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Tetrahydrolipstatin (THL, 1a) has been shown to inhibit both mammalian and bacterial α/β hydrolases. In the case of bacterial systems, THL is a known inhibitor of several Mycobacterium tuberculosis hydrolases involved in mycomembrane biosynthesis. Herein we report a highly efficient eight-step asymmetric synthesis of THL using a route that allowed modification of the THL α-chain substituent to afford compounds 1a through 1e. The key transformation in the synthesis was use of a (TPP)CrCl/Co(2)(CO)(8) -catalyzed regioselective and stereospecific carbonylation on an advanced epoxide intermediate to yield a trans-β-lactone. These compounds are modest inhibitors of Ag85A and Ag85C, two α/β hydrolases of M. tuberculosis involved in the biosynthesis of the mycomembrane. Among these compounds, 10d showed the highest inhibitory effect on Ag85A (34 ± 22 μM) and Ag85C (66 ± 8 μM) and its X-ray structure was solved in complex with Ag85C to 2.5 Å resolution. In contrast, compound 1e exhibited the best-in-class MICs of 50 μM (25 μg/mL) and 16 μM (8.4 μg/mL) against M. smegmatis and M. tuberculosis H37Ra, respectively, using a microtiter assay plate. Combining 1e with 13 well-established antibiotics synergistically enhanced the potency of few of these antibiotics in M. smegmatis and M. tuberculosis H37Ra. Compound 1e applied at concentrations 4-fold lower than its MIC enhanced the MIC of the synergistic antibiotic by 2 to 256-fold. In addition to observing synergy with first-line drugs, rifamycin and Isoniazid, the MIC of vancomycin against M. tuberculosis H37Ra is 65 μg/mL; however, the MIC was lowered to 0.25 μg/mL in the presence of 2.1 μg/mL 1e demonstrating the potential of targeting mycobacterial hydrolases involved in mycomembrane and peptidoglycan biosynthesis.

OBJECTIVE: Antibiotic prophylaxis is one of the most important steps to reduce surgical site infections. First-generation cephalosporin (cefazolin) is used prophylactically in the majority of operations. Rifamycin is a broad-spectrum semisynthetic antibiotic that is bactericidal against gram (+) and gram (˗) microorganisms. To the best of our knowledge, there are no studies on the use of rifamycin in antibiotic prophylaxis. In this study, we aimed to analyze whether there is a difference between the use of only cefazolin and only rifamycin in terms of surgical site infections. STUDY DESIGN: One hundred patients were included in this case-control study during the last quarter period of 2017. These patients (n=100) were divided into two groups according to their antibiotic use; 50 patients who received only 1 g cefazolin constituted Group 1, 50 patients who received only 250 mg topical rifamycin over the incision line based on surgeon’s preference constituted Group 2. RESULTS: The use of prophylactic topical rifamycin reduced the incidence of wound infection. compared with cefazolin. Surgical site infection was detected in 5 (10%) of the patients who received cefazolin, whereas surgical site infection was not observed in patients who received rifamycin (p=0.022). CONCLUSIONS: The use of topical rifamycin is effective but does not imply that systemic antibiotics should replace prophylaxis. The use of rifamycin would aid in systemic antibiotic prophylaxis.

Rifamycins are a class of antibiotics that were first discovered in 1957 and are known for their use in treating tuberculosis (TB). Rifamycins exhibit bactericidal activity against many Gram-positive and Gram-negative bacteria by inhibiting RNA polymerase (RNAP); however, resistance is prevalent and the mechanisms range from primary target modification and antibiotic inactivation to cytoplasmic exclusion. Further, phenotypic resistance, in which only a subpopulation of bacteria grow in concentrations exceeding their minimum inhibitory concentration, and tolerance, which is characterized by reduced rates of bacterial cell death, have been identified as additional causes of rifamycin failure. Here we summarize current understanding and recent developments regarding this critical antibiotic class.

The rifamycins are broad-spectrum antibiotics that are primarily utilized to treat infections caused by mycobacteria, including tuberculosis. Interestingly, various species of bacteria are known to contain an enzyme called Arr that catalyzes ADP-ribosylation of rifamycin antibiotics as a mechanism of resistance. Here, we study Arr modulation in relevant Gram-positive and -negative species. We show that a C-terminal truncation of Arr (ArrC), encoded in the genome of Mycobacterium smegmatis, activates Arr-mediated rifamycin modification. Through structural comparisons of mycobacterial Arr and human poly(ADP-ribose) polymerases (PARPs), we identify a known small molecule PARP inhibitor that can act as an adjuvant to sensitize M. smegmatis to the rifamycin antibiotic rifampin via inhibition of Arr, even in the presence of ArrC. Finally, we demonstrate that this rifampin/adjuvant combination treatment is effective at inhibiting growth of the multidrug-resistant (MDR) nontuberculosis pathogen Mycobacterium abscessus, which has become a growing cause of human infections in the clinic.

Opioids are one of the most prescribed classes of analgesic medications. Their narrow therapeutic index and metabolism through cytochrome p450 (CYP) enzymes can result in a drug interaction when used concomitantly with rifamycins. In clinical scenarios where concurrent therapy with an opioid and a rifamycin occurs, there is no standardized guidance for managing the interaction. The objective of this review was to examine literature which evaluates the concomitant use of opioids and rifamycins with clinically relevant CYP-inducing properties. A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria was performed. PubMed, Scopus, and OVID Embase were queried for studies from database inception to January 2020 related to rifamycin and opioid medications. Only full-text, peer-reviewed, English language articles addressing clinical outcomes from concomitant rifamycin and opioid therapy were included. The review isolated 12 articles for data extraction from an original 2260 citations identified. Rifampin (11; 92%) and rifabutin (2; 17%) were the rifamycins studied along with seven different opioids. Decreased effect of opioids with concomitant rifampin therapy manifested as withdrawal in numerous patients on methadone and a decreased analgesic effect from tramadol, morphine, and, most notably, oxycodone. Only the combinations of rifampin with buccal fentanyl and rifabutin with buprenorphine and methadone were found to have no clinically measurable interaction. Available literature suggests that a decrease in opioid clinical effects is appreciated with concomitant rifamycin therapy. Further research is needed to focus on specific mitigation strategies beyond opioid agent selection, such as dosing adjustment recommendations.

The list of clinically important nontuberculous mycobacteria (NTM) is growing as new species continue to be identified and older ones are found to be pathogenic. Molecular techniques such as real-time PCR and gene amplification and restriction length polymorphism are promising tools for rapid identification of NTM. Optimal therapy for a documented Mycobacterium gordonae infection remains undefined. The majority of isolates tested have been resistant in vitro to isoniazid and pyrazinamide, whereas many are susceptible to ethambutol, rifampin, clarithromycin, linezolid, and the fluoroquinolones. Unlike other nontuberculous mycobacteria, M. simiae produces niacin and thus may be confused with M. tuberculosis. M. simiae can colonize the respiratory tract, and the lung is the most commonly reported site of infection. The majority of reported infections have occurred in persons living near rivers or stagnant bodies of water. A recent open-label randomized trial conducted in Ghana compared two regimens for early, limited M. ulcerans infections. In this study, 73 of 76 patients who received streptomycin and rifampin for 8 weeks and 68 of 75 patients who received 4 weeks of streptomycin and rifampin followed by 4 weeks of rifampin and clarithromycin had healed lesions at 1 year after the start of treatment. Infections with M. xenopi have shown variable responses to drug therapy. Recommendations for initial therapy include isoniazid, a rifamycin, ethambutol, and clarithromycin with or without an initial course of streptomycin. Pyrazinamide and ciprofloxacin have been included in some successful regimens.

