Stress has long been correlated with susceptibility to microbial infection. One explanation for this phenomenon is the ability of pathogens to sense and respond to host stress-related catecholamines, such as norepinephrine (NE). In Gram-negative enteric pathogens, it has been proposed that NE may facilitate growth by mediating iron supply, or it may alter gene expression by activating adrenergic sensor kinases. The aim of this work was to investigate the relative importance of these processes in a model in which NE alters the outcome of Salmonella enterica serovar Typhimurium infection. A bovine ligated ileal loop model was used to study the effect of NE on enteritis induced by S. Typhimurium and on the bacterial in vivo replication rate. Mutants lacking putative adrenergic receptor genes were assessed in the loop model, in a calf intestinal colonization model, and in vitro. S. Typhimurium-induced enteritis was significantly enhanced by addition of 5 mM NE. This effect was associated with increased net bacterial replication in the same model. Exogenous ferric iron also stimulated bacterial replication in the medium used but not transcription of enteritis-associated loci. The putative adrenergic sensors QseC and QseE were not required for NE-enhanced enteritis, intestinal colonization of calves, or NE-dependent growth in iron-restricted medium and did not influence expression or secretion of enteritis-associated virulence factors. Our findings support a role for stress-related catecholamines in modulating the virulence of enteric bacterial pathogens in vivo but suggest that bacterial adrenergic sensors may not be the vital link in such interkingdom signaling in Salmonella.
Objective
To test and compare the efficacy of methenamine hippurate for prevention of recurrent urinary tract infections with the current standard prophylaxis of daily low dose antibiotics.
Design
Multicentre, open label, randomised, non-inferiority trial.
Setting
Eight centres in the UK, recruiting from June 2016 to June 2018.
Participants
Women aged ≥18 years with recurrent urinary tract infections, requiring prophylactic treatment.
Interventions
Random assignment (1:1, using permuted blocks of variable length via a web based system) to receive antibiotic prophylaxis or methenamine hippurate for 12 months. Treatment allocation was not masked and crossover between arms was allowed.
Main outcome measure
Absolute difference in incidence of symptomatic, antibiotic treated, urinary tract infections during treatment. A patient and public involvement group predefined the non-inferiority margin as one episode of urinary tract infection per person year. Analyses performed in a modified intention-to-treat population comprised all participants observed for at least six months.
Results
Participants were randomly assigned to antibiotic prophylaxis (n=120) or methenamine hippurate (n=120). The modified intention-to-treat analysis comprised 205 (85%) participants (antibiotics, n=102 (85%); methenamine hippurate, n=103 (86%)). Incidence of antibiotic treated urinary tract infections during the 12 month treatment period was 0.89 episodes per person year (95% confidence interval 0.65 to 1.12) in the antibiotics group and 1.38 (1.05 to 1.72) in the methenamine hippurate group, with an absolute difference of 0.49 (90% confidence interval 0.15 to 0.84) confirming non-inferiority. Adverse reactions were reported by 34/142 (24%) in the antibiotic group and 35/127 (28%) in the methenamine group and most reactions were mild.
Conclusion
Non-antibiotic prophylactic treatment with methenamine hippurate might be appropriate for women with a history of recurrent episodes of urinary tract infections, informed by patient preferences and antibiotic stewardship initiatives, given the demonstration of non-inferiority to daily antibiotic prophylaxis seen in this trial.
Trial registration
ISRCTN70219762
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Here we report that Salmonella enterica serovar Typhimurium pathogenicity island 4 carries a type I secretion system (siiCDF) which secretes an ∼600-kDa protein (encoded by siiE). SiiE is surface expressed, and its production is regulated by HilA. SiiE and SiiF influence colonization in cattle and the invasion of bovine enterocytes.
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TitleSurgical treatment for recurrent bulbar urethral stricture: A randomised open label superiority trial of open urethroplasty versus endoscopic urethrotomy (The OPEN Trial).
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