Streptococcus necrosis
Introduction
Introduction to streptococcus necrosis Streptococcal necrosis is caused by -hemolytic streptococcus infection, an acute suppurative disease characterized by flaky necrosis of the skin, so it is also called acute streptococcal skin necrosis. Beta-hemolytic streptococcus is highly pathogenic, producing hemolysin in the medium, resulting in a broad and transparent hemolysis ring around the colony. Invading the human body can quickly destroy local tissues and spread to the surrounding area, which can lead to hemolysis. The disease begins with the red, swollen and painful local skin, which is very similar to erysipelas, and has necrotic erysipelas and hospital necrosis. It can occur after limb trauma, and there is no obvious history of trauma. After the advent of penicillin, the disease is rare. basic knowledge The proportion of illness: 0.004%-0.007% Susceptible people: no special people Mode of infection: non-infectious Complications: sepsis
Cause
Streptococcal necrosis
(1) Causes of the disease
Streptococcal necrosis is a local infection caused by -hemolytic streptococcus attacking skin tissue. It occurs in patients with trauma to the extremities, and some people have no obvious history of trauma. Meleeny believes that this disease is Schwaltzman allergic reaction.
(two) pathogenesis
-hemolytic streptococcus invades the skin, releases hyaluronidase, dissolves the interstitial cells of the skin, bacteria rapidly multiply and spread in the skin tissue, and the small blood vessels of the skin are destroyed by infection, red blood cell exudation and small thrombus formation, further Aggravation of skin cell damage, blisters in skin tissue, effusion and large necrosis of the skin, -hemolytic streptococcus in the slurry; skin appendages and distributed sensory nerve endings, can also be affected by injury, after a few days, necrotic tissue dry knot It turns black and forms an eschar that resembles burns. After 2 to 3 weeks, the necrotic skin cells fall off, forming ulcers, and the ulcerated epidermis is full of defects. It may be accompanied by partial dermis and even subcutaneous fat defects, and the edge of the ulcers sneak.
Prevention
Streptococcal necrosis prevention
There is no effective preventive measure for this disease. Early detection and early diagnosis are the key to the prevention and treatment of this disease.
Complication
Streptococcal necrosis complications Complications sepsis
1. Septic -hemolytic streptococcus has a variety of toxins such as hyaluronidase, streptokinase, chain enzyme and hemolysin, which can cause severe poisoning symptoms after being absorbed into the blood, which is the main cause of death.
2. Intravascular hemolysis and tubular necrosis -hemolytic streptococcus has two kinds of hemolysin: SIO, which is a protein containing -SH group, which can dissolve red blood cells and destroy white blood cells and platelets; SLS, which is a small molecule glycopeptide, can cause Renal tubular necrosis.
Symptom
Streptococcus necrosis symptoms common symptoms subcutaneous tissue edema sensory disorder fatigue chills fever
1. chills, fever, infection, the beginning of the patient is chills, fever, pulse speed and fatigue and other systemic symptoms.
2. Redness, pain or sensory disturbance Infected local skin redness and swelling, the boundary between the suppurative foci and the surrounding normal tissue is unclear, local pain, if the sensory nerve in the skin is destroyed, it can also be expressed as a skin sensory disorder.
3. After 2 to 4 days of bloody secretions, the skin is dark red, forming blisters, containing bloody serum and bacteria, and no stench and pus.
4. Ulcer formation The lesion is gradually necrotic, dry, and looks like burned eschar, infection does not involve deep tissues such as muscles and bones. Necrotic skin falls off after 2 to 3 weeks, forming ulcers.
5. Subcutaneous tissue swelling due to the action of bacterial diffusion factor, the infection spreads rapidly under the necrotic subcutaneous, the pressure between the fascia is rapidly increased, the subcutaneous tissue is swollen, and the pain is intensified.
Examine
Streptococcal necrosis
Peripheral blood
(1) White blood cell count: elevated, often > 10 × 109 / L.
(2) Leukocyte differential count: elevated white blood cell count is often accompanied by elevated neutrophils.
2. Bacteriology identification
(1) Smear microscopy: take the smear of the secretion of the lesion, after Gram staining, microscopic examination, in line with the morphological characteristics of streptococcus.
(2) Secretion culture: The secretions of the lesions are inoculated on the blood plate to perform aerobic and anaerobic culture respectively, which is helpful for identifying -type hemolytic streptococcus or Streptococcus pneumoniae.
(3) Blood bacterial culture: using magnesium sulfate broth culture solution to precipitate growth, and there is a bottom-up hemolysis for -hemolytic streptococcus
3. The sugar decomposition test can decompose the sugar, and it is meaningful for the definition of human hemolytic streptococcus.
4. Strain identification test helps identify the type of streptococcus
(1) Hydrolysis of sodium urate: a producer of iron triphenyl benzoate precipitated as -hemolytic streptococcus.
(2) Bovine Milk Blue Test: The reduction of the blue to whitening is Streptococcus faecalis and Streptococcus faecalis.
B-mode ultrasound: Helps to understand the extent of subcutaneous tissue damage and help identify Clostridium muscle necrosis.
Diagnosis
Diagnosis and identification of streptococcus necrosis
Diagnostic criteria
1. Clinical typical symptoms of local redness, pain and thin bloody secretions; epidermal necrosis, subcutaneous tissue swelling; systemic poisoning symptoms.
2. Laboratory examination of white blood cells increased; secretion smear staining, visible streptococcus; bacterial culture in line with the characteristics of hemolytic bacteria.
Differential diagnosis
1. Cellulitis has a clear history of trauma, or history of skin infection in other parts; infection occurs under the skin, under the fascia, muscle gap or deep connective tissue, less blistering and necrotic eschar, pus odor .
2. The erysipelas is an infection caused by -hemolytic streptococcus invading the lymphatic network. The local skin has rosy spots, and the proximal lymph nodes are swollen. The boundary between the infected local and normal tissues is clearer and less purulent.
3. Clostridium muscle necrosis has a history of deep tissue damage. The pathogenic bacteria are anaerobic bacillus, so the swollen subcutaneous tissue contains a lot of gas, and the pus has a foul odor.
