Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
Departamento de Microbiología y Parasitología, Universidad de Navarra, Pamplona, Spain.
Microbiology (Reading). 2012 Aug;158(Pt 8):2117-2124. doi: 10.1099/mic.0.056994-0. Epub 2012 May 18.
Haemophilus parasuis is a porcine respiratory pathogen, well known as the aetiological agent of Glässer's disease. H. parasuis comprises strains of different virulence, but the virulence factors of this bacterium are not well defined. A neuraminidase activity has been previously detected in H. parasuis, but the role of sialylation in the virulence of this bacterium has not been studied. To explore the relationship between sialic acid (Neu5Ac) and virulence, we assessed the distribution of genes involved in sialic acid metabolism in 21 H. parasuis strains from different clinical origins (including nasal and systemic isolates). The neuraminidase gene nanH, together with CMP-Neu5Ac synthetase and sialyltransferase genes neuA, siaB and lsgB, were included in the study. Neuraminidase activity was found to be common in H. parasuis isolates, and the nanH gene from 12 isolates was expressed in Escherichia coli and further characterized. Sequence analysis showed that the NanH predicted protein contained the motifs characteristic of the catalytic site of sialidases. While an association between the presence of nanH and the different origins of the strains was not detected, the lsgB gene was predominantly present in the systemic isolates, and was not amplified from any of the nasal isolates tested. Analysis of the lipooligosaccharide (LOS) from reference strains Nagasaki (virulent, lsgB(+)) and SW114 (non-virulent, lsgB(-)) showed the presence of sialic acid in the LOS from the Nagasaki strain, supporting the role of sialylation in the virulence of this bacterial pathogen. Further studies are needed to clarify the role of sialic acid in the pathogenicity of H. parasuis.
副猪嗜血杆菌是一种猪呼吸道病原体，是众所周知的格拉泽氏病的病原体。副猪嗜血杆菌包含不同毒力的菌株，但该细菌的毒力因子尚未明确界定。先前已经在副猪嗜血杆菌中检测到神经氨酸酶活性，但尚未研究该细菌中唾液酸化在毒力中的作用。为了探讨唾液酸（Neu5Ac）与毒力之间的关系，我们评估了 21 株来自不同临床来源（包括鼻腔和系统性分离株）的副猪嗜血杆菌中参与唾液酸代谢的基因分布。神经氨酸酶基因 nanH 与 CMP-Neu5Ac 合成酶和唾液酸转移酶基因 neuA、siaB 和 lsgB 一起包含在研究中。发现神经氨酸酶活性在副猪嗜血杆菌分离株中很常见，并且 12 个分离株的 nanH 基因在大肠杆菌中表达并进一步进行了表征。序列分析表明，预测的 NanH 蛋白包含唾液酸酶催化位点的特征基序。虽然未检测到 nanH 的存在与菌株的不同来源之间存在关联，但 lsgB 基因主要存在于系统性分离株中，并且在所测试的任何鼻腔分离株中均未扩增。参考菌株长崎（毒力，lsgB(+)）和 SW114（非毒力，lsgB(-)）的脂寡糖（LOS）分析表明，长崎株的 LOS 中存在唾液酸，支持唾液酸化在该细菌病原体毒力中的作用。需要进一步研究来阐明唾液酸在副猪嗜血杆菌致病性中的作用。
