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Background: The antimicrobial activities of some new oxazolidinones against slowly growing mycobacteria (SGM) have never been well evaluated. Methods: We evaluate the in vitro susceptibility of 20 reference strains and 157 clinical isolates, pertaining different SGM species, against four oxazolidinones, ie, delpazolid, sutezolid, tedizolid and linezolid. In addition, the association of linezolid resistance and mutations in 23srRNA, rplC, rplD were also tested. Results: Sutezolid presented the strongest antimicrobial activity against the clinical isolates of M. intracellulare than the other oxazolidinones, with MIC50 at 2 μg/mL and MIC90 at 4 μg/mL. MICs of sutezolid were usually 4- to 8-fold lower than these of linezolid against M. intracellulare and M. avium. The tested isolates of M. kansasii were susceptible to all of the four oxazolidinones. According to the multiple sequence alignment, novel 23srRNA mutations (A2267C and A2266G) in M. intracellulare and rplD mutations (Thr147Ala) in M. avium were identified in this study which have plausible involvement in rendering resistance against linezolid. Conclusion: This study showed that sutezolid harbors the strongest inhibitory activity against M. intracellulare, M. avium and M. kansasii in vitro, which provided important insights on the potential clinical application of oxazolidinones for treating SGM infections. [ABSTRACT FROM AUTHOR]

Background A review of the scientific literature concluded that indirect smear can improve detection of TB in sputum compared to direct smear. However few laboratories have access to centrifugation in order to perform indirect smear. This study investigated whether an alternative method of magnetic bead concentration could enhance diagnosis of TB in China in laboratories which only perform direct smear microscopy. Methods A total of 129 sputum samples were investigated by direct smear microscopy, microscopy after TB-Bead extraction and by solid and liquid culture. Results Direct smear had a sensitivity of 40% by Ziehl-Neelsen (ZN) and 45% by auramine compared to combined culture results. After TB-Bead extraction, this increased to 65% for ZN and 70% for auramine. Conclusion Magnetic bead concentration of mycobacteria from sputum led to a significant improvement (p<0.05) in the sensitivity of microscopy compared with direct smear. [ABSTRACT FROM AUTHOR]

• The oxazolidinones exhibited in vitro activity against the rapidly growing mycobacteria (RGM) reference strains. • Tedizolid showed the strongest activity against Mycobacterium abscessus isolates with MIC 90 =2 μg/ml. • Delpazolid presented the best activity against Mycobacterium fortuitum isolates. The natural resistance of rapidly growing mycobacteria (RGM) to multiple antibiotics renders the treatment of the infections caused less successful. The objective of this study was to evaluate the in vitro susceptibilities of four oxazolidinones against different RGM species. The microplate alamarBlue assay was performed to identify the minimum inhibitory concentrations (MICs) of four oxazolidinones – delpazolid, sutezolid, tedizolid, and linezolid – for 32 reference strains and 115 clinical strains of different RGM species. The MIC breakpoint concentration was defined as 16 μg/ml for linezolid. Next, the gene fragments associated with oxazolidinone resistance were amplified and sequenced, and mutations were defined in contrast with the sequences of the reference strains. Tedizolid showed the strongest inhibitory activity against the Mycobacterium abscessus isolates. Delpazolid exhibited better antimicrobial activity against the Mycobacterium fortuitum isolates when compared to linezolid, with 4-fold lower MIC values. The protein alignment and structure-based analysis showed that there might be no correlation between oxazolidinone resistance and mutations in the rplC, rplD , and 23S rRNA genes in the tested RGM. Tedizolid had the strongest inhibitory activity against M. abscessus in vitro , while delpazolid presented the best inhibitory activity against M. fortuitum. This provides important insights into the potential clinical application of oxazolidinones to treat RGM infections. [ABSTRACT FROM AUTHOR]