Kozak Natalia A, Benson Robert F, Brown Ellen, Alexander Nicole T, Taylor Thomas H, Shelton Brian G, Fields Barry S
Centers for Disease Control and Prevention, Atlanta, GA 30033, USA.
J Clin Microbiol. 2009 Aug;47(8):2525-35. doi: 10.1128/JCM.02410-08. Epub 2009 Jun 24.
Approximately 84% of legionellosis cases are due to Legionella pneumophila serogroup 1. Moreover, a majority of L. pneumophila serogroup 1 clinical isolates react positively with monoclonal antibody 2 (MAb2) of the international standard panel. Over 94% of the legionellosis outbreaks investigated by the Centers for Disease Control and Prevention are due to this subset of L. pneumophila serogroup 1. To date, there is no complete explanation for the enhanced ability of these strains to cause disease. To better characterize these organisms, we subtyped 100 clinical L. pneumophila serogroup 1 isolates and 50 environmental L. pneumophila serogroup 1 isolates from the United States by (i) reactivity with MAb2, (ii) presence of a lag-1 gene required for the MAb2 epitope, and (iii) sequence-based typing analysis. Our results showed that the MAb2 epitope and lag-1 gene are overrepresented in clinical L. pneumophila serogroup 1 isolates. MAb2 recognized 75% of clinical isolates but only 6% of environmental isolates. Similarly, 75% of clinical isolates but only 8% of environmental isolates harbored lag-1. We identified three distinct lag-1 alleles, referred to as Philadelphia, Arizona, and Lens alleles, among 79 isolates carrying this gene. The Arizona allele is described for the first time in this study. We identified 59 different sequence types (STs), and 34 STs (58%) were unique to the United States. Our results support the hypothesis that a select group of STs may have an enhanced ability to cause legionellosis. Combining sequence typing and lag-1 analysis shows that STs tend to associate with a single lag-1 allele type, suggesting a hierarchy of virulence genotypes. Further analysis of ST and lag-1 profiles may identify genotypes of L. pneumophila serogroup 1 that warrant immediate intervention.
大约84%的军团病病例由嗜肺军团菌血清1型引起。此外，大多数嗜肺军团菌血清1型临床分离株与国际标准株的单克隆抗体2（MAb2）呈阳性反应。美国疾病控制与预防中心调查的军团病暴发中，超过94%是由嗜肺军团菌血清1型的这一亚群引起的。迄今为止，对于这些菌株致病能力增强的原因尚无完整解释。为了更好地描述这些微生物，我们通过以下方法对来自美国的100株嗜肺军团菌血清1型临床分离株和50株嗜肺军团菌血清1型环境分离株进行了亚型分析：（i）与MAb2的反应性；（ii）MAb2表位所需的lag-1基因的存在情况；（iii）基于序列的分型分析。我们的结果表明，MAb2表位和lag-1基因在嗜肺军团菌血清1型临床分离株中过度表达。MAb2识别75%的临床分离株，但仅识别6%的环境分离株。同样，75%的临床分离株携带lag-1，而环境分离株中仅8%携带。在携带该基因的79株分离株中，我们鉴定出三个不同的lag-1等位基因，分别称为费城、亚利桑那和伦斯等位基因。本研究首次描述了亚利桑那等位基因。我们鉴定出59种不同的序列型（STs），其中34种STs（58%）是美国特有的。我们的结果支持这样一种假设，即一组特定的STs可能具有增强的引起军团病的能力。结合序列分型和lag-1分析表明，STs倾向于与单一的lag-1等位基因类型相关联，这表明存在毒力基因型层次结构。对ST和lag-1谱的进一步分析可能会识别出需要立即干预的嗜肺军团菌血清1型基因型。
