HelR is a helicase-like protein that protects RNA polymerase from rifamycin antibiotics.

Rifamycin antibiotics such as rifampin are potent inhibitors of prokaryotic RNA polymerase (RNAP) used to treat tuberculosis and other bacterial infections. Although resistance arises in the clinic principally through mutations in RNAP, many bacteria possess highly specific enzyme-mediated resistance mechanisms that modify and inactivate rifamycins. The expression of these enzymes is controlled by a 19-bp cis-acting rifamycin-associated element (RAE). Guided by the presence of RAE sequences, we identify a helicase-like protein, HelR, in Streptomyces venezuelae that confers broad-spectrum rifamycin resistance. We show that HelR also promotes tolerance to rifamycins, enabling bacterial evasion of the toxic properties of these antibiotics. HelR forms a complex with RNAP and rescues transcription inhibition by displacing rifamycins from RNAP, thereby providing resistance by target protection . Furthermore, HelRs are broadly distributed in Actinobacteria, including several opportunistic Mycobacterial pathogens, offering yet another challenge for developing new rifamycin antibiotics.

Structural Basis of Mycobacterium tuberculosis Transcription and Transcription Inhibition.

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, which kills 1.8 million annually. Mtb RNA polymerase (RNAP) is the target of the first-line antituberculosis drug rifampin (Rif). We report crystal structures of Mtb RNAP, alone and in complex with Rif, at 3.8-4.4 Å resolution. The results identify an Mtb-specific structural module of Mtb RNAP and establish that Rif functions by a steric-occlusion mechanism that prevents extension of RNA. We also report non-Rif-related compounds-Nα-aroyl-N-aryl-phenylalaninamides (AAPs)-that potently and selectively inhibit Mtb RNAP and Mtb growth, and we report crystal structures of Mtb RNAP in complex with AAPs. AAPs bind to a different site on Mtb RNAP than Rif, exhibit no cross-resistance with Rif, function additively when co-administered with Rif, and suppress resistance emergence when co-administered with Rif.

Rifampin Based Therapy for Patients With Staphylococcus aureus Native Vertebral Osteomyelitis: A Systematic Review and Meta-analysis.

BACKGROUND: Native vertebral osteomyelitis (NVO) caused by Staphylococcus aureus is associated with high risk of treatment failure and increased morbidity. The role of rifampin-based therapy for the treatment of this condition is controversial. The goal of this systematic review and meta-analysis is to explore the efficacy and safety of rifampin-based therapy for the treatment of S. aureus NVO. METHODS: We searched Cochrane, Embase, Medline, Scopus, and Web of Science databases for studies published up to May 2023, focusing on adults with NVO treated with or without rifampin-containing regimens. A random-effects model meta-analysis estimated relative risks and risk difference with 95% confidence intervals (CI). RESULTS: Thirteen studies (2 randomized controlled trials and 11 comparative cohort studies), comprising 244 patients with S. aureus NVO who received rifampin and 435 who did not, were analyzed. Meta-analysis showed that rifampin-based regimens were associated with lower risk of clinical failure (risk difference, -14%; 95% CI, -19% to -8%; P < .001; I2 = 0%; relative risk, 0.58; 95% CI, .37-.92, P = .02, I2 = 21%). Only 1 study reported on adverse events. All studies had a high or uncertain risk of bias, and the certainty of evidence was rated as very low. CONCLUSIONS: Adjunctive rifampin therapy might be associated with lower risk of S. aureus NVO treatment failure; however, the low certainty of evidence precludes drawing definitive conclusions that would alter clinical practice. A randomized trial is necessary to corroborate these findings.

Phase 1 drug-drug interaction study to assess the effect of CYP3A4 inhibition and pan-CYP induction on the pharmacokinetics and safety of fosmanogepix in healthy participants.

