Polymorphic mutation frequencies in clinical isolates of Staphylococcus aureus: the role of weak mutators in the development of fluoroquinolone resistance

Authors

  • Shaochen Wang,

    1. Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
    2. Ministry of Food Safety Risk Assessment Key Laboratory, China National Center for Food Safety Risk Assessment (CFSA), Beijing, China
    3. College of Food Science and Technology, Nanjing Agricultural University, Nanjing, China
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  • Yang Wang,

    1. Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
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  • Jianzhong Shen,

    1. Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
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  • Yongning Wu,

    1. Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
    2. Ministry of Food Safety Risk Assessment Key Laboratory, China National Center for Food Safety Risk Assessment (CFSA), Beijing, China
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  • Congming Wu

    Corresponding author
    • Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China
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Correspondence: Cong-Ming Wu, Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, No. 2 West Yuanmingyuan Road, Beijing 100193, China. Tel.: +86 010 62733378; Fax: +86 010 62731032; e-mail: wucm@cau.edu.cn

Abstract

The polymorphic mutation frequencies for 154 Staphylococcus aureus isolates from Chinese bovine clinical mastitis cases were investigated. We found that nearly 29% of the isolates presented as weak mutators, while only two (1.3%) strong mutators were detected. Of the 15 weak mutators that exhibited ciprofloxacin resistance phenotypes, only one isolate was found to be mutS deficient. All of the ciprofloxacin-resistant isolates had the classic ciprofloxacin resistance mutations at codon 80 within the ParC subunit of topoisomerase IV and codon 84/88 within the GyrA subunit of DNA gyrase. The proportion of ciprofloxacin-resistant isolates among the weak mutators (34.1%) was significantly higher than that found in the normomutators (11.4%) and hypomutators (0%) (P < 0.001, Fisher's exact test), suggesting a positive correlation between weak mutators and ciprofloxacin resistance.

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