Salmonella is a large group of Gram-negative bacilli with similar morphology, biochemical properties and antigenic structure. Salmonella has no spores and no capsule. Most bacteria have flagella and pili all over their body and are motile. The colonies appear as medium-sized, smooth-surfaced colonies on ordinary culture media, colorless and translucent. It does not decompose lactose, sucrose and salicylic acid, but can decompose glucose and mannitol. Indole, urea decomposition test and V-P test were all negative. Salmonella can grow on simple media, and media containing brilliant green or selenite can inhibit the growth of E. coli and act as a bacterial enrichment. The optimal temperature for the growth of Salmonella is 35°C to 37°C, and the optimal pH value is 6.5 to 7.5. Bacteria of this genus are not very resistant and can be killed at 60°C for 30 minutes, 5% carbolic acid solution and 70% alcohol for 5 minutes. It can survive in water for 2 to 3 weeks, in feces for 1 to 2 months, and in ice for 3 months. Sensitive to chloramphenicol, ampicillin and co-trimoxazole. Its antigenic structure is an important basis for classification. Its antigens can be divided into three types: bacterial antigen (O antigen), flagellar antigen (H antigen) and surface antigen (Vi antigen). This type of bacteria can be divided into serogroups A, B, C, D, E, F, G, H, I and other serogroups according to the different bacterial antigen structures. Each serotype within the group can then be identified based on the different flagellar antigens. . Currently, more than 2,000 serotypes of Salmonella are known, and 161 serotypes have been discovered in my country. However, there are only 40 to 50 serotypes frequently isolated from humans and animals, of which only 10 are the main ones. serotype. The serotypes related to humans mainly belong to groups A to E, namely Typhi, Paratyphi A, B, and C, Typhimurium, Choleraesuis, Enteritidis, Salmonella anatipestifer, Salmonella Newport, etc., to name just a few. Pathogenic to humans, Salmonella typhimurium, Enteritidis, and Salmonella choleraesuis are the most common. How does Salmonella infect the human body? Since salmonellosis is transmitted through the fecal-oral route, ingestion of food or drinks contaminated with Salmonella is the only way to become infected. Salmonella has a wide range of hosts in nature. A small number of Salmonella are selective for hosts, and most are adapted to humans and animals. They can live in the gastrointestinal tracts of mammals, reptiles, birds, insects, and humans. A wide variety of domestic animals The infection rate of wild animals is between 1% and 20%. Therefore, various poultry and livestock have opportunities for contamination during processing such as feeding, slaughtering, transportation, and packaging. If poultry and livestock are slaughtered under poor sanitary conditions, Salmonella in the intestinal cavity can contaminate the meat. In addition, meat can also be contaminated with each other through various utensils or directly during storage, market sales, kitchen processing, etc. Among them, 1% to 58% of raw meat purchased in retail markets is contaminated with Salmonella. The source of contamination of eggs or egg products can be the ovaries or ureters of poultry, or it can be caused by Salmonella bacteria in feces, fertilizers, and soil passing through intact eggshells and entering the eggs. Generally, in many egg powders or other products made from mixed eggs, the infection rate is quite high; dairy and its products such as ice cream, packaged cooked food, etc. can also be contaminated by Salmonella. The various animal-derived foods listed above are the most common vectors for salmonella infections. Certain biological agents based on animal organs, such as enzymes, hormones, bile salts, food dyes, etc., can occasionally cause infections. Developing countries often have outbreaks caused by water pollution. Sewage irrigation and indiscriminate use of raw and cooked food are the most common causes of spread or epidemics within family groups. Direct person-to-person transmission often occurs through the hands of caregivers and medical equipment, which is the main cause of nosocomial infections or outbreaks in child care institutions. How does Salmonella make people sick? Salmonella enters the human body through the mouth, and its consequences are related to the body's resistance, the number of phagocytosis bacteria, serotype and its invasiveness. Under normal circumstances, the acidity in the stomach, food retention time, intestinal peristalsis, intestinal mucus covering mucosal epithelial cells, and normal intestinal flora constitute the body's non-specific barrier function. For example, the glycoproteins and glycolipids contained in the intestinal mucosa can prevent the adsorption of Salmonella, and the short-chain fatty acids produced by enterobacteria can inhibit the growth of Salmonella. Overeating, alcoholism, gastrectomy, and taking antacids, antiperistaltic drugs, and antimicrobial drugs all increase the body's susceptibility to Salmonella. The body's health status plays an important role in the pathogenesis, such as cellular immune mechanisms including macrophage function, which play an important role in resisting Salmonella infection.

