Pancotto Laura, De Angelis Gabriella, Bizzarri Esmeralda, Barocchi Michèle A, Del Giudice Giuseppe, Moschioni Monica, Ruggiero Paolo
Novartis Vaccines & Diagnostics, Research Center, Via Fiorentina 1, I-53100 Siena, Italy.
Sci Rep. 2013;3:2040. doi: 10.1038/srep02040.
Streptococcus pneumoniae pili contribute to adherence and virulence. The regulation of pilus-1 expression is bistable, thus piliated strains contain a variable proportion of pilus-1-non-expressing bacteria. We investigated whether such proportion changes during colonization. Pilus-1-expressing bacteria were quantified in nasopharyngeal washes and pharyngeal tissues from mice that received intranasally bacterial populations with high (H), medium (M) or low (L) pilus-1 expression rates. In nasopharyngeal washes, at early colonization stages, pilus-1 expression rates decreased in H population, while increased in L and M; at later stages, expression rates decreased or remained low. Similar trends were observed in pharyngeal tissues, where, however, at late stages the expression rates were medium-high. In conclusion, pilus-1 is preferentially expressed at early colonization stages, consistently with its role in adhesion, while at later stages the expression is partially switched off. Pilus-1 expression rates observed in clinical isolates in vitro may not reflect the actual rates during colonization/infection.
肺炎链球菌菌毛有助于黏附及致病。菌毛-1表达的调控具有双稳态，因此有菌毛菌株中包含可变比例的不表达菌毛-1的细菌。我们研究了在定殖过程中该比例是否发生变化。对经鼻内接种具有高（H）、中（M）或低（L）菌毛-1表达率细菌群体的小鼠的鼻咽灌洗液和咽部组织中的表达菌毛-1的细菌进行了定量分析。在鼻咽灌洗液中，在定殖早期，H群体中菌毛-1表达率下降，而L和M群体中表达率上升；在后期，表达率下降或维持在低水平。在咽部组织中观察到类似趋势，不过在后期表达率为中高水平。总之，菌毛-1在定殖早期优先表达，这与其在黏附中的作用一致，而在后期表达部分关闭。体外临床分离株中观察到的菌毛-1表达率可能无法反映定殖/感染期间的实际表达率。
