pinghang～熱血白袍～

                Streptococci

Group A  BETA-hemolytic: streptococcus pyogenes

這是一個造成很多人類疾病的鏈球菌。

要打敗敵人，一定要先了解敵人。

我們就從常見的Group A 鏈球菌開始，複習幾個重點疾病開始吧。

微生物特性

• G(+),  Lancefield  group A

• Encapsulated, (Hyaluronic acid構成)

Hyaluronic acid 同時存在我們人體很多結締組織，因此可以了解到，

理想上，這部分不能成為我們的抗體標的的部分否則後果不勘設想。

•  Beta-hemolytic , 可完全溶解血球，造成菌落周圍形成透明的區域。
•  Antigen : M protein ( at cell wall ) 他媽的重要!  大抵有兩個功用

1. anti-phagotic action
2. antigenic (strong response) micmic the myosin of the heart

•  Enzymes

       1. Pyrogenic exotoxin  

       a. Exotoxin A and C: scarlet fever, Toxic shock like syndrome

       b. Exotoxin B: Necrotizing fasciitis（就是這個機車酵素嚇死人～！）

       2. Streptokinase: plasminogen to plasmin

(use at dissolve fibrin…etc.) 

       3. DNAase

       4. Streptolysin O: antigenic, can test ASO antibody for prove recent infection, beta-hemolytic related. 臨床會用到！

• Important disease
  1. Impetigo
  2. Cellulitis(margin not well defined)and erysipelas(margin well-defined)
  3. Scarlet fever: 

     Strawberry tougue

     Pharyngitis

     Erythematous rash (face sparing) 

畫的很醜請見諒！應該看得懂啦吼～

                 4.Toxic shock like syndrome

                 5. Necrotizing fasciitis

接下來兩個疾病是今天的重頭戲！！！！！

• Rheumatic fever(type II hypersensitivity)

         Just pharyngitis makes it! Not other disease(ex.cellulitis…)

只有感染咽部的這群會造成，其他部位的不會。因此患者一定之前有喉嚨痛病史！

     Affects children 1-5 weeks after an episode of streptococcal pharyngitis(strep throat)

    Caused by molecular mimicry(bacterial M protein told before)

    Diagnosis by Jones criteria

1. Evidence of prior group A-β hemolytic streptococcal infection

(Elevated ASO or anti-DNase B titers. 

 ASO titers peak at 4-5 weeks after a streptococcal pharyngitis.)

Throat cultures possibly positive

2. with the presence of major and minor criteria (2大or 1大1小)

Minor criteria are non-specific

include fever and elevated ESR,CRP, absolute neutrophilic leukocytosis ,

arthralgia, previous RF or rheumatic heart disease, ECG: prolonged PR interval(1 degree AV block)。

Major criteria(用口訣！)

Major 1關節部分 (~75% of cases)

遊走性關節炎，通常牽連到一處大關節，幾天後緩解後又遊走到下一個大關節，

不過通常不會造成關節的傷害。Most common initial presentation of acute RF, no permanent joint damage

Major 2心臟部分(~35% of cases)

分為心內膜炎，心肌炎，心包膜炎

心內膜炎：mitral valve >aortic valve regurgitation

sterile, verrucous vegetations develop along the line of closure of the valve

心肌炎：Aschoff bodies:chronic inflammation,有幾個成員如以下

reactive histiocytes with slender,wavy nuclei(Anitschkow  cells)就是圖中有細細核的histiocyte!! 

 giant cells and fibrinoid materials 。

常以心臟衰竭表現為主。最常造成acute RF死亡的原因!     

<from slide share: rheumatic heart disease>

心包膜炎 : fibrinous pericarditis

Major 3  皮下結節(~10% cases)：

如橡膠般的結節出現在皮膚之下，不會痛!

常在骨頭，關節處。Occur on the extensor surfaces of the forearms.

Very similar to those seen in rheumatoid arthritis, centers of the nodules have fibrinoid necrosis.

Major 4邊緣性紅斑(~10% cases)：

具有由中心向外擴散的紅色邊緣。不會癢!!

Evanescent circular rings of C-shaped areas of erythema around the normal skin

Major 5 舞蹈症(~10% cases)：

無節制的四肢擺動，如跳舞。Reversible rapid, involuntary movements affecting all the muscles.

治療：Penicillin!  Aspirin with or without a murmur.

急性通常會緩解，但常常反覆感染變成慢性的類風濕心臟病。

Recurrent RF produces chronic  valvular disease

而造成mitral valve stenosis(fish mouth), fusion of commisures of aortic valve.

慢性也往往造成infecious endocarditis的風險上升。

• Acute post-streptococcal glomerulonephritis(PSGN)(type III hypersensitivity)

相對於rheumatic fever, PSGN只要是感染到此菌就會有造成的風險(皮膚的感染也會喔!)

通常在感染後兩週發生。要記住啊！！！！

1. Puffy face（臉腫）
2. Cola urine 可樂色的尿液（深褐色，其實是血尿）
3. Post-2-weeks-infection of strep. Pyogenes（兩星期前有喉嚨痛病史）
4. Penicillin not prevent  it（提早用抗生素也無法避免發生）

                 差不多啦！！額外贈送！

送！區別S. aures and group B streptococci.

catalase test !  S.aureus(+)        v.s.      group A streptococci(-)

Bacitracin test sensitivity!

group B streptococci: Bacitracin non-sensitive!

v.s.

group A streptococci: Bacitracin sensitive!

That's all   希望有幫到各位！