(1) Background: To investigate the risk factors associated with optic neuropathy (ON) and validate the hypothesis that concomitant isoniazid use and other causes of toxic ON affect the development of ON in ethambutol users. (2) Methods: This cohort study identified ethambutol users who initiated ethambutol therapy between January 2015 and December 2021 and had no ON prior to ethambutol therapy. ON incidence up to 31 December 2022 was evaluated. The users were grouped on the basis of the presence of ON. Demographic and clinical characteristics were investigated for risk factor analyses of ON. Odds ratios (ORs) were calculated using multivariate logistic regression analyses. (3) Results: Among 204,598 ethambutol users, 5277 (2.6%) patients developed ON over the study period. Patients with ON included a higher percentage of women and had a higher mean age than patients without ON. In the multivariate analyses, the risk factors for ON and visual impairment included sex, age, cumulative dose, extrapulmonary indications for ethambutol use, and systemic conditions such as diabetes, hypertension, hyperlipidemia, diabetes, kidney disease, and liver disease. Malnutrition or nutritional disorders significantly increased the risk of ON (OR = 1.27, 95% confidence interval [CI] = 1.19-1.34), whereas concomitant isoniazid use decreased the risk (OR = 0.78, 95% CI = 0.72-0.86). (4) Conclusion: An increased risk of ON in patients with systemic diseases and nutritional deficiency was identified, whereas concomitant isoniazid use was associated with a decreased risk of ON. Patients with these risk factors should be carefully monitored to minimize the vision-threatening ON.

Ethambutol is a first-line chemotherapeutic agent, which is commonly used in combination with other drugs for the treatment of tuberculosis. Ethambutol-induced optic neuritis is a serious and rare side effect that is either dose or duration-related and causes progressive painless vision loss, and cecocentral scotomas in the visual field. A rare case of ethambutol-induced optic neuritis was reported in a 52-year-old female who was taking anti-tubercular treatment for pulmonary tuberculosis for five months. She presented with painless diminished vision in both eyes. The patient was diagnosed with a rare case of optic neuritis through various examination methods. Ethambutol was stopped and therapy was continued with oral prednisone, zinc, and vitamin B complex being started along with anti-TB treatment. She showed no marked improvement in visual parameters until the last follow-up. The patient died due to cardiopulmonary arrest as a consequence of pulmonary tuberculosis.

Drug susceptibility testing (DST) is essential for effectively starting people on effective tuberculosis (TB) regimens. No accuracy data exists for the new high-throughput LiquidArray MTB-XDR (LA-XDR) test, which detects Mycobacterium tuberculosis complex (MTBC) and susceptibility to the fluoroquinolones, amikacin, ethambutol, and linezolid (the latter two drugs have no rapid molecular DSTs available). We enrolled (n=720) people with presumptive TB who provided two sputa for Xpert MTB/RIF Ultra and culture (MTBC reference standard). Phenotypic DST and Sanger sequencing served as a composite reference standard. Manual FluoroLyse and automated GenoXtract-fleXT (fleXT) DNA extraction methods were compared. For MTBC, LA-XDR using fleXT-extracted or FluoroLyse-extracted DNA had similar sensitivities (85-87%; which improved upon eluate retesting) and specificities (99%). Drug susceptibility sensitivities varied: 94% (86, 98) for fluoroquinolones, 64% (45, 80) for amikacin, and 88% (79, 93) for ethambutol (specificities 97-100%). LA-XDR detected 86% (6/7) phenotypically resistant linezolid isolates. LA-XDR with fleXT had indeterminate proportions of 8% (21/251) for fluoroquinolones, 1% (2/251) for ethambutol, 25% (63/251) for amikacin, and 37% (93/251) for linezolid. In a hypothetical population of 100 smear-negative fluoroquinolones-resistant cases, 24% (24/100) could be missed due to an unsuccessful result (1 fleXT error and, for LA-XDR, 2 invalid results, 15 MTBC-negative, 6 fluoroquinolone-indeterminate, 1 false-susceptible). LA-XDR met the minimum WHO target product profile for a next-generation sputum-based moderate complexity DST with high sensitivity for fluoroquinolones and ethambutol resistance, moderate sensitivity for amikacin resistance, and promise for linezolid resistance, for which more data are needed. Improved MTBC detection would reduce missed resistance.

