Itaconic acid inhibits nontuberculous mycobacterial growth in pH dependent manner while 4-octyl-itaconic acid enhances THP-1 clearance of nontuberculous mycobacteria in vitro.

Increasingly prevalent, nontuberculous mycobacteria (NTM) infections affect approximately 20% of people with cystic fibrosis (CF). Previous studies of CF sputum identified lower levels of the host metabolite itaconate in those infected with NTM. Itaconate can inhibit the growth of M. tuberculosis (MTB) in vitro via the inhibition of the glyoxylate cycle enzyme (ICL), but its impact on NTM is unclear. To test itaconic acid's (IA) effect on NTM growth, laboratory and CF clinical strains of Mycobacterium abscessus and Mycobacterium avium were cultured in 7H9 minimal media supplemented with 1-10 mM of IA and short-chain fatty acids (SCFA). M. avium and M. abscessus grew when supplemented with SCFAs, whereas the addition of IA (≥ 10 mM) completely inhibited NTM growth. NTM supplemented with acetate or propionate and 5 mM IA displayed slower growth than NTM cultured with SCFA and ≤ 1 mM of IA. However, IA's inhibition of NTM was pH dependent; as similar and higher quantities (100 mM) of pH adjusted IA (pH 7) did not inhibit growth in vitro, while in an acidic minimal media (pH 6.1), 1 to 5 mM of non-pH adjusted IA inhibited growth. None of the examined isolates displayed the ability to utilize IA as a carbon source, and IA added to M. abscessus isocitrate lyase (ICL) decreased enzymatic activity. Lastly, the addition of cell-permeable 4-octyl itaconate (4-OI) to THP-1 cells enhanced NTM clearance, demonstrating a potential role for IA/itaconate in host defense against NTM infections.

Treatment outcomes of Mycobacterium avium complex pulmonary disease according to disease severity.

Mycobacterium avium complex pulmonary disease (MAC-PD) requires long-term treatment. We analyzed the outcomes of 992 MAC-PD patients according to disease severity and compared the outcomes of intermittent and daily therapy for mild disease. Patients were divided into groups according to severity using the body mass index, age, cavity, erythrocyte sedimentation rate, and sex (BACES) system, and culture conversion rates were evaluated. We also evaluated the effects of intermittent treatment on the culture conversion rates in mild disease group. Using the BACES, 992 patients were divided into mild (n = 331), moderate (n = 503), and severe (n = 158) disease groups, and culture conversion at the end of treatment was achieved in 85% (282/331), 80% (403/503), and 61% (97/158), respectively. Differences in culture conversion among the severity groups were significant (p < 0.001). In patients with mild disease, culture conversion rates were similar between intermittent (84%, 166/198) and daily (87%, 116/133) treatment (p = 0.396), and intermittent antibiotic therapy did not negatively impact culture conversion (adjusted hazard ratio 1.08; confidence interval 0.83-1.41; p = 0.578). MAC-PD patients with mild disease had higher culture conversion rates. Daily and intermittent therapy yielded similar culture conversion rates for mild disease. Treatment strategies with lower pill burden may be applicable in mild MAC-PD.

In Vitro Resistance against DNA Gyrase Inhibitor SPR719 in Mycobacterium avium and Mycobacterium abscessus.

