Introduction The genus Listeria contains six species, two of which are considered pathogenic: Listeria monocytogenes and Listeria ivanovii. L. monocytogenes is the only species that is associated with listeriosis in humans (1). L. monocytogenes is a Gram-positive rod, facultative anaerobe; at room temperature, it exhibits tumbling motility due to peritrichous flagella (1). It has an optimal growth temperature of 32-35oC, but L. monocytogenes can grow between 0-45oC, pH 4.4-9.4, and a water activity as low as 0.90 (1).
Food processors take steps to control microbial growth at every stage of processing, and Listeria monocytogenes is of great concern for products post-processing. Viable cells have been found in soil, decaying vegetation, water,
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This was done by holding the plate up to the light to view the reaction on the agar. Afterward, the motility test medium was observed; motility appeared as an umbrella extending away from the stab line. Finally, the Micro-ID Listeria Test Procedure was followed:
1. After a 2-day incubation, the Micro-ID unit was placed flat on the bench and opened; 0.1 ml of 20% KOH was added to the inoculation well of the VP test only. The tray was then closed and held upright until the KOH flowed into the VP test solution.
2. The Micro-ID Listeria unit was then rotated clockwise at 90o so that the upper disks in the first five wells were moistened. The tray was help upright and tapped gently on the lab bench; this dislodged any suspension trapped under the upper disks.
3. All reactions were read immediately, except the VP test, as positive or negative per the color changes as listed in Appendix 1.
4. The color developed in the VP well for approximately 10 minutes prior to its reading.
Results
Day
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Due to contamination, the Micro-ID Listeria unit could not be used in the identification of the Listeria species used to inoculate it. This result may have something to do with the contamination visualized on our blood agar plate and oxidase test.
RTE foods are under scrutiny due to the widespread outbreaks of Listeriosis over the last 2 decades. Post-processing contamination is a common pathway for L. monocytogenes to be introduced into food products because it is so widely spread in the environment (1). Once contamination occurs, L. monocytogenes can proliferate at refrigerated temperatures prior to consumer use of the food (1). RTE foods are typically not further processed after being received by consumers or retailers, which allows for Listeria monocytogenes to proliferate and infect individuals under the right circumstances.
3. What methods would a food processing company typically use to test for
Listeria spp. and what tests would be used to distinguish between L. monocytogenes and L. innocua?
Upon receiving the unknown Microorganism (M.O.) #16, I prepared a slide by cleaning and drying it. Then, using a bottle of water I placed sterile drop of water on the slide and used an inoculating loop, flame sterilized, I took a small sample of the unknown growth in my agar slant and smeared it onto the slide in a dime sized circle and then heat fixed it for ten minutes. After ten minutes had passed, I collected the ingredients needed to perform a gram stain. I got the primary stain, crystal violet, and flooded my smear for sixty seconds, and then rinsed the color off with water until the water ran clear. I then flooded the smear with the mordant, grams iodine, and let that sit on the slide for sixty seconds as well. I then rinsed the grams iodine off with water and applied alcohol to the smear to decolorize the cells; however I made sure not to over decolorize and only put enough drops on the smear till the purple ran clear. I then rinsed the slide with water and flooded the smear with safranin the counter stain and let it sit for sixty seconds and then rinsed the color off with water. I blo...
The first day an unknown sample was assigned to each group of students. The first test applied was a gram stain to test for gram positive or gram-negative bacteria. The morphology of the two types of bacteria was viewed under the microscope and recorded. Then the sample was put on agar plates using the quadrant streak method for isolation. There were three agar plates; one was incubated at room temperature, the second at 30 degrees Celsius, and the third at 37 degrees Celsius. By placing each plate at a different temperature optimal growth temperature can be predicted for both species of bacteria.
In this lab project, the microbiology students were given 2 unknown bacteria in a mixed broth each broth being numbered. The goal of this project is to determine the species of bacteria in the broth. They had to separate and isolate the bacteria from the mixed broth and ran numerous tests to identify the unknown bacteria. The significance of identifying an unknown bacteria is in a clinical setting. Determining the exact bacteria in order to prescribe the right treatment for the patient. This project is significant for a microbiology students because it gives necessary skills to them for future careers relating to clinical and research work.
They can be found anywhere and identifying them becomes crucial to understanding their characteristics and their effects on other living things, especially humans. Biochemical testing helps us identify the microorganism present with great accuracy. The tests used in this experiment are rudimentary but are fundamental starting points for tests used in medical labs and helps students attain a better understanding of how tests are conducted in a real lab setting. The first step in this process is to use gram-staining technique to narrow down the unknown bacteria into one of the two big domains; gram-negative and gram-positive. Once the gram type is identified, biochemical tests are conducted to narrow down the specific bacterial species.
After the end of the experiment, the unknown 10 sample was Staphylococcus epidermidis. Come to this conclusion by first beginning with a Gram Stain test. By doing this test it would be easier to determine which route to take on the man-made flow chart. Gram positive and gram negative bacteria have a set of different tests to help determine the unknown bacterium. Based on the different tests that were conducted in lab during the semester, it was determined that the blood agar, MSA, and catalase tests are used for gram positive bacteria while Macconkey, EMB, TSI, and citrate tests are used for gram negative bacteria.