Immunocompromised patients are susceptible to fungal infections, and drug-drug interactions with antifungals may occur due to concomitant medications. Fosmanogepix [FMGX; active moiety manogepix (MGX)] targets glycosylphosphatidylinositol-anchored mannoprotein synthesis and maturation, essential for fungal virulence. This phase 1, fixed-sequence study in healthy participants evaluated the effect of strong CYP3A4 inhibitor itraconazole [Cohort 1 (n = 18); FMGX 500 mg intravenous (IV) twice a day (BID )+ itraconazole 200 mg oral once a day (QD)] and pan-CYP inducer rifampin [Cohort 2 (n = 18); FMGX 1,000 mg IV BID + rifampin 600 mg oral QD] on the pharmacokinetics of FMGX and MGX. In cohort 1, geometric mean (GM) MGX Cmax, AUC0-t, and AUCinf were almost similar with and without itraconazole administration. In Cohort 2, GM MGX Cmax was slightly lower and AUC0-t and AUCinf were significantly lower after rifampin administration, with the least squares GM ratio associated 90% confidence intervals (CIs) below 80 - 125% (no effect window). No deaths, serious adverse events (SAEs), or FMGX-related withdrawals were reported. In both cohorts, a total of 188 AEs (n = 30; 186 mild; two moderate) were reported. In all, 37 of 188 AEs (n = 12) were considered FMGX related (most frequent: headache, nausea, and hot flush). Administration of FMGX alone and with itraconazole or rifampin was safe and well tolerated. A strong CYP3A4 inhibitor had no effect on FMGX or MGX exposure. A strong pan-CYP inducer had no effect on FMGX exposure but demonstrated ~45% decrease in MGX exposure. CLINICAL TRIALS: This study is registered with ClinicalTrials.gov as NCT04166669 and with EudraCT as number 2019-003586-17.

Infection by a multidrug-resistant Corynebacterium diphtheriae strain: prediction of virulence factors, CRISPR-Cas system analysis, and structural implications of mutations conferring rifampin resistance.

Cases of diphtheria, even in immunized individuals, are still reported in several parts of the world, including in Brazil. New outbreaks occur in Europe and other continents. In this context, studies on Corynebacterium diphtheriae infections are highly relevant, both for a better understanding of the pathogenesis of the disease and for controlling the circulation of clones and antimicrobial resistance genes. Here we present a case of cutaneous infection by multidrug-resistant Corynebacterium diphtheriae and provide its whole-genome sequencing. Genomic analysis revealed resistance genes, including tet(W), sul1, cmx, rpoB2, rbpA and mutation in rpoB. We performed phylogenetic analyzes and used the BRIG to compare the predicted resistance genes with those found in genomes from other significant isolates, including those associated with some outbreaks. Virulence factors such as spaD, srtBC, spaH, srtDE, surface-anchored pilus proteins (sapD), nonfimbrial adhesins (DIP0733, DIP1281, and DIP1621), embC and mptC (putatively involved in CdiLAM), sigA, dtxR and MdbA (putatively involved) in post-translational modification, were detected. We identified the CRISPR-Cas system in our isolate, which was classified as Type II-U based on the database and contains 15 spacers. This system functions as an adaptive immune mechanism. The strain was attributed to a new sequence type ST-928, and phylogenetic analysis confirmed that it was related to ST-634 of C. diphtheriae strains isolated in French Guiana and Brazil. In addition, since infections are not always reported, studies with the sequence data might be a way to complement and inform C. diphtheriae surveillance.

Association between adjunctive rifampin and gentamicin use and outcomes for patients with staphylococcal prosthetic valve endocarditis: a propensity-score adjusted retrospective cohort study.

PURPOSE: Although guidelines recommend adjunctive rifampin and gentamicin use for patients with staphylococcal prosthetic valve endocarditis (PVE), evidence behind the recommendation is limited and conflicting. METHODS: We performed a retrospective cohort study of all patients with staphylococcal PVE within the Veterans Health Administration during 2003-2021. Patients were identified with diagnostic codes for prosthetic valves and positive blood cultures for Staphylococcus species and confirmed via manual chart reviews. The primary outcome was the composite of all-cause mortality or recurrence of staphylococcal PVE within one year from diagnosis. Inverse probability of treatment weighting (IPTW) was used to estimate the probability of individuals receiving rifampin using propensity scores. IPTW-adjusted multivariable Cox regression analysis was used to compare outcomes between patients who received rifampin and gentamicin, and those did not. RESULTS: Among 373 patients with staphylococcal PVE, 275 (73.7%) and 225 (60.3%) received at least one dose of rifampin and gentamicin, respectively. The incidence of staphylococcal PVE increased from 0.47 (2003-11) to 0.77 (2012-21) per 10,000 hospitalizations. Gentamicin use declined over time (70.1% in 2003-2011 to 54.8% in 2012-2021, p = 0.04) while rifampin use did not change significantly (76.1% in 2003-2011 to 72.4% in 2012-2021, p = 0.43). The composite outcome was observed in 209 (56.0%). Neither rifampin use (adjusted hazard ratio [HR] 0.77, 95% CI 0.48-1.24) and gentamicin use (adjusted HR 1.11, 95% CI 0.71-1.74) was associated with the composite outcome. CONCLUSION: No significant association was observed between adjunctive rifampin or gentamicin use and improved outcomes.