The aminobenzimidazole SPR719 targets DNA gyrase in Mycobacterium tuberculosis. The molecule acts as inhibitor of the enzyme's ATPase located on the Gyrase B subunit of the tetrameric Gyrase A2B2 protein. SPR719 is also active against non-tuberculous mycobacteria (NTM) and recently entered clinical development for lung disease caused by these bacteria. Resistance against SPR719 in NTM has not been characterized. Here, we determined spontaneous in vitro resistance frequencies in single step resistance development studies, MICs of resistant strains, and resistance associated DNA sequence polymorphisms in two major NTM pathogens Mycobacterium avium and Mycobacterium abscessus. A low-frequency resistance (10-8/CFU) was associated with missense mutations in the ATPase domain of the Gyrase B subunit in both bacteria, consistent with inhibition of DNA gyrase as the mechanism of action of SPR719 against NTM. For M. abscessus, but not for M. avium, a second, high-frequency (10-6/CFU) resistance mechanism was observed. High-frequency SPR719 resistance was associated with frameshift mutations in the transcriptional repressor MAB_4384 previously shown to regulate expression of the drug efflux pump system MmpS5/MmpL5. Our results confirm DNA gyrase as target of SPR719 in NTM and reveal differential resistance development in the two NTM species, with M. abscessus displaying high-frequency indirect resistance possibly involving drug efflux. IMPORTANCE Clinical emergence of resistance to new antibiotics affects their utility. Characterization of in vitro resistance is a first step in the profiling of resistance properties of novel drug candidates. Here, we characterized in vitro resistance against SPR719, a drug candidate for the treatment of lung disease caused by non-tuberculous mycobacteria (NTM). The identified resistance associated mutations and the observed differential resistance behavior of the two characterized NTM species provide a basis for follow-up studies of resistance in vivo to further inform clinical development of SPR719.

Targeting emerging Mycobacterium avium infections: perspectives into pathways and antimicrobials for future interventions.

Mycobacterium avium is an emerging opportunistic pathogen, globally. Infections caused by M. avium are laborious to treat and could result in drug resistance. This review discusses the importance of many factors including the cell wall in M. avium pathogenesis, since this unique structure modulates the pathogen's ability to thrive in various hosts and environmental niches including conferring resistance to killing by antimicrobials. More research efforts in future are solicited to develop novel therapeutics targeting M. avium. The complete eradication of M. avium infection in immunocompromised individuals would need a deeper understanding of the source of infection, unique underlying mechanisms and its uncharacterized pathways. This could, perhaps in future, hold the key to target and treat M. avium more effectively.

Copper(II) complexes based on thiosemicarbazone ligand: Preparation, crystal structure, Hirshfeld surface, energy framework, antiMycobacterium activity, in silico and molecular docking studies.

Considering the promising previous results on the remarkable activity exhibited by cobalt(III) and manganese(II) thiosemicarbazone compounds as antibacterial agents, the present study aimed to prepare and then evaluate the antibacterial activity of two different types of Cu(II) complexes based on a 2-acetylpyridine-N(4)-methyl-thiosemicarbazone ligand (Hatc-Me), a monomer complex [CuCl(atc-Me)] and a novel dinuclear complex [{Cu(µ-atc-Me)}2µ-SO4]. The compounds were characterized by infrared spectra, ultraviolet visible and CHN elemental analysis. In addition, the crystalline structures of the complexes were determined by single-crystal X-ray diffraction. In both cases, the Schiff base ligand coordinated in a tridentate mode via the pyridine nitrogen, imine nitrogen and sulfur atoms. The two Cu(II) atoms in the dimer are five coordinate, consisting of three NNS-donor atoms from the thiosemicarbazone ligand connected by a sulfate bridge. The Hirshfeld surface and energy framework of the complexes were additionally analyzed to verify the intermolecular interactions. The biological activity of the Cu(II) salts, the free ligand and its Cu(II) complexes was evaluated against six strains of mycobacteria including Mycobacterium tuberculosis. The complexes showed promising results as antibacterial agents for M. avium and M. tuberculosis, which ranged from 6.12 to 12.73 µM. Furthermore, molecular docking analysis was performed and the binding energy of the docked compound [{Cu(µ-atc-Me)}2µ-SO4] with M. tuberculosis and M. avium strains were extremely favorable (-11.11 and - 14.03 kcal/mol, respectively). The in silico results show that the complexes are potential candidates for the development of new antimycobacterial drugs.

Difference in drug susceptibility distribution and clinical characteristics between Mycobacterium avium and Mycobacterium intracellulare lung diseases in Shanghai, China.

