{"id":450,"date":"2019-03-11T19:13:03","date_gmt":"2019-03-11T19:13:03","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/sunyltnutrition\/?post_type=chapter&p=450"},"modified":"2019-04-15T13:47:24","modified_gmt":"2019-04-15T13:47:24","slug":"11-2-microbes-in-foods","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-ltnutrition\/chapter\/11-2-microbes-in-foods\/","title":{"raw":"11.2: Microbes in Foods","rendered":"11.2: Microbes in Foods"},"content":{"raw":"Bacteria and viruses are the most common cause of food poisoning, although toxins and parasites also can contribute. The symptoms and severity of food poisoning vary, depending on which bacteria or virus has contaminated the food.\r\n
\r\n

Bacteria<\/h2>\r\nBacteria\u00a0are a common cause of foodborne illness. In the\u00a0United Kingdom\u00a0during 2000, the individual bacteria involved were the following:\u00a0Campylobacter jejuni\u00a0<\/em>77.3%,\u00a0Salmonella\u00a0<\/em>20.9%,\u00a0Escherichia coli\u00a0<\/em>O157:H7\u00a01.4%, and all others less than 0.56%.\u00a0In the past, bacterial infections were thought to be more prevalent because few places had the capability to test for\u00a0norovirus\u00a0and no active surveillance was being done for this particular agent. Toxins from bacterial infections are delayed because the bacteria need time to multiply (Figure\u00a011.2.<\/span>1<\/span><\/span><\/span><\/span><\/span>11.2.1<\/span><\/span>). As a result, symptoms associated with intoxication are usually not seen until 12\u201372 hours or more after eating contaminated food. However, in some cases, such as Staphylococcal food poisoning, the onset of illness can be as soon as 30 minutes after ingesting contaminated food.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"232\"]\"E.coli-colony-growth.gif\" Figure 11.2.1:\u00a0False color time-lapse video of E. coli colony growing on microscope slide. Image used wtih permission (CC BY-SA 4.0\u00a0Stewart EJ, Madden R, Paul G, Taddei F (2005) - Aging and Death in an Organism That Reproduces by Morphologically Symmetric Division. PLoS Biol 3(2): e45.\u00a0https:\/\/doi.org\/10.1371\/journal.pbio.0030045.).<\/em>[\/caption]\r\n\r\n<\/div>\r\n
\r\n

Enterotoxins<\/h2>\r\nAn enterotoxin is a protein exotoxin released by a microorganism that targets the intestines. Enterotoxins are chromosomally encoded or plasmid encoded[2] exotoxins that are produced and secreted from several bacterial organisms. They are often heat-stable, and are of low molecular weight and water-soluble. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal (epithelial) cells of the intestinal wall. They are mostly pore-forming toxins (mostly chloride pores), secreted by bacteria, that assemble to form pores in cell membranes. This causes the cells to die.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"550\"]\"\" Figure\u00a011.2.2:\u00a0Cartoon representation of the molecular structure of staphylococcal enterotoxin\u00a0registered with 1uns code. Image used with permission (Public Domain;\u00a0Jawahar Swaminathan and MSD staff at the\u00a0European Bioinformatics Institute).<\/em>[\/caption]\r\n\r\nIn addition to disease caused by direct bacterial infection, some foodborne illnesses are caused by\u00a0enterotoxins\u00a0(exotoxins\u00a0targeting the intestines). Enterotoxins can produce illness even when the microbes that produced them have been killed. Symptom appearance varies with the toxin but may be rapid in onset, as in the case of enterotoxins of\u00a0Staphylococcus\u00a0<\/em>aureu<\/em>s\u00a0in which symptoms appear in one to six hours.\u00a0This causes intense\u00a0vomiting\u00a0including or not including diarrhea (resulting in\u00a0staphylococcal enteritis), and staphylococcal enterotoxins (most commonly\u00a0staphylococcal enterotoxin A\u00a0but also including\u00a0staphylococcal enterotoxin B) are the most commonly reported enterotoxins although cases of poisoning are likely underestimated.\u00a0It occurs mainly in cooked and processed foods due to competition with other biota in raw foods, and humans are the main cause of contamination as a substantial percentage of humans are persistent carriers of\u00a0S. aureus<\/em>. The CDC has estimated about 240,000 cases per year in the United States.\r\n\r\n<\/div>\r\n
\r\n

