Reed R P, Sinickas V G, Lewis C, Byron K A
Department of Microbiology, Royal Melbourne Hospital, Victoria, Australia.
Pathology. 1999 May;31(2):127-32. doi: 10.1080/003130299105313.
This study aimed to ascertain the ability of the microbiology laboratory to detect and identify catalase-negative Gram-positive cocci with particular reference to vancomycin-resistant enterococci (VRE). Twenty-seven reference strains and 42 prospectively collected catalase-negative Gram-positive cocci were screened by agar dilution breakpoint susceptibility and linked biochemical methods in routine use. Ability to speciate organisms was then compared using: (i) a multiplex polymerase chain reaction, designed to detect gene sequences specific to Enterococcus faecalis and E. faecium, and vancomycin resistance (van) genes; (ii) a commercial "API 20 strep" (iii) an algorithm using individual tests from a commercial API 20 strep strip; and (iv) the same algorithm utilising traditional phenotyping methods. All vancomycin resistant catalase-negative Gram-positive cocci were detected by an agar dilution screening plate containing 4 micrograms/ml of vancomycin. Polymerase chain reaction (PCR) detected all enterococci with van genes, speciated all vancomycin-sensitive E. faecalis and E. faecium isolates and excluded non-enterococcal vancomycin-resistant catalase-negative Gram-positive cocci. Algorithm-based methods speciated 41 of the 42 study isolates (98%). The API 20 strep correctly identified only 25 (60%) of these organisms, 38 of which were vancomycin-sensitive E. faecalis. VRE are detected by current screening methods for vancomycin-resistant catalase-negative Gram-positive cocci in this laboratory. API 20 strep, currently used to speciate catalase-negative Gram-positive cocci, is less reliable and should be replaced. Algorithm-based phenotyping by either method tested is more reliable for speciation than API 20 strep in its recommended form. Compared to the other methods tested, PCR is a rapid, accurate and inexpensive method of detecting and speciating vancomycin-resistant enterococci and it provides important extra information impacting on clinical therapy and infection control.
本研究旨在确定微生物实验室检测和鉴定过氧化氢酶阴性革兰氏阳性球菌的能力，尤其关注耐万古霉素肠球菌（VRE）。通过琼脂稀释断点药敏试验和常规使用的相关生化方法，对27株参考菌株和42株前瞻性收集的过氧化氢酶阴性革兰氏阳性球菌进行了筛查。然后使用以下方法比较鉴定生物体的能力：（i）多重聚合酶链反应，旨在检测粪肠球菌和屎肠球菌特有的基因序列以及万古霉素耐药（van）基因；（ii）商业“API 20 strep”；（iii）一种使用商业API 20 strep试纸条单项试验的算法；（iv）使用传统表型分析方法的相同算法。所有耐万古霉素的过氧化氢酶阴性革兰氏阳性球菌均通过含4微克/毫升万古霉素的琼脂稀释筛选平板检测到。聚合酶链反应（PCR）检测到所有带有van基因的肠球菌，鉴定出所有对万古霉素敏感的粪肠球菌和屎肠球菌分离株，并排除了非肠球菌性耐万古霉素过氧化氢酶阴性革兰氏阳性球菌。基于算法的方法鉴定了42株研究分离株中的41株（98%）。API 20 strep仅正确鉴定了其中25株（60%）生物体，其中38株为对万古霉素敏感的粪肠球菌。该实验室目前用于耐万古霉素过氧化氢酶阴性革兰氏阳性球菌的筛查方法可检测出VRE。目前用于鉴定过氧化氢酶阴性革兰氏阳性球菌的API 20 strep可靠性较差，应予更换。与推荐形式的API 20 strep相比，所测试的任何一种基于算法的表型分析方法在鉴定方面都更可靠。与其他测试方法相比，PCR是一种快速、准确且廉价的检测和鉴定耐万古霉素肠球菌的方法，它提供了对临床治疗和感染控制有重要影响的额外信息。
