Mastoparan, a tetradecapeptide component of wasp venom, is a potent activator of secretion in a variety of cell types, and has been shown to activate purified G-proteins reconstituted into phospholipid vesicles with a preferential activation of Gi over Gs (Higashijima, T., Uzu, S., Nakajima, T., and Ross, E. R. (1988) J. Biol. Chem. 263, 6491-6494). To identify the biochemical activities of mastoparan in a cellular system, we characterized the effects of mastoparan on signal transduction pathways in rat pulmonary alveolar type 2 epithelial cells, which synthesize and secrete pulmonary surfactant. Mastoparan inhibited adenylylcyclase activity in a manner that was dose-dependent (IC50 = 30 microM), but sensitive to neither guanine nucleotide nor pertussis toxin (PT). Mastoparan induced a PT-sensitive increase in cellular inositol trisphosphate and a rapid rise in cytosolic calcium released from intracellular stores; the time to onset of the calcium rise, but neither the rate nor the amplitude of the rise, were PT-sensitive. Mastoparan also caused a dose- (EC50 = 16 microM) and time-dependent activation of arachidonic acid release that was completely insensitive to pretreatment with PT. Secretion of pulmonary surfactant was increased by mastoparan approximately 8-fold over constitutive levels at 1 h with an EC50 = 20 microM, and mastoparan-stimulated secretion was partially sensitive to PT at late time points and to inhibitors of arachidonic acid metabolism, but not to the protein kinase C inhibitor H7. These findings are consistent with the activation of Gi proteins in type 2 cells by mastoparan, although the lack of predicted triphosphoguanine nucleotide and PT sensitivity for some activities indicates that mastoparan does not act in a manner strictly analogous to liganded receptors or that some activities are not mediated by activation of Gi. While mastoparan is a potent secretagogue in several cell types, its secretory activity appears to have only a limited dependence on the activation of Gi proteins in type 2 cells.
Abstract Background Rifampin-resistant tuberculosis is a leading cause of morbidity worldwide; only one-third of persons start treatment, and outcomes are often inadequate. Several trials demonstrate 90% efficacy using an all-oral, 6-month regimen of bedaquiline, pretomanid, and linezolid (BPaL), but significant toxicity occurred using 1200-mg linezolid. After US Food and Drug Administration approval in 2019, some US clinicians rapidly implemented BPaL using an initial 600-mg linezolid dose adjusted by serum drug concentrations and clinical monitoring. Methods Data from US patients treated with BPaL between 14 October 2019 and 30 April 2022 were compiled and analyzed by the BPaL Implementation Group (BIG), including baseline examination and laboratory, electrocardiographic, and clinical monitoring throughout treatment and follow-up. Linezolid dosing and clinical management was provider driven, and most patients had linezolid adjusted by therapeutic drug monitoring. Results Of 70 patients starting BPaL, 2 changed to rifampin-based therapy, 68 (97.1%) completed BPaL, and 2 of the 68 (2.9%) experienced relapse after completion. Using an initial 600-mg linezolid dose daily adjusted by therapeutic drug monitoring and careful clinical and laboratory monitoring for adverse effects, supportive care, and expert consultation throughout BPaL treatment, 3 patients (4.4%) with hematologic toxicity and 4 (5.9%) with neurotoxicity required a change in linezolid dose or frequency. The median BPaL duration was 6 months. Conclusions BPaL has transformed treatment for rifampin-resistant or intolerant tuberculosis. In this cohort, effective treatment required less than half the duration recommended in 2019 US guidelines for drug-resistant tuberculosis. Use of individualized linezolid dosing and monitoring likely enhanced safety and treatment completion. The BIG cohort demonstrates that early implementation of new tuberculosis treatments in the United States is feasible.
In well-resourced countries with a low incidence of tuberculosis (TB)16 (e.g., the US and Canada), a major focus of TB control efforts is the detection and treatment of latent TB infection (LTBI) to prevent reactivation to active TB disease. This approach is particularly relevant for healthcare workers (HCWs), and substantial resources are devoted to hospital TB-screening programs in low-incidence settings. Interferon γ–release assays (IGRAs), specifically the QuantiFERON-TB Gold In-Tube test (Cellestis) (QFT-GIT) and the T-SPOT. TB test (Oxford Immunotec), are used to detect and quantify the in vitro release of interferon γ from T cells stimulated by TB-specific antigens and can be used for LTBI diagnosis. Occupational-health and infection-control leaders in hospitals in low-incidence countries must decide whether to use IGRAs in their TB-screening programs in place of or in addition to the conventional tuberculin skin test (TST). This decision is complex, because IGRAs and the TST differ in terms of their costs and both their analytical and operational performance characteristics. Our understanding of the performance of these assays for baseline and serial testing in individuals with different risk factors for TB exposure and reactivation has been expanding rapidly. In this Q&A article, 5 experts in this field share their perspectives on the advantages and disadvantages of using IGRAs for screening HCWs for TB in settings of low TB incidence.
