McIver C J, Tapsall J W
Department of Microbiology, Prince of Wales Hospital, Randwick, New South Wales, Australia.
J Clin Microbiol. 1990 Sep;28(9):1947-51. doi: 10.1128/jcm.28.9.1947-1951.1990.
Cysteine-requiring strains of the family Enterobacteriaceae that are auxotrophic for this amino acid because of defects in the sulfur assimilatory pathway account for about 1.5% of urinary tract isolates of Escherichia coli and Klebsiella species. Forty Escherichia and eight Klebsiella cysteine-requiring strains were used to test the ease with which various test systems identified clinical isolates of cysteine auxotrophs. In a preliminary experiment, the growth yield of 10 cysteine-requiring E. coli in 10 solutions of commercially available peptones was in each instance less than that of prototrophic control and showed that these sources of nutrients were suboptimal for these strains. A significant proportion of the cysteine-requiring strains were not adequately identified by growth-dependent tests which used various peptones as a nutrient source. Problems were encountered with all test systems examined, which were as follows: conventional methods; the API 20E, Microbact, and Vitek systems; and two rapid methods for the identification of E. coli, the Rapidec coli and the beta-D-glucuronidase tests. The performance of the test systems was only partly improved when inocula were derived from appropriately supplemented media. However, the problems of the growth-dependent tests were resolved when a cysteine-supplemented suspension was used to inoculate each test system.
由于硫同化途径缺陷而对这种氨基酸营养缺陷的肠杆菌科半胱氨酸需求菌株约占大肠杆菌和克雷伯菌属尿道分离株的1.5%。使用40株大肠杆菌和8株克雷伯菌半胱氨酸需求菌株来测试各种检测系统鉴定半胱氨酸营养缺陷型临床分离株的难易程度。在一项初步实验中，10株半胱氨酸需求型大肠杆菌在10种市售蛋白胨溶液中的生长产量在每种情况下都低于原养型对照，表明这些营养来源对这些菌株而言并非最佳。很大一部分半胱氨酸需求菌株未被以各种蛋白胨作为营养源的依赖生长检测充分鉴定出来。在所检测的所有检测系统中都遇到了问题，具体如下：传统方法；API 20E、Microbact和Vitek系统；以及两种鉴定大肠杆菌的快速方法，即Rapidec coli检测和β-D-葡萄糖醛酸酶检测。当接种物来自适当补充培养基时，检测系统的性能仅部分得到改善。然而，当使用补充了半胱氨酸的悬液接种每个检测系统时，依赖生长检测的问题得到了解决。