Tuberculosis (TB) treatment becomes challenging due to the unique cell wall structure of Mycobacterium tuberculosis (M. tb). Among various components of the M.tb cell wall, mycolic acid (MA) is of particular interest because it is speculated to exhibit extremely low permeability for most of the drug molecules, thus helping M.tb to survive against medical treatment. However, no quantitative assessment of the thermodynamic barrier encountered by various well-known TB drugs in the mycolic acid monolayer has been performed so far using computational tools. On this premise, our present work aims to probe the permeability of some first and second line TB drugs, namely ethambutol, ethionamide, and isoniazid, through the modelled mycolic acid monolayer, using molecular dynamics (MD) simulation with two sets of force field (FF) parameters, namely GROMOS 54A7-ATB (GROMOS) and CHARMM36 (CHARMM) FFs. Our findings indicate that both FFs provide consistent results in terms of the mode of drug-monolayer interactions but significantly differ in the drug permeability through the monolayer. The mycolic acid monolayer generally exhibited a higher free energy barrier of crossing with CHARMM FF, while with GROMOS FF, better stability of drug molecules on the monolayer surface was observed, which can be attributed to the greater electrostatic potential at the monolayer-water interface, found for the later. Although both the FF parameters predicted the highest resistance against ethambutol (permeability values of 8.40 × 10-34 cm s-1 and 9.61 × 10-31 cm s-1 for the CHARMM FF and the GROMOS FF, respectively), results obtained using GROMOS were found to be consistent with the water solubility of drugs, suggesting it to be a slightly better FF for modelling drug-mycolic acid interactions. Therefore, this study enhances our understanding of TB drug permeability and highlights the potential of the GROMOS FF in simulating drug-mycolic acid interactions.

BACKGROUND: Isoniazid (INH) and Rifampicin (RIF) are two crucial drugs used in antitubercular therapy. INH is known for its potent bactericidal effects and has a relatively higher prevalence of resistance compared to RIF. However, RIF resistance has been the subject of more extensive research. On the other hand, Ethambutol (EMB) and Streptomycin (STR) resistance have not been thoroughly studied, particularly in the context of children and adolescents. To address this knowledge gap, a study was designed to investigate the resistance patterns of INH, EMB, and STR in RIF-sensitive pulmonary tuberculosis (PTB) cases among children and adolescents.
METHODS: Seventy-five newly diagnosed RIF sensitive PTB cases up to 18 years of age were enrolled. Retreatment cases were excluded. Sputum/gastric aspirate sample of these patients were sent for culture in Mycobacterium Growth Indicator Tube (MGIT) followed by drug susceptibility testing and Line Probe Assay.
RESULTS: INH, EMB and STR resistance among RIF sensitive PTB cases was found to be 5.7%, 0% and 0.7% respectively. RIF resistance detected by CBNAAT was found to be 8.4%.
CONCLUSIONS: Detection of INH resistance is as important as detecting RIF resistance as prevalence of INH resistance in RIF sensitive PTB among children and adolescents up to 18 years is around 6%.

In Mycobacterium tuberculosis, molecular predictions of ethambutol resistance rely primarily on the detection of mutations within embB. However, discordance between embB406 mutations and gold standard phenotypic drug sensitivity testing (DST) questions the significance of embB406 mutations used in molecular DST. This study tabulates embB mutations found in Canadian M. tuberculosis isolates and evaluates the impact of specific mutations on ethambutol resistance. The National Reference Centre for Mycobacteriology culture collection (n = 2796) was screened for isolates with embB mutations. Phenotypic DST was performed on the BACTEC™ MGIT™ 960 at ethambutol concentrations of 2-5 μg/mL. Whole genome sequencing was used for drug resistance predictions, phylogenomics and single nucleotide polymorphism analysis. Detection of resistance-associated embB mutations corresponded to a positive predictive value of 64.3%, negative predictive value of 99.2%, 98.7% specificity, and 73.3% sensitivity compared to phenotypic DST. Two embB406 mutation subtypes (Gly406Asp, Gly406Ala) were found among 16 isolates, of which 12 were sensitive at 5 µg/mL ethambutol with variable resistance between 2-4 µg/mL. A novel frameshift mutation in regulator embR (Gln258fs) was found in nine isolates. Mutations in embB406 were associated with low-level ethambutol resistance undetectable at the recommended critical concentration (5 μg/mL). These novel mutations may exacerbate variability in ethambutol resistance.

