Other Salmonella infections in children

　　1. Causes of Illness

　　In 1885, Salmon and Smith first discovered Salmonella cholerae suis, thus opening the curtain for the study of Salmonella. Salmonella is a zoonotic enteric pathogen with a variety of serotypes. According to the WHO Salmonella Center in 1983, there are a total of 2187 serotypes of Salmonella. Currently, China has at least 255 serotypes. In addition to typhoid and paratyphoid, Salmonella typhimurium, Salmonella cholerae suis, Salmonella enteritidis, and Salmonella infantis are the most common.

　　Salmonella is a Gram-negative short rod-shaped bacterium without a capsule, with most bacteria having flagella and pili, and is motile. It likes moisture, tolerates cold but not heat. It has strong resistance to the external environment, can survive for several years in soil, for several months in water, for 4 months in feces, for 10 months in dust, and although it does not reproduce at low temperatures, it still maintains vitality. It is inactivated at 60°C for 30 minutes, and is sensitive to disinfectants containing 0.2% to 0.4% residual chlorine in drinking water and phenols, and to sunlight. It can be detected throughout the year from wastewater. The use of urban wastewater for irrigation in vegetable fields causes pollution, which is a serious problem. Antigen structure: According to the 'O' antigen of the bacterial body, it can be divided into 50 groups, such as A, B, C, D, etc.; according to the 'H' antigen of the flagella, there are currently more than 2000 serotypes or variants. Among them, there are about 50 serotypes closely related to humans. The most common ones belong to 20 or so serotypes in groups B, C, D, and E, such as Salmonella typhimurium, Salmonella dublin, and Salmonella stanley in group B; Salmonella cholerae suis, Salmonella infantis, Salmonella potsdamer, Salmonella typhimurium, Salmonella manhattan in group C; Salmonella enteritidis in group D; Salmonella anatina, Salmonella gallinarum, Salmonella londiniensis in group E, etc.

　　2. Pathogenesis

　　Salmonella enters the human body through the mouth, and whether it causes illness is related to the amount of bacteria ingested, individual susceptibility, and serotype. Generally, the average amount of bacteria ingested for illness must be above 1 million to 10 million. Infants and the elderly can also become ill with fewer bacteria, with newborns needing only a few to dozens of bacteria to cause illness. Individuals with gastric resection and hypochlorhydria are more prone to illness.

　　Salmonella invasive bacteria, after the bacteria invade the intestines, they mainly multiply and invade the mucosal epithelial cells in the ileocecal junction, cecum, and colon, causing inflammation and producing mucus, pus, and bloody stools. Salmonella can also produce enterotoxins, which directly activate the adenylate cyclase of the intestinal epithelial cell membrane, and can also promote the synthesis of prostaglandins, leading to an increase in cyclic adenosine monophosphate (cAMP), which enhances intestinal secretion function and causes watery diarrhea. Therefore, the variety of stools in typhoid Salmonella disease is a characteristic. At the beginning, it is watery stools, followed by mucus, pus, and bloody stools, and then blood and water-like stools. Due to local necrosis of the intestinal mucosa, bacteria can enter the blood from the damaged intestinal mucosa and lymphatic barriers, causing sepsis.

　　The pathogenicity of different types of Salmonella varies significantly. For example, Salmonella pullorum often causes asymptomatic infection, Salmonella choleraesuis often causes septicemia and metastatic lesions, Salmonella typhimurium often causes dysentery-like symptoms, and Salmonella enteritidis often causes gastroenteritis.

　　The body's defense mechanism plays an important role in the onset of the disease. The decrease in gastric acid, the slowing of intestinal peristalsis, and the imbalance of intestinal microecology can increase the opportunity for Salmonella infection. Newborns with low immune function and the weak, the elderly, and those with chronic diseases or severe diseases are prone to infection. The use of hormones can suppress the immune system and increase the risk of Salmonella infection, and the mortality rate increases. The use of broad-spectrum antibiotics can increase the opportunity for Salmonella infection, possibly due to the disturbance of intestinal flora after the use of broad-spectrum antibiotics, which makes Salmonella more likely to grow.

　　It is often accompanied by dehydration and acidosis, prone to hyponatremia, paralytic ileus, enlargement of the liver and spleen, and in severe cases, necrotizing enterocolitis may occur, accompanied by intestinal perforation, convulsions, shock, DIC, cerebral edema, meningitis, often with intracranial hemorrhage, pericarditis, or urinary tract infection, bronchitis, or bronchopneumonia. Post-infarction sequelae may occur after intracranial lesions.

