Single-nucleotide polymorphisms related to fluoroquinolone and aminoglycoside resistance in Mycobacterium avium isolates.

Abstract

ObjectiveThe relationships between fluoroquinolone and aminoglycoside resistance and single-nucleotide polymorphisms (SNPs) in gyrA, gyrB, and rpsL genes were investigated in 95 clinical isolates of Mycobacterium avium from China.MethodsFluoroquinolone and aminoglycoside resistance were determined by the broth microdilution method. GyrA, gyrB, and rpsL were sequenced, SNPs were identified, and the corresponding amino acid mutations were recorded.ResultsThe M. avium isolates displayed high levels of ofloxacin (93.68%), ciprofloxacin (92.63%), and streptomycin (65.26%) resistance. Moxifloxacin (18.95%) and amikacin (2.11%) were highly active against the strains. Fluoroquinolone resistance involving gyrA and gyrB gene mutations was identified. For gyrA, the most frequent SNPs were T→C (71/95, 74.74%), followed by A→G (64/95, 67.37%) and T→C (62/95, 65.26%). The amino acid mutations occurred mainly at Gly2444Asp (GGT→GAT) (20/95, 21.05%), Ala2445Ser (GCC→TCC) (20/95, 21.05%), Ala2447Val (GCC→GTC) (20/95, 21.05%), Val2449Ile (GTC→ATC) (20/95, 21.05%), and Glu2450Gln (GAA→CAA) (20/95, 21.05%). Prominent SNPs in gyrB included A→C (69/95, 72.63%), C→T (51/95, 53.68%), and T→G (29/95, 30.53%), and their amino acid substitutions were Ile2160Val (ATT→GTT) (21/95, 22.11%), Ile2160Met (ATT→ATG) (20/95, 21.05%), and Ile2273Leu (ATC→CTC) (11/95, 11.58%). Among the strains with aminoglycoside resistance, SNPs in rpsL were identified mostly at position G→A (73/95, 76.84%). G→C (21/95, 22.11%) was commonly seen. The amino acid mutations primarily involved Ala1539985Thr (GCC→ACC) (19/95, 20.00%), His1539992Asp (CAC→GAC) (19/95, 20.00%), and Gln-1539983Glu (CAG→GAG) (18/95, 18.95%).ConclusionOur study provides valuable information that could be used for the future diagnosis and treatment of M. avium disease.