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001) increased compared to baseline. Patients without POR showed a decrease of Streptococcaceae (FDR=0.003) and Actinomycineae (FDR=0.06). The mucosa-associated microbiota profile had good discriminative power to predict POR, and was superior to clinical risk factors. At month 6, patients experiencing POR had a higher abundance of taxa belonging to Negativicutes (FDR=0.04) and Fusobacteria (FDR=0.04) compared to patients without POR. CONCLUSIONS Microbiota recolonization after ileocecal resection is different between recurrence and non-recurrence patients, with Fusobacteria as the most prominent player driving early POR. D-AP5 These bacteria involved in the early recolonization and POR represent a promising therapeutic strategy in the prevention of disease recurrence. © The Author(s) 2020. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.BACKGROUND AND AIMS Angiosperms vary remarkably in traits such as colour, size and shape of flowers, yet such variation generally tends to be low within species. In deceptive orchids, however, large variation in floral traits has been described, not only between, but also within populations. Nonetheless, the factors driving variation in floral traits in deceptive orchids remain largely unclear. METHODS To identify determinants of variation in floral traits, we investigated patterns of fruit set and selection gradients in the food-deceptive orchid Orchis purpurea, which typically presents large within-population variation in the colour and size of the flowers. Using long-term data, fruit set was quantified in two populations during sixteen consecutive years (2004-2019). Artificial hand pollination was performed to test the hypothesis that fruit set was pollinator limited and that selfing led to decreased seed set and viability. Annual variation (2016-2019) in selection gradients was calculated for three colour traits (brightness, contrast and the number of spots on the labellum), flower size (spur length, labellum length and width) and plant size (number of flowers, plant height). KEY RESULTS Fruit set was, on average, low (~12%) and severely pollinator limited. Opportunities for selection varied strongly across years, but we found only weak evidence for selection on floral traits. In contrast, there was strong and consistent positive selection on floral display. Selfing led to reduced production of viable seeds and hence severe inbreeding depression (δ = 0.38). CONCLUSION Overall, these results demonstrate that the large variation in flower colour and size that is regularly observed in natural O. purpurea populations is maintained by the consistent lack of strong selection pressures on these traits through time. © The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.BACKGROUND Retreatment tuberculosis (TB) disease is common in high-prevalence settings. The risk of repeated episodes of recurrent TB is unknown. We calculated the rate of recurrent TB per subsequent episode by matching individual treatment episodes over a period of 13 years. METHODS All recorded TB episodes in Cape Town between 2003-2016 were matched by probabilistic linkage of personal identifiers. Among individuals with a first episode notified in Cape Town and who completed their prior treatment successfully we estimated the recurrence rate stratified by subsequent episode and HIV status. We adjusted person-time to background mortality by age, sex and HIV status. RESULTS A total of 292,915 TB episodes among 263,848 individuals were included. The rate of recurrent TB was 16.4 per 1000 person-years (95% CI, 16.2-16.6), and increased per subsequent episode (8.4-fold increase, from 14.6 to 122.7 per 1000 from episode 2 to 6, respectively). These increases were similar stratified by HIV status. Rates among HIV positives were higher than among HIV negatives for episodes 2 and 3 (2 and 1.5-fold higher, respectively), and the same thereafter. CONCLUSIONS TB recurrence rates were high and increased per subsequent episode, independent of HIV status. This suggests that HIV-infection is insufficient to explain the high burden of recurrence; it is more likely due to a high annual risk of infection combined with an increased risk of infection or progression to disease associated with a previous TB episode. The very high recurrence rates would justify increased TB surveillance of patients with more than one episode. © The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America.Both canonical olfactory sensory neurons (OSNs) and sensory neurons belonging to the guanylate cyclase D (GCD) "necklace" subsystem are housed in the main olfactory epithelium, which is continuously bombarded by toxins, pathogens and debris from the outside world. Canonical OSNs address this challenge, in part, by undergoing renewal through neurogenesis; however, it is not clear whether GCD OSNs also continuously regenerate, and if so whether newborn GCD precursors follow a similar developmental trajectory to that taken by canonical OSNs. Here we demonstrate that GCD OSNs are born throughout adulthood and can persist in the epithelium for several months. Phosphodiesterase 2A is upregulated early in the differentiation process, followed by the sequential downregulation of β-tubulin and the upregulation of CART protein. The GCD and MS4A receptors that confer sensory responses upon GCD neurons are initially expressed midway through this process, but become most highly expressed once CART levels are maximal late in GCD OSN development. GCD OSN maturation is accompanied by a horizontal migration of neurons towards the central, curved portions of the cul-de-sac regions where necklace cells are concentrated. These findings demonstrate that - like their canonical counterparts - GCD OSNs undergo continuous renewal, and define a GCD-specific developmental trajectory linking neurogenesis, maturation and migration. © The Author(s) 2020. Published by Oxford University Press. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.