In vitro assessment of 17 antimicrobial agents against clinical Mycobacterium avium complex isolates.

BACKGROUND: Recently, Mycobacterium avium complex (MAC) infections have been increasing, especially in immunocompromised and older adults. The rapid increase has triggered a global health concern due to limited therapeutic strategies and adverse effects caused by long-term medication. To provide more evidence for the treatment of MAC, we studied the in vitro inhibitory activities of 17 antimicrobial agents against clinical MAC isolates. RESULTS: A total of 111 clinical MAC isolates were enrolled in the study and they were identified as M. intracellulare, M. avium, M. marseillense, M. colombiense, M. yongonense, and two isolates could not be identified at the species level. MAC strains had relatively low (0-21.6%) resistance to clarithromycin, amikacin, bedaquiline, rifabutin, streptomycin, and clofazimine, and the resistant rates to isoniazid, rifampin, linezolid, doxycycline, and ethionamide were very high (72.1-100%). In addition, M. avium had a significantly higher resistance rate than that of M. intracellulare for ethambutol (92.3% vs 40.7%, P < 0.001), amikacin (15.4% vs 1.2%, P = 0.049), and cycloserine (69.2% vs 25.9%, P = 0.004). CONCLUSIONS: Our results supported the current usage of macrolides, rifabutin, and aminoglycosides in the regimens for MAC infection, and also demonstrated the low resistance rate against new drugs, such as clofazimine, tedizolid, and bedaquiline, suggesting the possible implementation of these drugs in MAC treatment.

Investigating a pulmonary Mycobacterium abscessus infection outbreak among elderly inpatients in the intensive care ward.

INTRODUCTION: Mycobacterium abscessus is an opportunistic nontuberculous mycobacteria pathogen; however, the prevalence of nosocomial and community infections is increasing. In January 2016, several bedridden inpatients in the intensive care unit of a hospital had positive sputum smears for acid-fast bacilli, suggesting a mycobacteria outbreak. METHODOLOGY: Acid-fast bacilli smear microscopy, isolation, and culturing were performed twice using sputa from each suspected intensive care unit inpatient (n = 13); in addition, medical history was obtained for each inpatient with suspected infection. Furthermore, environmental specimens were surveyed, collected, and cultured. We used DNA microarray chip analysis to identify positive mycobacterial isolates at the species level and performed whole-genome sequencing and phylogenetic tree construction. RESULTS: Seven inpatients had M. abscessus pulmonary infection, confirmed by 2 positive cultures; five of the inpatients had only one positive culture, while one had two negative cultures. Six of 13 ventilator condensate samples were mycobacterial culture-positive, identified as M. abscessus; the other environmental samples were negative. The M. abscessus isolates (15 sputa and 4 environmental samples) clustered together in the phylogenic analysis with only one single-nucleotide polymorphism difference. All patients were symptom-free after 8 months of multi-drug treatment. CONCLUSIONS: We confirmed a pulmonary M. abscessus outbreak among 12 bedridden patients in the intensive care unit through microbiological, molecular epidemiological, and environmental investigations. The possible infection source was contaminated ventilator condensate. This outbreak reemphasizes the importance of standardized ventilator maintenance and disinfection for preventing ventilator-associated pneumonia and is a reminder that nontuberculous mycobacteria-related ventilator-associated pneumonia is possible.

Identification and characterization of nontuberculous mycobacteria isolated from suspected pulmonary tuberculosis patients in eastern china from 2009 to 2019 using an identification array system.

OBJECTIVE: Nontuberculous mycobacteria (NTM) species are increasingly being isolated and have become a key factor affecting public health by causing pulmonary diseases. Most NTM species do not respond to conventional tuberculosis (TB) drugs. This study aimed to identify NTM isolated from suspected pulmonary TB patients from the Zhejiang province and analyze their distribution in the region. METHODS: A total of 1,113 NTM isolates from patients suspected to be suffering from acid-fast bacilli-positive tuberculosis were identified at the species level, using the CapitalBio Mycobacterium identification array and polymerase chain reaction amplification and sequencing of 16S-23S gene internal transcribed spacer (ITS), 16S rRNA, and hsp65. RESULTS: Of the 23,138 isolates, we identified 1,102 NTM (4.8%), mainly including Mycobacterium intracellulare (54.81%, 604/1,102), M. chelonae-M. abscessus (16.52%, 182/1,102), M. avium (13.16%, 145/1,102), M. kansasii (8.17%, 90/1,102), and M. gordonae (3.27%, 36/1,102). CONCLUSION: The distribution of NTM species observed in patients with suspected pulmonary tuberculosis provides guidance for the diagnosis and treatment of NTM pulmonary diseases.

In vitro Susceptibility of Nontuberculous Mycobacteria to Tedizolid.

Objective: Nontuberculous mycobacteria (NTM) can cause pulmonary and extrapulmonary diseases. Tedizolid (TZD) is a new oxazolidinone with in vitro activity against NTM such as Mycobacterium avium complex (MAC), Mycobacterium fortuitum, and Mycobacterium abscessus complex. The aim of this study was to evaluate the TZD susceptibility profiles of clinical isolates of NTM. Methods: The microdilution method was used to identify the minimum inhibitory concentration (MIC) of TZD and linezolid (LZD) for 133 clinical NTM isolates. Broth microdilution chequerboard assays were used to investigate the synergistic effects of TZD and three antibiotics on two reference isolates and eleven clinical isolates of NTM. Results: The TZD MIC50 and MIC90 for M. abscessus complex were 2 and 4 µg/mL, 16 and >32 µg/mL for MAC, respectively. TZD exhibited lower MICs than that of LZD for most NTM, which were positively correlated. Due to the high MIC values of TZD against MAC, it is necessary to conduct drug sensitivity tests before TZD administration. TZD-clarithromycin combination had synergistic response on M. abscessus complex in 3 of the 8 isolates, which lasted only 3-5 days. TZD-cefoxitin had synergistic effect against all five M. fortuitum isolates. Conclusion: Our study demonstrates that TZD had greater in vitro potency than LZD, and synergy studies suggested that TZD may be an important component of multi-drug treatment regimen.

Identification and characterization of nontuberculous mycobacteria isolated from suspected pulmonary tuberculosis patients in eastern china from 2009 to 2019 using an identification array system

Abstract Objective Nontuberculous mycobacteria (NTM) species are increasingly being isolated and have become a key factor affecting public health by causing pulmonary diseases. Most NTM species do not respond to conventional tuberculosis (TB) drugs. This study aimed to identify NTM isolated from suspected pulmonary TB patients from the Zhejiang province and analyze their distribution in the region. Methods A total of 1,113 NTM isolates from patients suspected to be suffering from acid-fast bacilli-positive tuberculosis were identified at the species level, using the CapitalBio Mycobacterium identification array and polymerase chain reaction amplification and sequencing of 16S-23S gene internal transcribed spacer (ITS), 16S rRNA, and hsp65. Results Of the 23,138 isolates, we identified 1,102 NTM (4.8%), mainly including Mycobacterium intracellulare (54.81%, 604/1,102), M. chelonae-M. abscessus (16.52%, 182/1,102), M. avium (13.16%, 145/1,102), M. kansasii (8.17%, 90/1,102), and M. gordonae (3.27%, 36/1,102). Conclusion The distribution of NTM species observed in patients with suspected pulmonary tuberculosis provides guidance for the diagnosis and treatment of NTM pulmonary diseases.