When suffering from diseases such as leukemia, lymphoma, connective tissue disease, AIDS, reticuloendothelial cell "separation state" (such as dysentery, sickle cell anemia), and liver cirrhosis, the incidence of Salmonella infection increases, and the condition after infection also increases. heavier. The amount of pathogenic bacteria in adults needs to be as high as 100,000 or even 1 billion, while in children and those with a history of primary disease, the amount of bacteria required is much smaller. Swallowing a large amount of live bacteria can cause overt infection, and a small amount of bacteria often leads to a temporary carrier state. In salmonella gastroenteritis, the small intestine is the main site of disease, but the colon can also be involved, causing dysentery-like symptoms. Salmonella is invasive and causes an inflammatory reaction in the mucosa with neutrophil infiltration in the submucosa, sometimes deep into the lamina propria. Inflammatory cells produce and release prostaglandins, which increase the activity of adenylyl cyclase; Salmonella secretes enterotoxin, which directly stimulates the cyclase system, greatly increasing the secretion capacity of intestinal juice, exceeding the intestinal reabsorption capacity, causing diarrhea. Salmonella invasion of the bloodstream can be a complication of gastroenteritis, but more patients do not have gastroenteritis as a precursor disease. Blood-borne bacteria can stay in any location and cause purulent lesions in bones, joints, meninges, pleura or other locations. The invasiveness and pathogenicity of different serotypes of bacteria are significantly different. Salmonella anagi only causes asymptomatic gastrointestinal infections, while Salmonella choleraesuis and typhimurium often cause sepsis and migratory lesions. What is Salmonella infection and what is its incidence? Salmonella belongs to the Enterobacteriaceae family and can cause a variety of syndromes such as gastroenteritis, typhoid fever, sepsis and extraintestinal focal infection, collectively known as Salmonella infection (i.e. salmonellosis). Various syndromes sometimes overlap. Infections caused by typhoid and paratyphoid bacilli are not included. The disease can be seen throughout the year, with the peak incidence occurring from July to November. This is the summer and autumn season, when the weather is hot, and food is easily contaminated by bacteria. Because of the hot weather, people often like to eat cold food, and the gastrointestinal barrier function is weakened. There are many mosquitoes and flies, and there are many opportunities to contaminate food. This disease can occur at any age, but the young (especially those around 1 year old), the elderly, those with chronic wasting diseases, and those who have taken antibiotics in the recent past are more susceptible. Large or small epidemics often occur due to food contamination, often involving many people at the same table or in collective canteens. The most common pathogenic bacteria are Enteritis, Typhimurium, Choleraesuis, Duck and Newport Salmonella. Salmonella infection (i.e. salmonellosis) not only manifests as acute gastroenteritis, but also has symptoms of systemic infection such as fever, and bacteremia may occur in the early stage. After suffering from this disease, the immunity is not strong, and the infection can be repeated, or even the same serotype of bacteria can be infected again and the disease will occur again. What are the characteristics of the manifestations of Salmonella infection? The clinical manifestations of Salmonella infection are diverse. According to its main syndrome, it can be divided into four types: enteritis type, typhoid type, septicemia type and local purulent infection. (1) Enteritis type (food poisoning): It is the most common form of Salmonella infection, and the incubation period is generally 8 to 24 hours. The onset is sudden, often accompanied by aversion to chills and fever, but the fever is generally not very high. Symptoms such as abdominal cramps, flatulence, nausea, and vomiting also occur. Diarrhea then occurs, several to ten times a day or more, watery, dark yellow or greenish, sometimes with a foul odor. Feces are often mixed with undigested food and a small amount of mucus, and occasionally pus and blood. When inflammation spreads to the lower