Sweet syndrome following a positive Mantoux test due to pulmonary tuberculosis

New Practical Aspects of Sweet Syndrome

Sweet syndrome (SS), or acute febrile neutrophilic dermatosis, is an inflammatory, non-infectious skin reaction characterized clinically by tender, erythematous papules/plaques/pustules/nodules commonly appearing on the upper limbs, trunk, and head and neck; histologically, SS is characterized by dense neutrophilic infiltrate in the dermis. SS is accompanied by fever; an elevation of inflammatory markers (e.g., erythrocyte sedimentation rate, C reactive protein) in serum may also be observed. Although most cases of SS are idiopathic, SS also occurs in the setting of malignancy or following administration of an associated drug. SS has also been reported in association with pregnancy and a burgeoning list of infectious (most commonly upper respiratory tract infections) and inflammatory diseases; likewise, the litany of possible iatrogenic triggers has also grown. Over the past several years, a wider spectrum of SS presentation has been realized, with several reports highlighting novel clinical and histological variants. Corticosteroids continue to be efficacious first-line therapy for the majority of patients with SS, although novel steroid-sparing agents have been recently added to the therapeutic armamentarium against refractory SS. New mechanisms of SS induction have also been recognized, although the precise etiology of SS still remains elusive. Here, we catalogue the various clinical and histological presentations of SS, summarize recently reported disease associations and iatrogenic triggers, and review treatment options. We also attempt to frame the findings of this review in the context of established and emerging paradigms of SS pathogenesis.

The enemy from within: a prophage of Roseburia intestinalis systematically turns lytic in the mouse gut, driving bacterial adaptation by CRISPR spacer acquisition

Despite an overall temporal stability in time of the human gut microbiota at the phylum level, strong variations in species abundance have been observed. We are far from a clear understanding of what promotes or disrupts the stability of microbiome communities. Environmental factors, like food or antibiotic use, modify the gut microbiota composition, but their overall impacts remain relatively low. Phages, the viruses that infect bacteria, might constitute important factors explaining temporal variations in species abundance. Gut bacteria harbour numerous prophages, or dormant viruses, which can evolve to become ultravirulent phage mutants, potentially leading to important bacterial death. Whether such phenomenon occurs in the mammal's microbiota has been largely unexplored. Here we studied temperate phage-bacteria coevolution in gnotoxenic mice colonised with Roseburia intestinalis, a dominant symbiont of the human gut microbiota, and Escherichia coli, a sub-dominant member of the same microbiota. We show that R. intestinalis L1-82 harbours two active prophages, Jekyll and Shimadzu. We observed the systematic evolution in mice of ultravirulent Shimadzu phage mutants, which led to a collapse of R. intestinalis population. In a second step, phage infection drove the fast counter-evolution of host phage resistance mainly through phage-derived spacer acquisition in a clustered regularly interspaced short palindromic repeats array. Alternatively, phage resistance was conferred by a prophage originating from an ultravirulent phage with a restored ability to lysogenize. Our results demonstrate that prophages are a potential source of ultravirulent phages that can successfully infect most of the susceptible bacteria. This suggests that prophages can play important roles in the short-term temporal variations observed in the composition of the gut microbiota.