Kurzynski T A, Meise C K
J Clin Microbiol. 1979 Feb;9(2):189-93. doi: 10.1128/jcm.9.2.189-193.1979.
We compared the selective blood agar medium of Gunn et al. (J. Clin. Microbiol. 5:650-655, 1977) which contains sulfamethoxazole plus trimethoprim (SXT-BA) to the conventional blood agar surface plate (SBA) and a modified blood agar pour plate plus broth method for the recovery of group A streptococci from throat swabs. The influence of CO(2) and ambient air incubation of the SXT-BA and SBA plates was also evaluated. A total of 696 throat swabs from symptomatic children were cultured simultaneously by the five methods and observed after overnight incubation; 204 positive cultures were detected overall. Recovery rates of each individual method were: SXT-BA (CO(2)), 90.7%; SXT-BA (air), 87.7%; pour plate plus broth, 83.3%; SBA (CO(2)), 79.4%; and SBA (air) 77%. Approximately one-half of the false-negative cultures in the SXT-BA (CO(2)) and SXT-BA (air) methods had colony counts of >/=10 to 100 colonies per plate. In contrast, for the SBA (CO(2)), SBA (air), and pour plate plus broth methods, approximately 70% of the false-negative cultures had colony counts of >/=10 to 100/plate. False-positive cultures obtained by the SXT-BA (CO(2)) and SXT-BA (air) methods were 11 and 12.7%, respectively-one-half as high as the rates obtained by the remaining methods. Beta-hemolytic streptococci, groups C, F, and G, are inhibited on the SXT-BA plates and were the primary cause of the higher false-positive rates on SBA and pour plate plus broth methods. An additional 3% positive cultures were obtained by incubating SXT-BA (CO(2)) plates up to 48 h before discarding as negative. We recommend either the SXT-BA (CO(2)) or the SXT-BA (air) method with up to 48 h of incubation for routine use in throat cultures.
我们将冈恩等人（《临床微生物学杂志》5:650 - 655，1977年）的含有磺胺甲恶唑加甲氧苄啶（SXT - BA）的选择性血琼脂培养基与传统血琼脂平板（SBA）以及一种改良的血琼脂倾注平板加肉汤法进行比较，以从咽拭子中分离A群链球菌。还评估了SXT - BA和SBA平板在二氧化碳和环境空气培养条件下的影响。对696份有症状儿童的咽拭子同时采用这五种方法进行培养，并在过夜培养后观察；总共检测到204份阳性培养物。每种方法的回收率分别为：SXT - BA（二氧化碳），90.7%；SXT - BA（空气），87.7%；倾注平板加肉汤法，83.3%；SBA（二氧化碳），79.4%；SBA（空气），77%。SXT - BA（二氧化碳）和SXT - BA（空气）方法中约一半的假阴性培养物每平板菌落数≥10至100个菌落。相比之下，对于SBA（二氧化碳）、SBA（空气）和倾注平板加肉汤法，约70%的假阴性培养物每平板菌落数≥10至100个/平板。SXT - BA（二氧化碳）和SXT - BA（空气）方法获得的假阳性培养物分别为11%和12.7%，仅为其余方法获得率的一半。C、F和G群β溶血性链球菌在SXT - BA平板上受到抑制，这是SBA和倾注平板加肉汤法假阳性率较高的主要原因。将SXT - BA（二氧化碳）平板在作为阴性丢弃前培养长达48小时，可额外获得3%的阳性培养物。我们建议在咽拭子培养的常规操作中使用SXT - BA（二氧化碳）或SXT - BA（空气）方法，并培养长达48小时。