The divalproex (DVP) package insert states that rifampin may increase the oral clearance of valproate by 40% and that valproic acid derivative dose adjustments may be required when starting or stopping rifampin. However, the overall clinical significance of this drug-drug interaction remains unclear given that limited clinical outcome data has been published. This case describes a 52-year-old female with bipolar disorder, borderline personality disorder, and PTSD who was previously stable on a medication regimen consisting of DVP delayed-release 500 mg every morning and 1500 mg every evening (baseline steady-state trough 99.8 mcg/mL). Throughout rifampin therapy for latent tuberculosis treatment, she required an increase in both the frequency of DVP administration, from 2 to 3 times daily, and DVP dose by 75% to maintain clinical stability. Valproic acid trough concentrations ranged from 56.4 to 75.9 mcg/mL during the 4-month course of rifampin. This report supports that the DVP-rifampin interaction may be clinically significant and of a greater magnitude than suggested by the package insert.

Introduction: Tuberculosis, a disease of antiquity continues to cause high morbidity and mortality. In Sustainable Development Goals and End Tb Strategy proposed by WHO includes Drug Susceptibility Testing as major component. Conventional methods are time consuming and molecular methods are rapid but expensive and demanding. Resazurin assay is a rapid colorimetric redox indicator method of Drug Susceptibility Testing. Materials and Methods: 67 strains of M. tuberculosis isolated from pulmonary tuberculosis patients were tested using indirect absolute concentration method by resazurin assay and compared with drug incorporated Lowenstein – Jensen media for Isoniazid and Rifamycin. Results: There was 91.5 % and 91.7% concordance between both methods for INH and Rifamycin respectively. Resazurin assay for INH was 100% sensitive and 61.54% specific. Sensitivity and specificity for RMP was 98.04% and 62.5% respectively. The duration required for INH was 7.0 ± 2.07 and for RMP 6.58 ± 1.58 days. Conclusions: Resazurin assay is sensitive, rapid, cheap, technically simple drug susceptibility method. Keywords: M. tuberculosis, resazurin assay, drug susceptibility.

Objectives: To assess differential effects of different materials combined with allograft on bone-to-implant contact and newly formed bone formation in dental implants with coronal defects histomorphometrically. Materials and Methods: The study was conducted on 24 male New Zealand white rabbits. Dental implants (3.0 × 10 mm) were placed at the center of defects (9 mm diameter, 4 mm depth) created in the tibial bones of the rabbits. Graft (GF, n=8), graft + rifamycin (GR, n=8), and graft + black cumin oil via orogastric route (GB, n=8) were applied on the coronal aspects of the implants for 28 days. Undecalcified histomorphometric analyses were conducted on slides stained with toluidine blue. Results: Bone-to-implant contact was 46.57% ± 3.59% in the graft, 67.12% ± 3.64% in the graft+rifamycin, and 55.62% ± 4.37% in the graft+black cumin oil groups. The percentage of new bone formation at the defect area was 34.71% ± 4.11% in the graft, 55.37% ± 4.89% in the graft + rifamycin, and 45.75% ± 3.69% in the graft + black cumin oil groups. In terms of new bone formation and bone-to-implant contact, graft + rifamycin and graft + black cumin oil groups were significantly different from the graft group. The differences between the graft + rifamycin and graft + black cumin oil groups were also statistically significant. Conclusion: Allogreft + rifamycin and orogastric black cumin oil were found to have positive effects on bone healing at sites with coronal defects. Rifamycin showed significantly greater favorable effects on bone-to-implant contact and new bone formation compared to black cumin oil.

The expanded microbiological evaluation of a series of rifastures, novel spiropiperidyl rifamycin derivatives, against clinically relevant ESKAPE bacteria has identified several analogs with promising in vitro bioactivities against antibiotic-resistant strains of Enterococcus faecium and Staphylococcus aureus. Thirteen of the rifastures displayed minimum inhibitory concentrations (MICs) below 1 μg/ml against the methicillin- and vancomycin-resistant forms of S. aureus and E. faecium (MRSA, VRSA, VRE). Aryl-substituted rifastures 1, 11, and 12 offered the greatest bioactivity, with MICs reaching ≤0.063 μg ml(−1) for these human pathogens. Further analysis indicates that diphenyl rifasture 1 had greater antibiofilm activity against S. aureus and lower cytotoxicity in mammalian HEK cells than rifabutin.

Doravirine (DOR) is a non-nucleoside reverse transcriptase inhibitor indicated for the treatment of HIV-1. Its use in combination with rifapentine (RPT), an antituberculosis (TB) antibiotic, may reduce the exposure of DOR compromising viral suppression in those living with HIV-1 co-infected with TB. We conducted a prospective, phase I, open label, two-period, fixed sequence, drug interaction study to evaluate the effect of once-weekly RPT and isoniazid (INH) on the pharmacokinetics (PKs) of DOR in healthy volunteers. DOR 100 mg was administered alone twice-daily for 4 days in period 1. In period 2, once-weekly RPT + INH were co-administered with multiple doses of DOR 100 mg twice-daily for study days 7, 14, and 21. Plasma was obtained for DOR PKs when given alone and co-administered with RPT + INH. Eleven healthy volunteers enrolled and completed the study. The geometric mean ratios and 90% confidence intervals for DOR area under the concentration-time curve from zero to 12 hours (AUC0-12 ) and C12 in the presence of RPT + INH compared with DOR alone were 0.71 (0.60-0.85) and 0.69 (0.54-0.89), respectively. Although exposures were moderately reduced in the presence of RPT + INH, trough DOR values were within the concentration range associated with virological suppression. These results demonstrate that a modest decrease in DOR exposure would unlikely be clinically relevant in a virally suppressed patient co-administered once-weekly RPT + INH.

Amycolatopsis mediterranei S699 produces rifamycin B and successors of this strain are in use for the industrial production of rifamycin B. Semisynthetic derivatives of rifamycin B are used against Mycobacterium tuberculosis that causes tuberculosis. Although the rifamycin biosynthetic gene cluster was characterized two decades ago, the regulation of rifamycin B biosynthesis in Amycolatopsis mediterranei S699 is poorly understood. In this study, we analysed the genome and proteome of Amycolatopsis mediterranei S699 and identified 1102 transcription factors which comprise about 10% of the total genome. Using interactomics approaches we delineated 30 unique transcription factors directly involved in secondary metabolism that regulate rifamycin B biosynthesis. We also predict the role of RifN as hub in controlling the regulation of other genes involved in rifamycin biosynthesis. RifN is important for maintaining the integrity of the rifamycin-network. Thus, these transcription factor can be exploited to improve rifamycin B production in Amycolatopsis mediterranei S699.

Tuberculosis (TB) remains an important problem among children in the United States and throughout the world. There is no diagnostic reference standard for latent tuberculosis infection (also referred to as tuberculosis infection [TBI]). The tuberculin skin test (TST) has many limitations, including difficulty in administration and interpretation, the need for a return visit by the patient, and false-positive results caused by cross-reaction with Mycobacterium bovis–bacille Calmette-Guerin vaccines and many nontuberculous mycobacteria. Interferon-gamma release assays (IGRAs) are blood tests that use antigens specific for M tuberculosis; as a result, IGRAs yield fewer false-positive results than the TST. Both IGRAs and the TST have reduced sensitivity in immunocompromised children, including children with severe TB disease. Both methods have high positive predictive value when applied to children with risk factors for TBI, especially recent contact with a person who has TB disease. The advantages of using IGRAs and diminished experience with the placement and interpretation of the TST favor expanded use of IGRAs in children in the United States. There are now several effective and safe regimens for the treatment of TBI in children. For improved adherence to therapy, the 3 rifamycin-based regimens are preferred because of their short duration. Daily isoniazid can be used if there is intolerance or drug interactions with rifamycins. A TB specialist should be involved when there are questions regarding testing interpretation, selection of an appropriate treatment regimen, or management of adverse effects.

