Goerke C, Fluckiger U, Steinhuber A, Zimmerli W, Wolz C
Institute for General and Environmental Hygiene, University of Tübingen, Wilhelmstrasse 31, 72074 Tübingen, Germany.
Mol Microbiol. 2001 Jun;40(6):1439-47. doi: 10.1046/j.1365-2958.2001.02494.x.
The cytotoxic alpha-toxin (encoded by hla) of Staphylococcus aureus is regulated by three loci, agr, sarA and sae, in vitro. Here, we assess the regulation of hla in a guinea pig model of device-related infection by quantifying RNAIII (the effector molecule of agr) and hla directly in exudates accumulating in infected devices without subculturing of the bacteria. LightCycler reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify the transcripts. Strains RN6390 and Newman expressed considerably smaller amounts of RNAIII in the guinea pig than during in vitro growth. The residual RNAIII expression decreased during the course of infection and was negatively correlated with bacterial densities. As with RNAIII, the highest hla expression was detected in both strains early in infection. Even in strain Newman, a weak hla producer in vitro, a pronounced expression of hla was observed during infection. Likewise, four S. aureus isolates from cystic fibrosis (CF) patients expressed Q1hla despite an inactive agr during device-related infection as in the CF lung. Mutation of agr and sarA in strain Newman and RN6390 had no consequence for hla expression in vivo. In contrast, the mutation in sae resulted in severe downregulation of hla in vitro as well as in vivo. In conclusion, S. aureus seems to be provided with regulatory circuits different from those characterized in vitro to ensure alpha-toxin synthesis during infections.
金黄色葡萄球菌的细胞毒性α毒素（由hla编码）在体外受三个基因座agr、sarA和sae调控。在此，我们通过直接对感染器械中积聚的渗出液中的RNAIII（agr的效应分子）和hla进行定量，而不对细菌进行传代培养，来评估hla在豚鼠器械相关感染模型中的调控情况。使用LightCycler逆转录-聚合酶链反应（RT-PCR）对转录本进行定量。菌株RN6390和Newman在豚鼠体内表达的RNAIII量比体外生长时显著减少。在感染过程中，残余的RNAIII表达下降，且与细菌密度呈负相关。与RNAIII一样，在感染早期，这两种菌株中均检测到最高的hla表达。即使在体外hla产生较弱的Newman菌株中，在感染期间也观察到hla的明显表达。同样，来自囊性纤维化（CF）患者的4株金黄色葡萄球菌分离株在器械相关感染期间，尽管agr不活跃，但仍如在CF肺部感染时一样表达hla。Newman菌株和RN6390菌株中agr和sarA的突变对体内hla表达没有影响。相反，sae的突变导致hla在体外和体内均严重下调。总之，金黄色葡萄球菌似乎具有与体外特征不同的调控机制，以确保在感染期间合成α毒素。
