Sadowska Beata, Bonar Agnieszka, von Eiff Christof, Proctor Richard A, Chmiela Magdalena, Rudnicka Wieslawa, Róźalska Barbara
Department of Infectious Biology, Institute of Microbiology and Immunology, University of Lódź, Poland.
FEMS Immunol Med Microbiol. 2002 Feb 18;32(3):191-7. doi: 10.1111/j.1574-695X.2002.tb00553.x.
The colonization of respiratory tract by Staphylococcus aureus is a frequent feature of cystic fibrosis (CF), especially in pediatric patients. The formation of small colony variants (SCVs), which produce reduced amounts of alpha-toxin, is one of the proposed ways of staphylococcal accommodation in an intracellular niche. The aim of the present study was to compare some properties of S. aureus SCVs and their parent strains. A site-directed S. aureus hemB mutant and parent strain 8325-4 were included in the study (control pair). Normal and SCV strain pairs from CF patients as well as control strains were tested for the susceptibility to defensins, killing activity of professional phagocytes and adhesion to A549 cell line. Because S. aureus are exposed to many cationic proteins in the host, we challenged a clinical isolate with minimal subinhibitory concentration (subMIC) of protamine and found that hemin and menadione auxotrophic SCVs emerged. SCVs were more resistant than normal strains to protamine but not to dermaseptin. The susceptibility to the bactericidal activity of magainin was the same for normal and SCV strains. The protamine resistance of normal as well as SCVs was strongly enhanced by high salt concentration. The adhesion of some SCVs to A549 cells was higher than adhesion of parental strains. However, the number of adherent bacteria (SCVs) was diminished in the presence of hemin for hemin auxotrophs. The uptake of SCVs by granulocytes was lower than ingestion of normal strains, but SCVs were killed with equal or greater potency. SCVs are adapted to intracellular survival and persistence in the host under certain circumstances. The ability to form a variant subpopulation affords S. aureus additional survival options.
金黄色葡萄球菌在呼吸道的定植是囊性纤维化（CF）的常见特征，尤其是在儿科患者中。产生少量α-毒素的小菌落变体（SCV）的形成是金黄色葡萄球菌在细胞内生态位中生存的一种可能方式。本研究的目的是比较金黄色葡萄球菌SCV及其亲本菌株的一些特性。研究纳入了一个位点定向的金黄色葡萄球菌hemB突变体及其亲本菌株8325-4（对照配对）。对来自CF患者的正常菌株和SCV菌株对以及对照菌株进行了防御素敏感性、专业吞噬细胞的杀伤活性和对A549细胞系的黏附性测试。由于金黄色葡萄球菌在宿主体内会接触到许多阳离子蛋白，我们用最低亚抑菌浓度（亚MIC）的鱼精蛋白对一株临床分离株进行了挑战，发现出现了血红素和甲萘醌营养缺陷型SCV。SCV比正常菌株对鱼精蛋白更具抗性，但对皮肤抗菌肽不具抗性。正常菌株和SCV菌株对蛙皮素杀菌活性的敏感性相同。高盐浓度强烈增强了正常菌株和SCV对鱼精蛋白的抗性。一些SCV对A549细胞的黏附性高于亲本菌株。然而，对于血红素营养缺陷型菌株，在有血红素存在的情况下，黏附细菌（SCV）的数量会减少。粒细胞对SCV的摄取低于对正常菌株的摄取，但SCV被杀死的效力相同或更高。在某些情况下，SCV适应在宿主体内的细胞内存活和持续存在。形成变异亚群的能力为金黄色葡萄球菌提供了额外的生存选择。
