Ericsson C D, Carmichael M, Pickering L K, Mussett R, Kohl S
South Med J. 1978 Dec;71(12):1524-5. doi: 10.1097/00007611-197812000-00023.
During a two-month period, 6% of Gram stains of predominantly CSF specimens revealed gram-negative bacilli with no growth. The source of the false-positive Gram stain results was an alcohol storage bath from which slides were taken and flamed to remove residual alcohol. All 11 patients in the outbreak had further diagnostic tests or changes in therapy. In the laboratory, false-positive slides could be created by contaminating a slide bath with 10(5) bacilli/ml, flame drying, and staining. In addition, contaminated crystal violet caused a false-positive result when applied to a warm but not to a cool slide. To prevent false-positive Gram stain results, the storage of slides in alcohol baths should be abandoned, slides should not be flamed to remove alcohol, and specimens should be Gram-stained only when the heat-fixed slide has thoroughly cooled.
在为期两个月的时间里，主要取自脑脊液标本的革兰氏染色中有6%显示革兰氏阴性杆菌但无细菌生长。革兰氏染色结果出现假阳性的源头是一个酒精储存槽，从该储存槽取出载玻片并通过火焰加热以去除残留酒精。此次疫情中的所有11名患者都接受了进一步的诊断检测或治疗调整。在实验室中，通过用每毫升含10⁵个杆菌的菌液污染载玻片槽、火焰干燥并染色，能够制造出假阳性载玻片。此外，受污染的结晶紫在应用于温热载玻片而非冷载玻片时会导致假阳性结果。为防止革兰氏染色结果出现假阳性，应摒弃将载玻片储存在酒精槽中的做法，载玻片不应通过火焰加热来去除酒精，并且仅当热固定的载玻片彻底冷却后才应对标本进行革兰氏染色。
