Gram-negative bacterial capsules are associated with production of carbohydrates, frequently resulting in a mucoid phenotype. Infections caused by capsulated or mucoid A. baumannii are associated with increased clinical severity. Therefore, it is clinically and epidemiologically important to identify capsulated A. baumannii. Here, we describe a density-dependent gradient test to distinguish between capsulated and thin/non-capsulated A. baumannii. Thirty-one of 57 A. baumannii isolates displayed a mucoid phenotype. The density-dependent gradient test was comprised of two phases, with silica concentrations of 30% (top phase) and 50% (bottom phase). Twenty-three isolates migrated to the bottom phase, indicating thin or non-capsulated strains, and 34 migrated to the top phase, suggesting strains suspected to be capsulated. There was agreement between the mucoid and the non-mucoid phenotypes and the density-dependent gradient test for all but three isolates. Total carbohydrates extracted from strains suspected to be capsulated were significantly higher. Transmission electron microscopy confirmed the presence of a capsule in the six representative strains suspected to be capsulated. The density-dependent gradient test can be used to verify capsule presence in mucoid-appearing A. baumannii strains. Identifying capsulated strains can be useful for directing infection control measures to reduce the spread of hypervirulent strains.

中文翻译：

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使用密度相关梯度测试快速鉴定包囊鲍曼不动杆菌。

革兰氏阴性细菌胶囊与碳水化合物的产生有关，经常导致粘液表型。由有荚膜或粘液状鲍曼不动杆菌引起的感染与临床严重程度增加有关。因此，鉴定有荚膜的鲍曼不动杆菌在临床和流行病学上都很重要。在这里，我们描述了一种密度相关的梯度测试，以区分封装和薄/非封装的鲍曼不动杆菌。57 个鲍曼不动杆菌分离株中有 31 个显示粘液表型。密度相关梯度测试由两相组成，二氧化硅浓度为 30%（上相）和 50%（下相）。23 个分离株迁移到底部相，表明细菌株或非包膜菌株，34 个迁移到顶部相，表明菌株被怀疑被包膜。除了三个分离株外，其他所有分离株的粘液和非粘液表型以及密度依赖性梯度试验均一致。从怀疑被包裹的菌株中提取的总碳水化合物显着更高。透射电子显微镜证实在怀疑被包裹的六种代表性菌株中存在胶囊。密度相关梯度测试可用于验证出现黏液样的鲍曼不动杆菌菌株中是否存在胶囊。识别有荚膜菌株可用于指导感染控制措施以减少高毒力菌株的传播。透射电子显微镜证实在怀疑被包裹的六种代表性菌株中存在胶囊。密度相关梯度测试可用于验证出现黏液样的鲍曼不动杆菌菌株中是否存在胶囊。识别有荚膜菌株可用于指导感染控制措施以减少高毒力菌株的传播。透射电子显微镜证实在怀疑被包裹的六种代表性菌株中存在胶囊。密度相关梯度测试可用于验证出现黏液样的鲍曼不动杆菌菌株中是否存在胶囊。识别有荚膜菌株可用于指导感染控制措施以减少高毒力菌株的传播。