BACKGROUND: Tuberculosis (TB) lymphadenitis is the most common form of extra-pulmonary TB, and the treatment duration is six months. This non-inferiority based randomized clinical trial in South India evaluated the efficacy and safety of a four-month ofloxacin containing regimen in tuberculosis lymphadenitis (TBL) patients.
METHODS: New, adult, HIV-negative, microbiologically and or histopathologically confirmed superficial lymph node TB patients were randomized to either four-month oflaxacin containing test regimen [ofloxacin (O), isoniazid (H), rifampicin (R), pyrazinamide (Z) -2RHZO daily/ 2RHO thrice-weekly] or a six-month thrice-weekly control regimen (2HRZ, ethambutol/4RH). The treatment was directly observed. Clinical progress was monitored monthly during and up to 12 months post-treatment, and thereafter every three months up to 24 months. The primary outcome was determined by response at the end of treatment and TB recurrence during the 24 months post-treatment.
RESULTS: Of the 302 patients randomized, 298 (98.7%) were eligible for modified intention-to-treat (ITT) analysis and 294 (97%) for per-protocol (PP) analysis. The TB recurrence-free favourable response in the PP analysis was 94.0% (95% CI: 90.1-97.8) and 94.5% (95% CI: 90.8-98.2) in the test and control regimen respectively, while in the ITT analysis, it was 92.7% and 93.2%. The TB recurrence-free favourable response in the test regimen was non-inferior to the control regimen 0.5% (95% CI: -4.8-5.9) in the PP analysis based on the 6% non-inferiority margin. Treatment was modified for drug toxicity in two patients in the test regimen, while one patient had a paradoxical reaction.
CONCLUSIONS: The 4-month ofloxacin containing regimen was found to be non-inferior and as safe as the 6-month thrice-weekly control regimen.

UNASSIGNED: To explore the association between the variant mutations within embB and ubiA, and the degree of ethambutol (EMB) resistance of Mycobacterium tuberculosis (M. tuberculosis) isolates.
UNASSIGNED: A total of 146 M. tuberculosis isolates were used to determine the minimum inhibitory concentrations (MICs) of EMB with a 96-well microplate-based assay. The mutations within embB and ubiA among these isolates were identified with DNA sequencing. Moreover, a multivariate regression model and a computer model were established to assess the effects of mutations on EMB resistance.
UNASSIGNED: Our data showed that overall 100 isolates exhibited 28 mutated patterns within the sequenced embB and ubiA. Statistical analysis indicated that embB mutations Met306Val, Met306Ile, Gly406Ala, and Gln497Arg, were strongly associated with EMB resistance. Of these mutations, Met306Val and Gln497Arg were significantly associated with high-level EMB resistance. Almost all multiple mutations occurred in high-level EMB-resistant isolates. Although the mutation within ubiA accompanied with embB mutation presented exclusively in EMB-resistant isolates, four single ubiA mutations (Ala39Glu, Ser173Ala, Trp175Cys, and Val283Leu) leading to protein instability were observed in EMB-susceptible isolates.
UNASSIGNED: This study highlighted the complexity of EMB resistance. Some individual mutations and multiple mutations within embB and ubiA contributed to the different levels of EMB resistance.

Pulmonary Mycobacterium avium-intracellulare complex (MAC) disease is a typical non-tuberculous mycobacterial infection. The incidence of pulmonary MAC is increasing worldwide. This study aimed to clarify the pharmacokinetic parameters of anti-pulmonary MAC disease drugs in silkworms. The pharmacokinetic parameters investigated included maximum concentration, area under the concentration-time curve, total clearance, and volume of distribution at steady-state. In addition, protein-binding rates, fat body transferability, and drug-drug interactions were examined. Antibiotic concentrations were measured using a validated high-performance liquid chromatography-mass spectrometry method. Among the antibiotics investigated, amikacin was not eliminated from silkworms during the 48-h observation period. In contrast, dose-proportional pharmacokinetics were observed in silkworms for all antibiotics tested, except for amikacin. Protein-binding rates in hemolymph for clarithromycin, azithromycin, rifampicin, ethambutol, and amikacin were 39.6 ± 3.0%, 39.5 ± 4.3%, 76.3 ± 3.2%, 20.9 ± 4.2%, and 73.1 ± 4.7%, respectively (mean ± standard deviation). The distribution of antibiotics in the fat bodies of silkworms was related to drug lipophilicity. No drug-drug interactions were observed in the silkworms. The pharmacokinetics of these drugs in silkworms differed significantly from those in humans. Therefore, while it is challenging to predict the pharmacokinetics of these drugs in humans based on silkworm data, the silkworm infection model has facilitated a comprehensive assessment of the relationship between antibiotic exposure and efficacy.

