BackgroundPulmonary non-tuberculous mycobacteria (NTM) infection has become a public health concern in China and around the world. The objective of this study was to describe the longitudinal changes in the frequency and diversity of NTM in northern China.MethodsWe retrospectively analyzed data on mycobacterium species in Beijing Chest Hospital from January 2014 to December 2021. The isolates were identified to species level by targeted DNA sequencing.ResultsAfter excluding duplicates, 1,755 NTM strains were analyzed, which were from 27 provinces in China over 8 years. Among all mycobacteria, the proportion of NTM increased each year, from 4.24% in 2014 to 12.68% in 2021. Overall, 39 different NTM species were identified, including 23 slow growing mycobacteria (SGM) and 16 rapid growing mycobacteria (RGM). The most common species were M. intracellulare (51.62%), M. abscessus (22.22%), M. kansasii (8.32%), M. avium (7.75%) and M. fortuitum (2.05%). The number of NTM species identified also increased each year from 9 in 2014 to 26 in 2021. Most species showed stable isolation rates over the years; however, the proportion of M. avium increased from 3.85 to 10.42% during the study period. Besides, 81 non-mycobacteria strains, including Gordonia (21 isolates), Nocardia (19 isolates) and Tsukamurella (17 isolates), etc., were also discovered.ConclusionThe proportion of NTM and species diversity increased considerably in northern China from 2014 to 2021. M. intracellulare was the most common NTM isolated among respiratory specimens, followed by M. abscessus and M. kansasii. Rare NTM species and non-mycobacteria pathogens also need attention.
Introduction. Nontuberculous mycobacteria (NTM) infections are increasing worldwide and are relatively resistant to many of the first- and second-line drugs to treat tuberculosis. Macrolide antibiotics, such as clarithromycin and azithromycin, are the key drugs for treating NTM infections. Fidaxomicin is a macrolide antibiotic that is widely used in treating Clostridium difficle (C.difficile) infections, and has high in vitro activity against Mycobacterium tuberculosis especially multidrug-resistant tuberculosis (MDR-TB) and has no cross-resistance with rifampicin. Hypothesis. Fidaxomicin may have in vitro activity against NTM strains. Aim. To find that whether the macrolide antibiotic fidaxomicin has in vitro activity against NTM strains. Methodology. Fidaxomicin used in this study was firstly tested on C. difficile reference strains and has shown to be effective and workable. And then 28 rapidly growing mycobacteria (RGM), 12 slowly growing mycobacteria (SGM) reference strains and 103 NTM clinical isolates were tested by the microplate-based AlamarBlue assay (MABA) method to determine the MICs. Fidaxomicin, rifampicin and clarithromycin were tested against M. abcessus complex subspecies 14 M . abscessus and 5 M . massiliense strains for inducible resistance determination. Results. In total, 21 out of 28 RGM and 9 of 12 SGM reference strains have the MICs of fidaxomicin at or below 1 µg ml−1. Fidaxomicin also showed low MIC values for some clinical isolates including M. abscessus complex, M. avium complex, M. fortuitum , M. kansasii and M. parascrofulaceum . Fidaxomicin also has no inducible macrolide resistance in M. abscessus complex in comparison with clarithromycin. Conclusion. Fidaxomicin has high in vitro activity against most of the NTM reference strains and some prevalent NTM clinical isolates. This promising finding warrants further investigation on the actions of fidaxomicn in vivo and as a potential antibiotic for NTM treatment.
A conventional chiral metalens based on helical structures have the disadvantages of fixed chirality and low conversion efficiency of cross-circular polarization. In this study, a chirality-reversed bidirectional high-efficiency dichroic metalens based on hybrid helical surfaces (HHSs) is proposed and experimentally demonstrated, which is composed of a pair of half-pitch helical surfaces with left-and right-handedness. It is found that the cross-polarization conversion efficiency of the hybrid structure reaches 78.5%, which is ≈20 times higher than that (≈4%) of a conventional normal helical structure. The chirality of the hybrid structure can be flexibly switched between left-and right-handedness by simply flipping the metalens by 180°, rendering a chirality-reversed bidirectional operation. A comprehensive analysis of the physical mechanism and experimental verification are conducted. Two-photon laser direct writing and electron beam evaporation are employed to fabricate the dichroic metalens with a scale of a 101 × 101 HHS array, and dichroism focusing and imaging are successfully realized by lock-in thermography in the IR wavelength range from 3 to 5 𝝁m. The demonstrated high-efficiency bidirectional dichroic metalens promises important applications in polarimetric imaging and biomedical chirality detection.
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