Cost-effectiveness of interferon-γ release assay for screening of latent tuberculosis infection in individuals with schizophrenia.

Schizophrenia is recognized as a significant risk factor for tuberculosis (TB). This study aimed to evaluate the effectiveness and cost-effectiveness of interferon-γ release assay (IGRA) with preventive treatment for screening of latent tuberculosis infection (LTBI) in individuals with schizophrenia. A state transition model was developed from a healthcare payer perspective on a lifetime horizon. Ten strategies were compared by combining two different tests for LTBI, i.e. IGRA and tuberculin skin test (TST), and five different preventive treatments, i.e. 9-month isoniazid (9H), 3-month isoniazid and rifapentine (3HP) by directly observed therapy, 3HP by self-administered therapy, 3-month isoniazid and rifampin (3RH), and 4-month rifampin (4R). The main outcomes were costs, quality-adjusted life-years (QALYs), life expectancy life-years (LYs), incremental cost-effectiveness ratios, drug-sensitive tuberculosis (DS-TB) cases, and TB-related deaths. For both bacillus Calmette-Guérin (BCG)-vaccinated and non-BCG-vaccinated individuals, IGRA with 4R was the most cost-effective and TST with 3RH was the least effective. Among schizophrenic individuals in Japan, IGRA with 4R saved US$17.8 million, increased 58,981 QALYs and 935 LYs, and prevented 222 DS-TB cases and 75 TB-related deaths compared with TST with 3RH. In individuals with schizophrenia, IGRA with 4R is recommended for LTBI screening with preventive treatment to reduce costs, morbidity, and mortality from TB.

Integrative Inducer Intervention and Transcriptomic Analyses Reveal the Metabolism of Paralytic Shellfish Toxins in Azumapecten farreri.

Paralytic shellfish toxins (PSTs) are widely distributed neurotoxins, and the PST metabolic detoxification mechanism in bivalves has received increasing attention. To reveal the effect of phase I (cytochrome P450)-II (GST)-III (ABC transport) metabolic systems on the PST metabolism in Azumapecten farreri, this study amplified stress on the target systems using rifampicin, dl-α-tocopherol, and colchicine; measured PST levels; and conducted transcriptomic analyses. The highest toxin content reached 1623.48 µg STX eq/kg in the hepatopancreas and only 8.8% of that in the gills. Inducer intervention significantly decreased hepatopancreatic PST accumulation. The proportional reductions in the rifampicin-, dl-α-tocopherol-, and colchicine-induced groups were 55.3%, 50.4%, and 36.1%, respectively. Transcriptome analysis showed that 11 modules were significantly correlated with PST metabolism (six positive/five negative), with phase I CYP450 and phase II glutathione metabolism significantly enriched in negatively correlated pathways. Twenty-three phase I-II-III core genes were further validated using qRT-PCR and correlated with PST metabolism, revealing that CYP46A1, CYP4F6, GSTM1, and ABCF2 were significantly correlated, while CYP4F11 and ABCB1 were indirectly correlated. In conclusion, phase I-II-III detoxification enzyme systems jointly participate in the metabolic detoxification of PSTs in A. farreri. This study provides key data support to profoundly elucidate the PST metabolic detoxification mechanism in bivalves.

Periprosthetic Joint Infection: Current Clinical Challenges.

Over the last several decades, periprosthetic joint infection has been increasing in incidence and is occurring in more complex patients. While there have been advances in both surgical and medical treatment strategies, there remain important gaps in our understanding. Here, we share our current approaches to the diagnosis and management of periprosthetic joint infection, focusing on frequent clinical challenges and collaborative interdisciplinary care.