Introduction. Mycobacterium avium complex (MAC) has been reported as the most common aetiology of lung disease involving nontuberculous mycobacteria.Hypothesis. Antimicrobial susceptibility and clinical characteristics may differ between Mycobacterium avium and Mycobacterium intracellulare.Aim. We aimed to evaluate the differences in antimicrobial susceptibility profiles between two major MAC species (Mycobacterium avium and Mycobacterium intracellulare) from patients with pulmonary infections and to provide epidemiologic data with minimum inhibitory concentration (MIC) distributions.Methodology. Between January 2019 and May 2020, 45 M. avium and 242 M. intracellulare isolates were obtained from Shanghai Pulmonary Hospital. The demographic and clinical characteristics of patients were obtained from their medical records. The MICs of 13 antimicrobials were determined for the MAC isolates using commercial Sensititre SLOWMYCO MIC plates and the broth microdilution method, as recommended by the Clinical and Laboratory Standards Institute (CLSI; Standards M24-A2). MIC50 and MIC90 values were derived from the MIC distributions.Results. M. intracellulare had higher resistance rates than M. avium for most tested antimicrobials except clarithromycin, ethambutol, and ciprofloxacin. Clarithromycin was the most effective antimicrobial against both the M. avium (88.89 %) and M. intracellulare (91.32 %) isolates, with no significant difference between the species (P=0.601). The MIC90 of clarithromycin was higher for M. avium (32 µg ml-1) than M. intracellulare (8 µg ml-1). The MIC50 of rifabutin was more than four times higher for M. intracellulare (1 µg ml-1) than M. avium (≤0.25 µg ml-1). The percentages of patients aged >60 years and patients with sputum, cough, and cavitary lesions were significantly higher than among patients with M. intracellulare infection than M. avium infections.Conclusions. The pulmonary disease caused by distinct MAC species had different antimicrobial susceptibility, symptoms, and radiographic findings.

N-acetyl-cysteine mediates protection against Mycobacterium avium through induction of human ß-defensin-2 in a mouse lung infection model.

Mycobacterium avium complex is a causative organism for refractory diseases. In this study, we examined the effects of N-acetyl-cysteine on M. avium infection in vitro and in vivo. N-acetyl-cysteine treatment suppressed the growth of M. avium in A549 cells in a concentration-dependent manner. This effect was related to the induction of the antibacterial peptide human ß-defensin-2. In a mouse model, N-acetyl-cysteine treatment significantly reduced the number of bacteria in the lungs and induced murine ß-defensin-3. In interleukin-17-deficient mice, the effects of N-acetyl-cysteine disappeared, indicating that these mechanisms may be mediated by interleukin-17. Moreover, an additional reduction in bacterial load was observed in mice administered N-acetyl-cysteine in combination with clarithromycin. Our findings demonstrate the potent antimycobacterial effects of N-acetyl-cysteine against M. avium by inducing antimicrobial peptide, suggesting that N-acetyl-cysteine may have applications as an alternative to classical treatment regimens.

Redox homeostasis as a target for new antimycobacterial agents.

Despite early treatment with antimycobacterial combination therapy, drug resistance continues to emerge. Maintenance of redox homeostasis is essential for Mycobacterium avium (M. avium) survival and growth. The aim of the present study was to investigate the antimycobacterial activity of two pro-glutathione (pro-GSH) drugs that are able to induce redox stress in M. avium and to modulate cytokine production by macrophages. Hence, we investigated two molecules shown to possess antiviral and immunomodulatory properties: C4-GSH, an N-butanoyl GSH derivative; and I-152, a prodrug of N-acetyl-cysteine (NAC) and ß-mercaptoethylamine (MEA). Both molecules showed activity against replicating M. avium, both in the cell-free model and inside macrophages. Moreover, they were even more effective in reducing the viability of bacteria that had been kept in water for 7 days, proving to be active both against replicating and non-replicating bacteria. By regulating the macrophage redox state, I-152 modulated cytokine production. In particular, higher levels of interferon-gamma (IFN-γ), interleukin 1 beta (IL-1ß), IL-18 and IL-12, which are known to be crucial for the control of intracellular pathogens, were found after I-152 treatment. Our results show that C4-GSH and I-152, by inducing perturbation of redox equilibrium, exert bacteriostatic and bactericidal activity against M. avium. Moreover, I-152 can boost the host response by inducing the production of cytokines that serve as key regulators of the Th1 response.