colon, tenesmus may occur. The course of the disease is usually 2 to 4 days, and sometimes it lasts longer. When Salmonella Typhimurium is infected, diarrhea and high fever are the main symptoms, and purulent and bloody stools are common. Adults have less high fever, shorter fever duration, and more abdominal pain and tenesmus, while children have longer high fever, more vomiting and dehydration. Occasionally, there is a cholera-like fulminant gastroenteritis type. The patient has severe vomiting and diarrhea. The body temperature rises at the beginning of the disease and then drops immediately. The pulse is weak and rapid. Severe dehydration, electrolyte imbalance, muscle spasm, oliguria or urination may occur. If the rescue is not timely, death may occur due to acute renal failure or peripheral circulatory failure in a short period of time. (2) Typhoid type: Infection with non-typhoid Salmonella bacteria can cause clinical manifestations similar to typhoid fever, among which Choleraesuis is the most common. Symptoms are generally milder than those of typhoid fever, with long-term fever, gastrointestinal symptoms, or gastroenteritis as the precursor. Skin rashes are rare, diarrhea is frequent, splenomegaly can be seen, and the total number of white blood cells is low. Complications such as intestinal perforation and intestinal bleeding are rare. . The course of the disease is usually only 1 to 3 weeks, and relevant salmonella can be obtained by blood and stool culture. The chance of recurrence is greater than that of typhoid fever. (3) Sepsis type: In a host with normal immune function, the chance of sepsis caused by Salmonella infection is less than 10%, while that of AIDS can be as high as 45%. About 1/3 to 1/2 of patients with septicemia have primary diseases such as liver cirrhosis, systemic lupus erythematosus, leukemia, lymphoma, or neoplasms, and their prognosis is poor.

This type is characterized by long-term fever. The body temperature can be as high as 40°C or above, with irregular heat (flalaxant fever or intermittent fever), accompanied by repeated chills, sweating, headache, nausea, anorexia, and weight loss. Some patients have gastrointestinal symptoms. Symptoms of inflammation, splenomegaly is occasionally seen, and about 1/4 of the patients develop local infection lesions during the course of the disease, most commonly in the bones and joints, and can involve multiple joints, linger and not heal, forming fistulas. The meninges of newborns and infants are susceptible to invasion, and the mortality rate can be as high as more than 80%. Others include bronchopneumonia, lung abscess, pleurisy, empyema, pericarditis, endocarditis, pyelonephritis, etc. (4) Local purulent infection: It can occur in any part, but it is more likely to occur at sutures, fractures, tissue and organ transplant sites, atherosclerotic plaques, and tumors, etc. where there are original lesions or weak vitality. parts. This type has no gastroenteritis or systemic symptoms, only abscess formation, and it tends to become chronic. Pathogen examination is required to confirm the diagnosis. How to diagnose Salmonella infection? The diagnosis of Salmonella infection can be comprehensively analyzed from the following aspects. (1) Dietary history: There is a history of eating unclean food (especially animal products, etc.), and often the disease occurs among many people at the same table or in a collective canteen. (2) Clinical manifestations: fever, abdominal pain, diarrhea, nausea, vomiting and other symptoms of acute gastroenteritis suddenly appear within 1 to 2 days after eating unclean food; fever persists for more than 1 week, no obvious systemic symptoms, or gastrointestinal symptoms Manifestations include hepatosplenomegaly and local lesion formation. (3) Relevant laboratory tests ① Blood picture: The total number of white blood cells is mostly normal, but increases significantly when there are focal purulent lesions, up to 20×109/L to 30×109/L. ② Fecal examination: Some feces contain mucus and blood, and some may show increased neutrophils under the microscope, which is more common in infants and young children. ③Bacteriological examination: In gastroenteritis, pathogenic bacteria are easily isolated from vomitus and feces; in cases of extra-gastrointestinal infection, they can often be isolated from