The lengthy course of treatment with currently used anti-mycobacterial drugs and the resulting emergence of drug-resistant strains have intensified the need for alternative therapies against Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis. We show that Mtb and Mycobacterium marinum use Abl and related tyrosine kinases for entry and intracellular survival in macrophages. In mice, the Abl-family tyrosine kinase inhibitor, imatinib (Gleevec®), when administered prophylactically or therapeutically, reduced both the number of granulomatous lesions and bacterial load in infected organs, and was also effective against a rifampicin-resistant strain. Further, when co-administered with current first-line drugs, rifampicin or rifabutin, imatinib acted synergistically. These data implicate host tyrosine kinases in entry and intracellular survival of mycobacteria, and suggest that imatinib may have therapeutic efficacy against Mtb. Because imatinib targets host, it is less likely to engender resistance compared to conventional antibiotics, and may decrease the development of resistance against co-administered drugs.

Enteropathogenic Escherichia coli, enterohemorrhagic E. coli, and Citrobacter rodentium are classified as attaching and effacing pathogens based on their ability to adhere to the intestinal epithelium via actin-filled membranous protrusions (pedestals). Infection of mice with C. rodentium causes a breach of the intestinal epithelial barrier, leading to colitis via a vigorous inflammatory response resulting in diarrhea and a protective antibody response that clears the pathogen. Here we show that interleukin-1 receptor (IL-1R) signaling protects mice following infection with C. rodentium. Upon infection, mice lacking the type I IL-1R exhibit increased mortality together with severe colitis characterized by intramural colonic bleeding and intestinal damage including gangrenous mucosal necrosis, phenotypes also evident in MyD88-deficient mice. However, unlike MyD88 ؊/؊ mice, IL-1R ؊/؊ mice do not exhibit increased pathogen loads in the colon, delays in the recruitment of innate immune cells such as neutrophils, or defects in the capacity to replace damaged enterocytes. Further, we demonstrate that IL-1R ؊/؊ mice have an increased predisposition to intestinal damage caused by C. rodentium but not to that caused by chemical irritants, such as dextran sodium sulfate. Together, these data suggest that IL-1R signaling regulates the susceptibility of the intestinal epithelia to damage caused by C. rodentium.

Internalization of the pathogenic bacterium Pseudomonas aeruginosa by non-phagocytic cells is promoted by rearrangements of the actin cytoskeleton, but the host pathways usurped by this bacterium are not clearly understood. We used RNAi-mediated gene inactivation of ∼80 genes known to regulate the actin cytoskeleton in Drosophila S2 cells to identify host molecules essential for entry of P. aeruginosa. This work revealed Abl tyrosine kinase, the adaptor protein Crk, the small GTPases Rac1 and Cdc42, and p21-activated kinase as components of a host signaling pathway that leads to internalization of P. aeruginosa. Using a variety of complementary approaches, we validated the role of this pathway in mammalian cells. Remarkably, ExoS and ExoT, type III secreted toxins of P. aeruginosa, target this pathway by interfering with GTPase function and, in the case of ExoT, by abrogating P. aeruginosa–induced Abl-dependent Crk phosphorylation. Altogether, this work reveals that P. aeruginosa utilizes the Abl pathway for entering host cells and reveals unexpected complexity by which the P. aeruginosa type III secretion system modulates this internalization pathway. Our results furthermore demonstrate the applicability of using RNAi screens to identify host signaling cascades usurped by microbial pathogens that may be potential targets for novel therapies directed against treatment of antibiotic-resistant infections.

Background:We recently developed CoCites, a citation-based search method that is designed to be more efficient than traditional keyword-based methods. The method begins with identification of one or more highly relevant publications (query articles) and consists of two searches: the co-citation search, which ranks publications on their co-citation frequency with the query articles, and the citation search, which ranks publications on frequency of all citations that cite or are cited by the query articles. Methods:We aimed to reproduce the literature searches of published systematic reviews and meta-analyses and assess whether CoCites retrieves all eligible articles while screening fewer titles. Results: A total of 250 reviews were included. CoCites retrieved a median of 75% of the articles that were included in the original reviews. The percentage of retrieved articles was higher (88%) when the query articles were cited more frequently and when they had more overlap in their citations. Applying CoCites to only the highest-cited article yielded similar results. The co-citation and citation searches combined were more efficient when the review authors had screened more than 500 titles, but not when they had screened less. Conclusions: CoCites is an efficient and accurate method for finding relevant related articles. The method uses the expert knowledge of authors to rank related articles, does not depend on keyword selection and requires no special expertise to build search queries. The method is transparent and reproducible.

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Tuberculosis (TB) is a major public health concern worldwide with over 2 billion people currently infected. The rise of strains of Mycobacterium tuberculosis (Mtb) that are resistant to some or all first and second line antibiotics, including multidrug-resistant (MDR), extensively drug resistant (XDR) and totally drug resistant (TDR) strains, is of particular concern and new anti-TB drugs are urgently needed. Curcumin, a natural product used in traditional medicine in India, exhibits anti-microbial activity that includes Mtb, however it is relatively unstable and suffers from poor bioavailability. To improve activity and bioavailability, mono-carbonyl analogs of curcumin were synthesized and screened for their capacity to inhibit the growth of Mtb and the related Mycobacterium marinum (Mm). Using disk diffusion and liquid culture assays, we found several analogs that inhibit in vitro growth of Mm and Mtb, including rifampicin-resistant strains. Structure activity analysis of the analogs indicated that Michael acceptor properties are critical for inhibitory activity. However, no synergistic effects were evident between the monocarbonyl analogs and rifampicin on inhibiting growth. Together, these data provide a structural basis for the development of analogs of curcumin with pronounced anti-mycobacterial activity and provide a roadmap to develop additional structural analogs that exhibit more favorable interactions with other anti-TB drugs.

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Background & Aims-Expression of the di/tripeptide transporter PepT1 has been observed in the colon under inflammatory conditions, however, the inducing factors and underlying mechanisms remain unknown. Here, we address the effects of pathogenic bacteria on colonic PepT1 expression together with its functional consequences.