Rifamycins, such as rifampicin (Rif), are potent inhibitors of bacterial RNA polymerase (RNAP) and are widely used antibiotics. Rifamycin resistance is usually associated with mutations in RNAP that preclude rifamycin binding. However, some bacteria have a type of ADP-ribosyl transferases, Arr, which ADP-ribosylate rifamycin molecules, thus inactivating their antimicrobial activity. Here, we directly show that ADP-ribosylation abolishes inhibition of transcription by rifampicin, the most widely used rifamycin antibiotic. We also show that a natural rifamycin, kanglemycin A (KglA), which has a unique sugar moiety at the ansa chain close to the Arr modification site, does not bind to Arr from Mycobacterium smegmatis and thus is not susceptible to inactivation. We, found, however, that kanglemycin A can still be ADP-ribosylated by the Arr of an emerging pathogen, Mycobacterium abscessus. Interestingly, the only part of Arr that exhibits no homology between the species is the part that sterically clashes with the sugar moiety of kanglemycin A in M. smegmatis Arr. This suggests that M. abscessus has encountered KglA or rifamycin with a similar sugar modification in the course of evolution. The results show that KglA could be an effective antimicrobial against some of the Arr-encoding bacteria.

The inability to discover novel class of antibacterial agents, especially against Gram-negative bacteria (GNB), compel us to consider a broader non-conventional approach to treat infections caused by multidrug-resistant (MDR) bacteria. One such approach is the use of adjuvants capable of revitalizing the activity of current existing antibiotics from resistant pathogens. Recently, our group reported a series of tobramycin (TOB)-based hybrid adjuvants that were able to potentiate multiple classes of legacy antibiotics against various MDR GNB. Herein, we report the modification of TOB-based hybrid adjuvants by replacing TOB domain by the pseudo-disaccharide nebramine (NEB) through selective cleavage of the α- d -glucopyranosyl linkage of TOB. Potent synergism was found for combinations of NEB-based hybrid adjuvants with multiple classes of legacy antibiotics including fluoroquinolones (moxifloxacin and ciprofloxacin), tetracyclines (minocycline), or rifamycin (rifampicin) against both wild-type and MDR P. aeruginosa clinical isolates. We also demonstrated that a combination of the optimized NEB-CIP hybrid 1b and rifampicin protects Galleria mellonella larvae from the lethal effects of extensively drug-resistant (XDR) P. aeruginosa. Mechanistic evaluation of NEB-based hybrid adjuvants revealed that the hybrids affect the outer- and inner membranes of wild-type P. aeruginosa PAO1. This study describes an approach to optimize aminoglycoside-based hybrids to yield lead adjuvant candidates that are able to resuscitate the activity of partner antibiotics against MDR GNB.

Infections due to rapidly growing mycobacteria (RGM), and in particular the RGM species Mycobacterium abscessus (Mab), are very difficult to treat and reports on novel therapeutic options are scarce. A hallmark of all pathogenic RGM species is their resistance to the four first-line drugs used to treat infections with Mycobacterium tuberculosis including rifampicin. This study demonstrates that modification of the rifampicin scaffold can restore rifampicin activity against the three most commonly isolated pathogenic RGM species including Mab. We also note that the structure-activity relationship for Mab is different as compared to the non-pathogenic RGM species Mycobacterium smegmatis.

Rifamycin SV (rifamycin), is a member of the ansamycin family of antimicrobial compounds which kills bacteria commonly associated with infectious diarrhea and other enteric infections. Rifamycin has been found to be effective in experimental animal models of gut inflammation and its efficacy in these settings has been attributed partially to immunomodulatory non-bactericidal activities. This study aimed to further evaluate the anti-inflammatory activities of rifamycin by analyzing its effect on two key regulators of inflammation: PXR and NFκB. Rifamycin stimulated PXR transcriptional activity in two PXR reporter cell lines and induced expression of two genes known to be regulated by PXR and are directly involved in cellular detoxification: CYP3A4 and PgP. Moreover, CYP3A4 metabolic activity was induced by rifamycin in HepG2 cells. Rifamycin also antagonized TNFα and LPS-induced NFκB activities and inhibited IL1β-induced synthesis of inflammatory chemokine, IL8. Although reciprocal regulation of PXR and NFkB by rifamycin was not directly addressed, the data suggest that in the absence of PXR, inhibition of NFκB by rifamycin is not dependent on PXR stimulation. Thus, rifamycin exhibits potent anti-inflammatory activities, characterized by in vitro PXR activation and concomitant CYP3A4 and PgP induction, in parallel with potent NFκB inhibition and concomitant IL8 inhibition.

Rimocidin is a polyene macrolide that exhibits a strong inhibitory activity against a broad range of plant-pathogenic fungi. In this study, fermentation optimization and ribosome engineering technology were employed to enhance rimocidin production in Streptomyces rimosus M527. After the optimization of fermentation, rimocidin production in S. rimosus M527 increased from 0.11 ± 0.01 to 0.23 ± 0.02 g/L during shake-flask experiments and reached 0.41 ± 0.05 g/L using 5-L fermentor. Fermentation optimization was followed by the generation of mutants of S. rimosus M527 through treatment of the strain with different concentrations of gentamycin (Gen) or rifamycin. One Genr mutant named S. rimosus M527-G37 and one Rifr mutant named S. rimosus M527-R5 showed increased rimocidin production. Double-resistant (Genr and Rifr) mutants were selected using S. rimosus M527-G37 and S. rimosus M527-R5, and subsequently tested. One mutant, S. rimosus M527-GR7, which was derived from M527-G37, achieved the greatest cumulative improvement in rimocidin production. In the 5-L fermentor, the maximum rimocidin production achieved by S. rimosus M527-GR7 was 25.36% and 62.89% greater than those achieved by S. rimosus M527-G37 and the wild-type strain S. rimosus M527, respectively. Moreover, in the mutants S. rimosus M527-G37 and S. rimosus M527-GR7 the transcriptional levels of ten genes (rimA sr to rimK sr) located in the gene cluster involved in rimocidin biosynthesis were all higher than those in the parental strain M527 to varying degrees. In addition, after expression of the single rimocidin biosynthetic genes in S. rimosus M527 a few recombinants showed an increase in rimocidin production. Expression of rimE led to the highest production.

New rifamycin congeners (1-33) with incorporated amine and hydrazone substituents leading to lipophilic and/or basic nature and altered rigidity of modified C(3) arm were synthesized and structurally characterized in detail. NMR spectroscopic studies at different temperatures indicate two types of structures of rifamycin congeners that are realized in solution: zwitterionic and non-ionic forms in dependence of the basicity of modified C(3) arm. The presence of rifamycin congeners in these two possible forms has a significant impact on the physico-chemical parameters such as lipophilicity (clogP) and water solubility and different binding mode of the C(3) arm of antibiotic at RNAP binding pocket (molecular target) leading to different antibacterial potency. The highest antibacterial potency against S. aureus (including MRSA and MLSB strains) and S. epidermidis strains, even higher than reference rifampicin (Rif) and rifaximin (Rifx) antibiotics, was found for rifamycin congeners bearing at the C(3) arm relatively rigid and basic substituents (bipiperidine and guanidine groups). These modifications provide favorable docking mode and excellent water solubility resulting in high potency (MICs 0.0078 μg/mL what gives ∼ 8.5 nM), irrespective whether rifamycin congener is a tertiary amine (15) or hydrazone (29). In turn, for a higher antibacterial potency of rifamycin congeners against E. faecalis strain (MICs 0.5 μg/mL that is 0.6 μM) as compared to Rif and Rifx, the most crucial factors are: bulkiness and the lipophilic character of the end of the C(3) rebuilt arm.