Executive Summary: Periprosthetic Joint Infection-Current Clinical Challenges.

Over the last several decades, periprosthetic joint infection (PJI) has been increasing in incidence and is occurring in more complex patients. While there have been advances in both surgical and medical treatment strategies, there remain important gaps in our understanding. Here, we share our current approaches to the diagnosis and management of PJI, focusing on frequent clinical challenges and collaborative interdisciplinary care. The more detailed review including diagnosis, surgical considerations, and a detailed antimicrobial discussion is presented in the online version.

Limited Nosocomial Transmission of Drug-Resistant Tuberculosis, Moldova.

Applying whole-genome-sequencing, we aimed to detect transmission events of multidrug-resistant/rifampin-resistant strains of Mycobacterium tuberculosis complex at a tuberculosis hospital in Chisinau, Moldova. We recorded ward, room, and bed information for each patient and monitored in-hospital transfers over 1 year. Detailed molecular and patient surveillance revealed only 2 nosocomial transmission events.

Tuberculosis Variant with Rifampin Resistance Undetectable by Xpert MTB/RIF, Botswana.

GeneXpert MTB/RIF, a tool widely used for diagnosing tuberculosis, has limitations for detecting rifampin resistance in certain variants. We report transmission of a pre-extensively drug-resistant variant in Botswana that went undetected by GeneXpert. The public health impact of misdiagnosis emphasizes the need for comprehensive molecular testing to identify resistance and guide treatment.

Evaluation of Omadacycline Alone and in Combination with Rifampin against Staphylococcus aureus and Staphylococcus epidermidis in an In Vitro Pharmacokinetic/Pharmacodynamic Biofilm Model.

Biofilm-associated infections lead to substantial morbidity. Omadacycline (OMC) is a novel aminomethylcycline with potent in vitro activity against Staphylococcus aureus and Staphylococcus epidermidis, but data surrounding its use in biofilm-associated infections are lacking. We investigated the activity of OMC alone and in combination with rifampin (RIF) against 20 clinical strains of staphylococci in multiple in vitro biofilm analyses, including an in vitro pharmacokinetic/pharmacodynamic (PK/PD) CDC biofilm reactor (CBR) model (simulating human exposures). The observed MICs for OMC demonstrated potent activity against the evaluated strains (0.125 to 1 mg/L), with an increase of MICs generally observed in the presence of biofilm (0.25 to >64 mg/L). Furthermore, RIF was shown to reduce OMC biofilm MICs (bMICs) in 90% of strains, and OMC plus RIF combination in biofilm time-kill analyses (TKAs) exhibited synergistic activity in most of the strains. Within the PK/PD CBR model, OMC monotherapy primarily displayed bacteriostatic activity, while RIF monotherapy generally exhibited initial bacterial eradication, followed by rapid regrowth likely due to the emergence of RIF resistance (RIF bMIC, >64 mg/L). However, the combination of OMC plus RIF produced rapid and sustained bactericidal activity in nearly all the strains (3.76 to 4.03 log10 CFU/cm2 reductions from starting inoculum in strains in which bactericidal activity was reached). Furthermore, OMC was shown to prevent the emergence of RIF resistance. Our data provide preliminary evidence that OMC in combination with RIF could be a viable option for biofilm-associated infections with S. aureus and S. epidermidis. Further research involving OMC in biofilm-associated infections is warranted.

Simplified urine-based method to detect rifampin underexposure in adults with tuberculosis: a prospective diagnostic accuracy study.

