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<病史>
A 39-year-old man had been a drinker
and heavy smoker who had consumed 1 PPD of cigarette for more
than 20 years. He had painful external hemorrhoid and received
operation two years before admission in another hospital. He
had been well until 1 week prior to admission when he suffered
from progressive dyspnea and mild dry cough without fever. He
visited a local hospital 2 days later, where nebulized
brinchodilator was given to relieve the dyspnea associated
with bronchospasm. However, the symptoms recurred and
worsened. He came back to the hospital again where poor
arterial oxygenation was noted. He was intubated and
transferred to the ICU of our hospital for further treatment.
On arrival at our hospital, his BP was 124/73 mmHg,HR was
158/min and his body temperature was 38.5°C. The Glasgow coma
scale consciousness level was E3VtM4. Head CT was performed
due to impaired consciousness and showed no intracranial
hemorrhage or definite hypodense lesions. Auscultation of the
chest revealed marked crackles in bilateral lung fields and
CXR showed multiple pneumonic patches (Figure1)..
Lumbar puncture showed sterile CSF. Septic work-ups were
performed and the blood and sputum culture yielded methicillin
resistant Staphylococcus aureus (MRSA) which was susceptible
to vancomycin, gentamicin, trimethoprim/sulfamethoxazole and
minocycline. Vancomycin was given but the following blood
culture 3 days later still grew MRSA. Transesophageal and
transthoracic ultracardiograpghy revealed no vegetation so
that the diagnosis of infective endocarditis was excluded.
Anti-HIV was negative. Chest CT revealed bilateral multiple
septic emboli with cavitation and lung abscess formation (Figure2
). His fever subsided and
consciousness improved gradually. He was extubated
successfully 7days after admission and was transferred to the
general ward. After treatment with vancomycin for 42 days, the
chest X raynabnormailities nearly totally resolved. He was
discharged in stable condition without any sequelae.
<討論>
Methicillin抗藥性金黃色葡萄菌(methicillin-resistant Staphylococcus
aureus；MRSA)感染過去均認為是與院內感染有關，但在這近十年間有越來越多的報告指出在過去身體健康的年輕病人身上，社區型Methicillin抗藥性金黃色葡萄菌(community-acquired
MRSA;CA-MRSA)感染已經在社區流行，包含軍隊，監獄，運動員，或是美國局部地區包含台灣地區都有被報告有發生突發流行。CAMRSA感染之定義，根據美國為一年內沒有以下危險因子：
- receipt of systemic
antimicrobial treatment,
- residence in a long-term care
facility,
- prior admission to an acute
care facility,
- use of central intravenous
catheters or long-term venous access devices,
- use of urinary catheters,
- use of other long-term percutaneous
devices
- prior surgical procedures, and/or
- need of dialysis。
CA-MRSA與院內感染MRSA臨床表現不同，抗藥性表現型分佈不同，有較多的皮膚與軟組織感染，少數案例如此例會造成肺部膿瘍與膿胸，且用脈衝電泳分析基因型(pulsed-field
gel electrophoresis,
PFGE)分析，認為CA-MRSA來源並非來自院內感MRSA。CA-MRSA多以皮膚及軟組織感染表現，少數有壞死性肺炎;
CA-
MRSA感染有幾個特色:包含CA-MRSA菌株對其他抗生素(除beta-lactam)，呈現較感受性的狀態,比如此案例之
gentamicin, trimethoprim/sulfamethoxazole and minocycline等等。
CA-MRSA菌株常會帶有SCCmecIV或SCCmec V以及Panton-Valentine
leukocidin（PVL）。PVL被報告過與軟組織感染與壞死性肺炎有關。Leukocidin是一種金黃色葡萄球菌細菌的毒素，可以藉由在細胞膜上建立孔洞，因而使穿透力增加而使分子進出細胞沒有屏障，並釋放細胞激素，活化細胞內的蛋白脢，進而殺死白血球。法國學者分析從1986年到1998年帶有PVL基因的社區型金黃色葡萄球菌肺炎病例壞死性肺炎(necrotising
pneumonia)，發現在16個過去免疫力正常的年輕人，比36個PVL陰性的社區型金黃色葡萄球菌肺炎病例，有更高的機會發生致命力高的出血性肺炎
，而且這些病例之前常有類流行感冒的症狀。症狀常會快速惡化伴隨咳血，這些被帶有PVL基因之金黃色葡萄球菌感染的病人也容易會呈現成人呼吸窘迫症候群，伴隨多器官衰竭。
治療上來講，一般還是以傳統之抗MRSA藥物之glycopeptide為主，其他藥物包含抗藥性成敏感之gentamicin,
trimethoprim/sulfamethoxazole，ciprofloxacin，rifampin或是linezold可為alternative或為合併之選擇治療，若有化膿，常需要手術幫忙。
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Case Discussion
繼續教育考題