Characteristics of second-line anti-tuberculosis drug resistance and gene mutation of multidrug-resistant Mycobacterium tuberculosis in Ningbo

  Objective  To analyze the characteristics of second-line anti-tuberculosis (TB) drugs resistance and gene mutation of multidrug-resistant (MDR) Mycobacterium tuberculosis isolated in Ningbo.

  Methods  In 1597 M. tuberculosis isolates collected in the first drug resistance survey in Ningbo between 2018 and 2019, 133 MDR isolates, including 31 isolated from elderly group and 102 isolated from young and middle age group, were used in the study. All the isolates were detected using RD105 deletion-targeted multiplex PCR for Beijing genotype identification. Gene sequencing with PCR was conducted to detect the mutations of rrs, tlyA, eis, gidB, gyrA and gyrB genes. The conventional drug susceptibility test was used to detect the resistances to 5 second-line anti TB drugs (kanamycin, amikacin, capreomycin, ofloxacin, levofloxacin).

  Results  The multidrug resistance rate of M. tuberculosis isolates was 8.33% (133/1597) in Ningbo. The resistance rates of 133 MDR M. tuberculosis isolates to kanamycin, amikacin, capreomycin, ofloxacin and levofloxacin were 7.52% (10/133), 6.01% (8/133), 3.01% (4/133), 30.08% (40/133) and 29.32% (39/133). The rates of Pre-XDR and XDR of 133 MDR M. tuberculosis isolates were 28.57% (38/133) and 6.01% (8/133). The gene mutation rates of rrs, tlyA, eis, gidB, gyrA and gyrB of 133 MDR M. tuberculosis isolates were 6.77% (9/133), 7.52% (10/133), 1.50% (2/133), 3.76% (5/133), 34.59% (46/133) and 3.01% (4/133). There were 2 rrs mutations, 1 tlyA mutation, 2 eis mutations, 2 gidB mutations, 5 gyrA mutations and 4 gyrB mutations. Single base substitution was the main type.

  Conclusion  The resistance of MDR M. tuberculosis to second-line anti-TB drugs was serious in Ningbo, especially the resistance to fluoroquinolone. It is necessary to strengthen the prevention and control of second-line anti TB drugs resistances of MDR M. tuberculosis.