Different clinical features of patients with pulmonary disease caused by various Mycobacterium avium-intracellulare complex subspecies and antimicrobial susceptibility.

OBJECTIVES: Characteristics of the Mycobacterium avium-intracellulare complex pulmonary disease (MAC-PD) caused by distinct subspecies remain uncertain. METHODS: This study was conducted from 2013-2015 in three hospitals in Taiwan. RESULTS: Among the 144 patients with MAC-PD, 57 (39.6%), 37 (25.7%), 37 (25.7%), and 13 (9.0%) were infected with Mycobacterium intracellulare subspecies intracellulare (MIsI), Mycobacterium avium subspecies hominissuis (MAsH), Mycobacterium intracellulare subspecies chimaera (MIsC), and others, respectively. Patients with MAsH-PD were younger (p = 0.010) with higher human immunodeficiency virus infection rates (27.0%, 0.0%, 0.0%, and 7.7% for MAsH-PD, MIsC-PD, MIsI-PD, and others, respectively; p < 0.001). Twenty-two (15.3%) patients reported spontaneous culture-negative conversion, but 15 (10.4%) and 33 (22.9%) patients developed radiographic progression and unfavorable outcomes, especially MAsH-PD. The susceptibility rates to clarithromycin and inhaled amikacin were both 98.6%. MAsH demonstrated the lowest rate of resistance to moxifloxacin (66.7%, 97.3%, 89.1%, and 92.3% for MAsH-PD, MIsC-PD, MIsI-PD, and others, respectively; p = 0.001) and MIsI isolates had the highest rate of resistance to intravenous amikacin (25%, 13.5%, 38.2%, and 15.4% for MAsH-PD, MIsC-PD, MIsI-PD, and others, respectively; p = 0.024). CONCLUSIONS: Pulmonary disease caused by distinct MAC subspecies had different outcomes and drug susceptibility. The local prevalence of species needs to be monitored.

Steffimycin E, a new anti-mycobacterial agent against Mycobacterium avium complex, produced by Streptomyces sp. OPMA02852.

The marine actinomycete strain OPMA02852, identified as the genus Streptomyces, was found to produce anti-mycobacterial compounds against Mycobacterium avium complex (MAC). One new compound, designated as steffimycin E (1), was isolated together with three known steffimycins (steffimycin (2), 10-dihydrosteffimycin (3), and 8-demethoxysteffimycin (4)) from the culture broth of this producing microorganism by solvent extraction, ODS column chromatography, and preparative HPLC. Compound 1 has a tetracyclic quinone structure with a sugar moiety. Compound 1 exhibited anti-mycobacterial activity against M. intracellulare, M. bovis BCG, and M. smegmatis.

Synergistic Activity of Clofazimine and Clarithromycin in an Aerosol Mouse Model of Mycobacterium avium Infection.

