Hnot Melanie L, Cole Lynette K, Lorch Gwendolen, Papich Mark G, Rajala-Schultz Paivi J, Daniels Joshua B
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, 601 Vernon L. Tharp St., Columbus, OH, 43210, USA.
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, 1060 William Moore Drive, Raleigh, NC, 27607, USA.
Vet Dermatol. 2015 Oct;26(5):334-8, e70-1. doi: 10.1111/vde.12227. Epub 2015 Jul 28.
Using the US Clinical and Laboratory Standards Institute (CLSI) human tetracycline breakpoints to predict minocycline and doxycycline susceptibility of Staphylococcus pseudintermedius (SP) isolates from dogs is not appropriate because they are too high to meet pharmacokinetic/pharmacodynamic data using a standard dose. New breakpoints have been approved for doxycycline and proposed for minocycline. Revised breakpoints are four dilutions lower than tetracycline breakpoints, providing a more conservative standard for classification of isolates.
HYPOTHESIS/OBJECTIVES: The objectives of this study were to measure minimum inhibitory concentrations (MICs) of minocycline and doxycycline of 100 canine meticillin-resistant SP clinical isolates, compare their susceptibilities to minocycline and doxycycline based on current and revised standards, and document their tetracycline resistance genes.
E-test strips were used to determine MICs. PCR was used to identify tet genes.
Using the human tetracycline breakpoint of MIC ≤ 4 μg/mL, 76 isolates were susceptible to minocycline and 36 isolates were susceptible to doxycycline. In contrast, using the proposed minocycline breakpoint (MIC ≤ 0.25 μg/mL) and approved doxycycline breakpoint (MIC ≤ 0.125 μg/mL), 31 isolates were susceptible to both minocycline and doxycycline. Thirty-one isolates carried no tet genes, two had tet(K) and 67 had tet(M).
Use of the human tetracycline breakpoints misclassified 45 and five of the isolates as susceptible to minocycline and doxycycline, respectively. PCR analysis revealed that 43 and five of the isolates classified as susceptible to minocycline and doxycycline, respectively, possessed the tetracycline resistance gene, tet(M), known to confer resistance to both drugs. These results underscore the importance of utilizing the proposed minocycline and approved doxycycline canine breakpoints in place of human tetracycline breakpoints.
使用美国临床和实验室标准协会（CLSI）的人类四环素断点来预测犬源中间型葡萄球菌（SP）分离株对米诺环素和多西环素的敏感性并不合适，因为这些断点过高，无法满足标准剂量下的药代动力学/药效学数据。多西环素的新断点已获批准，米诺环素的新断点也已被提出。修订后的断点比四环素断点低四个稀释度，为分离株的分类提供了更保守的标准。
假设/目标：本研究的目的是测定100株犬源耐甲氧西林SP临床分离株对米诺环素和多西环素的最低抑菌浓度（MIC），根据当前和修订后的标准比较它们对米诺环素和多西环素的敏感性，并记录它们的四环素耐药基因。
使用E-test试纸条测定MIC。采用聚合酶链反应（PCR）鉴定tet基因。
按照人类四环素断点MIC≤4μg/mL，76株分离株对米诺环素敏感，36株分离株对多西环素敏感。相比之下，按照提议的米诺环素断点（MIC≤0.25μg/mL）和批准的多西环素断点（MIC≤0.125μg/mL），31株分离株对米诺环素和多西环素均敏感。31株分离株未携带tet基因，2株携带tet(K)，67株携带tet(M)。
使用人类四环素断点分别将45株和5株分离株错误分类为对米诺环素和多西环素敏感。PCR分析显示，分别被分类为对米诺环素和多西环素敏感的43株和5株分离株携带四环素耐药基因tet(M)，已知该基因可赋予对这两种药物的耐药性。这些结果强调了使用提议的米诺环素断点和批准的多西环素犬用断点来取代人类四环素断点的重要性。