　　1. Incubation period

　　The incubation period varies in length, the shortest being only a few hours for food poisoning, but most cases last for 1 to 3 days.

　　2. Clinical classification

　　Clinically, it can be divided into acute gastroenteritis type, septicemia type (typhoid type), and local infection type. There are also healthy carriers.

　　1. Acute gastroenteritis or food poisoning type

　　This type accounts for about 80%. The main pathogens are Salmonella enteritidis and Salmonella typhimurium. The disease is caused by eating food contaminated with these bacteria. If the food does not contain live bacteria but only a large amount of toxins produced by them, the clinical manifestation is acute food poisoning symptoms. The incubation period is only a few hours, with an acute onset and a short course of only 1 to 2 days. If the food contains a large number of live bacteria and a small amount of toxins, the incubation period can last up to 2 to 3 days. The onset is slower, and the course can last for more than a week. The symptoms include vomiting and diarrhea, with older children complaining of abdominal pain, accompanied by high fever. Diarrhea often shows resistance and is difficult to treat. The number of stools per day is 6 to 15. The nature of the stool is diverse, often starting with loose watery stools and then becoming mucous, purulent, or bloody stools, all with a foul smell. The children often have dehydration and acidosis. Due to the incomplete regulation of water and electrolyte metabolism in newborns, hyponatremia is prone to occur. Abdominal distension is common, and in severe cases, paralytic ileus may occur, accompanied by enlargement of the liver and spleen, cough, lung rales, congestive rash, jaundice, and in severe cases, necrotizing enterocolitis with intestinal perforation may occur.

　　2. Sepsis type (typhoid type)

　　Severe toxic symptoms, high fever, long fever duration, this type accounts for about 4% to 25%. It is characterized by listlessness, drowsiness, seizures, coma, and common hyperemic rashes. This type can occur alone or in conjunction with the gastrointestinal type, known as the mixed type. This type is prone to complications such as shock, DIC, and cerebral edema.

　　3. Local infection type

　　Common in infants.

　　(1) Meningitis: accounts for about 13%, most of which occur in children under 2 years of age. The highest incidence is in those under 3 months. Meningitis of the ventricles can also occur. The reason why neonates are more prone to meningitis may be related to birth trauma. This type of meningitis often occurs with intracranial hemorrhage, with a mortality rate of over 50%, and about 18% have sequelae after recovery.

　　(2) Local cellulitis: Presents with unexplained fever, crying and restlessness, followed by localized redness, swelling, heat, and pain in the skin and soft tissues, and finally forming an abscess. After the abscess is incised and drained, it heals quickly, and the pus can be cultured for Salmonella.

　　(3) Umbilical erysipelas: Salmonella Typhimurium is isolated from the umbilical secretion.

　　(4) Can be complicated by pericarditis or urinary tract infection.

　　(5) Pulmonary infection: Some children are admitted to the hospital with pulmonary infection and then develop diarrhea. Up to 20% to 50% of cases are accompanied by cough, and wheezing is often heard in the lungs, which can manifest as bronchitis or bronchopneumonia. It mainly depends on the epidemiological history, such as the presence of Salmonella infection in family members or in the same room as the patient; consumption of suspiciously contaminated food, with short-term mass illness among co-eaters; the food is often uncooked meat and eggs from livestock and poultry, or other foods contaminated by such food. Clinical symptoms include sudden onset of acute gastroenteritis within 1 to 2 days after consuming suspicious food, with initial abdominal pain, nausea, and vomiting, followed by diarrhea, accompanied by chills, shivering, and fever reaching 38 to 40℃. Stool initially appears loose, then turns into yellow watery stools with a strong odor, with less pus and blood. It can also manifest as typhoid-like symptoms, sepsis, or localized suppurative infection. Laboratory examination mainly depends on pathogenic examination, with pathogens cultured and isolated from vomit, stool, and suspicious food. Patients with typhoid or septicemia can have pathogens cultured and isolated from the blood. ELISA testing for Salmonella-specific antigens has the advantages of specificity and high sensitivity.

　　1. Have an awareness of the epidemic situation

　　Firstly, there must be an awareness of the epidemic situation and maintain a high level of vigilance.

　　2. Strict isolation measures

　　Immediate strict isolation should be implemented for suspected cases, and it is best to have a dedicated person in charge of medical staff in the isolation room. Wear isolation clothing and shoes, wash hands with running water after examining a patient, or use 2‰ hydrogen peroxide acetic acid or

　　After the discovery of Salmonella typhimurium cases in general pediatric wards, it is best to suspend the admission of infants under 3 years old and perform terminal disinfection in all rooms. The indoor walls and floors should be sprayed with

　　4. Routine disinfection

　　The diapers should be soaked in bleaching powder or 2‰ hydrogen peroxide acetic acid before routine disinfection. The mattresses and bedding should be fumigated with cyclochlorane or sprayed with 2‰ hydrogen peroxide acetic acid before being sunned for disinfection. Used baby bottles and bowls should be soaked in 2‰ hydrogen peroxide acetic acid before routine disinfection.