Rifampicin is an effective drug for treating tuberculosis (TB) but is not used to treat Mycobacterium abscessus infections due to poor in vitro activity. While rifabutin, another rifamycin, has better anti-M. abscessus activity, its activity is far from the nanomolar potencies of rifamycins against Mycobacterium tuberculosis. Here, we asked (i) why is rifabutin more active against M. abscessus than rifampicin, and (ii) why is rifabutin’s anti-M. abscessus activity poorer than its anti-TB activity? Comparative analysis of naphthoquinone- versus naphthohydroquinone-containing rifamycins suggested that the improved activity of rifabutin over rifampicin is linked to its less readily oxidizable naphthoquinone core. Although rifabutin is resistant to bacterial oxidation, metabolite and genetic analyses showed that this rifamycin is metabolized by the ADP-ribosyltransferase ArrMab like rifampicin, preventing it from achieving the nanomolar activity that it displays against M. tuberculosis. Based on the identified dual mechanism of intrinsic rifamycin resistance, we hypothesized that rifamycins more potent than rifabutin should contain the molecule’s naphthoquinone core plus a modification that blocks ADP-ribosylation at its C-23. To test these predictions, we performed a blinded screen of a diverse collection of 189 rifamycins and identified two molecules more potent than rifabutin. As predicted, these compounds contained both a more oxidatively resistant naphthoquinone core and C-25 modifications that blocked ADP-ribosylation. Together, this work revealed dual bacterial metabolism as the mechanism of intrinsic resistance of M. abscessus to rifamycins and provides proof of concept for the repositioning of rifamycins for M. abscessus disease by developing derivatives that resist both bacterial oxidation and ADP-ribosylation.

Tuberculosis (TB) remains the leading cause of death among people with human immunodeficiency virus (PWH). The diagnosis of latent TB infection (LTBI) and treatment with TB preventative therapy (TPT) can reduce morbidity and mortality in this population. Historically, isoniazid has been recommended for TPT in PWH due to the absence of drug-drug interactions with most antiretroviral therapy (ART). However, newer rifamycin-based regimens are safer, shorter in duration, associated with improved adherence, and may be as or more effective than isoniazid TPT. Current guidelines have significant heterogeneity in their recommendations for TPT regimens and acceptability of drug interactions with modern ART. In this Infectious Diseases learning unit, we review common questions on diagnosis, treatment, and drug interactions related to the management of LTBI among PWH., The repertoire of data-driven medication regimens to treat latent tuberculosis infection (LTBI) among people with HIV (PWH) is rapidly evolving, leading to heterogeneity in published guidelines. We review the emerging data regarding LTBI management among PWH to support patient-centered care.

Infections caused byMycobacterium abscessusare difficult to treat due to its intrinsic resistance to most antibiotics. Formation of biofilms and the capacity ofM. abscessusto survive inside host phagocytes further complicate eradication. Herein, we explored whether addition of a carbamate-linked group at the C25 position of rifamycin SV blocks enzymatic inactivation by ArrMab, an ADP-ribosyltransferase conferring resistance to rifampicin. Unlike rifampicin, 5j, a benzyl piperidine rifamycin derivative with a morpholino substituted C3 position, is not modified by purified ArrMab. Additionally, we show that the ArrMabD82 residue is essential for catalytic activity. Thermal profiling of ArrMabin the presence of 5j, rifampicin or rifabutin shows that 5j does not bind to ArrMab. We found that the activity of 5j is comparable to amikacin againstM. abscessusplanktonic cultures and pellicles. Critically, 5j also exerts potent antimicrobial activity againstM. abscessusin human macrophages and shows synergistic activity with amikacin and azithromycin.

Rifampicin (RIF) constitutes the frontline therapy against M. tuberculosis as well as most slow-growing non-tuberculous mycobacteria (NTM). However, RIF is completely ineffective against M. abscessus despite the absence of mutations in the rifampicin resistance determining region of Mab_rpoB. This has been attributed to the presence of an ADP-ribosyltransferase (Arr) activity that inactivates RIF. Rifabutin (RBT), a close analogue of RIF, has recently been shown to be effective against M. abscessus in vitro and in a mouse model and comprises a promising therapeutic against M. abscessus infections. Using RNA sequencing we show that exposure of M. abscessus to sublethal doses of RIF and RBT results in ∼25-fold upregulation of Mab_helR in laboratory and clinical isolates; an isogenic deletion of Mab_helR is hypersensitive to RIF and RBT, and over-expression of Mab_helR confers RIF tolerance in M. tuberculosis implying that helR constitutes a significant determinant of inducible RIF and RBT resistance. We demonstrate a preferential association of MabHelR with RNA polymerase in vivo in bacteria exposed to RIF and showed that purified MabHelR can rescue transcription inhibition in the presence of RIF in in vitro transcription assays. Furthermore, MabHelR can dissociate RNAP from RIF-stalled initiation complexes in vitro, a species we envisage accumulates upon RIF exposure. Lastly, we show that the tip of the PCh-loop of Mab_helR, in particular residues E496 and D497 that are in proximity to RIF, is critical for conferring RIF resistance without being required for RNAP dissociation from stalled complexes. This suggests that HelR may be additionally involved in displacing RIF bound to RNAP and function as an RNAP protection protein.Significance StatementBacterial RNA polymerase is a target for the potent and broad-spectrum rifamycin group of antibiotics. Mutations within rpoB and inactivation by a diverse group of enzymes constitute the most widespread mechanisms of resistance. Herein we report an unprecedented mechanism of rifamycin resistance in M. abscessus mediated by MabHelR, a putative SF1 like helicase, that involves disassembly of RIF-stalled initiation complexes, likely followed by displacement of the antibiotic, leading to RNAP recycling. The mechanism is reminiscent of the role of HflX and ribosome protection proteins in resistance to ribosome targeting antibiotics and suggests that removal of stalled macromolecular complexes and their recycling comprises a widespread but underappreciated mechanism of antibiotic resistance. Rifampicin (RIF) is pivotal in the control of M. tuberculosis infections but ineffective against M. abscessus. Identification of inducible rifamycin resistance determinants in M. abscessus is therefore particularly crucial for informing treatment strategies and development of novel therapeutic approaches.

SummaryRifamycin antibiotics such as rifampin are widely used for the management of tuberculosis and other bacterial infections. These drugs inhibit prokaryotic RNA polymerase (RNAP) by preventing elongation of mRNA resulting in cell death. Rifamycin resistance in the clinic is manifested primarily through amino acid substitutions in RNAP that decrease target affinity for the antibiotics. In contrast, environmental bacteria possess a wide variety of highly specific rifamycin enzyme-mediated resistance mechanisms that modify and inactivate the antibiotics by glycosylation, phosphorylation, ADP-ribosylation, or hydroxylation. Expression of rifamycin resistance is controlled by a common 19bp cis-acting rifamycin associated element (RAE) upstream of inactivating genes. Guided by the presence of RAE sequences, we identify an unprecedented ATP-dependent mechanism of rifamycin resistance that acts not by antibiotic inactivation but by protecting the RNAP target. We show that Streptomyces venezuelae encodes a helicase-like protein, HelR, which confers broad spectrum rifamycin resistance. Furthermore, HelR is essential for promoting rifamycin tolerance at inhibitory concentrations, enabling bacterial evasion of the toxic properties of these antibiotics. HelR forms a complex with RNAP in vivo and rescues transcription inhibition by rifampin in vitro. We synthesized a rifamycin photoprobe and demonstrated that HelR directly displaces rifamycins from RNAP. HelR-encoding genes associated with RAEs are broadly distributed in actinobacteria, including many opportunistic Mycobacterial pathogens, which cannot currently be treated with rifamycins. This first report of an RNAP protection protein conferring antibiotic resistance and offers guidance for developing new rifamycin antibiotics that can avoid this mechanism.

