analyses on 847 faecal samples from 262 patients with acute or chronic liver disease, we demonstrate that patients hospitalized for liver disease have reduced microbiome diversity and a paucity of bioactive metabolites, including short-chain fatty acids and bile acid derivatives, that impact immune defences and epithelial barrier integrity. We find that patients treated with the orally administered but non-absorbable disaccharide lactulose have increased densities of intestinal bifidobacteria and reduced incidence of systemic infections and mortality. Bifidobacteria metabolize lactulose, produce high concentrations of acetate and acidify the gut lumen in humans and mice, which, in combination, can reduce the growth of antibiotic-resistant bacteria such as vancomycin-resistant Enterococcus faecium in vitro. Our studies suggest that lactulose and bifidobacteria serve as a synbiotic to reduce rates of infection in patients with severe liver disease.

Immunomodulatory fecal metabolites are associated with mortality in COVID-19 patients with respiratory failure.

Respiratory failure and mortality from COVID-19 result from virus- and inflammation-induced lung tissue damage. The intestinal microbiome and associated metabolites are implicated in immune responses to respiratory viral infections, however their impact on progression of severe COVID-19 remains unclear. We prospectively enrolled 71 patients with COVID-19 associated critical illness, collected fecal specimens within 3 days of medical intensive care unit admission, defined microbiome compositions by shotgun metagenomic sequencing, and quantified microbiota-derived metabolites (NCT #04552834). Of the 71 patients, 39 survived and 32 died. Mortality was associated with increased representation of Proteobacteria in the fecal microbiota and decreased concentrations of fecal secondary bile acids and desaminotyrosine (DAT). A microbiome metabolic profile (MMP) that accounts for fecal secondary bile acids and desaminotyrosine concentrations was independently associated with progression of respiratory failure leading to mechanical ventilation. Our findings demonstrate that fecal microbiota composition and microbiota-derived metabolite concentrations can predict the trajectory of respiratory function and death in patients with severe SARS-Cov-2 infection and suggest that the gut-lung axis plays an important role in the recovery from COVID-19.