Enumerating Bacteria in Hamburger Meat from Various Sources in Flagstaff, AZ.
It is commonly known that bacteria can be found in places like bathrooms and sinks but they can also be found in unwanted places such as food. Over 70 million cases of food-borne illnesses are reported every year in the U.S. according to the Centers for Disease Control and Prevention (CDC) (Linscott, 2011). Although the government tries to regulate the amount of bacteria in meat that cause food borne illnesses, certain bacteria that cause illness don’t receive notice (Waters et al. 2011). Organizations, such as the National Antimicrobial Resistance ...view middle of the document...
The European Food Safety Authority, EFSA, have introduced a qualified presumption safety approach in order to assess the microorganisms throughout the food industry (Talon & Leroy, 2011). The assessment looks at qualifications like taxonomy and pathogenicity, along with the amount of bacteria found in meat. By enumerating bacteria and observing the concentration in meat, it can be determined if the governmental food regulation system is efficient.
For the experiment, samples of different hamburger meat from around the Flagstaff area were used to observe the amount of bacteria found in each sample. It can be determined how well the food contamination regulation system really is. It was hypothesized that if meat samples were handled correctly, the samples would have little to no bacteria on them. The experiment was done by distributing 1:10 serial dilutions of hamburger solution into four spread plates and four pour plates. After a week, the colonies on the plates were counted using a viable count assay on the pour and spread plates.
MATERIALS AND METHODS
All of the meat samples collected were from various locations in Flagstaff, Arizona. First a culture tube containing hamburger meat was made into 1:10 serial dilutions using .75% NaCl. Having different dilutions can ensure that there will be some plates with colonies between 30 and 300, otherwise the plate would be marked as NSS, not significant sample, or TCTC, too numerous to count.
For the five spread plates, 0.1 mL of the 10-2 dilution was placed onto the plate marked 10-3. A glass hockey stick was then dipped into ethanol and ignited using the Bunsen burner to sterilize it. Once the hockey stick cooled, the.1 mL of dilution was spread evenly over the surface of the plate. The stick was then flame sterilized again and the same procedure was repeated for the 10-3, 10-4, 10-5 tube dilutions. The last plate had .1mL of sterile diluents added to the plate for the control plate. The same process was repeated for the five pour plates except for after the dilution was added to each plate, molten NA was poured into the plate to cover bottom completely and gently mixed with the dilution and allowed to cool. Once cooled, the plates were incubated at room temperature for a week before each spread and pour plate were counted for colonies. Then the titer was determined by dividing the number of colonies found on each plate by the dilution.
All methods from Shand (2012).
The results show that each sample had at least 1.00X104 cfu/g. The sample with the highest amount of bacteria colonies was sample A with 8.04X10^7 cfu/g for the spread plate and 1.13X1068 cfu/gm for the pour plate. Sample B had the least amount of colonies on the pour plate. Sample D,C, and E had around the same amount of colony forming units for the spread plate and the pour plate.
Table 1: Average Concentration of Bacteria from Each Sample and Total Average of Spread/Pour Plates.
| A | B | C | D | E | Average...