< Presentation of Case >
A 28-year-old injection drug user, previously healthy, had been diagnosed as having HIV infection and HCV infection 8 years earlier before this admission, for which he received regular follow up but did not receive antiviral therapy for the two infections. While he claimed of having received methadone replacement therapy for 5 years, the last injection of heroin occurred about 5 days ago. He had been otherwise in his usual state of health until 2 weeks before admission, when left lumbar pain developed after a traffic accident. He did not recall wound or trauma of the whole body due to the accident. However, progressive symptoms including swelling, redness, local warmth, and pain at the left lumbar region developed, which were associated with night fever. He sought medical attention at the Emergency Department (ED) at this hospital, where physical examination revealed the temperature of 39.1℃, the blood pressure 94/56mmHg, the pulse rate 111 beats per minute, and the respiration 18 breaths per minute. A huge erythematous soft mass measured 10 x 8 cm in size was noted at the left lumbar region, with warmth and tenderness. Also, oral thrush and angular vesicles were seen. There were no lymphadenopathies, other skin rashes, throat exudates, cardiac murmurs, abnormal breath sounds, peritoneal signs or leg edema.
Computed tomography (CT) of the abdomen and pelvis disclosed extensive abscesses involving the left psoas muscle (Figure, arrow) and paraspinal muscle (Figure, arrow head), with suspected epidural involvement. He denied a history of recent operation, hospitalization, or animal contact. On admission, the patient underwent CT-guided drainage and a culture of the pus specimen revealed methicillin-sensitive Staphylococcus aureus.
The results of laboratory studies were as follows.
1. CBC and differential count:
WBC
/μl |
RBC
M/μl |
Hb
g/dl |
Plt
K/μl |
Hct
% |
MCV
fL |
Band
% |
Seg
% |
Baso
% |
Eos
% |
Mon
% |
Lym
% |
22660 |
3.51 |
9.4 |
491 |
28.9 |
82.3 |
0 |
86.8 |
0.1 |
0.6 |
5 |
7.5 |
2. Biochemistry:
ALT
U/L |
T-bil
mg/dL |
LDH
IU/L |
BUN
mg/dL |
Cre
mg/dL |
Na
mmol/L |
K
mmol/L |
Cl
mmol/L |
37 |
0.42 |
276 |
9.5 |
0.7 |
126 |
3.4 |
102 |
3. Microbiology and Virology:
CD8
(Suppressor T Cells)(%) |
CD19
(B Cells)(%) |
CD3
(Total T Cells)(%) |
CD4
(Helper T Cells)(%) |
CD4/CD8
Lymphocyte
SM-Infectious Disease |
HIV Viral Load
(copies/mL) |
38 |
16 |
79 |
33 |
0.88 |
45900 |
HBsAg (IU/ml) |
Anti-HBs (mIU/ml) |
Anti-Hepatitis C |
Anti-HAV |
Pus culture |
|
Negative |
Negative |
Positive |
Negative |
S. aureus 2+ |
|
Figure. CT of the abdomen and pelvis
< Discussion >
全世界約有2千萬(5%)人口使用毒品,而約有130萬人使用靜脈注射,且其中78%個案是在發展中國家。靜脈注射毒品者,易有各種感染,包括HIV病毒、B型或C型肝炎、感染性心內膜炎(infective endocarditis)、以及皮膚、肌肉骨骼、軟組織膿瘍(soft tissue abscess)或感染,甚至壞死性筋膜炎(necrotizing fasciitis)。另外,因此族群人較易群聚並常伴其他抽煙等習慣,感染社區型肺炎(community-acquired pneumonia)、肺結核等機率都較高。以下我們針對靜脈毒癮者常見的三類感染做一些討論和介紹。
Skin and soft tissue infections: 阿姆斯特丹的研究人員曾經進行一個前瞻性研究,他們發現靜脈毒癮者的膿瘍發生率約3年發生一次。若近30天內有用皮下注射毒品(skin-popped),感染機率較單純靜脈注射者又更為上升。靜脈毒癮者發生軟組織感染的危險因子有許多,例如:海洛因與古柯鹼混合(speed-balls)使用、注射頻率高、感染HIV、共用或使用不清潔的針頭、注射前未消毒、注射時重複flushing and pulling back (booting)。在軟組織膿瘍或感染中,最常見的菌種為表皮共生菌Staphylococcus aureus其次為Streptococcus species,而在有些社區型感染的致病菌種甚至會包含methicillin-resistant S. aureus (MRSA)或Clostridium species等。靜脈注射毒品者皮膚較易有移生(colonization),容易在注射時經由針孔穿刺帶入周圍組織與血液中。美國巴爾的摩研究顯示,注射藥品前從未消毒者,膿瘍發生率為每次都有消毒者的兩倍。若注射於femoral vein,不但增加常見菌感染風險,更增加格蘭氏陰性菌(Gram-negative bacteria)的感染。另外,共用器具、藥品混合物以及稀釋液都提高了前述病毒或細菌感染的機率。其次,根據不同製備藥品的方式,靜脈毒癮者也會感染不同且較少見的菌種;如pentazocine與tripelennamine混合(“Ts and Bleus”, or “TaBs”),曾造成P. aeurginosa感染性心內膜炎的群突發(outbreak)。
Musculoskeletal infections: 常見的肌肉骨骼感染途徑為血行傳播,與從局部的皮膚與軟組織感染的擴散,雖然後者較少見。這些感染的症狀,可能是病兆部位的疼痛和功能受到影響,有時唯一的症狀為沒有發燒的疼痛。靜脈毒癮者易有不尋常的感染位置,如sternoclavicular joints、sacroiliac joints,甚至是vertebral spine以及knee。感染這些少見位置的高危險群為:注射於jugular vein (pocket shot)或femoral vein (groin hit) 的靜脈毒癮者。
Endovascular infections: 心臟和血管的感染中,70%為S. aureus所造成的的三尖瓣心臟瓣膜炎(infective endocarditis of the tricuspid valve)。常見症狀為:發燒、喘、pleuritic chest pain與咳嗽。若造成左心的心臟瓣膜炎,則要小心病患可能在到醫院時或治療過程中由於septic emboli發生的併發症,如:腦膿瘍(brain abscess)、脾膿瘍(splenic abscess)。其次,靜脈毒癮者也是少見的多重菌種感染性心內膜炎(polymicrobial endocaridits)的危險族群。
以下表格,取自N Eng J Med 2005的綜論,顯示靜脈毒癮者常見的感染與菌種
就治療而言,開始使用抗生素前,先取得適當的臨床檢體進行格蘭氏染色和微生物培養,以利於後續抗微生物藥物的選擇。在細菌培養結果尚未得到前,我們必須選用針對最可能感染菌種的抗生素為一線治療。有膿瘍者,我們也必須照會相關外科醫師進行切開引流術。以下針對各種感染的治療,我們取自N Eng J Med 2005的綜論,整理如下
就預防感染的角度而言,最徹底的預防方式當然是停止使用靜脈毒品,但這實際上往往很困難,因此,降低感染率的減害計畫與注射毒品時的使用方式便是最重要的預防方法。醫療管控下的注射器材、針具交換計畫、無菌注射的街頭教學、煮沸藥品、用漂白水消毒器具與酒精消毒皮膚、避免共用針具與稀釋液,以及避免高風險的注射處,如:脖子及鼠蹊部等,都是目前能降低感染風險的方法。
< References >
N Eng J Med 2005;353:1945-54.
Lancet. 2008;372(9651):1733. |