Background

Chronic methicillin resistant Staphylococcus aureus (MRSA) in CF is associated with worse outcomes compared to early or intermittent infection. This observation could be related to adaptive bacterial changes such as biofilm formation or anaerobic growth.

Methods

MRSA isolates stored from incident and during chronic (>2 years) infection were included at two study sites. MRSA isolates were characterised by spa-typing, antimicrobial susceptibility testing, biofilm formation and haemolysis under aerobic and anaerobic culture conditions.

Results

Paired MRSA isolates from 49 patients were included. Mean age at incident infection was 9.7±1.2 years with mild to moderate lung disease (FEV₁ 74±4% predicted). Twenty-five subjects showed progression of disease/symptoms after onset of MRSA with significantly increased use of antibiotics. Most isolates belonged to t002 (38%) and t008 (36%) spa-types and 8 patients had a change in spa-type over time. Antimicrobial susceptibility testing showed few differences between incident and late isolates but significantly lower MIC under anaerobic vs. aerobic conditions for vancomycin, fusidic acid, rifampin but higher MIC for trimethoprim-sulfamethoxazole. Biofilm formation and haemolysis did not differ by stage of infection or disease course but both were lower under anaerobic conditions (biofilm p=0.018; haemolysis p=0.002) in multi-variate analyses that included study site, growth condition and stage of infection.

Conclusions

Persistent MRSA infection is frequently associated with clinical decline. Anaerobic growth conditions, which occur in CF airways, affect the expression of virulence factors and antibiotic susceptibility of MRSA more than duration of infection.

中文翻译：

---

囊性纤维化中事件和慢性 MRSA 分离株的表型特征

背景

与早期或间歇性感染相比，CF 中的慢性耐甲氧西林金黄色葡萄球菌(MRSA) 与更差的结果相关。这一观察结果可能与适应性细菌变化有关，例如生物膜形成或厌氧生长。

方法

两个研究地点包括从事件和慢性（> 2 年）感染期间储存的 MRSA 分离株。MRSA 分离株的特征是水疗分型、抗菌药敏试验、生物膜形成和有氧和厌氧培养条件下的溶血。

结果

包括来自 49 名患者的配对 MRSA 分离株。发生感染的平均年龄为 9.7±1.2 岁，患有轻度至中度肺部疾病（FEV ₁ 74±4% 预测值）。25 名受试者在 MRSA 发病后表现出疾病/症状的进展，抗生素的使用显着增加。大多数分离株属于 t002（38%）和 t008（36%）水疗类型，8 名患者水疗发生变化- 类型随着时间的推移。抗菌药物敏感性测试显示，新分离株和晚期分离株之间几乎没有差异，但在厌氧与有氧条件下万古霉素、夫西地酸、利福平的 MIC 显着降低，但甲氧苄啶-磺胺甲恶唑的 MIC 较高。生物膜形成和溶血在感染阶段或病程中没有差异，但在包括研究地点、生长条件和感染阶段的多变量分析中，两者在厌氧条件下均较低（生物膜p = 0.018；溶血p = 0.002）。

结论

持续性 MRSA 感染通常与临床衰退有关。CF 气道中发生的厌氧生长条件对 MRSA 毒力因子的表达和抗生素敏感性的影响大于感染持续时间。