Variable pharmacokinetics of rifampin in tuberculosis (TB) treatment can lead to poor outcomes. Urine spectrophotometry is simpler and more accessible than recommended serum-based drug monitoring, but its optimal efficacy in predicting serum rifampin underexposure in adults with TB remains uncertain. Adult TB patients in New Jersey and Virginia receiving rifampin-containing regimens were enrolled. Serum and urine samples were collected over 24 h. Rifampin serum concentrations were measured using validated liquid chromatography-tandem mass spectrometry, and total exposure (area under the concentration-time curve) over 24 h (AUC0-24) was determined through noncompartmental analysis. The Sunahara method was used to extract total rifamycins, and rifampin urine excretion was measured by spectrophotometry. An analysis of 58 eligible participants, including 15 (26%) with type 2 diabetes mellitus, demonstrated that urine spectrophotometry accurately identified subtarget rifampin AUC0-24 at 0-4, 0-8, and 0-24 h. The area under the receiver operator characteristic curve (AUC ROC) values were 0.80 (95% CI 0.67-0.90), 0.84 (95% CI 0.72-0.94), and 0.83 (95% CI 0.72-0.93), respectively. These values were comparable to the AUC ROC of 2 h serum concentrations commonly used for therapeutic monitoring (0.82 [95% CI 0.71-0.92], P = 0.6). Diabetes status did not significantly affect the AUC ROCs for urine in predicting subtarget rifampin serum exposure (P = 0.67-0.92). Spectrophotometric measurement of urine rifampin excretion within the first 4 or 8 h after dosing is a simple and cost-effective test that accurately predicts rifampin underexposure. This test provides critical information for optimizing tuberculosis treatment outcomes by facilitating appropriate dose adjustments.

Eradication of Staphylococcus epidermidis within Biofilms: Comparison of Systemic versus Supratherapeutic Concentrations of Antibiotics.

Biofilm-forming bacterial infections result in clinical failure, recurring infections, and high health care costs. The antibiotic concentrations needed to eradicate biofilm require further research. We aimed to model an in vitro prosthetic joint infection (PJI) to elucidate the activity of traditional systemic concentrations versus supratherapeutic concentrations to eradicate a Staphylococcus epidermidis biofilm PJI. We evaluated S. epidermidis high-biofilm-forming (ATCC 35984) and low-biofilm-forming (ATCC 12228) isolates in an in vitro pharmacodynamic biofilm reactor model with chromium cobalt coupons to simulate prosthetic joint infection. Vancomycin, daptomycin, levofloxacin, and minocycline were used alone and combined with rifampin to evaluate the effect of biofilm eradication. We simulated three exposures: (i) humanized systemic dosing alone, (ii) supratherapeutic doses (1,000× MIC), and (iii) and dosing in combination with rifampin. Resistance development was monitored throughout the study. Simulated humanized systemic doses of a lipoglycopeptide (daptomycin), a fluoroquinolone (levofloxacin), a tetracycline (minocycline), and a glycopeptide (vancomycin) alone failed to eradicate a formed S. epidermidis biofilm. Supratherapeutic doses of vancomycin (2,000 µg/mL) and minocycline (15 µg/mL) with or without rifampin (15 µg/mL) failed to eradicate biofilms. However, a levofloxacin supratherapeutic dose (125 µg/mL) with rifampin eradicated the high-biofilm-producing isolate by 48 h. Interestingly, supratherapeutic-dose exposures of daptomycin (500 µg/mL) alone eradicated high- and low-biofilm-forming isolates in established biofilms. The concentrations needed to eradicate biofilms on foreign materials are not obtained with systemic dosing regimens. The failure of systemic dosing regimens to eradicate biofilms validates clinical findings with recurring infections. The addition of rifampin to supratherapeutic dosing regimens does not result in synergy. Supratherapeutic daptomycin dosing may be effective at the site of action to eradicate biofilms. Further studies are needed.

Pharmacokinetics and safety of first-line tuberculosis drugs rifampin, isoniazid, ethambutol, and pyrazinamide during pregnancy and postpartum: results from IMPAACT P1026s.

