Grant P E, Brenner D J, Steigerwalt A G, Hollis D G, Weaver R E
Morehouse School of Medicine, Atlanta, Georgia.
J Clin Microbiol. 1990 Dec;28(12):2591-6. doi: 10.1128/jcm.28.12.2591-2596.1990.
CDC group M-6 is the vernacular name given to a gram-negative, oxidase-positive, aerobic, nonmotile, rod-shaped bacterium. This organism is biochemically similar to Kingella denitrificans and displays a cellular fatty acid profile consistent with CDC groups M-5 and EF-4 and with Neisseria elongata. Of the 95 M-6 strains referred to the Centers for Disease Control (CDC) for identification, 32 (64%) of the first 50 were from the throat or sputum and only 3 (6%) were from blood; only 5 (11%) of the next 45 isolates were from the upper respiratory tract and 23 (51%) were from blood, with many of these (15 or 65%) being associated with endocarditis. The major characteristics of CDC group M-6 include reduction of nitrate and nitrite with no gas formation; positive reaction for oxidase; negative reactions for catalase, urease, indole, and motility; and no acid production from carbohydrates. Guanine-plus-cytosine content determined spectrophotometrically by thermal denaturation was 55 to 58 mol % for six M-6 strains tested: 56 mol % for the N. elongata subsp. elongata type strain and for the N. elongata subsp. glycolytica type strain. By the hydroxyapatite method, DNAs from 24 M-6 strains showed an average of 78% relatedness to M-6 reference strain B1019 in reactions at 60 degrees C and 73% relatedness in reactions at 75 degrees C. M-6 strain B1019 was 79% related to the N. elongata type strain at 60 degrees C and 71% related at 75 degrees C; it was 75% related to the type strain N. elongata subsp. glycolytica at 60 degrees C and was 66% related at 75 degrees C. DNAs from CDC group EF-4, K. denitrificans, and CDC group M-5 were all less than 14% related to CDC group M-6 at 75 degrees C. The DNA relatedness data showed conclusively that all the M-6 strains belong in the species N. elongata. M-6 is different from N. elongata subsp. elongata in that M-6 reduces nitrate and sometimes weakly acidifies D-glucose, and it is different from N. elongata subsp. glycolytica in that it reduces nitrate and is negative for glucose and catalase. Because of the apparent clinical significance of M-6 compared with the clinical significance of N. elongata subsp. elongata and N. elongata subsp. glycolytica and the ease in distinguishing it biochemically, we propose M-6 as a third subspecies of N.elongata, N. elongata subsp. nitroreducens subsp. nov.
疾病控制中心（CDC）的M-6组是一种革兰氏阴性、氧化酶阳性、需氧、无动力、杆状细菌的俗称。该微生物在生化特性上与反硝化金氏杆菌相似，其细胞脂肪酸谱与CDC的M-5组和EF-4组以及长奈瑟菌一致。在送交疾病控制中心（CDC）鉴定的95株M-6菌株中，前50株中的32株（64%）来自咽喉或痰液，仅有3株（6%）来自血液；后45株分离株中仅有5株（11%）来自上呼吸道，23株（51%）来自血液，其中许多（15株或65%）与心内膜炎有关。CDC M-6组的主要特征包括硝酸盐和亚硝酸盐还原且不产生气体；氧化酶反应阳性；过氧化氢酶、脲酶、吲哚和动力反应阴性；碳水化合物不产酸。通过热变性分光光度法测定的6株M-6菌株的鸟嘌呤加胞嘧啶含量为55%至58摩尔%：长奈瑟菌 elongata亚种的模式菌株和长奈瑟菌 glycolytica亚种的模式菌株为56摩尔%。通过羟基磷灰石法，24株M-6菌株的DNA在60℃反应中与M-6参考菌株B1019的平均相关性为78%，在75℃反应中为73%。M-6菌株B1019在60℃时与长奈瑟菌模式菌株的相关性为79%，在75℃时为71%；在60℃时与长奈瑟菌 glycolytica亚种模式菌株的相关性为75%，在75℃时为66%。在75℃时，CDC EF-4组、反硝化金氏杆菌和CDC M-5组的DNA与CDC M-6组的相关性均低于14%。DNA相关性数据确凿地表明，所有M-6菌株都属于长奈瑟菌属。M-6与长奈瑟菌 elongata亚种不同，因为M-6能还原硝酸盐，有时还能微弱酸化D-葡萄糖，它与长奈瑟菌 glycolytica亚种不同，因为它能还原硝酸盐，且葡萄糖和过氧化氢酶反应阴性。由于与长奈瑟菌 elongata亚种和长奈瑟菌 glycolytica亚种相比，M-6具有明显的临床意义，且在生化特性上易于区分，我们提议将M-6作为长奈瑟菌的第三个亚种，即新亚种长奈瑟菌 nitroreducens。
