Abstract:

Objective To analyze the demographic characteristics, disease characteristics of patients infected with mycobacterium, and the drug resistance test results of clinical isolates in Nanjing. Methods A total of 1719 patients with positive mycobacterium treated in Nanjing Second Hospital from January 2017 to December 2019 were selected as the subjects, informations of age, gender, treatment history, whether concurrent AIDS and so on were collected. Of the 1719 strains of mycobacteria which were isolated and identified by PCR reverse dot blot hybridization, 308 (17.92%) were nontuberculous mycobacteria (NTM) and 1411 (82.08%) were Mycobacterium tuberculosis (MTB). Absolute concentration indirect method was used to test drug sensitivity of these strains with isoniazid (INH), rifampicin (RFP), streptomycin (Sm), ethambutol (EMB), kanamycin (Km), amikacin (Am), para-aminsalieylic acid (PAS), capreomycin (Cm) and levofloxacin (Lfx), etc., melting curve of fluorescence PCR was used to analyze the mutations of drug-resistant MTB strains. Results Of the 308 NTM isolates, the drug resistance rate of EMB was 40.58% (125/308), and the rates of other 8 drugs were all over 90.00%. In patients with MTB infection, the drug resistance rate and multidrug resistance rate were the highest in patients aged 35-<65-year group (36.01% (233/647) and 16.07% (104/647)); the drug-resistant rate, multidrug resistant rate and extensive drug resistant rate in retreated group were significantly higher than those in initial treatment group (34.17% (312/913) vs. 28.31% (141/498), χ ²=5.076, P=0.024; 14.13% (129/913) vs. 9.23% (46/498), χ ²=7.099, P=0.008; 2.63% (24/913) vs. 0.40% (2/498) χ ²=8.836, P=0.003). The order of drug resistance of the 1411 MTB isolates to 9 anti-tuberculosis drugs was: INH (17.65%, 249/1411) >Sm (17.15%, 242/1411) >RFP (13.39%, 189/1411) >Lfx (10.70%, 151/1411) >EMB (6.45%, 91/1411) >Am (4.39%, 62/1411) >Km (2.41%, 34/1411) >PAS (1.84%, 26/1411) >Cm (1.20%, 17/1411). The drug resistance rates of the isolates from retreated group to INH, Sm, RFP, EMB and Km were significantly higher than those from initial treatment group (19.39% (177/913) vs. 14.46% (72/498), χ ²=5.386, P=0.020; 18.51% (169/913) vs. 14.26% (71/498), χ ²=4.130, P=0.042; 14.90% (136/913) vs. 10.64% (53/498), χ ²=6.455, P=0.024; 8.00% (73/913) vs. 3.18% (29/913), χ ²=10.252, P=0.001; 3.61% (18/498) vs. 1.00% (5/498), χ ²=6.466, P=0.011). Drug resistance gene detection of drug-resistant MTB to INH, RFP, SM, EMB, fluoroquinolones and second-line anti-tuberculosis injection drugs showed that the main mutations were katG 315 (65.44%, 142/217), rpoB 529-533 (66.67%, 124/186), rpsL 43 (69.23%, 18/26), embB 306 (66.28%, 57/86), gyrA 88-94 (100.00%, 91/91) and rrs 1401 (100.00%, 26/26), respectively. The coincidence rates of genotype mutation and phenotype resistance were 87.15% (217/249), 98.41% (186/189), 86.67% (26/30), 94.51% (86/91), 100.00% (91/91) and 86.67% (26/30), respectively. Conclusion Mycobacterium infections in Nanjing were mainly occured in middle-aged and elderly population, and the drug resistance of mycobacteria was serious. The identification and baseline drug resistance test of mycobacteria should be popularized, the molecular biological examination of drug-resistant patients and the resistance of INH and quinolones should be paid more attention, the drug resistance monitoring in the treatment process should also be strengthened.

Key words: Mycobacterium infections, Mycobacterium tuberculosis, Mycobacterium infections,atypical, Drug resistance,bacterial, Genes, Mutation, Small-area analysis