Objective To isolate Staphylococcus aureus and Pseudomonas aeruginosa from samples of higher level unit for quality control.Methods Enrichment, separation and identification for quality control samples were adopted according to “Guideline for Technique of Sterilization”( 2002 edition ). Results Staphylococcus aureus and Pseudomonas aeruginosa were isolated. Conclusion The colonies of S. aureus are sometimes white in blood plates, so pigment is one of the factors for distinguishing Staphylococcus aureus. Inspector can not make decision only from color of pigment, which may easily make wrong conclusions. Pseudomonas pyocyanin 24 - hour test may be negative, if necessary, the incubation time can be extended. In Pseudomonas aeruginosa gelatin liquefaction test, the concentration of gelatin and amount of inoculated bacteria are properly determined according to actual situation, otherwise it can give false negative result and an error of identification for Pseudomonas aeruginosa may be made.%目的 从上级单位质控考核样本中分离金黄色葡萄球菌和铜绿假单胞菌.方法 按2002年版对质控样本进行增菌、分离和鉴定.结果 菌落特征:盲样样本在血平皿上呈白色并具有溶血环菌落,在十六烷三甲基溴化铵琼脂平皿上呈灰白色边缘不整齐菌落.形态染色结果:盲样样本中白色有溶血环、微凸起、边缘整齐的菌落和ATCC6538及ATCC12228为革兰阳性(G+)葡萄状球菌,盲样样本中白色有溶血环,扁平、边缘不整齐菌落和ATCC90278为革兰阴性(G-)无芽胞杆菌.将G+葡萄状球菌做金黄色葡萄球菌的生化鉴定,结果盲样样本和ATCC6538均为阳性,而ATCC12228只有H2O2酶试验和葡萄糖发酵试验为阳性;将G-无芽胞杆菌做铜绿假单胞菌的生化鉴定,结果盲样样本和ATCC90278的绿脓菌素在培养24 h为阴性,培养48 h为阳性,不能液化成品明胶和12%的明胶,能液化11%的明胶,能还原硝酸盐,42℃生长试验阳性.结论 金黄色葡萄球菌在血平板上有时为白色菌落,色素只是判别金黄色葡萄球菌多个因素中的一个因素,检验人员不能仅根据色素做出判定,否则容易做出错误的结论;铜绿假单胞菌绿脓菌素试验24 h可能为阴性,必要时可以延长培养时间;在铜绿假单胞菌明胶液化试验中,要根据实际情况把握好明胶的浓度和菌种的接种量,否则会造成假阴性,对铜绿假单胞菌的判定造成困惑.
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