Section E
INTRODUCTION
Any food product, either vegetable or animal origin, has a definite shelf life. If the recommended temperature and humidity conditions for its storage are not maintained, food spoils at a very fast ratequickly as bacteria and other parasites from the environment take over. Therefore, the food should be eaten as fresh as possible. It is, however, difficult in the contemporary modern world as the population centers are furtherar away from where the food actually grows or comes fromgrown. Consequently, food preservation and processing has become a big industry where innovative and latestmodern technologies are used to minimize the threats of bacterial contamination (Lee, 2010). Preservation of food is therefore a necessity and has developed into an intricate science. Public food regulatory authorities such as the FDA (Food and Drugs Administration (FDA) are responsible for ensuring that only the best food is made available to consumers throughout the United States. These institutional mechanisms prescribe uniform quality standards for food products which have to be adhered to by the producers and , processors, as well as marketers responsible for bringing them to the consumer (Mangalassary 2012).
Meat products specifically can pose serious risks to consumer health, due to their high susceptibility to bacterial degradation., can pose serious risks for consumer health. According to a recent report, the U.S. meat and poultry products have been found as contaminated with multi-drug resistant strains of Staphylococcus aureus, a dreaded pathogen (Waters et al. 2011). Contamination levels wereas found as high as 47 percent with 52 percent of the isolated strains exhibiting multi drug resistance (Waters et al. 2011). The problem is compounded by the factor thatprevalence of farmed meat animals beingare raised on low levels of antibiotics in their feed in the form ofas growth promoters which gives rise to multi- drug resistant strains (Waters et al, . 2011). Bacteria like Staphylococci, Escherichia coli, Salmonella and many others have been frequently isolated from off the shelf minced meat and hamburger samples with an incidence rate for contamination as high as 30-60% (Mousa et al. 2011).
In the following experiment, it was hypothesized that the locally available hamburgers were likely to be contaminated with bacteriawould illustrate different bacterial levels depending on the source. An attempt was made to detect contamination in hamburger Ssamples were collected from various randomly selected sources in Flagstaff, AZ, to test the hypothesis. Microorganisms, if present, can be detected by numerous techniques such as spectrophotometry, direct cell counting with a hemocytometer, electronic counting employing a Coulter counter and by colony counting by culturing bacteria on suitable mediums for their growth (Shand 2012). The latter method, i.e. viable count assay, was used in the experiment. Through the study, it was aimed to find whether, The aim of the study was to reveal whether bacterial contamination was present and the quantity and how much, bacteria contamination was there in the meat being used to prepare hamburgers. The experiment was considered as the first essential step in a research project which would will eventually conduct an extensive research looking into the deleterious implications of bacteria-contaminated hamburgers over theto consumer health. The presence of bacteria, and its level of contamination, would help lead further research in identifying the potential as well as real effects to the consumer health. Through this experiment, it was expected that the findings about the level of bacteria enumeration would lead to further investigations about implications over consumer health. In view of the hypothesis, it was predicted that the hamburgers contained bacteria. The prediction is that bacterial levels in hamburger samples collected from five different locations in Flagstaff, AZ will vary.
MATERIALS AND METHODS
TheA viable count assay for was used to determine levels ofing bacterial contamination in five hamburger samples collected from different grocery sources in Flagstaff, AZ was used in this experiment. The spread plate as well as the pour plate methods wasere employed. Ten grams of meat from each hamburger was put inside a vessel previously cleaned and sterilized with QT disinfectant and rinsed subsequently with sterile RO water. The blender was similarly sterilized and to each meat sample was added 90 mls of sterile, cold 0.75% NaCl solution was added to each meat sample to obtain countable amount of colonies. Blending was accomplished in small spurts lasting 10-20 seconds, in order to prevent frothing as well as over-heating. From the resultant five solutions, 1 ml of each was pipetted using sterile, separate pipettes and ejected into labeled 15 ml capacity conical tubes. Care was taken to avoid pipetting sediments or fat globules. Five, sterile culture tubes were labeled and. 4.5 ml of 0.75% NaCl was transferred aseptically into the mlabeled tubes. There were two sets labeled as “‘Spread Plates.”’. Another set of empty culture pPlates wereas labeled as “‘Pour Plates.”’.
