Sáenz Yolanda, Zarazaga Myriam, Briñas Laura, Ruiz-Larrea Fernanda, Torres Carmen
Area de Bioquímica y Biología Molecular, Universidad de La Rioja, Madre de Dios 51, 26006, Logroño, Spain.
J Antimicrob Chemother. 2003 Apr;51(4):1001-5. doi: 10.1093/jac/dkg168. Epub 2003 Mar 13.
Mutations in quinolone targets were analysed in 80 unrelated nalidixic acid-resistant (NALR) Escherichia coli strains whose nalidixic acid and ciprofloxacin MICs ranged from 32 to >256 mg/L and 0.03-64 mg/L, respectively. These strains were isolated from food products (23) and faecal samples from humans (15) and healthy animals (42). Thirteen nalidixic acid-susceptible (NALS) E. coli strains were also analysed. Mutations in gyrA and parC genes were studied by PCR and sequencing. No amino acid changes were detected in GyrA or ParC proteins of the 13 NALS strains. A single change in the GyrA protein was detected in all 61 NALR strains with ciprofloxacin MICs </= 2 mg/L with the following substitutions (number of strains): Ser-83-->Leu (54), Ser-83-->Ala (one), Ser-83-->Val (one), Asp-87-->Asn (two), Asp-87-->Tyr (two) and Asp-87-->Gly (one). A double change in GyrA was found in 18 of 19 NALR strains with ciprofloxacin MICs >/= 4 mg/L. Amino acid substitutions were Ser-83-->Leu, with an additional change [Asp-87-->Asn (15), Asp-87-->Tyr (two) or Asp-87-->His (one)]. The remaining strain (ciprofloxacin MIC 4 mg/L) showed a single Ser-83-->Leu substitution. In respect of the ParC protein, a single change at Ser-80 or Glu-84 was found in 25 of 42 strains, with ciprofloxacin MICs ranging from 0.5 to 32 mg/L. A double substitution (Ser-80-->Ile and Glu-84-->Gly) was found in one strain (ciprofloxacin MIC 64 mg/L). No amino acid changes were detected in the GyrB protein of 18 NALR strains.
对80株无亲缘关系的耐萘啶酸（NALR）大肠杆菌菌株进行了喹诺酮靶点突变分析，这些菌株的萘啶酸和环丙沙星MIC分别为32至>256mg/L和0.03 - 64mg/L。这些菌株分离自食品（23株）以及人类（15株）和健康动物（42株）的粪便样本。还分析了13株萘啶酸敏感（NALS）大肠杆菌菌株。通过PCR和测序研究了gyrA和parC基因的突变。在13株NALS菌株的GyrA或ParC蛋白中未检测到氨基酸变化。在环丙沙星MIC≤2mg/L的所有61株NALR菌株中检测到GyrA蛋白有单一变化，替换情况如下（菌株数量）：Ser-83→Leu（54株）、Ser-83→Ala（1株）、Ser-83→Val（1株）、Asp-87→Asn（2株）、Asp-87→Tyr（2株）和Asp-87→Gly（1株）。在环丙沙星MIC≥4mg/L的19株NALR菌株中的18株中发现GyrA有双重变化。氨基酸替换为Ser-83→Leu，并伴有额外变化[Asp-87→Asn（15株）、Asp-87→Tyr（2株）或Asp-87→His（1株）]。其余菌株（环丙沙星MIC 4mg/L）显示单一的Ser-83→Leu替换。关于ParC蛋白，在环丙沙星MIC为0.5至32mg/L的42株菌株中的25株中发现Ser-80或Glu-84有单一变化。在1株菌株（环丙沙星MIC 64mg/L）中发现双重替换（Ser-80→Ile和Glu-84→Gly）。在18株NALR菌株的GyrB蛋白中未检测到氨基酸变化。
