Species identification of microorganisms in MGIT960 positive tubes by MALDI-TOF MS method / 中国热带医学

@#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.

Molecular characterization of mutations associated with resistance among 72 multidrug-resistant strains of Mycobacterium tuberculosis by whole genome sequencing / 中国热带医学

@#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.

Influence of induced nitric oxide synthase expression on apoptosis of thymocyte in burn rats / 中华烧伤杂志

<p><b>OBJECTIVE</b>To investigate the influence of induced nitric oxide synthase (iNOS) expression on apoptosis of thymocyte in burn rats, and to explore the relationship between NO and pathological lesion of the thymus gland in burn rats.</p><p><b>METHODS</b>Fifty-six male Wistar rats were enrolled in the study and randomized into control( C, n = 8,without treatment) , burn ( B, n = 24) , and S-methylisothiourea( SMT, n = 24) groups. Equal amount of isotonic saline solution and SMT(7. 5 mg/kg) were respectively intravenously infused into the rats in B and SMT groups after being inflicted with 30% TBSA full-thickness burns. The weight of thymus gland in each group were weighed, and thymocyte apoptosis and iNOS expression were determined with TUNEL method and immunohistochemistry, respectively at 6,24,72 postburn hours( PBH) , with 8 rats at each time-point. The number of apoptotic cells and the density of iNOS positive cells in thymus was measured by stereological method.</p><p><b>RESULTS</b>The weight of thymus in B group at 24 and 72 PBH [ (153+/- 14) , (91+/-22) mg] were obviously heavier than those in C group, but much lighter than those in SMT group ( P < 0.01). A few apoptotic cells and iNOS positive cells were observed in cortex and medulla of thymus in C group, while they were observed in B group at 6 PBH, and the number of cells began to increase at 24 PBH, distributing in medulla,parenchyma, the boundary of cortex, and medulla under capsule. The iNOS positive cells in B group at 24 PBH were distributed around the interlobular septum. A large number of cortical cells with brown staining were observed in B group at 72 PBH, and the number of iNOS positive cells also increased, with scattered distribution and clear cell boundary. Fewer positive cells with uneven distribution, no iNOS positive cells, and few apoptotic foci were observed in SMT group after burns. The density of apoptotic cells in B group at 24 and 72 PBH was (2. 428 +/-0. 728) x 10(-5)/microm(3) and (5. 586 +/- 1.233) x 10(-5)/microm(3), respectively, which was obviously higher than that in C and SMT group. The density of iNOS positive cells in B group was increased in a time-dependent manner( P <0. 05).</p><p><b>CONCLUSION</b>The apoptotic rate of thymocyte in severely burn rats increases early after burns. The up-regulation of iNOS expression in thymus can promote apoptosis of thymocytes, while SMT can partially ameliorate this phenomenon.</p>

Two cases of Avian Influenza A(HSNI) in Anhui province of China / 中华传染病杂志

Objective To analyze the clinical features,epidemiologic information and outcome in confirmed cases of human infection with a highly pathogenic influenza A(H5N1).Methods The clinical features and epidemiologic findings in 2 confirmed cases of avian influenza A(H5N1)in Anhui province,in November 2005.Clinical data on vital signs,physical findings,laboratory tests and roentgenology were obtained by means of retrospective review of the hospital records.Epidemiologic data were collected through interviews of the patients and their relatives.Results In both cases,the diagnosis of influenza A(H5N1)was confirmed by means of viral culture and real-time polymerase chain reaction with specific primers for H5 and N1 in samples obtained from tracheal aspiration.All patients were previously healthy young women and resided in village.They had a clear history of di- rect contact with sick/dead poultry and prepared dead chickens at home for eating(removed feathers, washed,cut)hut no report of confirmed HSN1 animals in the village.The time between exposure and onset of illness were 5 days,no one else in family sick.The time between the onset of illness and hos- pitalization were 5 days and 6 days,respectively.Two patients have initial symptoms of high fever (typically a temperature more than 38℃).The prominent clinical features were those of influenza syndrome,including fever,cough,and shortness of breath.Upper respiratory tract symptoms were absent.The platelet counts were decreased.In both patients,there were marked abnormalities on chest radiography,radiographic changes include bilateral and unilateral lobular consolidations with air bronchograms,and had dramatic worsening of findings.Two patients developed acute respiratory dis- tress syndrome(ARDS)complicated multiple organ dysfunction syndrome(MODS)and died of pro- gressive respiratory failure.Conclusions Exposure to dead poultry within a week before the onset of illness was associated with Influenza A(H5N1)infection in humans,but no definitive evidence of hu man-to-human transmission has been found yet.Influenza A(HSNI)infection,characterized by fe- ver,an influenza-like illness with lower respiratory tract symptoms,carries a high risk of death.