Fleiszig S M, Wiener-Kronish J P, Miyazaki H, Vallas V, Mostov K E, Kanada D, Sawa T, Yen T S, Frank D W
School of Optometry, University of California, Berkeley 94720, USA.
Infect Immun. 1997 Feb;65(2):579-86. doi: 10.1128/iai.65.2.579-586.1997.
Pseudomonas aeruginosa, an opportunistic pathogen, is capable of establishing both chronic and acute infections in compromised hosts. Previous studies indicated that P. aeruginosa displays either a cytotoxic or an invasive phenotype in corneal epithelial cells. In this study, we used polarized MDCK cells for in vitro infection studies and confirmed that P. aeruginosa isolates can be broadly differentiated into two groups, expressing either a cytotoxic or an invasive phenotype. In vivo infection studies were performed to determine if cytotoxic and invasive strains displayed differential pathology. Invasion was assayed in vivo by in situ infection of mouse tracheal tissue followed by electron microscopy. Both cytotoxic and invasive strains entered mouse tracheal cells in situ; however, more necrosis was associated with the cytotoxic strain. In an acute lung infection model in rats, cytotoxic strains were found to damage lung epithelium more than invasive strains during the short infection period of this assay. The expression of cytotoxicity requires a functional exsA allele. In the strains tested, the ability to invade epithelial cells in vitro appears to be independent of exsA expression. Since ExsA is a transcriptional regulator of the exoenzyme S regulon, chromosomal preparations from invasive and cytotoxic strains were screened for their complement of exoenzyme S structural genes, exoS, encoding the 49-kDa ADP-ribosyltransferase (ExoS), and exoT, encoding the 53-kDa form of the enzyme (Exo53). Invasive strains possess both exoS and exoT, while cytotoxic strains appear to have lost exoS and retained exoT. These data indicate that the expression of cytotoxicity may be linked to the expression of Exo53, deletion of exoS and perhaps other linked loci, or expression of other ExsA-dependent virulence determinants. In the absence of a functional cytotoxicity pathway (exsA::omega strains), invasion of eukaryotic cells is detectable.
铜绿假单胞菌是一种机会致病菌，能够在免疫功能低下的宿主中引发慢性和急性感染。先前的研究表明，铜绿假单胞菌在角膜上皮细胞中表现出细胞毒性或侵袭性表型。在本研究中，我们使用极化的MDCK细胞进行体外感染研究，并证实铜绿假单胞菌分离株可大致分为两组，分别表达细胞毒性或侵袭性表型。进行体内感染研究以确定细胞毒性和侵袭性菌株是否表现出不同的病理学特征。通过对小鼠气管组织进行原位感染后进行电子显微镜检查来测定体内侵袭情况。细胞毒性和侵袭性菌株均可原位进入小鼠气管细胞；然而，细胞毒性菌株伴随更多的坏死。在大鼠急性肺部感染模型中，发现在该试验的短感染期内，细胞毒性菌株比侵袭性菌株对肺上皮的损伤更大。细胞毒性的表达需要功能性的exsA等位基因。在所测试的菌株中，体外侵袭上皮细胞的能力似乎与exsA表达无关。由于ExsA是外毒素S调节子的转录调节因子，因此对侵袭性和细胞毒性菌株的染色体制剂进行筛选，以寻找其外毒素S结构基因的互补情况，即编码49 kDa ADP-核糖基转移酶（ExoS）的exoS和编码该酶53 kDa形式（Exo53）的exoT。侵袭性菌株同时拥有exoS和exoT，而细胞毒性菌株似乎已失去exoS并保留了exoT。这些数据表明，细胞毒性的表达可能与Exo53的表达、exoS的缺失以及可能的其他连锁基因座的表达，或其他ExsA依赖性毒力决定因素的表达有关。在缺乏功能性细胞毒性途径（exsA::omega菌株）的情况下，可检测到真核细胞的侵袭。
