Bacterial food poisoning

作者：admin  点击次数：17  发布时间：2025-04-26

Bacterial food poisoning is an acute gastrointestinal disease caused by the intake of food contaminated by bacteria or bacterial toxins. Its main pathological feature is the inflammatory reaction of the gastrointestinal tract (exudative enteritis and secretory enteritis). The main clinical manifestations are: nausea, vomiting, abdominal pain and diarrhea. It is characterized by a short incubation period, rapid onset, short course of disease and rapid recovery. Compared with other intestinal bacterial infections such as cholera and bacillary dysentery, the condition is relatively mild and the prognosis is relatively good, but severe cases also have a certain mortality rate. Epidemiological history and bacteriological tests are the main basis for diagnosis. Clinically, it is divided into two types: gastrointestinal type and neurological type, with gastrointestinal type being more common. Among the foods that cause bacterial food poisoning, animal foods are the main ones, such as meat, eggs, milk, fish and their products, while plant foods are relatively rare. At present, the common pathogens that cause bacterial food poisoning are: Salmonella, Staphylococcus aureus, Proteus, Clostridium botulinum, Vibrio parahaemolyticus, pathogenic Escherichia coli, Pseudomonas aeruginosa, Wechslera (heat-resistant type), halophilic bacteria (Pseudomonas enteritidis), etc. According to domestic and foreign statistical data, the pattern of pathogens that cause bacterial food poisoning has also changed. In the 1980s and early 1990s, Salmonella, Vibrio parahaemolyticus, Shigella, and Staphylococcus accounted for the majority of food poisoning. However, in the mid-to-late 1990s, the proportion of these bacteria decreased, while food poisoning caused by Proteus, Escherichia coli, and Vibrio was on the rise. In recent years, there have been "0157" Escherichia coli and "0139" Vibrio cholerae.
The causes of bacterial food poisoning are relatively complex and varied. The main reasons are as follows.
(1) Food is contaminated by pathogenic bacteria during production, processing, packaging, transportation, storage, and sales. These contaminations mainly come from: ① Some animals carry bacteria before they die; ②) Food processing workers have poor hygiene; ③ The production environment has poor hygiene, such as contamination by flies, rats, cockroaches, dust, etc.
(2) Poor storage conditions. Food contaminated by pathogens is stored at a higher temperature. The sufficient moisture, suitable pH and nutritional conditions in the food cause the pathogens to grow and multiply in large quantities or produce toxins.
(3) Contamination by pathogenic microorganisms. Food is not cooked thoroughly or cooked food is cross-contaminated by raw food or contaminated by food workers who are carriers, resulting in poisoning after consumption. III. Common bacterial food poisoning Salmonella food poisoning Salmonella is still the most serious foodborne disease. Since 1985, the number of salmonella poisoning cases in Europe, the United States, Japan and other places has increased significantly.
(I) Salmonella food poisoning
1. Pathogens and their biological characteristics
Salmonella belongs to the Enterobacteriaceae family. It is a large group of Gram-negative rods that parasitize the intestines of humans and animals. It is spore-free, membrane-free, and facultatively anaerobic. There are many species of this genus. So far, more than 2,000 serotypes have been discovered. More than 100 serotypes have been discovered in my country, and only a few of them are pathogenic to humans. Causes of food poisoning The main types of Salmonella are: Salmonella Typhimurium (S.bphinurium), Salmonella Choleraesuis (S.choleraesuis), and Salmonella Enteritidis (S.eneritidis). In addition, there are reports of human food poisoning caused by Salmonella Newport, Salmonella Dublin, Salmonella Thompson, Salmonella Bovis, Salmonella Derby, Salmonella Duck, and Salmonella Sanftenberg.
The optimal growth and reproduction temperature of Salmonella is 20~37℃. It can survive in water for 2~3 weeks, in feces and ice for 1~2 months, and in It can survive for 75 days in meat containing 12%~19% salt. However, it dies immediately at 100℃, only survives for 5 minutes at 75℃, 15~30 minutes at 60℃, and can be killed at 55℃ for 1 hour. Since Salmonella does not decompose protein, there is usually no sensory change after food is contaminated, so you should pay attention. Salmonella food poisoning incidents can occur throughout the year, but they are more common from May to October, with the highest incidence in July to September. Salmonella does not produce exotoxins, and food poisoning is mainly caused by cannibalistic live bacteria. The more cannibalistic live bacteria, the greater the chance of poisoning. Due to the different pathogenicity of various serotypes of Salmonella, the amount of bacteria that cause food poisoning is also different. For children, the elderly and the weak, cannibalism of a small amount of Salmonella can cause food poisoning.
2. Foods and sources of contamination that cause poisoning Salmonella are widely distributed in nature and have a wide range of hosts in humans and animals. Salmonella food poisoning is mostly caused by animal foods, especially livestock meat and its products, followed by poultry meat, eggs, milk and their products.
(1) Poultry and livestock infection before death means that poultry and livestock are infected with Salmonella before slaughter. This infection is the main source of Salmonella in meat products.
(2) Salmonella contamination of livestock and poultry meat refers to contamination caused by water, soil, ice, containers, etc. during the slaughter process or in various links from slaughter to sales.
(3) Egg contamination by Salmonella has two pathways. One is contamination before laying eggs, that is, the sterilization effect of the reproductive organs of poultry is weakened due to certain diseases, and bacteria from the intestines can invade the yolk, causing the egg liquid to be contaminated with various bacteria; the other is contamination after laying eggs. After the eggs are laid from the birth canal of the poultry, for some reason, the surface of the eggshell is contaminated, and Salmonella can enter the egg through the pores, causing food poisoning under improper storage and processing. (4) Salmonella contamination in milk includes contamination before and after milking. The milk of dairy cows with salmonellosis may carry bacteria, which is called pre-milking contamination. The milk of healthy dairy cows may also be contaminated by feces or other dirt from sick cows and pathogen carriers (staff) after milking, which is called post-milking contamination.
(5) The contamination of salmonella in cooked food is mainly caused by cross-contamination between raw and cooked food and infected employees.
In addition, the salmonella contamination of aquatic products is mainly caused by water pollution.
3. Clinical manifestations of poisoning
The incubation period of salmonella food poisoning is generally 12~48h, the shorter is 6~8h, and it is rare to exceed 72h. The main symptoms are fever, nausea, vomiting, abdominal pain, and diarrhea. Generally, it will be relieved rapidly within 3~5 days, and the mortality rate is about 1%. According to its clinical characteristics, it can be divided into gastroenteritis type, cholera type, and cholerae type.