Infections with nontuberculous mycobacteria (NTM) have a poor prognosis in patients with underlying respiratory diseases. Clofazimine (CFZ) showed both experimental and clinical promising results against clinically relevant NTM. However, there are no data on CFZ in combination with the current recommended treatment; therefore, we aimed to study its in vivo activity in an aerosol mouse model of Mycobacterium avium In an aerosol infection BALB/c mouse model using M. avium strain Chester, we treated 58 mice with four combinations of rifampin (RIF) at 10 mg/kg, CFZ at 25 mg/kg, and clarithromycin (CLR) and ethambutol (EMB) at 100 mg/kg. Treatment efficacy was assessed on the basis of lung CFU counts after 2 (M2) and 4 (M4) months of treatment. At M2, CLR-RIF-EMB was slightly but significantly more efficient than CFZ-RIF-EMB (3.02 ± 0.12 versus 3.55 ± 0.28, respectively, P < 0.01), whereas CLR-CFZ-EMB and CLR-CFZ-RIF-EMB dramatically decreased lung CFU counts by 4.32 and 4.47 log10, respectively, compared to untreated group. At M4, CLR-RIF-EMB was significantly more efficient than CFZ-RIF-EMB (2 ± 0.53 versus 2.66 ± 0.22, respectively, P = 0.01). The addition of CLZ to CLR dramatically decreased the lung CFU count, with CFU counts 5.41 and 5.79 log10 lower in the CLR-CFZ-EMB and CLR-CFZ-RIF-EMB groups, respectively, than in the untreated group. The addition of CFZ to CLR seems to improve the efficacy of CLR as early as M2 and was confirmed at M4. CFZ, in addition to RIF and EMB, on the other hand, is less effective than CLR-RIF-EMB. These results need to be confirmed by similar studies along with CFZ potential for shortening treatment.

Brazilian Green Propolis: Chemical Composition of Essential Oil and Their In Vitro Antioxidant, Antibacterial and Antiproliferative Activities

Abstract Propolis is a resinous substance collected and processed by Apis mellifera from parts of plants, buds and exudates. In Minas Gerais (MG) state, Brazil, green propolis is produced from the collection of resinous substance found in shoot apices of Baccharis dracunculifolia. This paper aims to investigate the chemical composition and in vitro antioxidant, anti-Helicobacter pylori, antimycobacterial and antiproliferative activities of essential oil (EO) from Brazilian green propolis (BGP-EO). The oil showed high antibacterial activity against H. pylori (MIC = 6.25 µg/mL), Mycobacterium avium (MIC = 62.5 µg/mL) and M. tuberculosis (MIC = 64 µg/mL). Its antioxidant activity was evaluated in vitro by both DPPH (IC50 = 23.48 µg/mL) and ABTS (IC50 = 32.18 µg/mL) methods. The antiproliferative activity in normal (GM07492A, lung fibroblasts) and tumor cell lines (MCF-7, HeLa and M059J) was analyzed by the XTT assay. BGP-EO showed inhibition of normal cell growth at 68.93 ± 2.56 µg/mL. Antiproliferative activity was observed against human tumor cell lines, whose IC50 values were 56.17, 66.43 and -65.83 µg/mL for MCF-7, HeLa and M059J cells, respectively. Its major constituents, which were determined by GC-FID and GC-MS, were carvacrol (20.7 %), acetophenone (13.5 %), spathulenol (11.0 %), (E)-nerolidol (9.7 %) and β-caryophyllene (6.2 %). These results showed the effectiveness of BGP-EO as a natural product which has promising biological activities.

Amphiphilic Polymethyloxazoline-Polyethyleneimine Copolymers: Interaction with Lipid Bilayer and Antibacterial Properties.

Polycations, mimicking activity of antibacterial peptides, belong to an important class of molecules investigated as a support or as an alternative to antibiotics. In this work, studies of modified linear amphiphilic statistical polymethyloxazoline (PMOX) and polyethyleneimine copolymers (PMOX_PEI) series are presented. Variation of PEI content in the structure results in controllable changes of polymeric aggregates zeta potential. The structure with the highest positive charge shows the best antimicrobial activity, well visible in tests against model Gram-positive and Gram-negative bacteria, fungi, and mycobacterium strains. The polymer toxicity is evaluated with MTT and hemolysis assay as a reference. Quartz crystal microbalance (QCM-D) is used to investigate interaction between polycations and a model lipid membrane. Polymer activity correlates well with molecular structure, showing that amphiphilic component is altering polymer behavior in contact with the lipid bilayer.

Moxifloxacin resistance and genotyping of Mycobacterium avium and Mycobacterium intracellulare isolates in Japan.

