Brief Report: Performance of Tuberculosis Symptom Screening Among Hospitalized ART-Naive Children With HIV in Kenya.

BACKGROUND: The World Health Organization (WHO) recommends tuberculosis (TB) diagnostic evaluation for children with HIV (CHIV) who have history of TB contact, poor weight gain, cough, or fever. These screening criteria were developed based on studies of symptomatic CHIV with incomplete microbiologic confirmation. We performed routine TB microbiologic evaluation of hospitalized CHIV with and without symptoms to develop a data-driven TB symptom screen. METHODS: Among hospitalized antiretroviral therapy-naive Kenyan CHIV enrolled in the Pediatric Urgent Start of Highly Active Antiretroviral Therapy (PUSH) trial, we performed Xpert MTB/RIF and mycobacterial culture of respiratory and stool specimens independent of TB symptoms. We evaluated performance of WHO and other published pediatric TB screening criteria and derived optimized criteria using a combination of symptoms. RESULTS: Of 168 CHIV who underwent TB microbiologic evaluation, 13 (8%) had confirmed TB. WHO TB symptom screening had 100% sensitivity and 4% specificity to detect confirmed TB. Published TB screening criteria that relied on prolonged symptoms missed cases of confirmed TB (sensitivity 85%-92%). An optimized symptom screen including weight loss, cough, anorexia, or TB contact had 100% sensitivity and improved specificity (31%) compared with the WHO pediatric TB symptom screen. CONCLUSIONS: The WHO TB symptom screen was highly sensitive but resulted in a high proportion of hospitalized CHIV who would require TB diagnostic evaluation. Other published TB screening criteria missed CHIV with confirmed TB. Our optimized screening tool increased specificity while preserving sensitivity. Future multicenter studies are needed to improve TB screening tools for CHIV in both inpatient and outpatient settings.

Terrestrial support of aquatic food webs depends on light inputs: a geographically-replicated test using tank bromeliads.

Food webs of freshwater ecosystems can be subsidized by allochthonous resources. However, it is still unknown which environmental factors regulate the relative consumption of allochthonous resources in relation to autochthonous resources. Here, we evaluated the importance of allochthonous resources (litterfall) for the aquatic food webs in Neotropical tank bromeliads, a naturally replicated aquatic microcosm. Aquatic invertebrates were sampled in more than 100 bromeliads within either open or shaded habitats and within five geographically distinct sites located in four different countries. Using stable isotope analyses, we determined that allochthonous sources comprised 74% (±17%) of the food resources of aquatic invertebrates. However, the allochthonous contribution to aquatic invertebrates strongly decreased from shaded to open habitats, as light incidence increased in the tanks. The density of detritus in the tanks had no impact on the importance of allochthonous sources to aquatic invertebrates. This overall pattern held for all invertebrates, irrespective of the taxonomic or functional group to which they belonged. We concluded that, over a broad geographic range, aquatic food webs of tank bromeliads are mostly allochthonous-based, but the relative importance of allochthonous subsidies decreases when light incidence favors autochthonous primary production. These results suggest that, for other freshwater systems, some of the between-study variation in the importance of allochthonous subsidies may similarly be driven by the relative availability of autochthonous resources.

Dominant predators mediate the impact of habitat size on trophic structure in bromeliad invertebrate communities.

Local habitat size has been shown to influence colonization and extinction processes of species in patchy environments. However, species differ in body size, mobility, and trophic level, and may not respond in the same way to habitat size. Thus far, we have a limited understanding of how habitat size influences the structure of multitrophic communities and to what extent the effects may be generalizable over a broad geographic range. Here, we used water-filled bromeliads of different sizes as a natural model system to examine the effects of habitat size on the trophic structure of their inhabiting invertebrate communities. We collected composition and biomass data from 651 bromeliad communities from eight sites across Central and South America differing in environmental conditions, species pools, and the presence of large-bodied odonate predators. We found that trophic structure in the communities changed dramatically with changes in habitat (bromeliad) size. Detritivore : resource ratios showed a consistent negative relationship with habitat size across sites. In contrast, changes in predator: detritivore (prey) ratios depended on the presence of odonates as dominant predators in the regional pool. At sites without odonates, predator: detritivore biomass ratios decreased with increasing habitat size. At sites with odonates, we found odonates to be more frequently present in large than in small bromeliads, and predator: detritivore biomass ratios increased with increasing habitat size to the point where some trophic pyramids became inverted. Our results show that the distribution of biomass amongst food-web levels depends strongly on habitat size, largely irrespective of geographic differences in environmental conditions or detritivore species compositions. However, the presence of large-bodied predators in the regional species pool may fundamentally alter this relationship between habitat size and trophic structure. We conclude that taking into account the response and multitrophic effects of dominant, mobile species may be critical when predicting changes in community structure along a habitat-size gradient.