Leers W D
Can Med Assoc J. 1975 Jun 14;112(13 Spec No):59-63.
The invitro testing of Hemophilus influenzae and Streptococcus pyogenes for co-trimoxazole sensitivity requires certain "defined" media that have to be free of inhibitory substances. The use of Columbia agar base with Fildes extract for H. influenzae or of blood agar for S. pyogenes may produce "false-resistant" strains. The addition of thymidine phosphorylases in the form of gentlylysed horse blood (2 to 10%) does not remove all inhibitors in those tests, especially where "undefined" agar bases are used, and results in scanty growth of H. influenzae; the addition of more than 2% results in dark plates, making reading of sensitivities difficult. Fildes agar for testing H. influenzae may be made with enriched sheep or horse blood if the proper "defined" agar base is used. The use of Wellcotest or DST (Oxoid) agar is recommended with Fildes extract for H. influenzae or with blood for S. pyogenes for in vitro testing for co-trimoxazole sensitivity. The addition of thymidine phosphorylase in the form of 2% lysed horse blood does not interfere with reading. However, it results in scanty growth of H. influenzae. Proper inoculation of plates is important. The growth on the plates should be light, dense, but not confluent. Heavy growth may render some strains "false-resistant" even when defined media are used. Our results indicate that many of the previously reported resistant strains of H. influenzae and S. pyogenes may have been "false-resistant" because of the use of "undefined" media. We believe that, in view of our results, respiratory infections may be treated with co-trimoxazole until bacteriologic studies prove that this treatment is contraindicated, since H. influenzae and S. pyogenes are usually found sensitive in vitro under proper conditions.
对流感嗜血杆菌和化脓性链球菌进行复方新诺明敏感性的体外测试需要某些“特定的”培养基，这些培养基必须不含抑制物质。使用含菲尔德氏提取物的哥伦比亚琼脂基础培养基培养流感嗜血杆菌，或使用血琼脂培养化脓性链球菌，可能会产生“假耐药”菌株。以轻度裂解的马血（2%至10%）形式添加胸苷磷酸化酶并不能去除这些测试中的所有抑制剂，尤其是在使用“未明确的”琼脂基础培养基时，还会导致流感嗜血杆菌生长稀少；添加超过2%会导致平板变黑，使敏感性读数变得困难。如果使用合适的“特定的”琼脂基础培养基，用于测试流感嗜血杆菌的菲尔德氏琼脂可以用富集的羊血或马血制成。建议使用Wellcotest或DST（Oxoid）琼脂，添加菲尔德氏提取物用于流感嗜血杆菌测试，或添加血液用于化脓性链球菌测试，以进行复方新诺明敏感性的体外测试。以2%裂解马血形式添加胸苷磷酸化酶不会干扰读数。然而，它会导致流感嗜血杆菌生长稀少。平板的正确接种很重要。平板上的生长应该是轻度密集的，但不是融合的。即使使用特定培养基，大量生长也可能使一些菌株呈现“假耐药”。我们的结果表明，许多先前报道的流感嗜血杆菌和化脓性链球菌耐药菌株可能由于使用了“未明确的”培养基而成为“假耐药”。我们认为，鉴于我们的结果，在细菌学研究证明这种治疗有禁忌之前，呼吸道感染可以用复方新诺明治疗，因为在适当条件下，流感嗜血杆菌和化脓性链球菌通常在体外是敏感的。