I also inoculated a tryptic soy broth (TSB), a nutrient gelatin deep, a motility agar deep, a fluid thioglycollate medium (FTM) tube, and a TSA plate with my unknown culture. All of these inoculated media were incubated until the next class period (about 48 hours). Then when I came to class most of my inoculated tubes and my streak plate appeared to have growth. The next step I took was making a gram stain to determine the gram reaction and cellular morphology of my unknown. I used my working slant to do this, after careful examination of the gram stain, I learned that my unknown was a gram-positive bacterium. I then preceded by making a negative stain to see the size of the cells of my unknown bacteria. The cell shape was cocci and the cells occurred in clusters of tetrads. After discovering that my unknown bacteria was gram-positive cocci, I turned to page 207 of the lab manual to narrow down my options, there was only four out of the gram-positive list that were
—- . ”Tyson Foods: Living Food Safety." Tyson. Tyson, 28 Feb 2014. Web. 7 Apr 2014.
Jeni and her production workers are testing every batch of product that is created. Jeni tests the batches of product every single day. “Lowe wrote that the company had initiated routine testing of “every batch” since the first Listeria contamination was discovered last April. “It is with complete confidence that we can say all of the ice cream that has been served in our shops since reopening on May 22 has been safe and is 100% Listeria-free,”” Jeni’s manager John Lowe told the public about their company for an article on time.com. (time.com, 2015) Jeni also has professional inspectors come in to check her products as well to see if they get a different result. Only two out of 75 testing swabs came back positive for listeria before they decided to close and sterilize everything. “After two out of 75 swabs taken in January and February came back positive, according to a letter the FDA sent to Jeni 's CEO John Lowe earlier this month.” (Columbus Dispatch, 2016) The two swabs came from the production plants floor, which means that none of the product should have touched it. Listeria is known for growing and spreading rapidly, so Jeni is doing all she can to not let her products get contaminated with listeria. ““It can come through milk and other dairy products. Other organisms cannot survive at such low temperatures, but listeria can survive and sometimes even grow,” Bhunia told Fusion. “The only thing is to make sure the milk has been properly pasteurized.” Pasteurization, for those of you who don’t know, is basically when milk is passed through a high heat treatment (about 161°F or 280°F for “ultra-pasteurized”) for a short period of time (between 15 seconds and .5 seconds) to kill off bacteria. But even if the milk product is pasteurized, Bhunia said, listeria can develop in food processing plants, and there are countless potential sources of the bacteria: the floor, the air
Eastfield College Microbiology Laboratory Manual, 1st edition, Oliver, T. D. (Book Must Be Purchased New from Eastfield Bookstore and Cannot Be Sold Back to Bookstore at the End of the Semester), Kendall Hunt Publishing, 2013, Dubuque, IA. ISBN 9781465223784.
Infection with C. perfringens as a food-borne illness is acquired from consumption of food or water that has come in contact with the bacterium. Some possibilities include unwashed fruits and vegetables, undercooked me...
Around the world, Joseph Lister is considered to be the “father of modern surgery” (Pitt & Aubin, 2012). Joseph Lister was a surgeon in England that not only influenced the surgery techniques of surgeons in England, but who also played a major role in the sterilization techniques that surgeons use in our country. He realized that the infections and deaths that occurred after surgery were caused by bacteria and was able to come up with a sterilization technique that would minimize the deaths of the patients. The sterilization technique that Lister used was an antiseptic method. By using the antiseptic method that used carbolic acid, Lister was able to prevent any contamination of the wound or medical instruments that were involved in performing the surgery in order to decrease the amount of deaths that occurred from infections by bacteria. Through the creation of this antiseptic technique, Joseph Lister introduced to the world an invention that improved the safety of surgery and influenced the way surgeons in other countries, such as Germany and the United States, would view microorganisms’ effect on surgical wounds eventually leading to the modernization of surgery.
Listeria, also referred to by the name Listeriosis, is an infection that is caused by eating contaminated food containing the bacterium Listeria Monocytogenes. This particular disease can affect not only animals, but also older adults, pregnant women, newborns, and adults with weakened immune systems. When looking at these bacteria under a microscope, they appear to be small and rod-like and can sometimes be seen arranged in short chains (See Fig. 1). Because there are different species of Listeria, it may take further characterization in order to distinguish between each one. Listeria can be found in several different locations and factors. Soil is a big one, if the soil
Under the gram stain, N. meningitidis is a gram-negative diplococcus and often found within the PMN. This bacterium grows on both chocolate and blood agar culture plates. The colonies of N. meningitidis are mucoid gray and have a greenish tinge to it, whereas a non-pathogenic Neisseria colonies are dry looking. In the biochemical testing, N. meningitidis is oxidase and catalase positive. In carbohydrates utilization test, N. meningitidis is glucose and maltose positive. However, some strains of this bacterium are maltose negative. Immunologic tests are useful to see the antigen of N.
The most commonly recognized food borne infections are those caused by the bacteria Campylobacter, Salmonella, and E. coli 0157:H7, and by a group of viruses called Calicivirus, also know as the Norwalk viruses. “Thousands of types of bacteria are naturally present in our environment, but not all bacteria cause disease in humans.” (Schmutz 1)
Keeping the refrigerator at a temperature of 40 ° F or less, and the freezer at 0°F, to slow the growth of bacteria. Most importantly good hand washing is key and vital for good food safety sanitation, diarrhea and other foodborne illnesses can be cut in half with just kids and staff maintaining their hands clean. Proper Storage of food after cooking is important in preventing the spread of bacteria from raw foods. Which is why it is best that raw foods should usually be store at the bottom of the fridge in order to avoid juices from dripping onto other foods or fruits. Foods should always be covered, wrapped, and stored in airtight containers in order to protect the food from