Izano Era A, Sadovskaya Irina, Vinogradov Evgeny, Mulks Martha H, Velliyagounder Kabilan, Ragunath Chandran, Kher William B, Ramasubbu Narayanan, Jabbouri Saïd, Perry Malcolm B, Kaplan Jeffrey B
Department of Oral Biology, New Jersey Dental School, Newark, NJ 07103, USA.
Microb Pathog. 2007 Jul;43(1):1-9. doi: 10.1016/j.micpath.2007.02.004. Epub 2007 Mar 4.
Most field isolates of the swine pathogen Actinobacillus pleuropneumoniae form tenacious biofilms on abiotic surfaces in vitro. We purified matrix polysaccharides from biofilms produced by A. pleuropneumoniae field isolates IA1 and IA5 (serotypes 1 and 5, respectively), and determined their chemical structures by using NMR spectroscopy. Both strains produced matrix polysaccharides consisting of linear chains of N-acetyl-D-glucosamine (GlcNAc) residues in beta(1,6) linkage (poly-beta-1,6-GlcNAc or PGA). A small percentage of the GlcNAc residues in each polysaccharide were N-deacetylated. These structures were nearly identical to those of biofilm matrix polysaccharides produced by Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis. PCR analyses indicated that a gene encoding the PGA-specific glycoside transferase enzyme PgaC was present on the chromosome of 15 out of 15 A. pleuropneumoniae reference strains (serotypes 1-12) and 76 out of 77 A. pleuropneumoniae field isolates (serotypes 1, 5 and 7). A pgaC mutant of strain IA5 failed to form biofilms in vitro, as did wild-type strains IA1 and IA5 when grown in broth supplemented with the PGA-hydrolyzing enzyme dispersin B. Treatment of IA5 biofilms with dispersin B rendered them more sensitive to killing by ampicillin. Our findings suggest that PGA functions as a major biofilm adhesin in A. pleuropneumoniae. Biofilm formation may have relevance to the colonization and pathogenesis of A. pleuropneumoniae in pigs.
猪胸膜肺炎放线杆菌的大多数野外分离株在体外的非生物表面上形成坚韧的生物膜。我们从胸膜肺炎放线杆菌野外分离株IA1和IA5（分别为血清型1和5）产生的生物膜中纯化了基质多糖，并使用核磁共振光谱法确定了它们的化学结构。这两种菌株都产生了由β(1,6)连接的N-乙酰-D-葡萄糖胺（GlcNAc）残基线性链组成的基质多糖（聚-β-1,6-GlcNAc或PGA）。每种多糖中一小部分的GlcNAc残基发生了N-脱乙酰化。这些结构与大肠杆菌、金黄色葡萄球菌和表皮葡萄球菌产生的生物膜基质多糖的结构几乎相同。PCR分析表明，编码PGA特异性糖苷转移酶PgaC的基因存在于15株胸膜肺炎放线杆菌参考菌株（血清型1-12）中的15株以及77株胸膜肺炎放线杆菌野外分离株（血清型1、5和7）中的76株的染色体上。IA5菌株的pgaC突变体在体外无法形成生物膜，野生型菌株IA1和IA5在添加了PGA水解酶分散素B的肉汤中生长时也无法形成生物膜。用分散素B处理IA5生物膜使其对氨苄青霉素杀伤更敏感。我们的研究结果表明，PGA在胸膜肺炎放线杆菌中作为主要的生物膜黏附素发挥作用。生物膜形成可能与胸膜肺炎放线杆菌在猪体内的定植和发病机制有关。
