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  1. Which bacteria cause the greatest harm in the food industry?

    There are many bacteria that are harmful to the food in the food industry. Some of the major bacteria are described below.

    • Staphylococcus aureus:

    Staph.aureus are gram-positive bacteria that are cocci in shape. These bacteria can live in the presence or absence of oxygen, as they are facultative anaerobes. They are non-motile, non-spore forming, catalase-positive, and oxidase negative bacteria. They are normally present on the skin and cause contamination during mishandling. They are present in a high percentage in the nasal secretions and cause the contamination of food when personnel is suffering from flu, pyogenic infections, sore throat, and any skin infections. Toxin production is directly proportioned to the growth of bacteria. The more the bacteria grow, the more the toxins are produced. There are 17 different enterotoxins that are produced by bacteria during their growth in food. From the 17 enterotoxins, SEA and SEB are most important because they are neurotoxins. These toxins go into the stomach and activate the vagus nerve. This activation sends nerve impulse to the emetic center in brain, where the brain initiates the vomiting. Their toxins are heat stable and remain active in normal cooking temperatures. They become inactive when heat at 60ᴼC for 6 hours. For Staph.aureus enumeration, the Baird parker medium is used.

    • Salmonella enteritidis:

    Salmonella is a gram-negative rod-shaped bacteria. They are facultative anaerobes that can survive in the absence of oxygen. They are motile and non-spore forming. They are present in the human gut and excrete through feces. Sewage contamination in food leads to the contamination of foods. The sewage contaminations are due to pipe leakage and mixing of sewage water with the food. They don’t produce any toxins. Bacteria are present in the food that goes into the intestine by crossing the stomach. In intestine, it adheres with enterocyte and invades in the cell. Salmonella is an intracellular pathogen that increases the adenylate cyclase activity. This increases the cAMP level of the intestine that leads to diarrhea. The inflammation of intestine starts when cell lysis occurs. This inflammation is called gastroenteritis. Salmonella-Shigella agar is used for the detection of salmonella in the food.

    • Escherichia coli

    E.coli is a gram-negative and rod-shaped bacteria. They are also facultative anaerobes that can grow in the absence of oxygen. They are motile and non-spore forming. They are present in the human gut and excrete through feces. They are the primary indicator of fecal contamination in the food. Sewage contamination in food leads to the contamination of foods. The sewage contaminations are due to pipe leakage and mixing of sewage water with the food. They produced two types of toxins i.e. LT and ST. LT is the heat-labile toxins and has long chains of amino acids. ST is heat stable toxins and has small chains of amino acids. Bacteria are present in the food that goes into the intestine by crossing the stomach. In intestine, it adheres with enterocyte and produces toxins. These toxins increase the adenylate cyclase and guanylate cyclase activity. This increases the cAMP level and loss of Clions the intestine that leads to diarrhea. EMB agar is used for the detection of E.coli from food.

    • Shigella dysentery

    Shigella is also a member of the Enterobacteriaceae family. It shares the same characteristics as the above. It is also present in the feces and indicates the fecal contamination in food. It is gram-negative and rod-shaped bacteria. They are also facultative anaerobes that can grow in the absence of oxygen. They are non-motile and non-spore forming. They produce Shiga toxins. They enter the intestine and attach to the enterocytes. Then, they enter the cell and produce Shiga toxin. Shiga toxin inhibits the cell translation and then stops the protein synthesis of the cell. This leads to the death of cell. Bacteria move to other cells and cause cell lysis. The cell lysis causes bloody diarrhea that is also called dysentery. Salmonella-Shigella agar is used for the detection of Shigella in the food.

    • Campylobacter jejuni

    Campylobacter is a gram-negative rod-shaped bacteria. It is non-spore forming, curve bacteria that are Microaerophillic in nature. They are most fragile and motile. They also present in the GI tract of bird and their presence indicates the bird fecal contamination. It is the bacterium that most commonly causes food poisoning. The cytolethal distending toxin is produced by bacteria. The bacteria move into the intestine through food. They move to mucous membranes through chemotaxis. It attaches to mucous membranes and invades in cell. These invasions produce the toxin that causes cell lysis. Camp-cefix is used for the isolation of bacteria from food.

    • Listeria monocytogenes

    Listeria is gram-positive bacteria with rod shape. It is psychrotroph, facultative anaerobes. Some of the species are non-motile and some are motile. They are non-spore forming bacteria. They cause disease in an immune-compromised person. They also cause food contamination through fecal contamination. There is no toxin that is produced by this bacterium. Bacteria are present in the food that enters the intestine. It invades in the cell and through actin polymerizations go to the other cells. It grows in the intestine and then enters the blood. The bacteremia leads to meningitis when bacteria cross the blood-brain barrier. Half Frazer media is used for the detection of listeria.

    • Vibrio cholera

    Vibrio is gram-negative and curves shaped bacteria. They are facultative anaerobes, motile and non-spore former. They have poor flagella and give oxidase-positive results. They can be transmitted through seawater. They are present in the feces and indicate the fecal contamination in food.  Vibrio produced the cholera toxin in the intestine. Toxins have two sites A and B. A site for the intracellular activity of toxin and B is responsible for binding. Bacteria are present in the food that reaches the intestine through stomach. In intestine, these toxins bind with the enterocytes and invade in the cells. They are potent enhancer that sustains the increase in cAMP level. These toxins increase the chloride ion loss that leads to rice watery diarrhea. Total coliform bacterial count agar is used for the isolation of vibrio.

