Helicobacter pylori establishes lifelong infections of the gastric mucosa, a niche considered hostile to most microbes. While responses to gastric acidity and local inflammation are understood, little is known as to how they are integrated into homeostatic control of cell division and growth-stage gene expression. Here we investigate the essential orphan response regulator HP1043, a member of the OmpR/PhoB subfamily of transcriptional regulators that is unique to the Epsilonproteobacteria and that lacks phosphorylation domains. To test the hypothesis that conformational changes in the homodimer might lead to defects in gene expression, we sought mutations that might alter DNA-binding efficiency. Two introduced mutations (C215S, C221S) C terminal to the DNA-binding domain of HP1043 (HP1043CC11) resulted in a 2-fold higher affinity for its own promoter by footprinting. Modeling studies with the crystal structure of HP1043 suggested that C215S might affect the helix-turn-helix domain. Genomic replacement of the hp1043 allele with the hp1043CC11 mutant allele resulted in a 2-fold decrease in protein levels, despite a dramatic increase in mRNA. The mutations did not affect in vitro growth rates or colonization efficiency in a mouse model. Proteomic profiling (CC11 mutant strain versus wild type) identified many expression differences, and quantitative PCR further revealed that 11 out of 12 examined genes had lost growth-stage regulation and that 6 of the genes contained HP1043 binding consensus sequences within the promoter regions (fur, cagA, cag23, flhA, flip, and napA). Our studies show that mutations that affect DNA-binding affinity can be used to identify new members of the HP1043 regulon.
Metronidazole (MTZ) is often used in combination therapies to treat infections caused by the gastric pathogen Helicobacter pylori.Resistance to MTZ results from loss-of-function mutations in genes encoding RdxA and FrxA nitroreductases. MTZ-resistant strains, when cultured at sub-MICs of MTZ (5 to 20 g/ml), show dose-dependent defects in bacterial growth; depressed activities of many Krebs cycle enzymes, including pyruvate:ferredoxin oxidoreductase (PFOR); and low transcript levels of porGDAB (primer extension), phenotypes consistent with an involvement of a transcriptional regulator. Using a combination of protein purification steps, electrophoretic mobility shift assays (EMSAs), and mass spectrometry analyses of proteins bound to porG promoter sequences, we identified HP1043, an essential homeostatic global regulator (HsrA [for homeostatic stress regulator]). Competition EMSAs and supershift analyses with HsrA-enriched protein fractions confirmed specific binding to porGDAB and hsrA promoter sequences. Exposure to MTZ resulted in >10-fold decreases in levels of HsrA and in levels of the HsrA-regulated gene products PFOR and TlpB. Exposure to paraquat (PQ), hydrogen peroxide, or organic peroxides showed near equivalence with MTZ, revealing a common oxidative stress response pathway. Finally, direct superoxide dismutase (SOD) assays showed an inverse relationship between HsrA levels and SOD activity, suggesting that HsrA may serve as a repressor of sodB. As a homeostatic sentinel, HsrA appears to be ideally positioned to enable rapid shutdown of genes associated with metabolism and growth while activating (directly or indirectly) oxidative defense genes in response to low levels of toxic metabolites (MTZ or oxygen) before they reach DNA-damaging levels. Helicobacter pylori is a microaerobic bacterium that causes lifelong infections of the gastric mucosa of over 3 billion persons worldwide, and while most of these infections result in mild superficial gastritis, some infections progress to more serious diseases such as peptic and duodenal ulcers, mucosa-associated lymphoid tissue lymphoma, and gastric cancer (1-3). The remarkable ability of H. pylori to both colonize and persist in the gastric milieu is attributed to several systems that monitor local pH, including a novel pH-gated urea transporter (UreI) that modulates a powerful urease system (4, 5), a pH-sensing chemoreceptor (TlpB) that directs both colonization and avoidance of washout with mucus turnover (6), and a pH-sensing two-component regulatory system (ArsRS) that modulates expression of acid survival genes in sync with the daily cycling of stomach acid (7-10). In contrast to acid stress, little is known regarding the response to oxidative stress, yet H. pylori promotes gastric inflammation and the recruitment of neutrophils and macrophages, all of which produce reactive oxygen and nitrogen species (11, 12). While H. pylori responds to oxidative stress insults by increasing the expression levels of many genes, including catalase, alkyl hydroperoxide r...