Physiological changes during pregnancy may alter the pharmacokinetics (PK) of antituberculosis drugs. The International Maternal Pediatric Adolescent AIDS Clinical Trials Network P1026s was a multicenter, phase IV, observational, prospective PK and safety study of antiretroviral and antituberculosis drugs administered as part of clinical care in pregnant persons living with and without HIV. We assessed the effects of pregnancy on rifampin, isoniazid, ethambutol, and pyrazinamide PK in pregnant and postpartum (PP) persons without HIV treated for drug-susceptible tuberculosis disease. Daily antituberculosis treatment was prescribed following World Health Organization-recommended weight-band dosing guidelines. Steady-state 12-hour PK profiles of rifampin, isoniazid, ethambutol, and pyrazinamide were performed during second trimester (2T), third trimester (3T), and 2-8 of weeks PP. PK parameters were characterized using noncompartmental analysis, and comparisons were made using geometric mean ratios (GMRs) with 90% confidence intervals (CI). Twenty-seven participants were included: 11 African, 9 Asian, 3 Hispanic, and 4 mixed descent. PK data were available for 17, 21, and 14 participants in 2T, 3T, and PP, respectively. Rifampin and pyrazinamide AUC0-24 and C max in pregnancy were comparable to PP with the GMR between 0.80 and 1.25. Compared to PP, isoniazid AUC0-24 was 25% lower and C max was 23% lower in 3T. Ethambutol AUC0-24 was 39% lower in 3T but limited by a low PP sample size. In summary, isoniazid and ethambutol concentrations were lower during pregnancy compared to PP concentrations, while rifampin and pyrazinamide concentrations were similar. However, the median AUC0-24 for rifampin, isoniazid, and pyrazinamide met the therapeutic targets. The clinical impact of lower isoniazid and ethambutol exposure during pregnancy needs to be determined.

Performance Evaluation of the BACTEC MGIT 960 System for Rifampin Drug-Susceptibility Testing of Mycobacterium tuberculosis Using the Current WHO Critical Concentration.

The World Health Organization recently lowered the rifampin (RIF) critical concentration (CC) for drug-susceptibility testing (DST) of Mycobacterium tuberculosis complex (MTBC) using the mycobacterial growth indicator tube (MGIT) 960 system. Here, we evaluated the diagnostic performance of the MGIT system with the revised CC for determining MTBC RIF resistance with 303 clinical MTBC isolates, including 122 isolates with rpoB mutations, of which 32 had single borderline-resistance mutations, and 181 wild-type rpoB isolates. The phenotypic RIF resistance was determined via the absolute concentration method (AC) and via MGIT using both previous (1 mg/L) and revised (0.5 mg/L) CCs for the latter method. The diagnostic accuracy of each phenotypic DST (pDST) was assessed based on rpoB genotyping as the reference standard. The overall sensitivity of the AC was 95.1% (95% confidence interval [CI], 89.6 to 98.2%), while the MGIT results with previous and revised CCs were 82.0% (95% CI 74.0 to 88.3%) and 83.6% (95% CI 75.8 to 89.7%), respectively. The 32 MTBC isolates with single borderline-resistance mutations showed a wide range of MICs, and sensitivity was not significantly increased by reducing the MGIT CC. All 181 wild-type rpoB isolates were RIF-susceptible in the AC and with MGIT using the previous CC, whereas 1 isolate was misclassified as RIF-resistant with the revised CC. Our results demonstrate that the overall diagnostic performances of the MGIT DST with the revised RIF CC and previous CC were comparable. A further large-scale study is required to demonstrate the optimal RIF CC for MGIT.

Clinical Evaluation of the XDR-LFC Assay for the Molecular Detection of Isoniazid, Rifampin, Fluoroquinolone, Kanamycin, Capreomycin, and Amikacin Drug Resistance in a Prospective Cohort.

While the goal of universal drug susceptibility testing has been a key component of the WHO End TB Strategy, in practice, this remains inaccessible to many. Rapid molecular tests for tuberculosis (TB) and antituberculosis drug resistance could significantly improve access to testing. In this study, we evaluated the accuracy of the Akonni Biosystems XDR-TB (extensively drug-resistant TB) TruArray and lateral-flow-cell (XDR-LFC) assay (Akonni Biosystems, Inc., Frederick, MD, USA), a novel assay that detects mutations in seven genes associated with resistance to antituberculosis drugs: katG, the inhA promoter, and the ahpC promoter for isoniazid; rpoB for rifampin; gyrA for fluoroquinolones; rrs and the eis promoter for kanamycin; and rrs for capreomycin and amikacin. We evaluated assay performance using direct sputum samples from 566 participants recruited in a prospective cohort in Moldova over 2 years. The sensitivity and specificity against the phenotypic reference were both 100% for isoniazid, 99.2% and 97.9% for rifampin, 84.8% and 99.1% for fluoroquinolones, 87.0% and 84.1% for kanamycin, 54.3% and 100% for capreomycin, and 79.2% and 100% for amikacin, respectively. Whole-genome sequencing data for a subsample of 272 isolates showed 95 to 99% concordance with the XDR-LFC-reported suspected mutations. The XDR-LFC assay demonstrated a high level of accuracy for multiple drugs and met the WHO's minimum target product profile criteria for isoniazid and rifampin, while the sensitivity for fluoroquinolones and amikacin fell below target thresholds, likely due to the absence of a gyrB target in the assay. With optimization, the XDR-LFC shows promise as a novel near-patient technology to rapidly diagnose drug-resistant tuberculosis.

