Background

The nasal carriage of Staphylococcus aureus introduces risks for subsequent infections, the rate of which is particularly high in children. The colonization mechanisms of S. aureus are not fully understood.

Methods

The epidemiological characteristics of nasal colonizing strains from pediatric patients undergoing liver transplantation and healthy pre-school children were analyzed first. Phenotypes, including biofilm formation and hemolytic activity, were tested for all the isolates. Bacterial pathogenicity indicated by a mouse skin abscess model and resistance to antimicrobial peptides (AMPs) was compared between the predominant genotypes from each group.

Results

The ST188 clone dominated in healthy children, whereas ST59 was prevalent for the pediatric patients. Although ST22 was the second most abundant genotype in the patient group, it was rarely found in healthy children. Interestingly, the colonizing ST59 and ST22 genotypes were more virulent, as indicated by the increased ability for hemolysis in vitro and severe subcutaneous abscesses in the mouse model, compared with ST188. We observed that the virulent ST59 and ST22 displayed higher resistance to antibiotics compared with ST188. Most of the ST59 and ST22 were methicillin-resistant S. aureus (MRSA), and all of the ST188 strains were methicillin-susceptible (MSSA). Moreover, we observed that the virulent ST59 and ST22 can resist killing by human antimicrobial peptides (AMPs). Mechanically, upon stimulation by AMPs, the virulent S. aureus can induce high expression of a phenol-soluble modulin transporter (Pmt) system.

Conclusion

Pediatric patients can be colonized by virulent S. aureus clones, which are able to resist AMPs’ killing through the Pmt system. The residence of virulent strains necessitates the continuous monitoring of potential infections, as well as annealing, to take protective decolonization measures.

中文翻译：

---

剧毒金黄色葡萄球菌通过抵抗人类抗菌肽的杀伤来定植小儿鼻孔

背景

金黄色葡萄球菌的鼻腔携带会带来后续感染的风险，儿童的感染率尤其高。金黄色葡萄球菌的定植机制尚不完全清楚。

方法

首先分析了接受肝移植的儿科患者和健康学龄前儿童鼻腔定植菌株的流行病学特征。测试了所有分离株的表型，包括生物膜形成和溶血活性。比较了小鼠皮肤脓肿模型显示的细菌致病性和对抗菌肽 (AMP) 的耐药性，并在各组的主要基因型之间进行了比较。

结果

ST188 克隆在健康儿童中占主导地位，而 ST59 在儿科患者中很普遍。虽然 ST22 是患者组中第二丰富的基因型，但在健康儿童中很少发现。有趣的是，与 ST188 相比，定植的 ST59 和 ST22 基因型更具毒性，这表明小鼠模型的体外溶血能力和严重皮下脓肿的能力增加。我们观察到，与 ST188 相比，毒性 ST59 和 ST22 对抗生素的耐药性更高。大多数 ST59 和 ST22 是耐甲氧西林金黄色葡萄球菌(MRSA)，所有 ST188 菌株均对甲氧西林敏感 (MSSA)。此外，我们观察到毒性 ST59 和 ST22 可以抵抗人类抗菌肽 (AMP) 的杀伤。机械地，在 AMP 刺激下，剧毒金黄色葡萄球菌可诱导酚溶性调节蛋白转运蛋白 (Pmt) 系统的高表达。

结论

小儿患者可以被毒性金黄色葡萄球菌克隆定植，这些克隆能够通过 Pmt 系统抵抗 AMP 的杀伤。剧毒菌株的驻留需要持续监测潜在感染以及退火，以采取保护性非定植措施。