SUMMARY SETTING A referral hospital for tuberculosis (TB) in Irkutsk, the Russian Federation. OBJECTIVE To describe disease characteristics, treatment and hospital outcomes of TB-HIV (human immunodeficiency virus). DESIGN Observational cohort of HIV-infected patients admitted for anti-tuberculosis treatment over 6 months. RESULTS A total of 98 patients were enrolled with a median CD4 count of 147 cells/mm3 and viral load of 205 943 copies/ml. Among patients with drug susceptibility testing (DST) results, 29 (64%) were multidrug-resistant (MDR), including 12 without previous anti-tuberculosis treatment. Nineteen patients were on antiretroviral therapy (ART) at admission, and 10 (13% ART-naïve) were started during hospitalization. Barriers to timely ART initiation included death, in-patient treatment interruption, and patient refusal. Of 96 evaluable patients, 21 (22%) died, 14 (15%) interrupted treatment, and 10 (10%) showed no microbiological or radiographic improvement. Patients with a cavitary chest X-ray (aOR 7.4, 95%CI 2.3–23.7, P = 0.001) or central nervous system disease (aOR 6.5, 95%CI 1.2–36.1, P=0.03) were more likely to have one of these poor outcomes. CONCLUSION High rates of MDR-TB, treatment interruption and death were found in an HIV-infected population hospitalized in Irkutsk. There are opportunities for integration of HIV and TB services to overcome barriers to timely ART initiation, increase the use of anti-tuberculosis regimens informed by second-line DST, and strengthen out-patient diagnosis and treatment networks.
* Respondents were asked to rank from 1 to 5 their level of agreement with the statement: 5 = strongly agree; 4 = agree, 3 = neither agree nor disagree; 2 = disagree, and 1 = strongly disagree. ART= antiretroviral therapy; HIV = human immunodeficiency virus; TB = tuberculosis. Public Health Action Improving art initiation in Siberia 254 CONCLUSIONSInitiatives aimed at TB-HIV integration were significantly associated with improved ART initiation at a regional referral hospital in Irkutsk, Siberia. While the bundle of initiatives was cumulatively found to be effective, TB clinicians ranked the component of administrative prioritisation as most important. Further operational studies in Irkutsk and similarly co-infected populations in the Russian Federation should focus on TB clinician-prescribed ART and patient-centred models of care that include substance abuse treatment. 9 traités pour TB (34,1% avec une TB multi-résistante ou ultrarésistante) ont significativement augmenté de seulement 14 (17%) avant l'intervention à 44 (54%) après l'intervention (P 0,001). Une enquête auprès du personnel de la TB a identifié la priorisation administrative comme l'initiative la plus importante dans l'augmentation de l'initiation du TAR. ReferencesSe evaluó un conjunto de iniciativas encaminadas a integrar los servicios de atención de la infección por el virus de la inmunodeficiencia humana (VIH) y la tuberculosis (TB), con el objeto de determinar la repercusión de la integración sobre el comienzo del tratamiento antirretrovírico (TAR) en el hospital de referencia de la TB de Irkutsk, en la Federación de Rusia, de febrero del 2014 a diciembre del 2015. La tasa de iniciación del TAR en 166 pacientes que nunca lo habían recibido y que estaban en curso de tratamiento antituberculoso (34,1% con TB multirresistente o extremadamente multirresistente) aumentó de manera significativa de solo 14 pacientes antes de la intervención (17%) a 44 pacientes después de la misma (54%; P 0,001). Al interrogar al personal encargado de la TB en este hospital de referencia, se puso en evidencia que la priorización administrativa del TAR constituía la iniciativa de más había influido en el incremento de su utilización.Public Health Action (PHA) The voice for operational research.Published by The Union (www.theunion.org), PHA provides a platform to fulfil its mission, 'Health solutions for the poor'. PHA publishes high-quality scientific research that provides new knowledge to improve the accessibility, equity, quality and efficiency of health systems and services.
In Irkutsk, Siberia, there is a high prevalence of HIV and tuberculosis (TB) coinfection. Mobile health (mHealth) strategies have shown promise for increasing linkage to and engagement in care for people living with HIV (PLWH) in other contexts. We evaluated outcomes for a cohort of PLWH, TB, and substance use in Irkutsk after participation in a multi-feature mHealth intervention called MOCT. Sixty patients were enrolled during hospitalization for TB. We evaluated participant app usage, linkage to HIV care postdischarge, perception of self-efficacy related to HIV care, and HIV-related clinical outcomes at 6 months. We also performed an exploratory analysis to compare a subset of 49 patients with a pre-intervention cohort matched for age and gender. Participants demonstrated engagement with app features examined at 6 months. The majority linked to HIV care by 6 months (83%). Self-scoring of confidence in ability to communicate with HIV providers improved from baseline (median score 8, scale 1–10) to 6 months (10, p = 0.004). A higher proportion of the MOCT subset refilled antiretroviral therapy (69% vs. 43% in pre-intervention cohort, p = 0.01), with fewer deaths in the MOCT subset at 6 months (1 death vs. 10 deaths in pre-intervention cohort, p = 0.02) and a decreased likelihood of developing the composite outcome of death/failure to achieve viral suppression at 6 months (adjusted odds ratio = 0.33, p = 0.029). This study demonstrates preliminary intervention uptake and improvement in short-term outcomes for an urban cohort of PLWH, TB, and substance use enrolled in a multi-feature mHealth intervention, a novel strategy for the context. Clinical Trial Registration Number: NCT03819374.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.