FOOD MICROBIOLOGY By: Kimberly Le Background Information Microbiology: the study of microorganisms/ Food Microbiology: the study of microbes which are a diverse group of simple microorganisms that inhibit, create, or life-forms including bacteria, archaea, algae, contaminate food. fungi, protozoa's, and virus. ◦ The foods we eat are rarely sterile, they carry microbes that interact with food. Microbes in food may display their presence in several ways: ◦ They can cause food spoilage ◦ They can cause foodborne illnesses This Photo by Unknown Author ◦ They can transform food’s properties in a beneficial way (food fermentation) Antonie van Leeuwenhoek, Louis Pasteur, father of food first scientist to observe and microbiology. Created describe microorganisms. pasteurization (prevent food Also designed the first spoilage) and developed microscope. vaccines. This Photo by Unknown Author This Photo by Unknown Author Food Spoilage ◦ According to the Oxford dictionary, to spoil is to “deprive of good or effective qualities”. ◦ Food characteristics change when spoiled and is no longer acceptable for consumption. Spoiled does not always come from microbiological in origin but the majority is caused by microbial activity. (Ex: insect damage, drying out, discoloration, staling or rancidity.) ◦ Visible microbial growth on surface of food product (slime or colonies), loss of texture, or chemical production of microbial metabolism (gas, pigmentation, off-odors, and flavors) are indicators. ◦ Spoilage is an indicator of quality. An individual may view it as unacceptable while the other does not due to According to the Food and Agriculture Organization social or cultural views. (Ex: matured cheese or game (FAO), an estimated 1/3 of birds) the food produced globally is either lost or wasted, amounting to 1.3 billion tons per year. Foodborne Illnesses ◦ The World Health Organization (WHO) defines foodborne disease as “Any disease of an infectious or toxic nature caused by, or thought to be caused by, the consumption of food or water”. ◦ Foodborne illnesses (also known as food poisoning) are commonly caused by different types of bacteria and symptoms vary among different types. ◦ Most common symptoms include nausea, vomiting, stomach cramps, and diarrhea. Maybe severe or sometimes life threatening. ◦ Five common germs that cause illnesses in the United States according to CDC: ◦ Norovirus ◦ Salmonella ◦ Clostridium perfringens ◦ Campylobacter ◦ Staphylococcus aureus ◦ Three that are considered zero tolerance (potentially dangerous at any level when ingested, does not cause illness but are more likely to lead to hospitalization): ◦ Salmonella ◦ E.coli ◦ Listeria monocytogenes Leading Norovirus cause of foodborne illness in (NoV) the US ◦ There are at least 33 different norovirus genotypes but there are only 3 genogroups that infect humans. ◦ Very contagious virus that causes projectile and explosive vomiting, followed by diarrhea among people of all ages. A person usually develops symptoms 12 to 48 hours after exposure and the symptoms may last 1 to 3 days. ◦ Able to contract the virus by direct contact with an infected person, consuming contaminated food or water, or touching a contaminated surface. ◦ Common settings of outbreaks includes healthcare facilities, restaurants, schools, childcare centers, and cruise ships. ◦ Sources: ◦ Contaminated water ◦ Seafood ◦ Meat According to the CDC, ◦ Fruit and vegetables there are about 2,500 reports of Norovirus outbreaks each year in the US. Most common from November to April. This Photo by Unknown Author is licensed under CC BY-SA-NC Salmonella bacterium Salmonella is more common in the summer Salmonella due to warmer weather and unrefrigerated foods creating an ideal ◦ A motile, non-spore forming, gram negative, rod- condition for the bacteria shape bacterium. to grow. ◦ Divided into two species: S. enterica and S. bongori with subspecies but is further subdivided by serotypes. ◦ Can cause two types of illnesses, depending on serotype: nontyphoidal and typhoid. ◦ Typhoid (S. Typhi and S. Paratyphi A. which is found only in humans) This Photo by Unknown Author is licensed under CC BY-ND ◦ Duration is longer than nontyphoidal ◦ Most severe and has a higher rate of mortality ◦ Usually associated with contaminated drinking water Bacteria was discovered by an ◦ Nontyphoidal (caused by serotypes other than those American caused by typhoid) scientist, Daniel E. Salmon in ◦ Sources: 1885. ◦ Contaminated water ◦ Food sources (Ex: meat, poultry, eggs, milk, fish, This Photo by Unknown Author is licensed under CC BY-SA produce, etc.) This Photo by Unknown Author is Growth of Salmonella on Xylose ◦ Cross contamination licensed under CC Lysine Deoxycholate agar (XLD) BY-SA plate. C. perfringens under the