　　5. Avoid the spread of infection

　　Cancel the companion, in order to prevent the spread of infection. If it is necessary to breastfeed, the mother should wear a protective clothing and follow the isolation rules.

　　6. Avoid the source of infection

　　Detection and treatment of carriers: If the pregnant woman has diarrhea before admission, the stool should be examined to exclude Salmonella typhimurium. The staff in the ward should regularly undergo stool culture, and the carrier should be transferred to the baby ward in time. After the stool is negative after treatment, return to work in the baby ward.

　　The total number of peripheral blood white blood cells is mostly between 10,000 to 20,000, with a higher incidence in septicemia type, greater than 30,000, and visible toxic granules. The diagnosis should be based on bacterial culture.

　　Cultivation of Salmonella typhimurium must use enrichment method, and the specimens placed by applying saltwater cotton swabs to the stool, pus, cerebrospinal fluid, and environmental items should be enriched in sodium selenite enrichment broth at 37℃ incubator for 18 hours, and then inoculated into SS medium.

　　The best blood culture is to collect 5-10ml of blood without anticoagulant and directly place it in glucose broth or glucose broth with bile salt culture agent for culture. The appropriate culture temperature is 42-43℃.

　　Rapid diagnosis: Use the bacterial body immune agglutination test.

　　1. Choose easily digestible liquid foods such as vegetable soup, thin porridge, egg soup, egg custard, and milk.

　　2. The diet should be light and low in oil, which not only meets the nutritional needs but also enhances appetite. White rice porridge, millet porridge, soybean porridge, accompanied by sweet sauce vegetables, radish, pickled vegetables, or bean curd, should be served in a light and refreshing manner.

　　Ensure adequate fluid intake, you can drink more acidic fruit juice such as hawthorn juice, kiwi juice, jujube juice, fresh orange juice, watermelon juice, etc. to promote the secretion of gastric juice, increase appetite.

　　I. Treatment

　　1. Supportive therapy

　　It is very important to first do a good job in fluid therapy. Correct water and electrolyte imbalance. Severe patients should be given plasma or fresh blood. In patients with prolonged course, intravenous hyperalimentation can be used.

　　2. Abdominal distension

　　Gastrointestinal decompression and anal tube exhaust. Phenylephrine can be used, 0.5mg/kg each time, once every 2 to 4 hours, added to the small壶静点.

　　3. DIC

　　Severe patients often have DIC, and it is necessary to promptly apply anisodamine (654-2) to improve microcirculation, low molecular weight dextran to reduce blood viscosity, 1ml/kg each time. Heparin 1mg/kg, intravenous infusion or intravenous injection every 4 to 8 hours. If hyperfibrinolysis occurs, add aminocaproic acid or tranexamic acid (carboxybenzamine).

　　4. In case of shock or cerebral edema

　　Corresponding treatment should be taken in a timely manner.

　　5. Infants and immunocompromised individuals

　　It is necessary to promptly detect sepsis and local infections and treat them. It should be emphasized that breastfeeding should be emphasized and antibiotics should not be滥用.

　　6. Antibiotics

　　Some scholars believe that mild gastrointestinal cases should not use antibiotics and rely on their own immunity to control infection. Because Salmonella typhi is resistant to commonly used antibiotics such as gentamicin, sulfamethoxazole/trimethoprim (cotrimoxazole), ampicillin (ampicillin), and first and second-generation cephalosporins, most of which are resistant, see Table 1. The use of non-susceptible antibacterial drugs not only cannot control infection but also causes intestinal flora disorder and prolongs the time of excretion. For severe and septicemia children, especially Salmonella typhi with multiple drug resistance and small infants, immunodeficient individuals, especially extraintestinal infections, treatment is more difficult, such as the mortality rate of meningitis reaching 43% to 87.5%. Antibiotics can be used. Currently, it is considered that fluoroquinolones and third-generation cephalosporins have strong antibacterial activity against Salmonella. Experiments have shown that ciprofloxacin has a MIC against Salmonella.

　　II. Prognosis

　　The mortality rate is between 2% to 24%. Among them, the neonatal mortality rate reaches 20% to 30% or more. The younger the age, the longer the time of excretion, and it has been reported that the longest case of excretion time reached 156 days.