BACKGROUND: Although fluoroquinolones are considered as alternative therapies of pulmonary Mycobacterium avium complex (MAC) disease, the association between fluoroquinolone resistance and MAC genotypes in clinical isolates from individuals not previously treated for MAC infection is not fully clear. METHODS: Totals of 154 M. avium isolates and 35 Mycobacterium intracellulare isolates were obtained from treatment-naïve patients with pulmonary MAC disease at the diagnosis of MAC infection at 8 hospitals in Japan. Their susceptibilities of moxifloxacin were determined by broth microdilution methods. Moxifloxacin-resistant isolates were examined for mutations of gyrA and gyrB. Variable numbers of tandem repeats (VNTR) assay was performed using 15 M. avium VNTR loci and 16 M. intracellulare VNTR loci. RESULTS: Moxifloxacin susceptibility was categorized as resistant and intermediate for 6.5% and 16.9%, respectively, of M. avium isolates and 8.6% and 17.1% of M. intracellulare isolates. Although the isolates of both species had amino acid substitutions of Thr 96 and Thr 522 at the sites corresponding to Ser 95 in the M. tuberculosis GyrA and Gly 520 in the M. tuberculosis GyrB, respectively, these substitutions were observed irrespective of susceptibility and did not confer resistance. The VNTR assays showed revealed three clusters among M. avium isolates and two clusters among M. intracellulare isolates. No significant differences in moxifloxacin resistance were observed among these clusters. CONCLUSIONS: Although resistance or intermediate resistance to moxifloxacin was observed in approximately one-fourth of M. avium and M. intracellulare isolates, this resistance was not associated with mutations in gyrA and gyrB or with VNTR genotypes.

Modifications on C6 and C7 Positions of 3-Phenylquinolone Efflux Pump Inhibitors Led to Potent and Safe Antimycobacterial Treatment Adjuvants.

Nontuberculous mycobacteria (NTM) are ubiquitous microbes belonging to the Mycobacterium genus. Among all NTM pathogens, M. avium is one of the most frequent agents causing pulmonary disease, especially in immunocompromised individuals and cystic fibrosis patients. Recently, we reported the first ad hoc designed M. avium efflux pump inhibitor (EPI; 1b) able to strongly boost clarithromycin (CLA) MIC against different M. avium strains. Since the 3-phenylquinolone derivative 1b suffered from toxicity issues toward human macrophages, herein we report a two-pronged medicinal chemistry workflow for identifying new potent and safe NTM EPIs. Initially, we followed a computational approach exploiting our pharmacophore models to screen FDA approved drugs and in-house compounds to identify "ready-to-use" NTM EPIs and/or new scaffolds to be optimized in terms of EPI activity. Although nicardipine 2 was identified as a new NTM EPI, all identified molecules still suffered from toxicity issues. Therefore, based on the promising NTM EPI activity of 1b, we undertook the design, synthesis, and biological evaluation of new 3-phenylquinolones differently functionalized at the C6/C7 as well as N1 positions. Among the 27 synthesized 3-phenylquinolone analogues, compounds 11b, 12b, and 16a exerted excellent NTM EPI activity at concentrations below their CC50 on human cells, with derivative 16a being the most promising compound. Interestingly, 16a also showed good activity in M. avium-infected macrophages both alone as well as in combination with CLA. The antimycobacterial activity observed for 16a only when tested in the ex vivo model suggests a high therapeutic potential of EPIs against M. avium, which seems to need functional efflux pumps to establish intracellular infections.

Chronic Mycobacterium avium skin and soft tissue infection complicated with scalp osteomyelitis possibly secondary to anti-interferon-γ autoantibody formation.

