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UNASSIGNED: To investigate the prevalence of Mycobacterium abscessus complex (MABC), drug resistance characteristics, and the relationship between clarithromycin (CLA) susceptibility and MABC genotype in Chongqing, China.
UNASSIGNED: A total of 434 NTM patient isolates were collected between October 2018 and October 2019. Isolates confirmed to be non-tuberculous mycobacteria (NTM) were tested for minimal inhibitory concentrations of antimicrobial agents. In addition, rrl and erm(41) gene sequences were used to analyze the acquired macrolide resistance and inducible macrolide resistance.
UNASSIGNED: Overall, 17 different NTM species were detected, of which M. abscessus (22.6 %, 91/403) was most prevalent. Amikacin, CLA, azithromycin and cefoxitin exhibited potent activities against MABC organisms, but no significant differences were observed in drug resistance rates between M. abscessus and M. massiliense (P > 0.05). On day 3 of culture, the acquired resistance rate against CLA was 7.4 % (9/121). Of 41 MABC isolates with inducible CLA resistant, 95.1 % (39/41) isolates belonged to the erm(41) T28 sequevar, while the remaining 4.9 % (2/41) possessed the M. massiliense genotype. All erm(41) C28 sequevar isolates were sensitive to CLA on day3 and day 14 of culture. Meanwhile, of the 5 erm(41) T28 isolates with acquired resistance, all possessed rrl 2058/2059 mutations, including 3 isolates with A2058C mutation and 2 isolates with A2059G mutation. While 2 of the 4 M. massiliense isolates with acquired resistance possessed the A2059G mutation, and one isolate possessed the A2058G mutation.
UNASSIGNED: Erm(41) and rrl gene could serve as useful markers for predicting macrolide susceptibility of MABC complex isolates.

This study evaluated the antimicrobial potency of the combination of isepamicin (ISP) for Mycobacterium abscessus species (MABS). 34 clinical MABS strains were isolated from clinical samples. Of them, 11 (32.4 %) were M. abscessus subsp. abscessus (Mab), 22 (64.7 %) were M. abscessus subsp. massiliense (Mma), and one (2.9 %) was M. abscessus subsp. bolletii (Mbo). We compared susceptibility to sitafloxacin (STFX)-ISP and clarithromycin (CLR)-ISP combinations with those of the antimicrobial agents alone, and synergistic effects were observed in 41.2 % and 17.6 % when treated with STFX-ISP and CLR-ISP. By hierarchical cluster analysis, the isolates divided into treatment-sensitive and treatment-resistant groups. Non-Mma or rough colony isolates were significantly likely to belong to the treatment-sensitive group (p = 0.024, p < 0.001, respectively). These results suggest that the ISP-containing combination could be a new therapeutic strategy for MABS, especially in cases of non-Mma: treatment-refractory subspecies, and rough morphotypes: high-virulence morphotypes.

The Mycobacterium chelonae species and the M. avium and M. abscessus complexes are emerging pathogens that cause mycobacteriosis. Treatment depends on the species and subspecies identified. The drugs of choice are macrolides and aminoglycosides. However, due to the resistance identified to these drugs, determining the microbe’s sensitivity profile will allow clinicians to improve the understanding of the prognosis and evolution of these pathologies.
To describe the macrolide and aminoglycoside susceptibility profile of cultures identified by Colombia’s Laboratorio Nacional de Referencia de Mycobacteria from 2018 to 2022, as Mycobacterium avium complex, M. abscessus complex, and M. chelonae. Materials and methods. This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method.
This descriptive study exposes the susceptibility profile to macrolides and aminoglycosides of cultures identified as M. avium complex, M. abscessus complex, and M. chelonae using the GenoType® NTM-DR method.
We identified 159 (47.3 %) cultures as M. avium complex, of which 154 (96.9 %) were sensitive to macrolides, and 5 (3.1 %) were resistant; all were sensitive to aminoglycosides. From the 125 (37.2 %) cultures identified as M. abscessus complex, 68 (54.4 %) were sensitive to macrolides, 57 (45.6 %) were resistant to aminoglycosides, and just one (0.8 %) showed resistance to aminoglycosides. The 52 cultures (15.5 %) identified as M. chelonae were sensitive to macrolides and aminoglycosides.
The three studied species of mycobacteria have the least resistance to Amikacin. Subspecies identification and their susceptibility profiles allow the establishment of appropriate treatment schemes, especially against M. abscessus.
Introducción. Mycobacterium chelonae y los complejos Mycobacterium avium y M. abscessus, son agentes patógenos emergentes causantes de micobacteriosis. El tratamiento de esta infección depende de la especie y la subespecie identificadas. Los fármacos de elección son los macrólidos y aminoglucósidos, contra los cuales se ha reportado resistencia; por esta razón, el determinar el perfil de sensibilidad le permite al médico tratante comprender mejor el pronóstico y la evolución de estas infecciones. Objetivo. Describir los perfiles de sensibilidad ante macrólidos y aminoglucósidos, de los cultivos identificados como complejo Mycobacterium avium, complejo M. abscessus o especie M. chelonae, en el Laboratorio Nacional de Referencia de Micobacterias durante los años 2018 a 2022. Materiales y métodos. Se llevó a cabo un estudio descriptivo del perfil de sensibilidad a macrólidos y aminoglucósidos, de los cultivos identificados como complejo M. avium, complejo M. abscessus o M. chelonae, mediante la metodología GenoType® NTM-DR. Resultados. Los cultivos del complejo M. avium fueron 159 (47,3 %), de los cuales, 154 (96,9 %) fueron sensibles y 5 (3,1 %) resistentes a los macrólidos; todos fueron sensibles a los aminoglucósidos. Del complejo M. abscessus se estudiaron 125 (37,2 %) cultivos, 68 (54,4 %) resultaron sensibles y 57 (45,6 %) resistentes a los macrólidos; solo un cultivo (0,8 %) fue resistente a los aminoglucósidos. De M. chelonae se analizaron 52 cultivos (15,5 %), todos sensibles a los macrólidos y aminoglucósidos. Conclusiones. En las tres especies de micobacterias estudiadas, la resistencia contra la amikacina fue la menos frecuente. La identificación de las subespecies y los perfiles de sensibilidad permiten instaurar esquemas de tratamiento adecuados, especialmente en las micobacteriosis causadas por M. abscessus.

