Jorgensen J H, Lee J C
Am J Clin Pathol. 1977 Mar;67(3):264-8. doi: 10.1093/ajcp/67.3.264.
The emergence of ampicillin-resistant strains of Haemophilus influenzae has emphasized the need for an improved practical method for routine susceptibility testing of clinical isolates. We have previously described a simplified medium for quantitative dilution susceptibility testing that is composed of Mueller-Hinton medium plus Supplement C (Difco). In the present study, paired broth-dilution and disk-diffusion susceptibility tests with ampicillin and chloramphenicol were performed on 100 strains of Haemophilus (95 H. influenzae and five H. parainfluenzae), including 30 strains with previously documented ampicillin resistance. Disk-diffusion tests were performed in exactly the same manner as the standardized Kirby-Bauer procedure used for less fastidious organisms, except that supplemented Mueller-Hinton agar plates were incubated in an increased-CO2 atmosphere. Using this method, ampicillin-susceptible strains of Haemophilus produced zone diameters of 22 mm or more, while ampicillin-resistant strains produced zones of 18 mm or less. All strains were chloramphenicol-susceptible and produced zone diameters of 30 mm or more. This method would allow routine disk-diffusion testing of isolates of H. influenzae by hospital diagnostic laboratories, using a clear medium that closely resembles unsupplemented Mueller-Hinton agar.
流感嗜血杆菌氨苄西林耐药菌株的出现凸显了对一种改进的临床分离株常规药敏试验实用方法的需求。我们之前描述了一种用于定量稀释药敏试验的简化培养基，它由穆勒-欣顿培养基加补充剂C（迪夫科公司）组成。在本研究中，对100株嗜血杆菌（95株流感嗜血杆菌和5株副流感嗜血杆菌）进行了氨苄西林和氯霉素的肉汤稀释法与纸片扩散法药敏试验配对，其中包括30株先前记录有氨苄西林耐药的菌株。纸片扩散试验的操作方式与用于不那么苛求的微生物的标准化柯氏-鲍氏程序完全相同，只是补充了穆勒-欣顿琼脂平板在增加二氧化碳的气氛中孵育。使用这种方法，流感嗜血杆菌的氨苄西林敏感菌株产生的抑菌圈直径为22毫米或更大，而氨苄西林耐药菌株产生的抑菌圈直径为18毫米或更小。所有菌株对氯霉素敏感，产生的抑菌圈直径为30毫米或更大。这种方法将允许医院诊断实验室对流感嗜血杆菌分离株进行常规纸片扩散试验，使用一种与未补充的穆勒-欣顿琼脂非常相似的透明培养基。