Abstract: Rifamycins are considered a milestone for tuberculosis (TB) treatment because of their proficient sterilizing ability. Currently, available TB treatments are complicated and need a long duration, which ultimately leads to failure of patient compliance. Some new rifamycin derivatives, i.e., rifametane, TNP-2092 (rifamycin-quinolizinonehybrid), and TNP-2198 (rifamycin-nitromidazole hybrid) are under clinical trials, which are attempting to overcome the problems associated with TB treatment. The undertaken review is intended to compare the pharmacokinetics, pharmacodynamics and safety profiles of these rifamycins, including rifalazil, another derivative terminated in phase II trials, and already approved rifamycins. The emerging resistance of microbes is an imperative consideration associated with antibiotics. Resistance development potential of microbial strains against rifamycins and an overview of chemistry, as well as structure-activity relationship (SAR) of rifamycins, are briefly described. Moreover, issues associated with rifamycins are discussed as well. We expect that newly emerging rifamycins shall appear as potential tools for TB treatment in the near future.

Introduction Short‐course preventive therapy with 1‐month course of daily administration of isoniazid (300‐mg) plus rifapentine (600‐mg) (1HP) and 3‐month course of weekly administration of isoniazid (900‐mg) plus rifapentine (900‐mg) (3HP) has higher completion rates than 9‐month course of daily isoniazid (9H) for individuals with latent tuberculosis infection (LTBI). We aimed to evaluate the effect, safety and tolerability of 1HP in people living with HIV (PLWH) and LTBI who received coformulated bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF). Methods PLWH testing positive by interferon‐gamma release assay and having received BIC/FTC/TAF for >2 weeks with plasma HIV RNA load (PVL)

Rifamycin antibiotics include the WHO essential medicines rifampin, rifabutin, and rifapentine. These are semisynthetic derivatives of the natural product rifamycins, originally isolated from the soil bacterium Amycolatopsis rifamycinica. These antibiotics are primarily used to treat mycobacterial infections, including tuberculosis. Rifamycins act by binding to the β-subunit of bacterial RNA polymerase, inhibiting transcription, which results in cell death. These antibiotics consist of a naphthalene core spanned by a polyketide ansa bridge. This structure presents a unique 3D configuration that engages RNA polymerase through a series of hydrogen bonds between hydroxyl groups linked to the naphthalene core and C21 and C23 of the ansa bridge. This binding occurs not in the enzyme active site where template-directed RNA synthesis occurs but instead in the RNA exit tunnel, thereby blocking productive formation of full-length RNA. In their clinical use to treat tuberculosis, resistance to rifamycin antibiotics arises principally from point mutations in RNA polymerase that decrease the antibiotic's affinity for the binding site in the RNA exit tunnel. In contrast, the rifamycin resistome of environmental mycobacteria and actinomycetes is much richer and diverse. In these organisms, rifamycin resistance includes many different enzymatic mechanisms that modify and alter the antibiotic directly, thereby inactivating it. These enzymes include ADP ribosyltransferases, glycosyltransferases, phosphotransferases, and monooxygenases.ADP ribosyltransferases catalyze group transfer of ADP ribose from the cofactor NAD+, which is more commonly deployed for metabolic redox reactions. ADP ribose is transferred to the hydroxyl linked to C23 of the antibiotic, thereby sterically blocking productive interaction with RNA polymerase. Like ADP ribosyltransferases, rifamycin glycosyl transferases also modify the hydroxyl of position C23 of rifamycins, transferring a glucose moiety from the donor molecule UDP-glucose. Unlike other antibiotic resistance kinases that transfer the γ-phosphate of ATP to inactivate antibiotics such as aminoglycosides or macrolides, rifamycin phosphotransferases are ATP-dependent dikinases. These enzymes transfer the β-phosphate of ATP to the C21 hydroxyl of the rifamycin ansa bridge. The result is modification of a critical RNA polymerase binding group that blocks productive complex formation. On the other hand, rifamycin monooxygenases are FAD-dependent enzymes that hydroxylate the naphthoquinone core. The result of this modification is untethering of the ansa chain from the naphthyl moiety, disrupting the essential 3D shape necessary for productive RNA polymerase binding and inhibition that leads to cell death.All of these enzymes have homologues in bacterial metabolism that either are their direct precursors or share common ancestors to the resistance enzyme. The diversity of these resistance mechanisms, often redundant in individual bacterial isolates, speaks to the importance of protecting RNA polymerase from these compounds and validates this enzyme as a critical antibiotic target.

Rifamycins are integral part of the combination regimen for treatment of pulmonary Mycobacterium avium-complex [MAC] infection, but different practitioners prefer different rifamycins. The objective of the study was to compare microbial kill and resistance emergence of rifamycins using principles of pharmacokinetics/pharmacodynamics. First, we identified rifamycin MICs in 20 MAC isolates from patients followed by concentration-response studies in test-tubes. Next, we examined efficacy and resistance suppression of three doses of each rifamycin in the hollow fiber system model of pulmonary MAC [HFS-MAC], mimicking human like concentration-time profile of the drugs. HFS-MAC units were repetitively sampled for total and drug-resistant MAC burden and for drug concentration measurements. Inhibitory sigmoid E max model, linear regression, and analysis of variance was used for data analysis. For rifabutin 90% of isolates had MIC ≤ 0.125 mg/L while for both rifampin and rifapentine this was ≤2.0 mg/L. There was no statistically significant difference (p > 0.05) in maximal kill and effective concentration mediating 50% of the bacterial kill among three rifamycins in the static concentration experiment. In the HFS-MAC, the bactericidal kill (day 0–4) for rifampin was 0.89 (95% Confidence Interval (CI): 0.43–1.35), for rifapentine was 1.05 (95% CI: 0.08–1.23), and for rifabutin was 0.92 (95% CI: 0.61–1.24) log10 CFU/ml, respectively. Rifamycins monotherapy failed after just 4-days of treatment and entire MAC population was drug resistant on day 26 of the study. There was no dose dependent difference in MAC kill or resistance suppression among the three rifamycins tested in the HFS-MAC. Therefore, replacing one rifamycin, due to emergence of drug-resistance, with other may not be beneficial in clinical setting.

Rifamycins have been clinically utilized against mycobacterial infections for more than 50 years; however, their biosynthesis has not been fully elucidated. Here, on the basis of in vivo gene deletions, in vitro enzyme assays, isotope labeling, and site-directed mutations, we found that a flavin-dependent monooxygenase encoded by a rifamycin biosynthetic gene cluster, Rif-Orf17, not only converted the naphthoquinone chromophore of rifamycin S into benzo-γ-pyrone but also linearized rifamycin SV through phenolic hydroxylation. Both oxidation routes lead to inactivation of rifamycins.

Rifamycin antibiotics were discovered during the 1950s, and their main representative, rifampicin, remains a cornerstone treatment for TB. The clinical use of rifamycin is restricted to mycobacteria and Gram-positive infections because of its poor ability to penetrate the Gram-negative outer membrane. Rifabutin, a rifamycin antibiotic approved for the prevention of Mycobacterium avium complex disease, makes an exception to this rule by hijacking the iron uptake system of Acinetobacter baumannii, resulting in potent activity against this important Gram-negative pathogen. Here, we describe recent findings on the specific activity of rifabutin and provide evidence of the need for the development of an intravenous formulation of rifabutin (BV100) for the treatment of difficult-to-treat carbapenem-resistant A.baumannii infections.

