Salmonella and test

There are four kinds of syndromes in Salmonella and human salmonellosis: salmonellosis; typhoid; non typhoid septicemia and asymptomatic carriers Salmonella gastroenteritis is caused by any type of Salmonella other than Salmonella typhi, usually with mild, persistent diarrhea Typhoid is actually caused by Salmonella typhi The mortality rate of untreated patients can be more than 10%, while that of properly treated patients is less than 1% Survivors can become chronic asymptomatic Salmonella carriers These asymptomatic carriers do not show that symptoms can still spread microbes to other people (the traditional example is Typhoid Mary) Non typhoid type of Salmonella septicemia can be caused by various types of Salmonella infection, can affect all organs, and sometimes cause death Survivors can become chronic asymptomatic Salmonella carriers 1、 The incubation period of Pathogenic Salmonella gastroenteritis is generally 6-72 hours The main symptoms are nausea, vomiting, abdominal colic, diarrhea, fever, chills and headache The course of disease is usually 1-2 days or longer The infection dose was 15-20 bacteria, and the mortality was 1-4% Zui susceptible groups are young children, the weak, the elderly, the immunodeficient and so on The main source of pollution is human and livestock feces Salmonella is often found in animals, especially poultry and pigs It also exists in many environments Bacteria have been found in water, soil, insects, surfaces of factories and kitchen facilities, and animal waste They can be found in a variety of foods, including raw meat, poultry, dairy products and eggs, fish, shrimp and drumsticks, yeast, coconut, soy sauce and salad dressing, cake powder, cream sandwich dessert, top ingredients, dried gelatin, peanut dew, orange juice, cocoa and chocolate Salmonella is also a thermophilic bacteria It grows well in medium temperature, neutral pH, low salt and high water activity The low water activity of growing Zui was 0.94 Facultative anaerobic, sensitive to moderate heating Similarly, it can adapt to acid environment Through sanitation to prevent secondary pollution; cooking; pasteurization control Normal family cooking and personal hygiene can prevent the secondary pollution of cooked food, as well as the control of time and temperature can generally fully prevent the occurrence of salmonellosis 2、 Because Salmonella is a common food borne bacterial pathogen in Zui, this section focuses on the detection of Salmonella Salmonella is one of the most active food borne pathogens In order to isolate and identify Salmonella from food, the current general method is divided into five steps: 1 Pre enrichment - * step enables food samples to increase bacteria in non selective medium containing nutrition, and restores the damaged Salmonella cells to a stable physiological state 2 Selective enrichment - a step in which the sample is further enriched in a growth promoting medium containing selective inhibitors This medium allows Salmonella to continue to proliferate while preventing most other bacteria from proliferating 3 Selective plate separation - in this step, solid selective medium is used to inhibit the growth of non Salmonella bacteria and provide the identification of pure colonies of suspected Salmonella bacteria visible to the naked eye 4 Biochemical screening - elimination of most non Salmonella It also provides a preliminary identification of Salmonella culture 5 Serology technology provides identification of culture strains These five steps represent the ideal situation However, an experienced inspector may see the characteristics and differences in one or several steps At present, Salmonella in food is tested on the basis of statistical sampling plan, and 25g food is the standard analytical unit 3、 Preparation of Salmonella sample from food the following method is to take 25g sample as the detection unit, and the ratio of sample: broth is 1:9 Unless otherwise specified, according to the mixing degree, add enough broth to maintain the proportion of 1:9 For samples that do not need to be accurately weighed for testing, for example, field chicken leg, please refer to the specific method description 1 Dried egg yolk, dried protein, dried whole egg, liquid milk (degreased milk, containing 2% fat milk, whole milk, and skimmed milk), powdered prepared food (cake, sweet cake, doughnut, biscuit and bread), baby food, oral food or soft tube food with egg: the frozen sample Zui before the test shall not be unfrozen If the frozen sample must be softened to obtain the part to be tested, thaw the required part as quickly as possible to reduce the number of competing bacteria or reduce the possible damage of Salmonella The defrosting temperature shall be below 45 ℃, and the water bath pot with automatic thermostat shall be continuously stirred for 15 minutes or defrosted within 2-50; 5 ℃ and 18 hours For aseptic operation, weigh 25g of the sample and put it into a sterilization wide mouth bottle with a screw cap (500ml) or other suitable containers Add 225ml of sterile Lactose Broth to the non powdered sample If the product is in powder form, add about 15ml of sterilized Lactose Broth, mix with sterilized glass rod, spoon or sterilized tongue depressor to form a uniform suspension Add 3 more Lactose Broth 10ml, 10ml, 190ml to make the total amount 225ml Stir well until the sample is completely suspended and free of lumps Cover the bottle tightly and leave it at room temperature for 60min Shake well and measure the pH value with test paper If necessary, adjust the pH to 6.8 ± 0.2 with 1nnaoh or 1nhcl Before measuring the final pH of Zui, close the bottle cap and mix well Then unscrew the cap for about 1 / 4 turn, and culture at 35 ℃ for 24 ± 2 hours The following steps are as follows: 1-10 2 Eggs: A eggs with shells: wash the eggs with a hard brush under the water The eggs were immersed in 