Ecological drift during colonization drives within-host and between-host heterogeneity in an animal-associated symbiont.

Specialized host-microbe symbioses canonically show greater diversity than expected from simple models, both at the population level and within individual hosts. To understand how this heterogeneity arises, we utilize the squash bug, Anasa tristis, and its bacterial symbionts in the genus Caballeronia. We modulate symbiont bottleneck size and inoculum composition during colonization to demonstrate the significance of ecological drift, the noisy fluctuations in community composition due to demographic stochasticity. Consistent with predictions from the neutral theory of biodiversity, we found that ecological drift alone can account for heterogeneity in symbiont community composition between hosts, even when 2 strains are nearly genetically identical. When acting on competing strains, ecological drift can maintain symbiont genetic diversity among different hosts by stochastically determining the dominant strain within each host. Finally, ecological drift mediates heterogeneity in isogenic symbiont populations even within a single host, along a consistent gradient running the anterior-posterior axis of the symbiotic organ. Our results demonstrate that symbiont population structure across scales does not necessarily require host-mediated selection, as it can emerge as a result of ecological drift acting on both isogenic and unrelated competitors. Our findings illuminate the processes that might affect symbiont transmission, coinfection, and population structure in nature, which can drive the evolution of host-microbe symbioses and microbe-microbe interactions within host-associated microbiomes.

Prognostic factors for multisystem inflammatory syndrome in children: A systematic review and meta-analysis.

AIM: Multisystem inflammatory syndrome in children (MIS-C) is a novel condition that can occur post-SARS-CoV-2 infection in children and adolescents. There is a paucity of evidence on the prognostic factors associated with MIS-C. The aim of this systematic review and meta-analysis was to summarise the prognostic factors for MIS-C development. METHODS: Five databases were systematically searched from January 2020 to May 2023 for studies reporting on prognostic factors for MIS-C using multivariable regression models. Random-effects meta-analyses were conducted to pool odds ratios for each prognostic factor. Risk of bias was rated using QUIPS and the GRADE framework was used to assess the certainty of evidence for each unique factor. RESULTS: Twelve observational studies (N = 18 024) were included, and 13 unique prognostic factors were amenable to meta-analysis. With moderate certainty, age <12 years, male sex and Black race probably increase the risk of MIS-C. Malignancy and underlying respiratory disease probably decrease the risk of MIS-C. Low-certainty evidence suggests that Asian race may increase the risk of MIS-C, and comorbidity may decrease the risk of MIS-C. CONCLUSION: Current literature presents several prognostic factors related to MIS-C following SARS-CoV-2 infection. Further research is necessary to elucidate the pathophysiologic mechanisms related to MIS-C.

Specialized acquisition behaviors maintain reliable environmental transmission in an insect-microbial mutualism.

Understanding how horizontally transmitted mutualisms are maintained is a major focus of symbiosis research.1,2,3,4 Unlike vertical transmission, hosts that rely on horizontal transmission produce symbiont-free offspring that must find and acquire their beneficial microbes from the environment. This transmission strategy is inherently risky since hosts may not obtain the right symbiont every generation. Despite these potential costs, horizontal transmission underlies stable mutualisms involving a large diversity of both plants and animals.5,6,7,8,9 One largely unexplored way horizontal transmission is maintained is for hosts to evolve sophisticated mechanisms to consistently find and acquire specific symbionts from the environment. Here, we examine this possibility in the squash bug Anasa tristis, an insect pest that requires bacterial symbionts in the genus Caballeronia10 for survival and development.11 We conduct a series of behavioral and transmission experiments that track strain-level transmission in vivo among individuals in real-time. We demonstrate that nymphs can accurately find feces from adult bugs in both the presence and absence of those adults. Once nymphs locate the feces, they deploy feeding behavior that results in nearly perfect symbiont acquisition success. We further demonstrate that nymphs can locate and feed on isolated, cultured symbionts in the absence of feces. Finally, we show this acquisition behavior is highly host specific. Taken together, our data describe not only the evolution of a reliable horizontal transmission strategy, but also a potential mechanism that drives patterns of species-specific microbial communities among closely related, sympatric host species.

Long-Term Clinical Outcomes of Biodegradable-Polymer Drug-Eluting Stents Versus Second-Generation Durable-Polymer Drug-Eluting Stents for ST-Segment Elevation Myocardial Infarction.

BACKGROUND: Biodegradable polymer drug eluting stents (BP-DES) may offer the advantage of vascular healing in ST-segment elevation myocardial infarction (STEMI). Long-term outcome data comparing BP-DES and second-generation durable polymer drug eluting stents (DP-DES) in STEMI is lacking. This study aims to compare the long-term clinical outcomes of BP-DES versus second-generation DP-DES in STEMI. METHODS: This is an observational study of consecutive patients with STEMI who received either BP-DES (n = 854) or DP-DES (n = 708) during primary percutaneous coronary intervention (PCI) from 1st February 2007 to 31st December 2016. The primary outcome was target lesion failure (TLF), a composite of cardiac death, target vessel myocardial infarction (MI), and target lesion revascularization with follow up till 30th November 2019. RESULTS: The baseline demographics, lesion and procedural characteristic were similar between the two groups except for more prior MI and chronic obstructive pulmonary disease in the BP-DES group. At a median follow up of 4.2 years (interquartile range: 2.6-6.2 years), the incidence of TLF was similar between BP-DES and DP-DES (adjusted hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.70-1.26). Likewise, incidence of major adverse cardiovascular events (MACE: all-cause death, any MI or target vessel revascularization) and definite stent thrombosis were similar in both groups (MACE: adjusted HR 1.04, 95% CI 0.82-1.32; definite stent thrombosis: adjusted HR 1.06, 95% CI 0.31-3.64). CONCLUSION: Among patients with STEMI who underwent primary PCI, BP-DES and DP-DES implantation was associated with similar long-term clinical outcomes.