The minimum bactericidal concentration (MBC) of antibiotics is an important parameter for the potency of a drug in eradicating a bacterium as well as an important measure of the potential of a drug candidate in research and development. We have established a fluorescence-based microscopy method for the determination of MBCs against the non-tuberculous mycobacterium Mycobacterium abscessus (Mycobacteroides abscessus) to simplify and accelerate the performance of MBC determination compared to counting colony forming units on agar. Bacteria are labelled with the trehalose-coupled dye 3HC-2-Tre and analysed in a 96-well plate. The results of the new method are consistent with MBC determination by plating on agar. The method was used to evaluate the bactericidality of the antibiotics rifabutin, moxifloxacin, amikacin, clarithromycin and bedaquiline. Bactericidal effects against M. abscessus were observed, which are consistent with literature data.

In adults requiring protease inhibitor (PI)-based antiretroviral therapy (ART), replacing rifampicin with rifabutin is a preferred option, but there is lack of evidence to guide rifabutin dosing in children, especially with PIs. We aimed to characterize the population pharmacokinetics of rifabutin and 25-O-desacetyl rifabutin (des-rifabutin) in children and optimize its dose. We included children from three age cohorts: (i) <1-year-old cohort and (ii) 1- to 3-year-old cohort, who were ART naïve and received 15- to 20-mg/kg/day rifabutin for 2 weeks followed by lopinavir/ritonavir (LPV/r)-based ART with 5.0- or 2.5 mg/kg/day rifabutin, respectively, while the (iii) >3-year-old cohort was ART-experienced and received 2.5-mg/kg/day rifabutin with LPV/r-based ART. Non-linear mixed-effects modeling was used to interpret the data. Monte Carlo simulations were performed to evaluate the study doses and optimize dosing using harmonized weight bands. Twenty-eight children were included, with a median age of 10 (range 0.67-15.0) years, a median weight of 11 (range 4.5-45) kg, and a median weight-for-age z score of -3.33 (range -5.15 to -1.32). A two-compartment disposition model, scaled allometrically by weight, was developed for rifabutin and des-rifabutin. LPV/r increased rifabutin bioavailability by 158% (95% confidence interval: 93.2%-246.0%) and reduced des-rifabutin clearance by 76.6% (74.4%-78.3%). Severely underweight children showed 26% (17.9%-33.7%) lower bioavailability. Compared to adult exposures, simulations resulted in higher median steady-state rifabutin and des-rifabutin exposures in 6-20 kg during tuberculosis-only treatment with 20 mg/kg/day. During LPV/r co-treatment, the 2.5-mg/kg/day dose achieved similar exposures to adults, while the 5-mg/kg/day dose resulted in higher exposures in children >7 kg. All study doses maintained a median Cmax of <900 µg/L. The suggested weight-band dosing matches adult exposures consistently across weights and simplifies dosing.

Tuberculous meningitis (TBM) has a high mortality, possibly due to suboptimal therapy. Drug exposure data of antituberculosis agents in the central nervous system (CNS) are required to develop more effective regimens. Rifabutin is a rifamycin equivalently potent to rifampin in human pulmonary tuberculosis. Here, we show that human-equivalent doses of rifabutin achieved potentially therapeutic exposure in relevant CNS tissues in a rabbit model of TBM, supporting further evaluation in clinical trials.

Inhalable microparticle-based anti TB drug delivery systems are being investigated extensively for Tuberculosis [TB] treatment as they offer efficient and deep lung deposition with several advantages over conventional routes. It can reduce the drug dose, treatment duration and toxic effects and optimize the drug bioavailability. Yeast derived β-glucan is a β-[1-3/1-6] linked biocompatible polymer and used as carrier for various biomolecules. Due to presence of glucan chains, particulate glucans act as PAMP and thereby gets internalized via receptor mediated phagocytosis by the macrophages. In this study, β-glucan microparticles were prepared by adding l-leucine as excipient, and exhibited 70% drug [Rifabutin] loading efficiency. Further, the sizing and SEM data of particles revealed a size of 2-4 µm with spherical dimensions. The FTIR and HPLC data confirmed the β-glucan composition and drug encapsulations efficiency of the particles. The mass median aerodynamic diameter [MMAD] and geometric standard deviation [GSD] data indicated that these particles are inhalable in nature and have better thermal stability as per DSC thermogram. These particles were found to be non-toxic upto a concentration of 80 µg/ml and were found to be readily phagocytosed by human macrophage cells in-vitro as well as in-vivo by lung alveolar macrophage. This study provides a framework for future design of inhalable β-glucan particle based host-directed drug delivery system against pulmonary TB.