200 ppm chloride solution containing 0.1% SDS for 30 minutes Add 8ml 5.25% sodium hypochlorite to 992ml distilled water containing 1g SDS to prepare 200ppm Cl - / 0.1% SDS solution This disinfectant needs to be prepared temporarily before use Aseptic operation: open the egg, use the sterilized egg separator and discard the protein In aseptic operation, weigh 25g egg yolk into a 500ml conical flask or other suitable container for sterilization Add 225ml tryptone (pancreatide) soybean broth (TSB) and shake to mix well Allow to stand at room temperature for 60 minutes Shake it well and measure the pH value with test paper If necessary, adjust the pH value to 6.8 ± 0.2 and culture at 35 ℃ for 24 ± 2 hours The following steps are as follows: 1-10 B liquid whole egg (uniform): put 25g of sterile operation scale into sterile 500ml conical flask or other suitable containers Add 225mltsb and shake to mix well Continue as described above C hard boiled eggs (eggs, duck eggs or other eggs): at present, it is not known whether the Salmonella inhibitor in the protein has thermal stability Therefore, protein and yolk were separated by aseptic operation Weigh 25g of powdered yolk solid into a sterile 500ml conical flask or other suitable container Add 225mltsb and rotate to mix well Continue as described above 3 Skimmed milk powder a, instant solution: weigh 25g of sample in aseptic operation, and add it into sterilization beaker (250ml) or other suitable containers After sterilizing glass or paper funnel (rolled with tape for high-pressure sterilization), pour 25g detection unit slowly into 500ml conical flask or other suitable containers (containing 225ml of brilliant green water) for sterilization to cover the surface of brilliant green water It is also possible to pour more than 25g inspection units into the surface of the corresponding parts of the green water in proportion Add 2ml of 1% brilliant green solution to every 1000ml of sterilized distilled water to prepare brilliant green water Allow the container containing the sample & ා0; pre enrichment medium to stand for 60 ± 5 minutes Loosely cover the container lid, do not need to mix or adjust the pH value, culture at 35 ℃ for 24 ± 2 hours, and continue the following steps as per 4, 1-10 B non instant solution: it is carried out according to the above method of a skimmed milk powder, but it is not allowed to combine multiple inspection units for inspection in proportion 4 Whole milk powder: the aseptic operation is to take 25g of sample and add it into a sterile, wide mouth bottle with screw cap (500ml) or other suitable containers Add 225ml of sterilized distilled water and shake to mix well Cover tightly and let stand at room temperature for 60 minutes Mix it well and measure the pH value with test paper Adjust the pH value to 6.8 ± 0.2 if necessary Before measuring the final pH of Zui, close the bottle cap and mix well Then add 0.45 ml 1% brilliant green dye solution and mix well Unscrew the cap for about 1 / 4 turn, and then culture at 35 ℃ for 24 ± 2 hours The following steps are as follows: 4, 1-10 5 Casein: in aseptic operation, weigh 25g of sample, add 225ml of sterilized Lactose Broth to the aseptic homogenizing cup, and homogenize for 2 minutes Aseptic operation, transfer the homogenized mixture into a sterilized, 500mL wide mouth bottle with screw cap or other suitable container Cover tightly and let stand at room temperature for 60 minutes Shake well and measure the pH value with test paper Adjust the pH value to 6.8 ± 0.2 if necessary Before measuring the final pH of Zui, close the bottle cap and mix well After loosening the cap for about 1 / 4 turn, culture at 35 ℃ for 24 ± 2 hours, and continue with the following steps as per 4, 1-10 6 Soybean powder: in aseptic operation, weigh 25g of sample and add it into sterilization beaker (250ml) or other suitable containers Pour 25g detection unit slowly into a 500ml conical flask or other suitable container filled with 225ml Lactose Broth with sterilized glass or paper funnel (rolled with tape for high pressure sterilization) to cover the Lactose Broth surface The testing unit (25g) shall not be mixed for testing in proportion Allow the container to stand for 60 ± 5 minutes Loosely cover the container lid, do not need to mix or adjust the pH value, culture at 35 ℃ for 24 ± 2 hours, and continue the following steps as per 4, 1-10 7 Egg products (noodles, omelets, macaroni, spaghetti), cheese, dough, prepared salad (ham, eggs, chicken, tuna, Turkey), fresh, frozen, or dried fruits and vegetables, nuts, crustaceans (shrimp, crab, crawfish, Langostinos, lobster) and fish: Before the test, the frozen sample Zui does not need to be unfrozen If the frozen sample must be softened to take its test part, it should be unfrozen within 15 minutes in a 45 ℃ water bath with continuous mixing and automatic thermostat control Or it can be carried out within 2 & ා 0; 5 ℃ and 18 hours In aseptic operation, 25g sample is weighed and added into the sterilized homogenizer Add 225ml of sterilized Lactose Broth and homogenize for 2 minutes Then transfer the homogenized mixture into a sterile wide mouth bottle with a screw cap (500ml) or other suitable container Close the cap and allow to stand at room temperature for 60 minutes Shake it well and measure the pH value with test paper Adjust the pH value to 6.8 ± 0.2 if necessary Mix well Unscrew the cap for about 1 / 4 turn, and then culture at 35 ℃ for 24 ± 2 hours The following steps are as follows: 4, 1-10 8 Dry yeast: in aseptic operation, weigh 25g of the sample and put it into a sterilization wide mouth bottle with a screw cap (500ml), or other suitable containers Add 225ml of sterilized tryptone (pancreatification) soybean broth, mix well to form a uniform suspension of yeast Close the cap and let stand at room temperature for 60 minutes Shake it well and measure the pH value with test paper.