Objective: To evaluate the efficacy and safety of first-line anti-tuberculosis (TB) drugs combined with linezolid in treatment of children with tuberculous meningitis (TBM). Methods: A retrospective cohort study design was performed. Eight-nine Children diagnosed as TBM during January 1st 2016 and December 31st 2023 in Department of Infectious Disease, Children\'s Hospital of Chongqing Medical University were enrolled in the study. According to different treatment regimens, children were divided into a group of first-line anti-tuberculous drugs (isoniazid, rifampicin, pyrazinamide, ethambutol (HRZE)) and a group of HRZE and linezolid combination (HRZEL). The efficacy and safety of the 2 regimens were compared and the relationship between linezolid drug concentration and adverse reactions were analyzed. Comparisons between groups were performed using χ2 test and Mann-Whitney U test. Results: The 89 children with TBM included 53 males and 36 females with an onset age of 4.6 (1.4, 9.6) years. There were 27 cases in the HZREL group and 62 cases in the HRZE group. Before treatment, positive rate of interferon-gamma release assays (IGRA) in HRZEL group was lower than that in HRZE group (64% (16/25) vs.92% (55/60), χ2=9.82, P<0.05), but protein level of cerebrospinal fluid (CSF) was higher than that in HRZE group (1.2 (1.0, 2.0) vs.0.8 (0.4,1.4) g/L, Z=0.32, P<0.05). By the end of the intensive phase, there were no significant differences of rates of CSF improvement and etiology negativity between HRZEL group and HRZE group (both P>0.05).The 44 TBM children with high CSF protein (>1 g/L) included 25 males and 19 females with an onset age of 6.7 (3.0, 11.8) years. There were 21 cases in the HZREL group and 23 cases in the HRZE group accordingly. Before treatment, there were no significant differences of positive rate of IGRA test and CSF protein level between the 2 groups (62% (13/21) vs. 87% (20/23), 1.7 (1.1, 2.2) vs. 1.5 (1.2, 1.9) g/L, χ2=3.67, Z=0.23, both P>0.05). There were no significant differences in CSF indicators, etiology negativity or imaging remission between the two groups by the end of intensive phase (all P>0.05). Higher frequencies of granulocytopenia, gastrointestinal symptoms as well as withdrawal or change of drugs were found in HRZEL group when compared to those in HRZE group (44% (12/27) vs. 19% (12/62), 7% (2/27) vs. 0, 33% (9/27) vs. 3% (2/62), χ2=6.01, 4.70, 15.74, all P<0.05). Conclusions: The efficacy of HRZEL regimen is similar to conventional HRZE regimen in children with TBM, but with higher adverse effect. Prudentially evaluating the pros and cons of linezolid in the usage of drug-susceptible TB and carefully monitoring of linezolid associated adverse effects is suggested.
目的： 评估一线抗结核药物联合利奈唑胺治疗儿童非耐药结核性脑膜炎的效果及安全性。 方法： 回顾性队列研究。选择2016年1月1日至2023年12月31日于重庆医科大学附属儿童医院感染科收治的89例非耐药结核性脑膜炎患儿为研究对象。根据初治用药方案分为一线抗结核药物［异烟肼、利福平、吡嗪酰胺、乙胺丁醇（HRZE）］组和HRZE联合利奈唑胺（HRZEL）组，比较两种方案的效果及安全性，并分析利奈唑胺药物浓度与不良反应的关系。采用χ2检验和Mann-Whitney U检验进行组间比较。 结果： 89例非耐药的结核性脑膜炎患儿中，男53例、女36例，起病年龄4.6（1.4，9.6）岁。HRZEL组27例、HRZE组62例，治疗前HRZEL组干扰素阳性率低于HRZE组［64%（16/25）比92%（55/60），χ2=9.82，P<0.05］，脑脊液蛋白水平高于HRZE组［1.2（1.0，2.0）比0.8（0.4，1.4）g/L，Z=0.32，P<0.05］。强化期结束时，HRZEL组与HRZE组脑脊液蛋白、病原学阴转率比较差异均无统计学意义（均P>0.05）。44例高脑脊液蛋白（>1 g/L）患儿中，男25例、女19例，起病年龄6.7（3.0，11.8）岁，其中HRZEL组21例、HRZE组23例。治疗前HRZEL组与HRZE组干扰素阳性率和脑脊液蛋白水平比较差异均无统计学意义［62%（13/21）比87%（20/23），1.7（1.1，2.2）比1.5（1.2，1.9）g/L，χ2=3.67、Z=0.23，均P>0.05］。强化期结束时，HRZEL组与HRZE组脑脊液蛋白水平、病原学阴转率和影像学缓解率比较差异均无统计学意义（均P>0.05）。HRZEL组粒细胞减少、胃肠道症状及停或换药发生率均高于HRZE组［44%（12/27）比19%（12/62），7%（2/27）比0，33%（9/27）比3%（2/62），χ2=6.01、4.70、15.74，均P<0.05］。 结论： 对于非耐药的儿童结核性脑膜炎，HRZEL方案在病原学阴转及脑脊液改善上的效果与HRZE方案接近。利奈唑胺治疗儿童结核性脑膜炎的过程中需密切监测药物不良反应。.