Progressive necrotizing infection of deep subcutaneous fascia

Introduction Cellulitis caused by surgical wound infection can often lead to bacteremia, the most serious is necrotizing fasciitis, which is a progressive necrotizing infection of subcutaneous deep fascia and fat. The process infection begins with trauma (inconspicuous trauma). Or the local redness and heat pain in the operation quickly spread outward. The color of the lesion changed from red to purple at 24 to 48 hours, and then turned blue to form blister and bullae containing yellow liquid. On the 4th to 5th day of the disease, the purple area began to be necrotic, and the skin with clear and necrotic borders fell off at 7 to 10 days, revealing extensive necrotic tissue under the skin. Patients with high fever and slow response are prone to bacteremia and sepsis. In fact, patients with TSLS are often accompanied by severe soft tissue infection.

Cause

A streptococcus group is a type B hemolysis reaction. In the past, it was called type B hemolytic streptococcus, and M protein was an important factor in the pathogenic ability of streptococcus. It is resistant to the phagocytosis of white blood cells by the body. If there is no M protein, it is non-virulent. After infection, the body can obtain specific immunity against M protein and can remain for several years. The cell wall has lipoteic acid and is also an important virulence factor. It can attach bacteria to the host mucosa and cell membrane. The pathogenicity of the A streptococcus group also comes from the production of toxins and extracellular protein toxins:

1 Pyrogenic exotoxin, also known as erythema toxin, is a heat-resistant protein that has antigenic properties in addition to causing scarlet fever-like rash on the skin, but also has purulent cytotoxicity and enhances endotoxin toxicity. It also has a superantigen effect, and at least three kinds of ABC (someone thinks that there are four) different antigenic types that do not produce erythema toxin and a phage that can produce erythema toxin can become a toxigenic strain.

2 Streptococcal hemolysin dissolves red blood cells, kills white blood cells, platelets and damages the heart. There are two kinds of streptococcal hemolysin. O-streptolysin can produce antibodies after antigenic infection and can be maintained for several months. Therefore, it can be used as one of the signs of recent infection of streptococcus; S-streptolysin is not antigenic or antigenic, and its antibody has not been detected in the body.

The extracellular proteins produced by the A streptococcus group are:

1 hyaluronidase can dissolve the interstitial hyaluronic acid to make bacteria easily spread in tissues;

2 streptokinase, also known as fibrinolytic enzyme, converts plasminogen in the blood into plasmin, thereby preventing blood from coagulating or dissolving coagulated blood clots.

3 chain enzymes, also known as deoxyribonuclease (which can dissolve highly viscous DNA). This enzyme has four different serotypes of ABCD, and antigenicity produces antibodies.

4 Nicotinamide adenine dinucleotide nucleosidase can decompose the corresponding tissue components to destroy certain defense capabilities of the body such as white blood cells can be killed.

5 serum turbidity factor) is an alpha lipoproteinase, which can make horse serum turbidity and inhibit the body's specific and non-specific immune response.

an examination

Related inspection

Blood and bone marrow bacterial culture sputum bacterial culture

Mainly based on bacterial culture, in addition to hemolytic reactions, the classification and type should be determined by serum classification. It is diagnostically useful to detect the anti-streptolysin O antibody titer in the patient's serum above 1:400.

Differential diagnosis

1. Acute pharyngitis Acute tonsillitis: patients with more children, mostly in the winter and spring, patients may have fever, sore throat and other symptoms, examination of pharyngeal and tonsil congestion and edema and purulent exudate can form pseudomembrane recovery Some patients may have rheumatism or nephritis.

2. erysipelas: when the skin has minor damage (such as athlete's foot) or when it is degraded (old age), it is beneficial to the occurrence of erysipelas. After the bacteria enters the damaged area, it can spread through the lymph. Patients may have systemic symptoms such as fever and headache, general malaise, and several hours. The local skin appears erythema, the boundary is clear and the normal skin is severe. The blisters containing purulent fluid and the lymph nodes near the tissue necrosis may be swollen and tender.

3. Skin and soft tissue infections: neonatal umbilical infection; infants and young children may suffer from impetigo; cellulitis such as surgical wound infection can often lead to bacteremia, the most serious is necrotizing fasciitis, Subcutaneous deep fascia and fat progressive necrotic infection, the process of infection mostly begins with trauma (inconspicuous trauma) or localized redness and heat pain in the operation, and it expands rapidly. The color of the lesion changes from red to purple at 24 to 48 hours. Blue forms blisters and bullae that contain yellow liquid. On the 4th to 5th day of the disease, the purple area began to be necrotic, and the skin with clear and necrotic boundaries at 7 to 10 days showed extensive necrotic tissue under the skin. The patient has high fever, weakness, and unresponsiveness, which can easily cause bacteremia and sepsis.

Mainly based on bacterial culture, in addition to hemolytic reactions, the classification and type should be determined by serum classification. It is diagnostically useful to detect the anti-streptolysin O antibody titer in the patient's serum above 1:400.

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