Fidaxomicin jams Mycobacterium tuberculosis RNA polymerase motions needed for initiation via RbpA contacts.

Fidaxomicin (Fdx) is an antimicrobial RNA polymerase (RNAP) inhibitor highly effective against Mycobacterium tuberculosis RNAP in vitro, but clinical use of Fdx is limited to treating Clostridium difficile intestinal infections due to poor absorption. To identify the structural determinants of Fdx binding to RNAP, we determined the 3.4 Å cryo-electron microscopy structure of a complete M. tuberculosis RNAP holoenzyme in complex with Fdx. We find that the actinobacteria general transcription factor RbpA contacts fidaxomycin, explaining its strong effect on M. tuberculosis. Additional structures define conformational states of M. tuberculosis RNAP between the free apo-holoenzyme and the promoter-engaged open complex ready for transcription. The results establish that Fdx acts like a doorstop to jam the enzyme in an open state, preventing the motions necessary to secure promoter DNA in the active site. Our results provide a structural platform to guide development of anti-tuberculosis antimicrobials based on the Fdx binding pocket.

Use of Rome criteria for the diagnosis of irritable bowel syndrome in primary care: a survey among European countries.

BACKGROUND AND OBJECTIVES: The majority of patients with irritable bowel syndrome (IBS) are diagnosed and treated in primary care. The aim of this study was to investigate the implementation of the Rome criteria in daily primary care clinical practice and adherence of general practitioners (GPs) to recommended diagnostic approaches for IBS. PATIENTS AND METHODS: A survey consisting of 18 questions was distributed across 11 European countries and was used to assess GPs' diagnostic approach of IBS, the use of Rome criteria in daily practice and GPs' perspective on the aetiology of the disorder. RESULTS: Overall, 185 GPs completed the survey. In daily clinical practice, 32% of GPs reported that they usually make a positive diagnosis on the basis of symptoms only, whereas 36% of GPs reported regular use of the Rome criteria to diagnose IBS. Furthermore, 62% of the responders reported that they applied additional diagnostics, such as blood tests, 31% found it necessary to perform endoscopy to make a positive diagnosis of IBS and 29% referred patients with IBS to a specialist. Psychological factors were the most frequently selected potential aetiological factor of IBS (88% of GPs). Overall, 52% of GPs reported systematically including questions on psychological symptoms in the assessment of history of IBS. CONCLUSION: Only about one-third of GPs regularly used the Rome criteria to diagnose IBS. In daily primary care practice, IBS largely remains a diagnosis of exclusion. This has implications in terms of GPs' specialty training and questions the applicability of IBS guidelines in daily care, which advocate an early, positive, symptom-based diagnosis.