blood, bone marrow, pus and other body fluids such as pleural effusion, cerebral effusion, joint effusion, etc. Pathogens were detected. Because bacteria enter the blood intermittently, repeated culture can increase the positive rate. ④ Serum agglutination test: Use the patient's serum and bacterial antigens made from known bacterial species for an agglutination test. If the agglutination titer is greater than 1:160, or two weeks after the onset of the disease, the agglutination titer will be 4 times that at the onset of the disease. Anyone with an increase above can be considered to be diagnosed with this disease. How to prevent and treat Salmonella infection? The treatment of this disease mainly involves symptomatic treatment and pathogen-specific treatment. (1) Symptomatic treatment: Patients with gastroenteritis should focus on maintaining water and electrolyte balance, supplemented by necessary symptomatic treatment. Mild or moderate dehydration can be treated with oral glucose-electrolyte solution, while severe dehydration requires intravenous rehydration. After the situation improves, oral rehydration can be used. The elderly, young or weak should be actively treated. Those with severe poisoning symptoms and circulatory failure should pay attention to maintaining effective blood volume. Adrenocortical hormones can be used if necessary. Abdominal pain and diarrhea can often be significantly improved after fasting. Severe patients can try anti-secretory drugs such as berberine, chlorpromazine, propranolol, calcium gluconate, indomethacin, etc. Antispasmodics are suitable for short-term use. (2) Pathogenic treatment: For patients with uncomplicated gastroenteritis, it is not necessary to use antibiotics. Because the application of antibacterial drugs does not shorten the course of the patient's disease, it instead promotes the production of drug-resistant strains of bacteria in the intestines, prolongs the time for bacterial excretion, and causes treatment difficulties. For severe gastroenteritis or the elderly, infants (especially infants under 4 months old), malnourished, and those with chronic diseases or immune deficiencies, corresponding antibacterial drugs should be added. For extra-gastrointestinal infections and septicemia, typhoid, and local suppurative infections, antibiotics should be administered systemically. In the past, chloramphenicol, co-trimoxazole, ampicillin or ampicillin were generally used for Salmonella infection, and most of the fever subsided within 4 to 6 days after treatment. However, some patients may relapse, but re-administration is still effective. In recent years, the resistance of pathogenic bacteria has been increasing, so it is best to select appropriate antibiotics based on the drug susceptibility results. At present, third-generation fluoroquinolone antibacterial drugs and third-generation cephalosporins, such as ciprofloxacin, flufenac, lomefloxacin, and ibosperin, are commonly used in clinical practice and often have good curative effects. Convalescent carriers do not need antimicrobial treatment. To prevent Salmonella infection, we should focus on the following aspects: (1) Control the source of infection ① Patients in the acute phase should be isolated, and patients in the recovery phase or chronic carriers should be temporarily removed from eating or childcare work. ② Care should be taken to avoid Salmonella infection when raising poultry and livestock, and the feed should not be contaminated by this bacteria. ③Properly dispose of patient and animal excrement and protect water sources. ④Do not eat the meat and offal of sick animals and poultry. (2) Cut off the transmission route ① Pay attention to food and drinking water hygiene.

Cooking utensils and tableware must be cleaned and disinfected frequently, raw and cooked food must be separated into containers, and knives and boards must be separated when cutting. Cook thoroughly when eating. Do not drink raw water. ② Pay attention to food processing management. Sanitary inspections must be carried out regularly for livestock slaughtering, and hygienic operating procedures must be followed during the slaughtering process to avoid intestinal bacteria contaminating the meat. Cleaning and disinfection must be paid attention to during the processing, transportation and storage of meat, milk, etc.