Background and Objective: Rescue Helicobacter pylori eradication can be challenging. Rifabutin (RBT) demonstrates high activity against Helicobacter pylori and is incorporated into various rescue eradication regimens. This exploratory study was performed to evaluate the efficacy and safety of a rescue regimen comprising RBT, metronidazole (MNZ), and vonoprazan (VPZ). Methods: This prospective, single-center, single-arm, interventional study was performed in Japan. Eligible patients were those who underwent failed primary eradication treatment (7-day treatment with three drugs: VPZ or a proton pump inhibitor [PPI], amoxicillin [AMPC], and clarithromycin) and secondary eradication treatment (7-day treatment with three drugs: VPZ or a PPI, AMPC, and MNZ) and those who were unable to receive first- and second-line therapy because of penicillin allergy. Twenty Helicobacter pylori-positive patients were treated with RBT (150 mg twice daily), MNZ (250 mg twice daily), and VPZ (20 mg twice daily) for 10 days (RBT-MNZ-VPZ therapy). Eradication success was evaluated using the urea breath test. Drug susceptibility test results were available in 16 patients. This study is registered in the Japan Registry of Clinical Trials (jRCT031220504). Results: The intention-to-treat (ITT) and per-protocol (PP) eradication rates of RBT-MNZ-VPZ therapy were 70% (90% confidence interval [CI]: 49.2%-86.0%) and 72.2% (95% CI: 50.2%-88.4%), respectively. In the MNZ-susceptible subgroup, the ITT (n = 8) and PP (n = 7) eradication rates were 100% (90% CI: 68.8%-100%) and 100% (90% CI: 65.2%-100%). In the MNZ-resistant subgroup, the ITT (n = 8) and PP (n = 7) eradication rates were both 62.5% (90% CI: 28.9%-88.9%). All infections were RBT-susceptible. Conclusions: These findings suggest that RBT-MNZ-VPZ therapy may be a promising rescue regimen, especially in MNZ- and RBT-susceptible infections or patients with penicillin allergy.

BACKGROUND: Rifampicin (RIF) is considered the backbone of TB treatment, but adverse effects often limit its use.
METHODS: This retrospective cohort study examined patients treated for TB disease at our institution, and compared those who received RIF to those who were intolerant to RIF.
RESULTS: A total of 829 patients were included. Seventy-six patients (9%) were intolerant to RIF. Patients with RIF intolerance were significantly older (median age: 67 years, IQR 50-78 vs. 48 years, IQR 31-70; P < 0.0001), and were more likely to be female (57% vs. 41%; P = 0.01) and have concurrent diabetes mellitus (37.3% vs. 19%; P < 0.0001) compared to those who tolerated RIF. RIF intolerance was most commonly due to transaminitis (25%), cytopenia (14.5%), rash (17.1%) and gastro-intestinal intolerance (7.8%). Twenty patients were subsequently challenged with rifabutin, and this was successful in 70%. The mean treatment duration was significantly longer in patients who were intolerant to RIF (335 vs. 270 days; P < 0.001). There was no significant difference in treatment outcomes.
CONCLUSIONS: RIF intolerance is more common in older patients, females, and those with concurrent diabetes mellitus. Patients who could not tolerate RIF had a longer duration of therapy, but no difference in treatment outcomes. When attempted, rifabutin was well tolerated in most patients with a previous RIF-related adverse event.
BACKGROUND: La rifampicine (RIF) est généralement considérée comme le pilier du traitement de la TB, cependant, ses effets indésirables limitent fréquemment son utilisation.
UNASSIGNED: Dans cette étude de cohorte rétrospective nous avons examiné les patients traités pour la TB dans notre institution et avons comparé ceux qui ont reçu la RIF à ceux qui n\'ont pas pu la tolérer.
UNASSIGNED: Au total, 829 patients ont été inclus. Soixante-seize patients (9%) étaient intolérants au RIF. Les patients intolérants au RIF étaient significativement plus âgés (âge médian : 67 ans, IQR 50–78 vs. 48 ans, IQR 31–70 ; P < 0,0001), et étaient plus susceptibles d\'être des femmes (57% vs. 41% ; P = 0,01) et d\'avoir un diabète sucré concomitant (37,3% vs. 19% ; P < 0,0001) par rapport à ceux qui toléraient le RIF. L\'intolérance au RIF était principalement due à une transaminite (25%), une cytopénie (14,5%), une éruption cutanée (17,1%) et une intolérance gastro-intestinale (7,8%). Vingt patients ont ensuite été soumis à un test de provocation à la rifabutine, avec un taux de succès de 70%. La durée moyenne du traitement était significativement plus longue chez les patients intolérants au RIF (335 vs. 270 jours ; P < 0.001). Aucune différence significative n’a été observée dans les résultats du traitement.
CONCLUSIONS: L\'intolérance au RIF est plus courante chez les patients plus âgés, les femmes et les patients atteints de diabète sucré. Les patients qui n\'ont pas pu tolérer le RIF ont suivi un traitement plus long, mais cela n’a pas entrainé de différence dans les résultats du traitement. Lorsqu\'elle a été tentée, la rifabutine a été bien tolérée par la plupart des patients ayant déjà présenté un effet indésirable lié au RIF.