The tale of abate in antibiotics continued defense mechanisms that chaperone the rise of drug-defying superbugs—on the other hand, the astray in antibacterial drug discovery and development. Our salvation lies in circumventing the genesis of resistance. Considering the competitive advantages of antibacterial chemotherapeutic agents equipped with multiple warheads against resistance, the development of hybrids has rejuvenated. The adoption of antibiotic hybrid paradigm to macrocycles has advanced novel chemical entities to clinical trials. The multi-targeted TD-1792, for instance, retained potent antibacterial activities against multiple strains that are resistant to its constituent, vancomycin. Moreover, the antibiotic conjugation of rifamycins has provided hybrid clinical candidates with desirable efficacy and safety profiles. In 2020, the U.S. FDA has granted an orphan drug designation to TNP-2092, a conjugate of rifamycin and fluoroquinolone, for the treatment of prosthetic joint infections. DSTA4637S is a pioneer antibacterial agent under clinical development and represents a novel class of bacterial therapy, that is, antibody–antibiotic conjugates. DSTA4637S is effective against the notorious persistent S. aureus bacteremia, a revelation of the abracadabra potential of antibiotic hybrid approaches.

Staphylococcus epidermidis is a major cause of periprosthetic joint infection (PJI); its intracellular persistence within osteoblasts may compromise therapy if that therapy is not intracellularly active. The intracellular activity of rifampin, rifapentine, and rifabutin was assessed against five rifampin-susceptible and two rifampin-resistant S. epidermidis isolates. Compared to no treatment, treatment resulted in a ≥2-fold log(10) reduction of intracellular rifampin-susceptible, but not rifampin-resistant, S. epidermidis. These findings show activity of rifampin, rifapentine, and rifabutin against intraosteoblast PJI-associated S. epidermidis.

Bacterial RNA polymerase is a target of the potent and broad-spectrum rifamycin group of antibiotics. Mutations within rpoB and inactivation by a diverse group of enzymes constitute the most widespread mechanisms of resistance. Rifampicin (RIF) constitutes the frontline therapy against M. tuberculosis as well as most slow-growing non-tuberculous mycobacteria (NTM) but is completely ineffective against M. abscessus. This high level of RIF resistance is despite the absence of mutations in the rifampicin resistance determining region of Mab_rpoB and is partially attributed to the presence of an ADP-ribosyltransferase (Arr) activity that inactivates RIF. Rifabutin (RBT), a close analogue of RIF, has recently been shown to be effective against M. abscessus in vitro and in a mouse model and comprises a promising therapeutic against M. abscessus infections. Using RNA sequencing we show that exposure of M. abscessus to sublethal doses of RIF and RBT results in ~25-fold upregulation of Mab_ helR in laboratory and clinical isolates; an isogenic deletion mutant of Mab_ helR is hypersensitive to RIF and RBT, and over-expression of Mab_ helR confers RIF tolerance in M. tuberculosis implying that Mab_helR constitutes a significant determinant of inducible RIF and RBT resistance. We demonstrate a preferential association of MabHelR with RNA polymerase in vivo in bacteria exposed to RIF and show that purified MabHelR can rescue transcription inhibition in the presence of RIF in in vitro transcription assays. Furthermore, MabHelR can dissociate RNAP from RIF-stalled initiation complexes in vitro, a species we envisage accumulates upon RIF exposure. Lastly, we show that the tip of the PCh-loop of Mab_ helR, in particular residues E496 and D497 that are in proximity to RIF, is critical for conferring RIF resistance without being required for dissociation of antibiotic-stalled RNAP complexes. This suggests that HelR may be additionally involved in displacing RIF bound to RNAP and function as an RNAP protection protein.

AIM Rifaximin is recommended as treatment for hepatic encephalopathy (HE) that targets intestinal bacterial flora. Although combined use with synthetic disaccharides is the standard of care worldwide, the therapeutic effects of rifaximin for overt encephalopathy (OHE) in Japanese patients have not been examined sufficiently. We examined the therapeutic effects of rifaximin for OHE in Japanese patients. METHODS A total of 76 patients who developed OHE of West Haven grade II or higher at least once within the 12 months before starting rifaximin were included. Blood ammonia levels and the incidence of OHE during the 12 months before and after starting rifaximin therapy were compared in a before-and-after study. Rifaximin efficacy and predictors of efficacy were also examined. RESULTS Post-treatment blood ammonia levels were significantly lower than pretreatment levels. The mean annual number of OHE incidents and intravenous branched-chain amino acid preparations used per patient were significantly lower after starting rifaximin therapy (2.51 vs. 0.76 times/year, p

The combination of rifamycin (RFP), ethambutol (EB), and macrolides is currently the standard regimen for treatment of Mycobacterium avium complex pulmonary disease (MAC-PD). However, poor adherence to the standardized regimens recommended by current guidelines have been reported. We undertook a single-centred retrospective cohort study to evaluate the long-term outcomes in 295 patients with MAC-PD following first line treatment with standard (RFP, EB, clarithromycin [CAM]) or alternative (EB and CAM with or without fluoroquinolones (FQs) or RFP, CAM, and FQs) regimens. In this cohort, 80.7% were treated with standard regimens and 19.3% were treated with alternative regimens. After heterogeneity was statistically corrected using propensity scores, outcomes were superior in patients treated with standard regimens. Furthermore, alternative regimens were significantly and independently associated with sputum non-conversion, treatment failure and emergence of CAM resistance. Multivariate cox regression analysis revealed that older age, male, old tuberculosis, diabetes mellitus, higher C-reactive protein, and cavity were positively associated with mortality, while higher body mass index and M. avium infection were negatively associated with mortality. These data suggest that, although different combination regimens are not associated with mortality, first line administration of a standard RFP + EB + macrolide regimen offers the best chance of preventing disease progression in MAC-PD patients.

Background The treatment of tuberculosis (TB) in solid organ transplant (SOT) recipients is challenging owing to interactions between rifampin and immunosuppressive drugs. Rifabutin, a rifamycin with excellent activity against Mycobacterium tuberculosis and that induces cytochrome p450 less, may facilitate treatment. We report our experience with rifabutin for treating TB in SOT recipients and review the available literature. Methods A retrospective observational study of all SOT recipients with TB between January 2000 and December 2019. The clinical characteristics and outcomes of patients treated with and without rifabutin-containing regimens were compared and a literature review was conducted. Results We included 31 SOT recipients with TB, among whom 22 (71%) were men and the median age was 62 years (interquartile range 50-20). There were no significant differences between patients treated with rifabutin (n = 12), rifampin (n = 14), and non-rifamycins (n = 5) in clinical cure rates (83.3%, 64.3%, and 100%, respectively; P = .21), side effects (25%, 37.5%, and 20%, respectively; P = .74), or mortality (16.7%, 35.7%, and 0%, respectively; P = .21). Only one patient, treated with rifampin, suffered graft rejection. The literature review identified 59 SOT recipients with TB treated with rifabutin-containing regimens from 8 publications. Overall, the clinical cure, graft rejection, and mortality rates were 93.2%, 5.1%, and 6.8%, respectively. Conclusions Rifabutin-containing regimens offer a reliable alternative to rifampin when treating TB in SOT recipients.

