Impact on Macrolide Resistance of Genetic Diversity of Mycobacterium abscessus Species

Identification of Mycobacterium abscessus using the peaks of ribosomal protein L29, L30 and hemophore-related protein by MALDI-MS proteotyping

Mycobacteroides (Mycobacterium) abscessus, which causes a variety of infectious diseases in humans, is becoming detected more frequently in clinical specimens as cases are spreading worldwide. Taxonomically, M. abscessus is composed of three subspecies of M. abscessus subsp. abscessus, M. abscessus subsp. bolletii, and M. abscessus subsp. massiliense, with different susceptibilities to macrolides. In order to identify rapidly these three subspecies, we determined useful biomarker proteins, including ribosomal protein L29, L30, and hemophore-related protein, for distinguishing the subspecies of M. abscessus using the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) profiles. Thirty-three clinical strains of M. abscessus were correctly identified at the subspecies-level by the three biomarker protein peaks. This study ultimately demonstrates the potential of routine MALDI-MS-based laboratory methods for early identification and treatment for M. abscessus infections.

Nitric oxide-releasing prodrug for the treatment of complex Mycobacterium abscessus infections

Non-tuberculosis mycobacteria (NTM) can cause severe respiratory infection in patients with underlying pulmonary conditions, and these infections are extremely difficult to treat. In this report, we evaluate a nitric oxide (NO)-releasing prodrug [methyl tris diazeniumdiolate (MD3)] against a panel of NTM clinical isolates and as a treatment for acute and chronic NTM infections in vivo. Its efficacy in inhibiting growth or killing mycobacteria was explored in vitro alongside evaluation of the impact to primary human airway epithelial tissue. Airway epithelial tissues remained viable after exposure at concentrations of MD3 needed to kill mycobacteria, with no inherent toxic effect from drug scaffold after NO liberation. Resistance studies conducted via serial passage with representative Mycobacterium abscessus isolates demonstrated no resistance to MD3. When administered directly into the lung via intra-tracheal administration in mice, MD3 demonstrated significant reduction in M. abscessus bacterial load in both acute and chronic models of M. abscessus lung infection. In summary, MD3 is a promising treatment for complex NTM pulmonary infection, specifically those caused by M. abscessus, and warrants further exploration as a therapeutic.

Analysis of Phenotypic and Genotypic Susceptibility to Clarithromycin and Amikacin of Mycobacterium abscessus Complex Strains Isolated from Cystic Fibrosis Patients

Mycobacterium abscessus complex infections are ever on the rise. To curb their increasing evolution, we performed an in-depth study of 43 clinical isolates of cystic fibrosis patients obtained from 2009 to 2020. We identified their subspecies, uncovered their genotypic resistance profiles, characterised their antibiotic-resistant genes, and assessed their phenotypic antibiotic susceptibilities. The phenotypic and genotypic methods showed total agreement in terms of resistance to clarithromycin and amikacin. Of the 43 clinical strains, 28 belonged to M. abscessus subsp. abscessus (65.1%), 13 to M. abscessus subsp. massiliense (30.2%), and 2 to M. abscessus subsp. bolletii (4.6%). The resistant rates for clarithromycin and amikacin, the two main drugs against M. abscessus complex pulmonary infections, were 64.2% and 14.2%, respectively. We found three strains of M. abscessus subsp. abscessus that showed heteroresistance in the rrl and rrs genes, and these strains also presented double-resistance since they were macrolide- and aminoglycoside-resistant. M. abscessus subsp. abscessus showed a high minimum inhibitory concentration (MIC) and a resistant percentage larger than or equal to 88% to cefoxitin, ciprofloxacin, moxifloxacin, doxycycline, imipenem, and trimethoprim-sulfamethoxazole. These results show a panorama of the high resistance of Mycobacterium abscessus complex to current drugs for cystic fibrosis patients. Thus, other treatment methods are urgently needed.

Clinical characteristics and drug susceptibility profiles of Mycobacterium abscessus complex infection at a medical school in Thailand

OBJECTIVES

This study investigated the differences in epidemiological and clinical data, and antimicrobial susceptibilities among different subspecies of Mycobacterium abscessus complex (MABSC) clinical isolates at a medical school in Thailand.

METHODS

A total of 143 MABSC clinical isolates recovered from 74 patients were genotypically analyzed for erm(41), rrl, and rrs mutations, and antimicrobial susceptibilities were determined using a broth microdilution method. Patient characteristics and clinical outcomes were reviewed from the medical records.

RESULTS

Seventy-four patients were infected with 28/74 (37.8%) M. abscessus subspecies abscessus (MAB), 43/74 (58.1%) M. abscessus subsp. massiliense (MMA), and 3/74 (4.1%) M. abscessus subsp. bolletii (MBO). The clinical findings and outcomes were generally indistinguishable between the three subspecies. All three subspecies of MABSC clinical isolates exhibited high resistance rates to ciprofloxacin, doxycycline, moxifloxacin, TMP/SMX, and tobramycin. MAB had the highest resistance rates to clarithromycin (27.8%, 20/72) and amikacin (6.9%, 5/72) compared to MBO and MMA, with p < 0.001 and p = 0.004, respectively. In addition, the rough morphotype was significantly associated with resistance to amikacin (8.9%, 5/56), clarithromycin (26.8%, 15/56), and imipenem (76.8%, 43/56) (p < 0.001), whereas the smooth morphotype was resistant to linezolid (57.1%, 48/84) (p = 0.002). In addition, T28 of erm(41), rrl (A2058C/G and A2059C/G), and rrs (A1408G) mutations were detected in 87.4% (125/143), 16.1% (23/143), and 9.1% (13/143) of MABSC isolates, respectively.

CONCLUSIONS

Three MABSC subspecies caused a variety of infections in patients with different underlying comorbidities. The drug susceptibility patterns of the recent circulating MABSC strains in Thailand were different among the three MABSC subspecies and two morphotypes.