Widal reaction positive

Introduction The fatda test, that is, the typhoid serum agglutination test, that is, the fat-to-fat reaction, has an auxiliary diagnostic value for typhoid fever. Typhoid fever is an acute infectious disease caused by typhoid bacillus with persistent bacteremia, reticuloendothelial involvement, minimal abscess at the distal ileum and ulceration. The typical clinical features include persistent high fever, abdominal discomfort, and liver. The splenomegaly is low, and some patients have rose rash and relatively slow pulse. This disease is also known as enteric fever (enteric fever), but the clinical manifestations of this disease are mainly caused by the spread of pathogens through the blood to the whole body of the body, but not caused by local intestinal lesions.

Cause

The pathogen of this disease is Salmonella typhimurium D (group), Gram-negative, short rod-shaped 1 ~ 3.5m, width 0.5 ~ 0.8m, weekly flagella can move, no spores, no pods membrane. It can grow on ordinary medium. Since tryptophan and lipids in bile can be used as nutrients of typhoid bacillus, they grow well in a medium containing bile.

The typhoid bacillus has a strong viability in nature. It can survive for 2 to 3 weeks in water and can last for 1 to 2 months in feces. It can not only survive and reproduce in milk, but also can withstand low temperatures and can survive in a frozen environment. Months but the resistance to light, heat, dryness and disinfectant is weaker than direct sunlight for several hours. It is heated to 60 ° C for 30 minutes or immediately after boiling. It is killed in disinfected drinking water for 5 minutes in 3% carbolic acid. Up to 0.2 ~ 0.4mg / L can quickly kill.

Salmonella typhimurium only infects humans and does not infect animals under natural conditions. The bacteria itself does not produce exotoxin, and can release strong endotoxin when the cells are lysed, which plays an important role in the occurrence and development of the disease. Injection of small amounts of endotoxin into the veins of humans or rabbits can cause chills, fever and discomfort, and leukopenia. These phenomena are very similar to those of typhoid patients.

The typhoid bacillus can be killed by gastric acid after the contaminated water or food enters the digestive tract. If the number of invading bacteria is large, or the pathogenic bacteria are lacking, the pathogenic bacteria can enter the small intestine and rely on flagella to invade the intestinal mucosa. The phagocytic cells are phagocytosed and propagated in the cytoplasm, and then enter the ileum collecting lymph nodes through the lymphatic vessels, and grow in the isolated lymphoid follicles and mesenteric lymph nodes. At this stage, the patient is asymptomatic and is equivalent to a clinical incubation period.

Salmonella typhimurium continuously proliferates and dies in lymphoid tissues (mainly mesenteric lymph nodes), releasing endotoxin and swelling lymphatic tissue. At the same time, typhoid bacillus can cause bacteremia by transiently invading the bloodstream through the lymphatic vessels. Toxins in the blood cause toxemia, causing fever and other symptoms. At this time, if blood culture is performed, it is easy to be positive. Because the reticuloendothelial cells in the bone marrow take up the most typhoid bacillus and last longer, the culture positive rate is the highest. This is equivalent to the first week of the disease.

Subsequently, Salmonella typhimurium spreads with the bloodstream to the whole body to grow and multiply. Due to the large number of organs such as liver, spleen, bone marrow and lymph nodes, which are rich in reticuloendothelial tissues, it causes more serious systemic poisoning and lesions of various organs. Causes a second severe bacteremia and releases strong endotoxin, causing clinical symptoms such as fever and general malaise, and skin rose rash and liver and splenomegaly. At this time, corresponding to the second to third week of the disease course, the symptoms of venom are gradually aggravated, the blood culture is often positive, and the typhoid bacillus in the bone marrow is the most, and the duration is longer, so the culture positive rate is the highest in the second to third weeks. After entering the intestine through the bile duct, it is excreted with the feces and excreted in the urine. At this time, the feces and urine culture can obtain the typhoid bacillus that enters the intestine through the bile duct, and partially penetrate the intestinal mucosa and invade the intestinal lymphatic tissue again. In the intestinal lymphatic tissue, severe inflammatory reaction and mononuclear cell infiltration (ie, type hypersensitivity) cause necrosis, which can cause ulceration. If the blood vessels affect the lesion can cause bleeding, if it invades the muscle layer and the serosa layer. Can cause intestinal perforation, in addition, typhoid bacillus can also cause purulent inflammation in other tissues such as osteomyelitis, renal abscess, cholecystitis, meningitis, pericarditis and so on.

At the 4th week of the disease, the immunity produced by the human body gradually strengthened. The expression of humoral immunity and cellular immune function was enhanced. The phagocytic cells strengthened and the typhoid bacilli gradually disappeared from the bloodstream and organs. The ulcer of the intestinal wall gradually healed and the disease was finally obtained. get well. In a small number of cases, due to insufficient immune function, typhoid bacilli lurking in the body can reproduce and invade the bloodstream to cause recurrence.

an examination

Related inspection

Feidashi reaction typhoid fever, paratyphoid serum agglutination test (fat test, fatda reaction, Widal)

(1) Diagnostic criteria

1. Clinical diagnostic criteria

In the typhoid epidemic season and region, there is persistent high fever (40 ~ 41 °C) for more than 1 to 2 weeks and a special poisoned face appears, relatively slow pulse, skin rose rash splenomegaly, peripheral blood leukocyte count is low, eosinophilic There are typhoid cells (ring cells) in the disappeared bone marrow of the cells, which can be diagnosed as typhoid fever.

2. Diagnostic criteria

Suspected diseases such as one of the following items can be diagnosed

(1) From the blood marrow, urine, fecal rose rash scraping, any specimen is isolated to Salmonella typhi.

(2) Serum-specific antibody positive drug Dar's reaction "O" antibody agglutination titer 1:80, "H" antibody agglutination titer 1:160, recovery period titer increased by more than 4 times.

Differential diagnosis

1. The characteristic performance of typhoid fever (within the first week) has not been revealed, and should be differentiated from viral infection, malaria leptospirosis, acute viral hepatitis and other diseases.

2, the extreme stage of typhoid fever (after the second week) most cases without typical typhoid fever, must be differentiated from sepsis, miliary tuberculosis brucellosis, endemic typhus, tuberculous meningitis.

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