    • Bacillus cereus:

    Bacillus is gram-positive, rod-shaped bacteria and spore former. it produced central spores and spores that can tolerate even pasteurization temperature. It is facultative anaerobes that are present in air and soil. This infection is commonly produced by using starchy food such as rice, potato and etc. They produced two types of toxins; Emetic toxin and Diarrheagenic toxin. These toxins are produced when bacteria adhere to enterocytes and invades in the cell. This increases the cAMP level of the intestine that leads to diarrhea. The inflammation of intestine starts when cell lysis occurs. This inflammation is called gastroenteritis. Salmonella-Shigella agar is used for the detection of salmonella in the food.

    • Clostridium perferinges:

    Clostridium is a gram-positive rod-shaped bacteria. They are anaerobic bacteria that grow in the absence of oxygen. They are spore-forming bacteria that produced terminal spore. Their spores are killed at 115ᴼC. they are commonly present in the canned food, canned meat due to anaerobic environment and cause food-borne illness. Toxins are produced during sporulation. There are 4 types of toxins caused by bacteria i.e.  Alfa-toxin, beta-toxin, epsilon-toxin, and tau-toxin.

    The type A toxin is most important that caused food poisoning and gas gangrene. The gastroenteritis is the same as other bacteria. The toxin produced in the intestine causes an increase in cAMP level. This leads to inflammation and diarrhea.  RCM is used to isolate clostridium from food.

    • Clostridium botulinum:

    Cl.botulinum is gram-positive rod-shaped bacteria. They are anaerobic bacteria that grow in the absence of oxygen. They are spore-forming bacteria that produced terminal spore. Their spores are killed at 115ᴼC. there are two groups of these bacteria.

    • Proteolytic bacteria are the group that can break proteins. These grow at 10-48ᴼC.
    • Non-proteolytic bacteria are the group that cannot break proteins. These grow at 4-40ᴼC.

    Their normal habitat is soil. The spores and vegetative bacteria cause the contamination of food during mishandling and poor environmental conditions. They produced a heat-sensitive toxin that can inactivate at 60-70ᴼC. the toxins that are produced by this bacterium are called botulinum that is also neurotoxins. There are 8 different variants of these toxins and 2 different sides. A side is responsible for activation while B site is used for binding. These toxins go into the stomach and then to the intestine. From intestine, these toxins cross the cells and enter in bloodstream and lead to toxemia. From blood, they reach the brain where they bind with the neurons. The binding with the neurons inhibits the SNARE that stops acetylcholine. This inhibition of acetylcholine stops the nerve impulse that causes flaccid paralysis. This flaccid paralysis leads to the death of person. Cl.botulinum is enumerated on reinforced clostridial media.

  2. Bacteria play an important role in the food industry. Bacteria are responsible for two types of feedback.

    • Positive feedback:

    In positive feedback, all the bacteria are beneficial to the food. They are responsible for the manufacturing of food and for food preservation. For example, lactobacillus species are used in the manufacturing of yogurt. They give a good texture of yogurt.

    • Negative feedback:

    Bacteria are harmful to the food in negative feedback. These bacteria cause food spoilage and foodborne disease. The food spoilage cause when other pathogenic bacteria are mixed with the food due to

    • Poor environment
    • Less care
    • Lack of food safety testing
    • Poor handling
    • Poor control of contamination

    Foodborne diseases are also caused by pathogenic bacteria. There are three types of food-borne illnesses that are caused by bacteria.

    1. Food intoxication
    2. Food infection
    3. Food toxico-infection

     

    1. Food intoxication:

    Food intoxications refer to the illness that is caused by the toxins of the pathogenic bacteria in food. Toxins are produced by the bacteria present in the food. Bacteria don’t produce toxins in the intestine. For food intoxication, three class plan system is used. The bacteria in food are enumerated by growing the food sample in selective media. The bacteria that cause intoxications are as follows:

    • Staphylococcus aureus
    • Clostridium botulinum

     

    1. Food infection:

    Food infection refers to the food-borne illness that is caused by vegetative bacteria. Bacteria are present in the food. The bacteria go into the intestine and then produced toxins that cause food-borne illness. There is two class sampling plan in case of food infection caused by this pathogen. Two classes plan involves either the acceptance of food or the rejection of food. there is no bacterial enumeration in the two-class plan system. The bacteria that cause food infection are as follows:

    • Salmonella enteritidis
    • Escherichia coli
    • Shigella dysentery
    • Campylobacter jejuni
    • Listeria monocytogenes
    • Vibrio cholera

     

    1. Food toxico-infection:

    Food toxico-infections refer to the illness that is caused by the toxins or the vegetative cell of the pathogenic bacteria in food. Toxins are produced by the bacteria present either in the food or in the intestine. The bacteria that cause toxico-infections are as follows:

    1. Bacillus cereus
    2. Clostridium perferinges

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