microscope Clostridium perfringens ◦ Anaerobic (but aerotolerant), gram positive, spore-forming rod that produces an enterotoxin. Spores can persist in soil, Non-pathogenic C. perfringens is distributed in the environment sediments, and areas subject to ◦ human or animal fecal pollution and is found in the intestines of humans. ◦ Can take on 2 forms in foodborne illnesses: ◦ Gastroenteritis form ◦ Common and self limiting ◦ Depending on strain, can cause more severe damage This Photo by Unknown Author is licensed under CC BY-SA ◦ Enteritis necroticans (“pig-bel disease”) ◦ Rare in the US C. Perfringens on egg yolk agar plate ◦ More severe than other form of illnesses and often fatal All Clostridium ◦ Sources: species have ◦ Raw meats and poultry peritrichous flagella ◦ Dried or pre-cooked foods with an exception of C. perfringens ◦ Prepared food in large quantities and kept warm a long time ◦ Vegetable products ◦ Spices and herbs This Photo by Unknown Author is licensed under CC BY-SA This Photo by Unknown Author is licensed under CC BY-SA Campylobacter Bacteria Third leading Campylobacter bacterial cause of foodborne ◦ Non-spore forming, gram negative, rod with a curve or S illness in the shaped morphology, and a flagellum at one or both ends of the U.S. bacterium. ◦ Are microaerophilic (grow at lower than atmospheric oxygen concentration), causing them to be fragile in an ambient environment. ◦ More than 80% of the infection are caused by C. jejuni. ◦ Common in low-resource countries Blood Agar Plate ◦ Many animals can show no signs of illness as the bacteria is carried throughout the body and can be transferred to edible parts when an animal is slaughtered. This Photo by Unknown Author is licensed under CC BY-SA ◦ Fruits and vegetables can be contaminated through contact with the soil or water containing feces from other animals. ◦ Sources: Pets can carry the Campylobacter ◦ Improper handling or undercooked poultry products bacteria and other ◦ Unpasteurized milk and cheese germs that can make ◦ Contaminated water you sick. ◦ Vegetables ◦ Seafood This Photo by Unknown Author is licensed under CC BY-NC Staph bacteria under microscope Staphylococcus Staphylococci are mesophilic and the aureus optimum temperature of growth for S. aureus is 35°C ◦ Gram positive, non-motile, small spherical bacteria, appears in chains or grape like clusters, and can produce heat stable enterotoxins. ◦ A gastrointestinal illness caused by eating food contaminated with toxins produced by Staph bacteria ◦ Staph bacteria can be killed in cooking, but the toxins are not destroyed which will still be able to cause illness. ◦ Food contaminated with the toxin may not smell bad or look spoiled. ◦ Common contamination by Staph is due to the handling of This Photo by Unknown Author is licensed food with unwashed hands under CC BY-SA ◦ About 25% of people and animal have Staph on their skin and in their nose, which usually does not cause illness. ◦ Source: Strains of S. ◦ Widely distributed in the environment (Ex: air, dust, food, aureus are highly surfaces, animals, humans, etc.) tolerant to salts and ◦ Meat, meat products, poultry, and egg products sugars ◦ Bakery and dairy products ◦ Contamination when handling food products Staph colonies on a TSA plate This Photo by Unknown Author is licensed under CC BY-SA-NC E.coli and M. luteus on TSA plate STEC live in the gut of ruminant animals Escherichia coli (E.coli) and the major source for human illnesses is cattle. STEC does not ◦ Toxin-producing Shiga-toxigenic E.coli (STEC) are Gram generally make negative, rod-shaped bacteria, with peritrichous flagella. animals sick but they ◦ A subset of STEC which is enterohemorrhagic are able to pick up STEC from the Escherichia coli (EHEC) includes O517:H7 which is the environment and may predominant strand that accounts for 75% of EHEC spread it. infections worldwide. ◦ E.coli 0517:H7 is common in North America and was first identified in 1982. E. coli bacterium ◦ Less is known about non-O517 STEC subgroups but cause a less severe illness than O517. ◦ Some people can get less serious infections (range to no This Photo by Unknown Author is licensed symptoms to diarrhea) but the infection can progress into under CC BY life threating form of the illness such as kidney failure. ◦ Sources: Around 5-10% of ◦ Raw or undercooked ground beef those diagnosed with ◦ Unpasteurized milk or fruit juice STEC can develop ◦ Acidic foods hemolytic uremic syndrome (HUS) ◦ Contaminated water which effects the ◦ Vegetables (Ex: sprouts, lettuce, and spinach) kidneys. This Photo by Unknown Author is licensed under CC BY-ND Listeria monocytogenes bacteria Pregnant women are 10 times Listeria more likely than other people to get the infection. It can pass on to their newborns