What are Some Symptoms of Salmonella?

Salmonella is a common foodborne pathogen. The traditional methods of Salmonella identification are mainly based on morphological characteristics, culture characteristics, physiological and biochemical characteristics, antigen characteristics, phage characteristics, etc. ^[1] . In 1885, Salmonella isolated S. choleraesuis during the cholera epidemic, so it was named Salmonella. Some Salmonella species are pathogenic to humans, some are pathogenic to animals, and others are pathogenic to humans and animals. Salmonellosis is a general term for different forms of human, livestock and wild animals caused by various types of salmonella. Contamination of food by the feces of people infected with Salmonella or carriers can cause food poisoning. According to statistics, in various types of bacterial food poisonings in various countries around the world, food poisoning caused by Salmonella is often ranked first. Salmonella also ranks first in inland areas of China ^[2] .

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The biochemical reaction is very active, and it can decompose many kinds of sugars and alcohols ^[4]

Meat contamination

The detection rate of salmonella in meat and its products is 20% -25% in the United States, 9.9% in the United Kingdom, and the pollution rate of imported poultry in Japan is 10.3%. The detection rate of salmonella in domestic meat is 1.1% -39.5%. ^[5]

Salmonella infection is a zoonotic infectious disease, mainly caused by consumption of contaminated food, and is an important source of food poisoning in many countries ^[6]

Salmonella is American

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Cell nucleic acid DNA and RNA are the only macromolecules that can carry information. Since all cells contain this molecule, it can be used as a target for detection. The target is usually a specific nucleic acid sequence that can be detected by using complement nucleic acid molecules as probes. Similar to immunological methods, the probes also need to be appropriately labeled, such as radioisotopes, enzymes, or luminescent labels. Fitts et al. Introduced the first generation of DNA-RNA hybridization technology in the detection of food Salmonella. The probe used in this method contains a Salmonella typhimurium DNA fragment labeled with a radioactive isotope. The detection limit can reach 108 bacteria / ml, but because of the use of radioisotopes, it can only be applied in specialized laboratories. The advantages of this method have been offset. To this end, a second-generation technology based on nucleic acid hybridization, a colorimeter, has been developed. This method relies on the detection of ribosomal RNA (rRNA), a nucleic acid component stored during the development of ribosomes. The ribosome is part of the cellular protein synthesizer. There are 5000 to 20,000 replicas in each bacterial cell, compared with only 2 to 10 chromosomal DNA replicas. This naturally rich rRNA target sequence makes detection possible without radiometer, while maintaining sensitivity comparable to or higher than that of radioisotope methods. Another advantage is that because rRNA is single-stranded (and DNA is double-stranded), no denaturation step is required before hybridization. To obtain a positive result, this method requires 105 target cells / ml, so for Salmonella detection, pre-proliferation and selective enrichment are required for a total of about 50 hours. The rRNA probe method is more time-consuming than the Salmonella ELISA (enzyme-linked immunoassay), but the cost is similar. The latest development of food bacterial detection methods is the development of chemical amplification systems, namely polymerase chain reaction (PCR), which can be used to amplify bacterial DNA from prepared samples, making it easier to use methods such as gel electrophoresis Or colorimetric ELISA method. PCR methods have been established for the detection of Salmonella and other food-borne pathogens, and some of them have shown excellent sensitivity. However, this method is difficult to automate and must be selectively enriched to dilute certain components that may interfere with the detection reaction. A complete PCR-based method takes 2 days to complete, largely offsetting its advantages of high sensitivity, but this method has a low Salmonella or Salmonella "injury" and it is difficult to recover. Samples that still hold salmonella rRNA are particularly effective ^[9] .