What are the advantages and disadvantages of using IGRAs, compared to the TST, for baseline screening for LTBI in newly hired HCWs in low-incidence settings?
Madhukar Pai: There is considerable evidence that both the TST and IGRAs are valid but imperfect tests for LTBI. While the TST has high specificity in persons who have not received the bacillus Calmette–Guerin (BCG) vaccine, its specificity is lower and variable in those who have received BCG postinfancy or via multiple vaccinations. In …
An epidemic of isoniazid (INH)- and streptomycin (SM)-resistant tuberculosis began among Boston's homeless population in 1984. Individuals with skin test conversions who agreed to preventive therapy received either INH, rifampin, or a combination of INH and rifampin. A total of 204 individuals with documented tuberculin skin test conversions who did not have active tuberculosis at the time of the clinical evaluation for their positive skin test were eligible for preventive therapy. Data on type and length of preventive therapy were obtained from the Tuberculosis Clinic and the Boston Tuberculosis Registry records at Boston City Hospital. The individuals were followed for development of active tuberculosis. Six of 71 (8.6%) individuals who received no therapy, 3 of 38 (7.9%) in the INH group, and none in the rifampin or rifampin plus INH groups (49 and 37 persons, respectively) developed active tuberculosis. Patients in the rifampin group were significantly less likely to develop tuberculosis than patients in the no therapy group (p = 0.04; odds ratio [OR] = 0.00, 95% confidence interval [CI] = 0.00-0.91). Treatment with any rifampin-containing preventive therapy (rifampin or rifampin plus INH) was effective (p < 0.01 ) in preventing development of active disease. The three INH failures were with organisms that were resistant to INH.
We designed a prospective study of endotracheal intubations and reintubations in our inner city Level 1 Trauma Center, to determine the frequency and causes of reintubation and evaluate the impact of an educational intervention aimed at minimizing unplanned extubations (UEs). After an initial 3-month phase, efforts were instituted to educate healthcare providers to the causes of reintubation noted. An identical 3-month period was then studied to evaluate the efficacy of the interventions. There were 862 patients, all adults, in the initial phase of the study, with 40 reintubation events in 22 patients; of the 808 in the second phase, there were 16 reintubations in 13 patients. The reintubation rate decreased from 4.4% to 1.9% (p = 0.005). Reintubations after UEs decreased from 14% to 5.2% (rate ratio, 0.374; 95% confidence interval = 0.141, 0.990). Multiple reintubation events decreased from 45% to 18.8% (p = 0.07). Increased provider education and protocol changes were associated with lower reintubation rates.
Abstract The activation of human phagocytic leukocytes by immune complexes (IC) or opsonized microbes via their Fc and complement receptors has been well-described (for reviews, see refs. [1–3]). The mechanisms involved in this process are complex and depend on the receptors involved. The biochemical events that lead to the destruction of invading organisms in turn display varying degrees of interdependence, but the controlling elements that lead to the ultimate killing of ingested organisms within phagosomes by lysosomal enzymes and reactive oxygen intermediates are still not completely understood. We have addressed these mechanisms by following and correlating the kinetics of responses by individual cells, using multiparameter flow cytometry [3, 4]. Using nonopsonized IC as stimuli, we document here the presence of a novel Ca2+/H+ voltage-independent channel in human neutrophils, which helps to control their cytoplasmic pH.
To the Editor: Ethionamide (Trecator-SC, Wyeth-Ayerst) is an antimycobacterial drug used as a second-line agent in the treatment of multidrug-resistant tuberculosis. It is structurally similar to m...
Introduction/Objectives: In the US, reactivation of latent tuberculosis infection (LTBI) accounts for 80% of new cases. In 2016, the US Preventive Services Task Force provided a new recommendation that primary care providers (PCPs) should conduct LTBI screening, whereas in the past, LTBI cases were evaluated and treated by specialty providers. This shift in care revealed knowledge gaps surrounding LTBI treatment among PCPs. This study assessed changes in PCPs’ confidence for performing key aspects of LTBI care before and after participation in an LTBI Extension for Community Healthcare Outcomes (ECHO) course. Methods: The ECHO Model™ is an evidence-based telementoring intervention. Participants were primary care team members from clinics throughout Massachusetts who voluntarily enrolled in the ECHO course. In this mixed-methods evaluation, primary outcomes were PCP self-reported confidence changes by pre- and post-course surveys and post-course semi-structured interviews. Results: Twenty PCPs (43% of registered PCPs) attended at least 3 of the 6 sessions and 24 PCPs (31% of registered PCPs) completed at least one survey. Confidence increased in selecting a test ( P = .004), interpreting tuberculosis infection test results ( P = .03), and selecting a treatment regimen ( P = .004). Qualitative interviews with 3 PCPs revealed practice changes including switching to interferon gamma release assays for testing and using rifampin for treatment. Conclusions: Use of the ECHO model to train PCPs in LTBI management is feasible and efficacious. For continuing medical education, ECHO courses can be leveraged to reduce health disparities in settings where PCPs’ lack of familiarity about a treatment topic contributes to poor health outcomes.