Background Rifapentine exposure is associated with bactericidal activity against Mycobacterium tuberculosis, but high interindividual variation in plasma concentrations is encountered. Objectives To investigate a genomic association with interindividual variation of rifapentine exposure, SNPs of six human genes involving rifamycin metabolism (AADAC, CES2), drug transport (SLCO1B1, SLCO1B3) and gene regulation (HNF4A, PXR) were evaluated. Methods We characterized these genes in 173 adult participants in treatment trials of the Tuberculosis Trials Consortium. Participants were stratified by self-identified race (black or non-black), and rifapentine AUC from 0 to 24 h (AUC0–24) was adjusted by analysis of covariance for SNPs, rifapentine dose, sex, food and HIV coinfection. This study was registered at ClinicalTrials.gov under identifier NCT01043575. Results The effect on rifapentine least squares mean AUC0–24 in black participants overall decreased by –10.2% for AADAC rs1803155 G versus A allele (Wald test: P = 0.03; false discovery rate, 0.10). Black participants with one G allele in AADAC rs1803155 were three times as likely to have below target bactericidal rifapentine exposure than black participants with the A allele (OR, 2.97; 95% CI: 1.16, 7.58). With two G alleles, the OR was greater. In non-black participants, AADAC rs1803155 SNP was not associated with rifapentine exposure. In both black and non-black participants, other evaluated genes were not associated with rifapentine exposure (P > 0.05; false discovery rate > 0.10). Conclusions Rifapentine exposure in black participants varied with AADAC rs1803155 genotype and the G allele was more likely to be associated with below bactericidal target rifapentine exposure. Further pharmacogenomic study is needed to characterize the association of the AADAC rs1803155 with inadequate rifapentine exposure in different patient groups.

Tuberculosis (TB) is a communicable airborne infectious disease caused by the Mycobacterium tuberculosis (MTB) that primarily affects the lungs, and can disseminate to other parts of the body. MTB is one of the most dangerous pathogens, killing about 1.4 million people annually worldwide. Although the standard treatment of TB is comprised of four anti-TB drugs, the emergence of multidrug-resistant (MDR) and extensive drug-resistant (XDR) strains in the recent past and associated side effects have affected the tailor-made regimens. Notably, existing therapies approved by the World Health Organisation (WHO) can only treat less than 50% of drug-resistant TB. Therefore, an expeditious pace in the TB research is highly needed in search of effective, affordable, least toxic novel drugs with shorter regimens to reach the goals viz. 2020 milestones End TB strategy set by the WHO. Currently, twenty-three drug-like molecules are under investigation in different stages of clinical trials. These newer agents are expected to be effective against the resistant strains. This article summarizes the properties, merits, demerits, and the probability of their success as novel potential therapeutic agents.

Background Treatment options are limited for TB/HIV-coinfected children who require PI-based ART. Rifabutin is the preferred rifamycin for adults on PIs, but the one study evaluating rifabutin with PIs among children was stopped early due to severe neutropenia. Methods We evaluated rifabutin safety and plasma pharmacokinetics among coinfected children 3–15 years of age receiving rifabutin 2.5 mg/kg daily with standard doses of lopinavir/ritonavir. The AUC0–24 at 2, 4 and 8 weeks after rifabutin initiation was described using intensive sampling and non-compartmental analysis. Clinical and laboratory toxicities were intensively monitored at 12 visits throughout the study. Results Among 15 children with median (IQR) age 13.1 (10.9–14.0) years and weight 25.5 (22.3–30.5) kg, the median (IQR) rifabutin AUC0–24 was 5.21 (4.38–6.60) μg·h/mL. Four participants had AUC0–24 below 3.8 μg·h/mL (a target for the population average exposure) at week 2 and all had AUC0–24 higher than 3.8 μg·h/mL at the 4 and 8 week visits. Of 506 laboratory evaluations during rifabutin, grade 3 and grade 4 abnormalities occurred in 16 (3%) and 2 (0.4%) instances, respectively, involving 9 (60%) children. Specifically, grade 3 (n = 4) and grade 4 (n = 1) neutropenia resolved without treatment interruption or clinical sequelae in all patients. One child died at week 4 of HIV-related complications. Conclusions In children, rifabutin 2.5 mg/kg daily achieved AUC0–24 comparable to adults and favourable HIV and TB treatment outcomes were observed. Severe neutropenia was relatively uncommon and improved with ongoing rifabutin therapy. These data support the use of rifabutin for TB/HIV-coinfected children who require lopinavir/ritonavir.

Background The use of rifamycin antibiotics for TB prevention carries a risk of detrimental drug–drug interactions with concomitantly used ART. Objectives To evaluate the interaction of the antiretroviral drug nevirapine in combination with 4 weeks of daily rifapentine and isoniazid for TB prevention in people living with HIV. Methods Participants were individuals enrolled in the BRIEF-TB study receiving nevirapine and randomized to the rifapentine/isoniazid arm of the study. Participants provided sparse pharmacokinetic (PK) sampling at baseline and weeks 2 and 4 for trough nevirapine determination. Nevirapine apparent oral clearance (CL/F) was estimated and the geometric mean ratio (GMR) of CL/F prior to and during rifapentine/isoniazid was calculated. Results Seventy-eight participants had evaluable PK data: 61 (78%) female, 51 (65%) black non-Hispanic and median (range) age of 40 (13–66) years. Median (IQR) nevirapine trough concentrations were: week 0, 7322 (5266–9302) ng/mL; week 2, 5537 (3552–8462) ng/mL; and week 4, 5388 (3516–8243) ng/mL. Sixty out of 78 participants (77%) had nevirapine concentrations ≥3000 ng/mL at both week 2 and 4. Median (IQR) nevirapine CL/F values were: week 0 pre-rifapentine/isoniazid, 2.03 (1.58–2.58) L/h; and during rifapentine/isoniazid, 2.62 (1.81–3.42) L/h. The GMR (90% CI) for nevirapine CL/F was 1.30 (1.26–1.33). Conclusions The CL/F of nevirapine significantly increased with concomitant rifapentine/isoniazid. The decrease in nevirapine trough concentrations during rifapentine/isoniazid therapy suggests induction of nevirapine metabolism, consistent with known rifapentine effects. The magnitude of this drug–drug interaction suggests daily rifapentine/isoniazid for TB prevention should not be co-administered with nevirapine-containing ART.

Rifamycin derivatives, such as rifampicin, have potent antibiotic activity and have long been used in the clinic as mainstay components for the treatment of tuberculosis, leprosy, and AIDS-associated mycobacterial infections. However, the extensive usage of these antibiotics has resulted in the rapid development of bacterial resistance. The resistance mechanisms mainly include mutations of the rifamycin target RNA polymerase of bacteria and enzymatic modifications of rifamycin antibiotics. One modification is the recently characterized rifamycin degradation catalyzed by Rox enzymes, which belong to the widely occurring flavin monooxygenases. Intriguingly, our recent sequence analysis revealed the rifamycin producers also encode Rox homologs that are not yet characterized. In this work, we expanded the study of the Rox-catalyzed rifamycin degradation. We first showed that the Rox proteins from rifamycin producers have the enzymatic rifamycin SV-degrading activity. Then we used the structurally diverse rifamycin compounds rifampicin and 16-demethylrifamycin W to probe the substrate scope and found that they each have a slightly different substrate scope. Finally, we demonstrated that Rox proteins can also catalyze the transformation of 16-demethylsalinisporamycin to 16-demethylsaliniketal A. Since 16-demethylsalinisporamycin and 16-demethylsaliniketal A are the counterpart analogs of salinisporamycin and saliniketal A, our biochemical findings not only uncover a previously uncharacterized self-resistance mechanism in the rifamycin producers, but also bridge the gap between the biosynthesis of the potential antitumor compound saliniketal A.

