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@#Abstract: Objective To understand the characteristics of mutations associated with resistance among 72 multidrug-resistant tuberculosis (MDR-TB) strains using whole genome sequencing (WGS) and to evaluate the performance of WGS for predicting MDR-TB drug resistance. Methods The clinical strains isolated from patients who visited the outpatient department of Tianjin Center for Tuberculosis Control from January to September in 2020 were collected. Identification tests using p-nitrobenzoic acid (PNB) medium were performed. Drug susceptibility tests (proportion method) on L-J medium were performed. After excluding duplicate strains, 72 MDR-TB strains were selected for WGS. Data were analyzed by using online databases and the phenotypic drug susceptibility test results were compared with resistance profiles predicted by WGS. Results All of 72 MDR-TB strains belonged to linage 2, and there was no significant difference in rate of pre-extensive drug-resistant tuberculosis (pre-XDR-TB) between modern type and ancestral type (χ2=0.287, P=0.592). A total of 81 mutation types were found from resistance-related genes for 12 anti-tuberculosis drugs, and the common mutation types in different drug-resistant strains were: streptomycin (SM): rpsL Lys43Arg; isoniazid (INH): katG Ser315Thr; rifampicin (RIF): rpoB Ser450Leu; ethambutol (EMB): embB Met306Val; ofloxacin (OFX), levofloxacin (LFX), moxifloxacin (MFX): gyrA Asp94Gly; kanamycin (KAM), capreomycin (CAP), amikacin (AMK): rrs 1401a>g; para-aminosalicylic acid (PAS): folC Ile43Thr. Nine mutation types were found in 9 prothionamide (PTO)-resistant strains, one type for each strain. The sensitivity and specificity of WGS for predicting resistance to different drugs were SM: 98.15% and 88.89%, INH: 90.28% and -, RIF: 98.62% and -, EMB: 79.49% and75.76%, OFX: 97.30% and 85.71%, KAM: 85.71% and 98.46%, PAS: 27.27% and 95.08%, PTO: 81.82% and 60.66%, CAP: 60.00% and 98.51%, LFX: 97.22% and 83.33%, MFX: 97.30% and 85.71%, AMK:100.00% and 100.00%, respectively. Conclusion WGS is a rapid and promising method which has high consistency with the phenotypic drug sensitivity test. Therefore, it has good application prospects in predicting drug resistance in MDR-TB.
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@#Abstract： Objective To analyze the species distribution of microorganisms in culture tubes reported positive byBACTEC™ MGIT960 (hereafter referred to as "MGIT960") after species identification using matrix-assisted laser desorption/ionization time of flight massspectrometry (MALDI-TOF MS) technique. Methods From 2021 to 2022, a total of 2 662 positive tubes reported by the MGIT 960 instrument at Tuberculosis Reference Laboratory of Tianjin Center for Tuberculosis Control were collected. Liquid cultures were independently inoculated to blood plate and neutral L-J medium, and the resulting isolate strains were identified using the MALDI-TOF MS method. According to the MALDI-TOF MS results, the non-repetitive results of the same patient on the same culture medium were analyzed for the composition ratio of strain distribution. For the strains not identified by MALDI-TOF MS, 38 strains were selected for 16S rRNA gene sequencing. Results A total of 605 isolates were obtained from blood plates, and 501 of those were analyzed. Among them, Mycobacterium accounted for 17.76% (89/501), predominant by Mycobacterium abscess 10.18% (51/501) and Mycobacterium fortuitum 3.19% (16/501). Bacteria other than Mycobacterium accounted for 68.06% (341/501), with the main ones being Nocardia farcinica 15.57% (78/501), Gordonia sputa 9.38% (47/501) and Gordonia bronchialis 7.58% (38/501). There were 71 unidentifiable strains, making up 14.17% (71/501). A total of 2 378 strains were isolated from neutral L-J mediums, 1 748 of which were used in the incoming analysis. Among these, 78.72% (1 376/1 748) were Mycobacterium, 60.53% (1 058/1 748) were Mycobacterium tuberculosis (MTB), 4.69% (82/1 748) were Mycobacterium chimaer intracellulare group and 3.55% (62/1 748) were Mycobacterium Lentiflavum. Bacteria other than Mycobacterium accounted for 17.11% (299/1 748) in neutral L-J medium isolates, with Nocardia farcinica 4.35% (76/1 748), Gordonia sputa 2.69% (47/1 748) and Gordonia bronchialis 2.12% (37/1 748) as the main species. There were 73 strains that couldn't be identified, comprising 4.18% (73/1 748). The 38 strains that not identified by MALDI-TOF MS were all found to be Actinobacteria and Firmicutes by sequencing. Conclusions A variety of nontuberculous Mycobacterium and bacteria other than Mycobacterium were found in the positive culture tubes reported by the MGIT960 instrument, most of which could be quickly identified by mass spectrometry. Bacteria other than Mycobacterium are mainly Nocardia and Gordonia, which should be paid attention to in differential diagnosis.