BACKGROUND: Nontuberculous mycobacterial (NTM) disease is commonly an opportunistic infection frequently found in immunocompromised individuals, but sometimes can also be found in the immunocompetent hosts, especially in East Asians. The NTM separation rate in China is increasing, which reminds us to focus on NTM infections in immunocompromised populations. CASE PRESENTATION: A 43-year-old woman with a recurrent fever for more than 8-month and a right forehead surgical wounds unhealed for more than 6-month was admitted to our hospital on February 22, 2018. On arrival, several elliptic ulcers were obvious on the right forehead with pus and fibrin exudation, and the skin around the lesions was tender, reddish, no sense of fluctuation. The result of HIV serology test was negative. CD4+ T cell count was normal and tuberculosis antibody was negative. CT of the chest and head showed bone destruction. Skin biopsy on the right forehead was performed on March 13, 2018, and pathological examination of the excisional biopsy specimen found inflammatory granuloma and suppurative inflammatory changes. Broad-spectrum antibiotics were treated but the effect seemed discontent. Then debridement and skin grafting were performed on the right frontal ulcer under general anesthesia on April 3, 2018. The skin tissue culture that resected on March 13, 2018 found Nontuberculous mycobacteria grown after 78 days, so clarithromycin, ethambutol, protionamide, and amoxicillin clavulanate potassium were prescribed for anti-nontuberculous mycobacteria treatment beginning on May 31, 2018. In reviewing the case, Mycobacterium avium (M. avium) was identified in the skin tissue resected on April 3, 2018 by polymerase chain reaction (PCR) and the serum test of anti-interferon-γ autoantibodies was positive. CONCLUSIONS: This is a case report of "Mycobacterium avium SSTI (skin and soft tissue infection) and OM (osteomyelitis) with possible secondary immunodeficiency syndrome induced by anti-interferon-γ autoantibody".

Tuberculosis and atypical mycobacterial infections in ruxolitinib-treated patients with primary or secondary myelofibrosis or polycythemia vera.

Ruxolitinib is a JAK-1/JAK-2 inhibitor indicated for the treatment of polycythemia vera and primary or secondary myelofibrosis. Only one patient (0.2%) was diagnosed with tuberculosis among the 485 patients receiving ruxolitinib in the four pivotal trials. Fourteen cases of tuberculosis have since been reported. We observed two (3%) mycobacterial infections (one due to Mycobacterium tuberculosis and one due to Mycobacterium avium complex) in our cohort of 65 patients receiving ruxolitinib. This observation suggests that the rate of mycobacterial infection might be higher than that observed in the pivotal trials and that atypical mycobacterial infections can also occur.

Differential drug susceptibility patterns of Mycobacterium chimaera and other members of the Mycobacterium avium-intracellulare complex.

OBJECTIVES: To determine MIC distributions for Mycobacterium chimaera, Mycobacterium intracellulare, Mycobacterium colombiense and Mycobacterium avium, and to derive tentative epidemiological cut-off (ECOFF) values. METHODS: A total of 683 bacterial isolates (M. chimaera, n = 203; M. intracellulare, n = 77; M. colombiense, n = 68; M. avium, n = 335) from 627 patients were tested by broth microdilution according to CLSI protocol M24-A2 on Sensititre RAPMYCOI plates. MICs were interpreted based on CLSI breakpoints for clarithromycin, and tentative breakpoints for amikacin, moxifloxacin and linezolid. Tentative ECOFFs were determined by visual approximation and the ECOFFinder algorithm. RESULTS: Modal MIC, MIC50 and MIC90 values were within ± one dilution step from the respective aggregated data set for 47/48 (97.9%), 48/48 (100%) and 48/48 (100%) species-drug combinations. Clarithromycin wild-type populations were mostly classified as susceptible (MIC90 4-8 mg/L; S ≤8 mg/L). Rifabutin MICs were lower than those of rifampicin. Tentative moxifloxacin, linezolid and amikacin breakpoints split wild-type populations. No ECOFFs could be set for rifampicin, ethambutol, ciprofloxacin, isoniazid, trimethoprim/sulfamethoxazole and doxycycline because of truncation of MIC distributions. Agreement between the visually determined and the modelled 97.5% ECOFFs was 90.9%. All 99.0% ECOFFs were one titre step higher than by visual approximation. CONCLUSIONS: Drug susceptibility patterns of M. chimaera are comparable to those of closely related species. Except for clarithromycin, breakpoints for Mycobacterium avium-intracellulare complex should be re-evaluated. Statistical determination of the 99.0% ECOFF may be superior to visual approximation.