以鼻腔移生菌預測蜂窩性組織炎之病因:前瞻性研究

Abstract

研究背景與目的 蜂窩性組織炎通常由移生在皮膚或質附屬物上的內生性菌叢所引起，如金黃色葡萄球菌或鏈球菌等。但是，蜂窩性組織炎如果沒有膿瘍或開放性傷口時，有時很難建立確切的病因，尤其，近年來，社區型MRSA（具甲氧西林抗藥性的金黃色葡萄球菌）在台灣出現，是否會改變蜂窩性組織炎病患的流行病學，目前仍不清楚。鼻腔拭子目前是用來檢測病患是否為MRSA帶原者的工具，但其在預測軟組織感染病因的部分目前仍不清楚。本研究目的即在建立台灣成年的蜂窩性組織炎患者，其「鼻腔金黃色葡萄球菌」帶菌的流行學及臨床資料，並了解是否可利用「鼻腔的金黃色葡萄球菌」的帶菌情形來接間預測蜂窩性組織炎的病患的病因。 方法 本前瞻性研究納入年齡超過20歲，診斷為蜂窩組織炎的患者。收集其鼻腔拭子抹片結果，及與蜂窩織炎患部有關的檢體。同時也收集病患其他的臨床相關的資料。 結果 共有89名蜂窩性組織炎患者參加了這個為期兩年的觀察性研究。有6位 (6.7%)病患發生甲氧西林敏感金黃色葡萄球菌（MSSA）的感染，5位 (5.4%)為MRSA感染，2位 (2.2%)為溶血性鏈球菌的感染。而89位病患中，金黃色葡萄球菌鼻腔帶原率為17％（n = 15），其中12.4％（n = 11）為MSSA而4.5％（n = 4）為MRSA。研究中並沒有發現特定的因素可以預測帶原狀況，僅發現若有金黃色葡萄球菌鼻腔帶原的患者，發病時傾向於有較高的體溫（38.1 vs 37.4，p = 0.06）和較高的膿液形成率（47％ vs 23％，p = 0.06）。而MRSA的帶原者，其年齡較大於MSSA（62 vs 44，p = 0.06）的帶原者。在臨床治療的部分，有無金黃色葡萄球菌帶原，以及有無經驗性的給予抗MRSA的抗生素並不影響病人治療及預後。然而，治療過程中若有MRSA膿液形成則與延遲的臨床反應有強烈相關 (1.4% vs 20%, p=0.008)。而鼻腔的MSSA帶原對於軟組織感染的病原菌可達相當好的預測力; 但若無鼻腔的MRSA帶原，則有中度的陰性預測力來排除MRSA的感染。鼻腔帶原的金黃色葡萄球菌與同時的發生的膿液之抗生素敏感性實驗結果具有相當好的相關性。 結論 罹患蜂窩性組織炎的成年病患中，約5.4%為有抗藥性金黃色葡萄球菌感染，而鼻腔金黃色葡萄球菌的帶原率為4.5%。病患若有MRSA的膿瘍形成則會顯著的延遲治療反應。而鼻腔的MSSA帶原對於軟組織感染的病原菌可達相當好的預測力。而根據目前台灣的MRSA在蜂窩性組織炎的盛行率而言，若病患沒有MRSA鼻腔帶原，則有中度的排除MRSA感染的機會。而鼻腔帶原菌株的抗生素檢測的結果也可以做為抗生素選擇的參考。

Cellulitis is usually caused by indigenous flora colonizing on the skin and appendages, such as Staphylococcus or Streptococcus. When absence of culture evidence, we prescribed antibiotics dependent on local epidemiologic data. In the recent years, community- acquired MRSA (methicillin-resistant Staphylococcus aureus) emerges in Taiwan. The epidemiologic revolution in cellulitis of adult in Taiwan needs to be established. In addition, nasal swab is a tool to detect MRSA carriage but its role in early predicting etiology of skin soft tissue infection is limited. Patients and Methods Patients, aged over 20, with diagnosis of cellulitis were prospectively enrolled. Nasal swab, specimen related to cellulitis, demographic information and clinical response were collected. Results Totally, 89 patients were enrolled in the two-year observational study. Staphylococcus aureus infection was the most common etiology of purulent cellulitis. Staphylococcus aureus nasal colonization rate was 17% (n=15), including 4.5% (n=4) of MRSA. No specific demographic factors can predict the carriage status. There were no significant differences in their treatment course and prognosis between patients with and without S. aureus carriage and between patients with or without be prescribed empiric anti-MRSA antibiotics. MRSA pus formation was strongly associated with delayed clinical response (1.4% vs 20%, p=0.008). MSSA nasal colonization offers a good positive predict value (100%) and MRSA nasal colonization has a good specificity (87.5%) and a suboptimal negative predict value (63.6%) in concurrent soft tissue infection. Conclusion Adult patients with cellulitis in Taiwan have 5.6% probability resulted from MRSA infection and either S. aureus or MRSA nasal colonization rate is not higher than general population. MRSA pus formation would significant delay clinical treatment response. Nasal MSSA colonization can be an excellent predictor in concurrent purulent soft tissue infection. Given the prevalence of MRSA infection in cellulitis in Taiwan, without nasal MRSA nasal colonization can be a moderate negative predictor to exclude MRSA infection.