Mirajkar Nandita S, Gebhart Connie J
Department of Veterinary and Biomedical Sciences (Mirajkar, Gebhart), College of Veterinary Medicine, University of Minnesota, Saint Paul, MNVeterinary Diagnostic Laboratory (Gebhart), College of Veterinary Medicine, University of Minnesota, Saint Paul, MN
Department of Veterinary and Biomedical Sciences (Mirajkar, Gebhart), College of Veterinary Medicine, University of Minnesota, Saint Paul, MNVeterinary Diagnostic Laboratory (Gebhart), College of Veterinary Medicine, University of Minnesota, Saint Paul, MN.
J Vet Diagn Invest. 2016 Mar;28(2):133-43. doi: 10.1177/1040638716629154.
Production-limiting diseases in swine caused by Brachyspira are characterized by mucohemorrhagic diarrhea (B. hyodysenteriae and "B. hampsonii") or mild colitis (B. pilosicoli), while B. murdochii is often isolated from healthy pigs. Emergence of novel pathogenic Brachyspira species and strains with reduced susceptibility to commonly used antimicrobials has reinforced the need for standardized susceptibility testing. Two methods are currently used for Brachyspira susceptibility testing: agar dilution (AD) and broth microdilution (BMD). However, these tests have primarily been used for B. hyodysenteriae and rarely for B. pilosicoli. Information on the use of commercial susceptibility testing products such as antibiotic gradient strips is lacking. Our main objective was to validate and compare the susceptibility results, measured as the minimum inhibitory concentration (MIC), of 6 antimicrobials for 4 Brachyspira species (B. hyodysenteriae, "B. hampsonii", B. pilosicoli, and B. murdochii) by BMD and AD (tiamulin, valnemulin, lincomycin, tylosin, and carbadox) or antibiotic gradient strip (doxycycline) methods. In general, the results of a high percentage of all 4 Brachyspira species differed by ±1 log2 dilution or less by BMD and AD for tiamulin, valnemulin, lincomycin, and tylosin, and by BMD and antibiotic gradient strip for doxycycline. The carbadox MICs obtained by BMD were 1-5 doubling dilutions different than those obtained by AD. BMD for Brachyspira was quicker to perform with less ambiguous interpretation of results when compared with AD and antibiotic gradient strip methods, and the results confirm the utility of BMD in routine diagnostics.
由短螺旋体引起的猪生产限制疾病的特征是黏液出血性腹泻（猪痢疾短螺旋体和“汉普森短螺旋体”）或轻度结肠炎（结肠短螺旋体），而默多克短螺旋体常从健康猪中分离出来。对常用抗菌药物敏感性降低的新型致病性短螺旋体物种和菌株的出现，强化了标准化药敏试验的必要性。目前有两种方法用于短螺旋体药敏试验：琼脂稀释法（AD）和肉汤微量稀释法（BMD）。然而，这些试验主要用于猪痢疾短螺旋体，很少用于结肠短螺旋体。缺乏关于使用抗生素梯度条等商业药敏试验产品的信息。我们的主要目标是通过BMD和AD（替米考星、沃尼妙林、林可霉素、泰乐菌素和卡巴多司）或抗生素梯度条（多西环素）方法，验证并比较6种抗菌药物对4种短螺旋体物种（猪痢疾短螺旋体、“汉普森短螺旋体”、结肠短螺旋体和默多克短螺旋体）的药敏结果（以最低抑菌浓度（MIC）衡量）。总体而言，对于替米考星、沃尼妙林、林可霉素和泰乐菌素，通过BMD和AD测定的所有4种短螺旋体物种中，高比例结果的差异在±1个log2稀释度或更小；对于多西环素，通过BMD和抗生素梯度条测定的结果差异也是如此。通过BMD获得的卡巴多司MIC与通过AD获得的结果相差1 - 5倍稀释度。与AD和抗生素梯度条方法相比，短螺旋体的BMD操作更快，结果解释更明确，结果证实了BMD在常规诊断中的实用性。