Is to study the efficacy of treatment of exacerbation of chronic tubotympanic purulent otitis media with Otofa drug with the active substance Rifamycin.Performed a retrospective analysis of 37 medical histories of patients who applied to the otorhinolaryngology clinic with a diagnosis of exacerbation of chronic purulent tubotympanic otitis media in the period from January 2019 to December 2019.Noted relief of symptoms such as throbbing noise and pain in patients receiving the topical Otofa drug (active ingredient Rifamycin) by the 3th day of therapy. Otofa also reduced otorrhea by the 5th day of therapy.The study showed the high clinical efficacy of Otofa ear drops containing the Rifamycin antibiotic.Изучить эффективность лечения обострения хронического туботимпанального гнойного среднего отита препаратом Отофа с действующим веществом рифамицин (Rifamycin).Проведен ретроспективный анализ 37 историй болезни пациентов, обратившихся в клинику оториноларингологии с диагнозом «обострение хронического гнойного туботимпанального среднего отита» в период с января 2019 г. по декабрь 2019 г.У пациентов, получающих местно препарат Отофа (действующее вещество — рифамицин), уже к 3-му дню терапии было отмечено купирование таких симптомов, как пульсирующий шум и боль, а также снижение выраженности отореи к 5-му дню терапии.Исследование показало высокую клиническую эффективность ушных капель Отофа, содержащих антибиотик рифамицин.

OBJECTIVES: Drug-resistant TB remains a public health challenge. Rifamycins are among the most potent anti-TB drugs. They are known to target the RpoB subunit of RNA polymerase; however, our understanding of how rifamycin resistance is genetically encoded remains incomplete. Here we investigated rpoB genetic diversity and cross-resistance between the two rifamycin drugs rifampicin and rifabutin. METHODS: We performed WGS of 1003 Mycobacterium tuberculosis clinical isolates and determined MICs of both rifamycin agents on 7H10 agar using the indirect proportion method. We generated rpoB mutants in a laboratory strain and measured their antibiotic susceptibility using the alamarBlue reduction assay. RESULTS: Of the 1003 isolates, 766 were rifampicin resistant and 210 (27%) of these were rifabutin susceptible; 102/210 isolates had the rpoB mutation D435V (Escherichia coli D516V). Isolates with discordant resistance were 17.2 times more likely to harbour a D435V mutation than those resistant to both agents (OR 17.2, 95% CI 10.5–27.9, P value

Background Treatment of latent tuberculosis (LTBI) is important for tuberculosis (TB) prevention, and short course rifamycin-based therapies are preferred. Once-weekly isoniazid-rifapentine by self-administered therapy (3HP-SAT) has never been compared with 4 months of daily rifampin (4R). Methods Retrospective cohort study of adults ≥18 years of age initiating LTBI treatment with either 3HP-SAT or 4R in a United States (US)–based TB clinic between 11 April 2016 and 31 December 2018. We evaluated treatment completion through pharmacy fills and reviewed charts for reasons of noncompletion, including adverse events (AEs). The χ 2 test and a log-binomial multivariable model were used to compare treatment completion and AEs. Results Five hundred sixty individuals (42%) initiated 3HP-SAT and 773 (58%) initiated 4R. Median age was 38, 55% were female, and 89% were born outside of the US. Among those aged 18–49 years, treatment completion with 3HP-SAT was 79% compared to 68% with 4R (adjusted risk ratio [aRR], 1.17 [95% CI, 1.17–1.27]; P < .0001). Among individuals aged ≥50 years, treatment completion with 3HP-SAT was 87% compared to 64% with 4R (aRR, 1.35 [95% CI, 1.19–1.52]; P < .0001). Compared to 4R, there was no difference in risk of AEs in the 18–49 age group (aRR, 0.93 [95% CI, .58–1.48]; P = .75). Reduced risk of AEs was noted among patients aged ≥50 years who received 3HP-SAT (aRR, 0.37 [95% CI, .16–.85]; P = .02). Conclusions 3HP-SAT was associated with higher LTBI treatment completion and lower rates of AEs compared to 4R in individuals aged 50 and older. Expanding 3HP-SAT as an option for patients with LTBI may enhance TB prevention strategies in the US.

Silica–collagen type I nanocomposite hydrogels are evaluated as medicated dressings to prevent infection in chronic wounds. Two antibiotics, gentamicin and rifamycin, are encapsulated in a single step within plain silica nanoparticles. Their antimicrobial efficiency against Pseudomonas aeruginosa and Staphylococcus aureus is assessed. Gentamycin-loaded 500 nm particles can be immobilized at high silica dose in concentrated collagen hydrogels without modifying their fibrillar structure or impacting on their rheological behavior and increases their proteolytic stability. Gentamicin release from the nanocomposites is sustained over 7 days, offering an unparalleled prolonged antibacterial activity. Particle immobilization also decreases their cytotoxicity towards surface-seeded fibroblast cells. Rifamycin-loaded 100 nm particles significantly alter the collagen hydrogel structure at high silica doses. The thus-obtained nanocomposites show no antibacterial efficiency, due to strong adsorption of rifamycin on collagen fibers. The complex interplay of interactions between drugs, silica and collagen is a key factor regulating the properties of these composite hydrogels as antibiotic-delivering biological dressings and must be taken into account for future extension to other wound healing agents. Fil: Alvarez, Gisela Solange. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina Fil: Hélary, Christophe. Universite Pierre et Marie Curie; Francia. Universite de Paris VI; Francia. Centre National de la Recherche Scientifique; Francia Fil: Mebert, Andrea Mathilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina Fil: Wang, Xiaolin. Universite Pierre et Marie Curie; Francia. Universite de Paris VI; Francia. Centre National de la Recherche Scientifique; Francia Fil: Coradin, Thibaud. Universite Pierre et Marie Curie; Francia. Universite de Paris VI; Francia. Centre National de la Recherche Scientifique; Francia Fil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina

RNA polymerases (RNAPs) accomplish the first step of gene expression in all living organisms. However, the sequence divergence between bacterial and human RNAPs makes the bacterial RNAP a promising target for antibiotic development. The most clinically important and extensively studied class of antibiotics known to inhibit bacterial RNAP are the rifamycins. For example, rifamycins are a vital element of the current combination therapy for treatment of tuberculosis. Here, we provide an overview of the history of the discovery of rifamycins, their mechanisms of action, the mechanisms of bacterial resistance against them, and progress in their further development.

Mycobacterium avium complex (MAC) is the major pathologic nontuberculous mycobacteria causing lung disease (LD) in humans worldwide. Although the burden of MAC-LD has increased over the past two decades, treatment remains difficult because of intolerance of long-term antibiotics, lack of adherence to guidelines, and disease recurrence. The current guidelines recommend antibiotic initiation for patients with MAC-LD and severe disease and in those with disease progression. Thus, physicians should consider antibiotic treatment for patients with MAC-LD and cavitary pulmonary lesions or symptomatic non-cavitary nodular bronchiectasis pattern at initial visits and also for those with clinical deterioration during follow-up. The standard three-drug regimen should be macrolide, rifamycin, and ethambutol. Physicians should monitor side effects in patients and maintain the regimen for 12 months, beginning from when sputum conversion has been obtained. With adherence to guideline-based therapy, treatment is successful in two thirds of treatment-naive patients without macrolide resistance. Without adherence, macrolide resistance can occur, which leads to poor outcomes in patients with MAC-LD. Although the discovery of new treatment options is warranted, adherence to guidelines remains most crucial in treating patients with MAC-LD. It is worth mentioning that the majority of current recommendations are based on observational studies or small-scale clinical trials.