Kapogiannis Bill G, Satola Sarah, Keyserling Harry L, Farley Monica M
Division of Infectious Diseases, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, USA.
Clin Infect Dis. 2005 Dec 1;41(11):e97-103. doi: 10.1086/498028. Epub 2005 Oct 25.
Recent reports of invasive Haemophilus influenzae non-b capsular serotypes in the era since development of conjugate vaccines have prompted concern about serotype replacement. Unusual clusters of invasive infection due to H. influenzae serotype a with clinical features that resemble those of infection due to H. influenzae serotype b have been described. A unique feature often associated with more-virulent H. influenzae serotype a isolates is the IS1016-bexA partial deletion, which was previously identified in the capsule locus of H. influenzae serotype b strains. We report the clinical, epidemiologic, and molecular genetic features of 2 cases of severe disease caused by H. influenzae serotype a.
Invasive H. influenzae isolates were serotyped with standard serological methods, and molecular typing was done with PCR. The capsular genotype of each isolate was characterized with PCR, partial sequencing, and Southern blot hybridization. Further strain typing was performed with pulsed-field gel electrophoresis.
We identified 2 children with severe invasive disease due to H. influenzae serotype a. Both H. influenzae serotype a isolates contained the identical pulsed-field gel electrophoresis pattern and capsular genotype. An IS1016-bexA partial deletion in the capsule gene locus similar to that found in H. influenzae serotype b was identified in both isolates by means of PCR and sequencing of the IS1016-bexA junction.
We describe 2 cases of severe invasive disease due to H. influenzae serotype a with the putative virulence-enhancing IS1016-bexA partial deletion and duplication of the capsule locus. Our data support the hypothesis that this mutation may be associated with virulence in non-b capsular serotypes of H. influenzae.
自结合疫苗研发以来，近期有关于侵袭性非b型流感嗜血杆菌血清型的报道，引发了对血清型替换的担忧。已描述了由a型流感嗜血杆菌引起的侵袭性感染异常聚集情况，其临床特征与b型流感嗜血杆菌感染相似。通常与毒性更强的a型流感嗜血杆菌分离株相关的一个独特特征是IS1016-bexA部分缺失，该缺失先前在b型流感嗜血杆菌菌株的荚膜基因座中被鉴定出来。我们报告了2例由a型流感嗜血杆菌引起的严重疾病的临床、流行病学和分子遗传学特征。
采用标准血清学方法对侵袭性流感嗜血杆菌分离株进行血清分型，并用聚合酶链反应（PCR）进行分子分型。通过PCR、部分测序和Southern印迹杂交对每个分离株的荚膜基因型进行鉴定。用脉冲场凝胶电泳进行进一步的菌株分型。
我们鉴定出2名因a型流感嗜血杆菌引起严重侵袭性疾病的儿童。两个a型流感嗜血杆菌分离株具有相同的脉冲场凝胶电泳图谱和荚膜基因型。通过PCR和IS1016-bexA连接点测序，在两个分离株中均鉴定出与b型流感嗜血杆菌中发现的类似的荚膜基因座中的IS1016-bexA部分缺失。
我们描述了2例由a型流感嗜血杆菌引起的严重侵袭性疾病，其具有假定的增强毒力的IS1016-bexA部分缺失和荚膜基因座重复。我们的数据支持这一假设，即这种突变可能与流感嗜血杆菌非b型血清型的毒力有关。
