PDF(Pubmed)
Abstract：
Microbial pathogenicity often depends on the route of infection. For instance, P. aeruginosa or S. marcescens cause acute systemic infections when low numbers of bacteria are injected into D. melanogaster flies whereas flies succumb much slower to the continuous ingestion of these pathogens, even though both manage to escape from the gut compartment and reach the hemocoel. Here, we have developed a latent P. aeruginosa infection model by feeding flies on the bacteria for a short period. The bacteria stably colonize internal tissues yet hardly cause any damage since latently-infected flies live almost as long as noninfected control flies. The apparently dormant bacteria display particular characteristics in terms of bacterial colony morphology, composition of the outer cell wall, and motility. The virulence of these bacteria can however be reactivated upon wounding the host. We show that melanization but not the cellular or the systemic humoral response is the predominant host defense that establishes latency and may coerce the bacteria to a dormant state. In addition, the lasting activation of the melanization responses in latently-infected flies provides a degree of protection to the host against a secondary fungal infection. Latent infection by an ingested pathogen protects against a variety of homologous or heterologous systemic secondary infectious challenges, a situation previously described for the endosymbiotic Wolbachia bacteria, a guard against viral infections.
摘要：
微生物的致病性通常取决于感染途径。例如,当低数量的细菌被注射到黑腹果蝇中时，铜绿假单胞菌或粘质链球菌会导致急性全身感染。即使两者都设法从肠腔逃脱并到达血液。这里,我们已经建立了一种潜伏的铜绿假单胞菌感染模型，方法是短期以苍蝇为食。细菌稳定地定植于内部组织，但几乎不会造成任何损害，因为潜伏感染的苍蝇几乎与未感染的对照苍蝇一样存活。明显休眠的细菌在细菌菌落形态方面表现出特殊的特征，外细胞壁的组成，和运动性。然而,这些细菌的毒力可以在伤害宿主时重新活化。我们表明，黑化而不是细胞或全身体液反应是主要的宿主防御，它建立了潜伏期并可能迫使细菌进入休眠状态。此外,潜伏感染的果蝇中黑化反应的持续激活为宿主提供了一定程度的保护，以抵抗继发性真菌感染。由摄入的病原体引起的潜伏感染可防止各种同源或异源的全身性继发性感染挑战，先前描述的内共生Wolbachia细菌的情况，抵御病毒感染的警惕.