Effect of CYP3A4 induction and inhibition on the pharmacokinetics of SHR0302 in healthy subjects.

AIMS: SHR0302 is a selective Janus kinase (JAK) 1 inhibitor under clinical investigation for the treatment of rheumatoid arthritis (RA). As SHR0302 is metabolized mainly by cytochrome P450 (CYP) 3A4, clinical studies were performed to evaluate the effects of a strong CYP3A4 inducer, rifampin, and a strong CYP3A4 inhibitor, itraconazole, on the pharmacokinetics of SHR0302 in healthy subjects. METHODS: Two phase I, open-label, fixed-sequence drug interaction studies enrolled 28 subjects. In Study A, 14 subjects received 8 mg SHR0302 on Days 1 and 10, and 600 mg rifampin once daily on Days 3-11. In Study B, 14 subjects received 4 mg SHR0302 on Days 1 and 8, and 200 mg itraconazole once daily on Days 4-10. Blood samples were collected to measure SHR0302 concentrations. Pharmacokinetic parameters were calculated using non-compartmental analysis. Treatment comparisons were made using mixed-effect models. RESULTS: Co-administration with rifampin decreased the exposures of SHR0302 with geometric mean ratios (GMRs) (90% confidence intervals [CIs]) for AUC0-inf of 0.51 (0.49, 0.54) and Cmax of 0.91 (0.84, 0.98). Co-administration with itraconazole increased the exposures of SHR0302 with GMR (90% CIs) for AUC0-inf of 1.48 (1.41, 1.56) and Cmax of 1.06 (0.982, 1.14). Single oral doses of SHR0302 administered with or without rifampin or itraconazole were generally safe. CONCLUSIONS: Strong CYP3A4 induction and inhibition both resulted in a weak effect on the clinical exposures of SHR0302. These present studies provided valuable information that helps inform SHR0302 dosing instructions and concomitant medication precautions.

Amino acid substitutions in the region between RpoB clusters II and III on rifampin susceptibility in Haemophilus influenzae.

BACKGROUND: Rifampin is a potent chemoprophylactic antibiotic for Haemophilus influenzae infection, and the resistance rate in H. influenzae is low. In this study, we assessed rifampin resistance-related genetic variations in H. influenzae. METHODS: Rifampin susceptibility testing and whole-genome sequencing were performed in 51 H. influenzae isolates. Variations associated with rifampin resistance were identified using Fisher's exact tests. Functional assays were performed to evaluate the effect of RpoB substitutions on rifampin susceptibility. RESULTS: Using the genome of the Rd KW20 H. influenzae strain as the reference, we detected 40 genetic variations in rpoB, which resulted in 39 deduced amino acid substitutions among the isolates. Isolate A0586 was resistant to rifampin, with a minimum inhibitory concentration (MIC) = 8 µg/mL. Phylogenetic analyses revealed that the RpoB sequence of isolate A0586 was distinct from other isolates. Five substitutions, including H526N located in cluster I and L623F, R628C, L645F, and L672F in the region between clusters II and III, were unique to isolate A0586. In two rifampin-susceptible H. influenzae isolates, RpoB-H526N alone and in combination with RpoB-L672F increased the MICs of rifampin to 4 and 8 µg/mL, respectively. RpoB-L672F did not affect cell growth and transcription in H. influenzae isolates. No amino acid substitutions in the AcrAB-TolC efflux pump or outer membrane proteins were found to be associated with rifampin resistance in H. influenzae. CONCLUSIONS: Our findings indicate that L672F substitution in the region between RpoB clusters II and III has an aggravating effect on rifampin resistance in H. influenzae.