Viruses<\/h2>\r\nViral\u00a0infections make up perhaps one third of cases of food poisoning in developed countries. In the US, more than 50% of cases are viral and\u00a0noroviruses\u00a0are the most common foodborne illness, causing 57% of outbreaks in 2004. Foodborne viral infection are usually of intermediate (1\u20133 days)\u00a0incubation period, causing illnesses which are self-limited in otherwise healthy individuals; they are similar to the bacterial forms described above.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"307\"]\"\" Figure\u00a011.2.3:\u00a0Rotavirus. Note the wheel-like appearance of some of the rotavirus particles. The observance of such particles gave the virus its name ('rota' being the Latin word meaning wheel). Bar = 100 nanometers.IMpage used with permission (Public Domain;\u00a0F.P. Williams, U.S. EPA).<\/em>[\/caption]\r\n\r\n<\/div>\r\n
\r\n

Natural Toxins<\/h2>\r\nSeveral foods can naturally contain\u00a0toxins, many of which are not produced by bacteria. Plants in particular may be toxic; animals which are naturally poisonous to eat are rare. In evolutionary terms, animals can escape being eaten by fleeing; plants can use only passive defenses such as poisons and distasteful substances, for example\u00a0capsaicin\u00a0in\u00a0chili peppers (Figure\u00a011.2.<\/span>4<\/span><\/span><\/span><\/span><\/span>11.2.4<\/span><\/span>) and pungent\u00a0sulfur\u00a0compounds in\u00a0garlic\u00a0and\u00a0onions. Most animal poisons are not synthesized by the animal, but acquired by eating poisonous plants to which the animal is immune, or by bacterial action.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"450\"]\"1920px-Red_hot_chilli_peppers.jpg\" Figure 11.2.4:\u00a0Capsaicin\u00a0is an active component of chili peppers, which are plants belonging to the genus Capsicum. It is an irritant for mammals, including humans, and produces a sensation of burning in any tissue with which it comes into contact.\u00a0Red Cubanelle chili peppers. Image used with permission (CC BY-SA 4.0;\u00a0\u00a9 Tomas Castelazo, www.tomascastelazo.com \/ Wikimedia Commons).<\/em>[\/caption]\r\n\r\n<\/div>\r\n
\r\n

Parasites<\/h2>\r\nFood poisoning caused by parasites is not as common as food poisoning caused by bacteria and viruses, but parasites spread through food are still very dangerous. Toxoplasma is the parasite seen most often in cases of food poisoning (Figure\u00a011.2.<\/span>5<\/span><\/span><\/span><\/span><\/span>11.2.5<\/span><\/span>). It\u2019s typically found in cat litter boxes. Parasites can live in your digestive tract undetected for years. However, people with weakened immune systems and pregnant women risk serious side effects if parasites take up residence in their intestines.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"550\"]\"Toxoplasma_gondii_Life_cycle_PHIL_3421_lores.png\" Figure\u00a011.2.4:\u00a0This is an illustration of the life cycle of Toxoplasma gondii, the causal agent of toxoplasmosis.\u00a0This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #3421. Note: Not all PHIL images are public domain; be sure to check copyright status and credit authors and content providers. Image used with permission (Public Domain;\u00a0CDC\/Alexander J. da Silva, PhD\/Melanie Moser).<\/em>[\/caption]\r\n\r\n<\/div>\r\n
\r\n

Contributors<\/h3>\r\n