Archives of Microbiology, 2020.202(8), 2255-2261, DOI: https://doi.org/10.1007/s00203-020-01906-y

Single‑nucleotide polymorphisms in a vancomycin‑resistant Staphylococcus aureus strain based on whole‑genome sequencing

Jung Wook Kim, Kwang Jun Lee

Abstract

The emergence of vancomycin-resistant Staphylococcus aureus (VRSA) threatens global health. The mechanism of vancomycin resistance of VRSA without vanA gene acquisition was not fully elucidated. Therefore, we aimed to determine the mechanism of vancomycin resistance of VRSA besides that by vanA gene acquisition. In this study, we obtained vancomycinresistant strains (V036-V64; MIC = 64 μg /ml) from susceptible strain (V036; MIC = 0.5 μg /ml) by exposure of vancomycin in vitro and examined the phenotypic characteristics and antibiotic susceptibility profiles of the resistant strain (V036-V64). To identify the genetic variations caused vancomycin resistance, we determined the complete genome sequences of V036 and V036-V64 and analyzed for single-nucleotide polymorphisms (SNPs) between two strains. Morphologically, V036-V64 had a twofold thicker cell wall compared with V036. Linezolid, rifampicin, and ceftaroline had similar MIC ranges against V036-V64 and V036, but V036-V64 showed lower susceptibilities to daptomycin and telavancin. We detected eight singlenucleotide polymorphisms differing between V036-V64 and V036: rimM (G16D), ssaA2 (G128A), rpsK (P60R), rpoB (R917C), walK (T492R), d-alanyl-d-alanine carboxypeptidase (L307I), vraT (A152V), and chromosome segregation ATPase (T440I). This study demonstrates that, under selective pressure, by the accumulation of mutations in genes related to cell wall synthesis, vancomycin-susceptible S. aureus can develop thicker cell walls and, hence, develop high vancomycin resistance. Thus, we highlight a novel vanA-negative mechanism for VRSA emergence.

• DOI: https://doi.org/10.1007/s00203-020-01906-y
• ISBN or ISSN: 0302-8933

• 본 연구는 질병관리본부 연구개발과제연구비를 지원받아 수행되었습니다.
• This research was supported by a fund by Research of Korea Centers for Disease Control and Prevention.