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Mycobacteroides abscessus (Mab or Mycobacterium abscessus) is a fast-growing mycobacterium that is ubiquitous in the environment and can cause opportunistic disease in people with lung comorbidity and immunodeficiency. There are no Food and Drug Administration-approved drugs for this disease, and repurposed antibiotics have a poor microbiological response. To address the need for effective new antibiotics, we determined the efficacy of epetraborole (EBO) against three Mab clinical isolates in a mouse model of lung Mab infection. Reduction in lung Mab burden over 4 weeks of treatment was the study end point. EBO was administered orally once daily at doses of 25 and 50 mg/kg, which achieved exposures approximating the once-daily dosing of 250 mg and 500 mg, respectively, in humans. EBO administration led to a gradual reduction in the lung Mab burden. After 4 weeks of treatment, the efficacies of 25 and 50 mg/kg EBO against isolates ATCC 19977 and M9501 were comparable. However, against isolate M9530, 50 mg/kg EBO was more efficacious than 25 mg/kg and comparable with parenteral imipenem, one of the most efficacious antibiotics against Mab. We also undertook a dose-ranging study by evaluating the efficacies of once-daily oral administration of 0.5, 5, 10, 25, and 100 mg/kg EBO against M9501 over 4 weeks. Once-daily oral 100 mg/kg EBO was as effective as twice-daily 100 mg/kg imipenem injection. Our study suggests that EBO could address the unmet need for effective oral treatment options for Mab lung disease, given the high rates of Mab drug resistance and limited tolerable intravenous options.

The incidence of nontuberculous mycobacteria infections has surged over recent decades. Mycobacterium abscessus is one example that can present unique diagnostic challenges due to its variable antibiotic resistance profile and its clinical similarities to Actinomycoses israelii in postodontogenic infections. The authors report a case of a 22-year-old healthy female presenting with bilateral mandibular nodules following wisdom teeth extraction. After a presumptive diagnosis of actinomycosis, cultures revealed a Mycobacterium abscessus infection susceptible to macrolides. Magnetic resonance imaging depicted bilateral sinus tracts without osteomyelitis. The patient opted for dual antibiotic therapy, consisting of azithromycin and omadacycline, without surgical intervention. Given her clinical and radiographic improvement after three months, the patient elected to continue dual antibiotic therapy for 12 months with appropriate clinical and radiographic monitoring. This case underscores the importance of early microbial cultures to guide diagnosis and treatment, particularly considering Mycobacterium abscessus\'s similarities with other pathogens and its variable macrolide susceptibility due to genetic mutations. As highlighted in this case, clinicians must successfully differentiate between and appropriately treat various nontuberculous mycobacteria.

Mycobacterium abscessus infections are emerging in cystic fibrosis patients, and treatment success rate in these patients is only 33% due to extreme antibiotic resistance. Thus, new treatment options are essential. An interesting target could be Lsr2, a nucleoid-associated protein involved in mycobacterial virulence. Zafirlukast is a Food and Drug Administration (FDA)-approved drug against asthma that was shown to bind Lsr2. In this study, zafirlukast treatment is shown to reduce M. abscessus growth, with a minimal inhibitory concentration of 16 µM and a bactericidal concentration of 64 µM in replicating bacteria only. As an initial response, DNA condensation, a known stress response of mycobacteria, occurs after 1 h of treatment with zafirlukast. During continued zafirlukast treatment, the morphology of the bacteria alters and the structural integrity of the bacteria is lost. After 4 days of treatment, reduced viability is measured in different culture media, and growth of M. abscessus is reduced in a dose-dependent manner. Using transmission electron microscopy, we demonstrated that the hydrophobic multilayered cell wall and periplasm are disorganized and ribosomes are reduced in size and relocalized. In summary, our data demonstrate that zafirlukast alters the morphology of M. abscessus and is bactericidal at 64 µM. The bactericidal concentration of zafirlukast is relatively high, and it is only effective on replicating bacteria but as zafirlukast is an FDA-approved drug, and currently used as an anti-asthma treatment, it could be an interesting drug to further study in in vivo experiments to determine whether it could be used as an antibiotic for M. abscessus infections.

Mycobacterium abscessus pulmonary infections are increasingly problematic, especially for immunocompromised individuals and those with underlying lung conditions. Currently, there is no reliable standardized treatment, underscoring the need for improved preclinical drug testing. We present a simplified immunosuppressed mouse model using only four injections of cyclophosphamide, which allows for sustained M. abscessus lung burden for up to 16 days. This model proved effective for antibiotic efficacy evaluation, as demonstrated with imipenem or amikacin.