Phagocytosis, an essential process for host defense, requires the coordination of a variety of signaling reactions. MT-II, an enzymatically inactive Lys49 phospholipase A2 (PLA2) homolog, and MT-III, a catalytically-active Asp49 PLA2, are known to activate phagocytosis in macrophages. In this study, the signaling pathways mediating phagocytosis, focusing on protein kinases, were investigated. Macrophages from male Swiss mice peritoneum were obtained 96 h after intraperitoneal thioglycolate injection. Phagocytosis was evaluated using non-opsonized zymosan particles in the presence or absence of specific inhibitors, as well as PKC and PKC-α localization by confocal microscopy. Moreover, protein kinase C (PKC) activity was assessed by γP32 ATP in macrophages stimulated by both PLA2s. Data showed that both sPLA2s increased phagocytosis. Cytochalasin D, staurosporine/H7, wortmannin, and herbimycin, inhibitors of actin polymerization, PKC, phosphoinositide 3-kinase (PI3K), and protein tyrosine kinase (PTK), respectively, significantly reduced phagocytosis induced by both PLA2s. PKC activity was increased in macrophages stimulated by both PLA2s. Actin polymerization and talin were evidenced by immunofluorescence and talin was recruited 5 min after both PLA2s stimulation. PKC and PKC-α localization within the cell were increased after 60 min of MT-II and MT-III stimulation. These data suggest that the effect of both PLA2s depends on actin cytoskeleton rearrangements and the activation of PKC, PI3K, and PTK signaling events required for phagocytosis.

Since 1999, doxycycline and hydroxychloroquine have been the recommended treatment for chronic Q fever, a life-threatening disease caused by the bacterial pathogen, Coxiella burnetii. Despite the duration of its use, the treatment is not ideal due to the lengthy treatment time, high mortality rate, resistant strains, and the potential for contraindicated usage. A literature search was conducted to identify studies that screened large panels of drugs against C. burnetii to identify novel targets with potential efficacy against C. burnetii. Twelve candidate antimicrobials approved for use in humans by the US Food and Drug Administration were selected and minimum inhibitory concentrations (MICs) were determined against the low virulence strain Nine Mile phase II. Rifabutin and rifaximin were the best performing antibiotics tested with MICs of ≤0.01 µg mL-1. Further screening of these top candidates was conducted alongside two drugs from the same class, rifampin, well-characterized, and rifapentine, not previously reported against C. burnetii. These were screened against virulent strains of C. burnetii representing three clinically relevant genotypes. Rifapentine was the most effective in the human monocytic leukemia cell line, THP-1, with a MIC ≤0.01 µg mL-1. In the human kidney epithelial cell line, A-498, efficacy of rifapentine, rifampin, and rifabutin varied across C. burnetii strains with MICs between ≤0.001 and 0.01 µg mL-1. Rifampin, rifabutin, and rifapentine were all bactericidal against C. burnetii; however, rifabutin and rifapentine demonstrated impressive bactericidal activity as low as 0.1 µg mL-1 and should be further explored as alternative Q fever treatments given their efficacy in vitro.
OBJECTIVE: This work will help inform investigators and physicians about potential alternative antimicrobial therapies targeting the causative agent of Q fever, Coxiella burnetii. Chronic Q fever is difficult to treat, and alternative antimicrobials are needed. This manuscript explores the efficacy of rifamycin antibiotics against virulent strains of C. burnetii representing three clinically relevant genotypes in vitro. Importantly, this study determines the susceptibility of C. burnetii to rifapentine, which has not been previously reported. Evaluation of the bactericidal activity of the rifamycins reveals that rifabutin and rifapentine are bactericidal at low concentrations, which is unusual for antibiotics against C. burnetii.

This case report presents an unusual occurrence of miliary tuberculosis with thyroid tuberculosis in a 75-year-old male patient, who successfully completed the treatment with rifabutin after rifampicin-induced thrombocytopenia. The patient has been suffering from diabetes mellitus and chronic heart failure, and had coronavirus disease of 2019 (COVID-19) just before being diagnosed with miliary tuberculosis. The patient had not been prescribed immunosuppressants and steroids. Chest computed tomography (CT) scans revealed multiple tiny nodules diffusely and equally distributed in bilateral lung fields. Subsequently, polymerase chain reaction (PCR) techniques on the urine samples and culture of sputum demonstrated positivity for Mycobacterium tuberculosis. Thus, we conclusively identified miliary tuberculosis and initiated treatment using anti-tuberculosis drugs. During treatment, the patient developed thyroid tuberculosis, resulting in an enlarged thyroid and hoarseness, but these symptoms improved with continued use of the anti-tuberculosis drugs. Moreover, regarding treatment, the rifabutin dosage was completed after changing drugs due to rifampicin-induced thrombocytopenia. Notably, miliary tuberculosis is rarely complicated by thyroid tuberculosis as a paradoxical reaction, and the substitution of rifabutin for rifampicin-induced thrombocytopenia is not fully studied. We present this case alongside relevant prior data for comprehensive clinical insight.

Rifampicin is a strong inducer of cytochrome P450 (CYP3A4) and P-glycoprotein (P-gp/ABCB1), leading to profound drug-drug interactions. In contrast, the chemically related rifabutin does not show such pronounced induction properties in vivo. The aim of our study was to conduct a comprehensive analysis of the different induction potentials of rifampicin and rifabutin in primary human hepatocytes and to analyze the mechanism of potential differences. Therefore, we evaluated CYP3A4/ABCB1 mRNA expression (polymerase chain reaction), CYP3A4/P-gp protein expression (immunoaffinity-liquid chromatography-mass spectrometry, IA-LC-MS/MS), CYP3A4 activity (testosterone hydroxylation), and considered intracellular drug uptake after treatment with increasing rifamycin concentrations (0.01-10 µM). Furthermore, rifamycin effects on the protein levels of CYP2C8, CYP2C9, and CYP2C19 were analyzed (IA-LC-MS/MS). Mechanistic analysis included the evaluation of possible suicide CYP3A4 inhibition (IC50 shift assay) and drug impact on translational efficiency (cell-free luminescence assays). Rifabutin accumulated 6- to 15-fold higher in hepatocytes than rifampicin, but induced CYP3A4 mRNA comparably to rifampicin (e. g. rifampicin 61-fold vs. rifabutin 44-fold, 72 h). While rifampicin for example enhanced protein (10 µM: 21-fold) and activity levels considerably (53-fold), rifabutin only slightly increased CYP3A4 protein expression (10 µM: 3.3-fold) or activity (11-fold) compared to rifampicin after 72 h. Both rifamycins similarly influenced expression of other eliminating proteins. A potential CYP3A4 suicide inhibition by a specific rifabutin metabolite or disruption of ribosome function were excluded experimentally. In conclusion, the lack of protein enhancement, could explain rifabutin\'s weaker induction-related drug-drug interaction risk in vivo.