Each blended hamburger sample tube was labeled as having 10-1 dilution of the original sample and was taken as the starting dilution. From these five stock solutions, serial dilutions in a ratio of 1:10 were done for the spread plates as well as the pour plates by taking 0.5 ml from the original tube, adding it to the subsequent 10-2 tube, and so on, using separate pipettes for each step until the last tube with the maximum dilution was ready.
For preparingTo prepare the spread plates for culture, 0.1ml of solution from the tube labeled 10-2 was placed onto the spread plate labeled “‘10-3 spread”’ and the contents smeared evenly using a sterile glass hockey stick. Similar smears were prepared from all culture tubes except for the one labeled 10--66. The control spread plate was smeared only with sterile diluent solution.
The glass hockey stick was sterilized with ethanol at each interval. For preparing each petri dish for the pour plates, starting with the 10-3 dilution, 1.0 ml of the solution from the original tube was poured into each petri dish and molten NA (Nutrient Agar) was added in order to cover the surface of the petri dish. Each petri dish was rotated to blend the cultures and cooled before incubation. The pour plates and the spread plates (petri dishes) were incubated at 370C for 1 week. The plates were examined for bacterial growth at this time. Plates with intense growth and colonies were labeled as TNTC (Too Numerous to Count). If the number of colonies was less than 30 the plates were labeled as NSS (Not Statistically Significant). However, the plates with 30 or more colonies and not TNTC, growth which could bewere measured in the examined cultures in terms of CFUs (Colony Forming Units). Average titer was calculated as the number of colonies per dilution (CFU/ml) (Shand 2013). is depicted in the tables below, selecting only the tubes and dishes from which appropriate counting was feasible.
for subsequent microbiological examination.
RESULITS
On examining the plates for bacterial growth after one week, the pooled samples revealed that in some plates and petri dishes, there was intense growth and colonies were too numerous to count. Such plates were labeled as TNTC (Too Numerous to Count).There was no growth in others, hence were labeled as NSS (Not Statistically Significant). However, the growth which could be measured in the examined cultures in terms of CFUs (Colony Forming Units) is depicted in the tables below, selecting only the tubes and dishes from which appropriate counting was feasible.
Spread Plates: The highest number of CFUs/ml was recorded from spread plates from Source A, for which the mean figure of the titer obtained was 2.70E+05 (Table 1I; Fig. 1I). The lowest titer was observed in spread plates from Source D, for which the average titer was 7.90E+04 (Table 1I; Fig. 1I). The data obtained for spread plates in The B category B was statistically insignificant (NSS; Table 1I).
Pour Plates: In the pour plates section, the highest number of CFUs/ml was recorded from Pour the pour plates from Source E. The average titer obtained was 2.90E+05 (Table 1I). Lowest titer was observable from pour plates from Source D, for which average titer was calculated as 8.40E+04 CFUs/ml (Table I1; Fig. I1). As in the case of spread plates, the pour plates from Source B too gave no statistically significant results (NSS; Table I1).
Figure 1: Variations in Number of Colonies Encountered in Samples from 5 Different Locations in Falgstaff, AZ.
Bacterial Concentration in Samples A-D.
DISCUSSION
The objective of this experiment was to compare the level of bacterial contamination, if any, from in hamburger samples collected from various sources in Flagstaff, AZ. The hypothesis, that it was more likely than unlikely that hamburgers collected from various sources in Flagstaff, AZ would show had differences in levels of bacterial contamination , was supported, as is evident from the results of this experimentsupported. The experiment also aimed at looking at the level of contamination in various sources and discrepancies in such levels. Conducted properly, the experiment revealed that some samples had high bacterial contamination, therefore there were found discrepancies in the level of bacterial contamination, although the contamination was found in all the samples. The mean titer of 2.70E+05 CFU/ml in Spread spread plates from Source A and 2.90E+05 CFUs/ml in Pour pour Plates plates from Source D, shows that the respective samples were highly contaminated (Table I1; Fig. I1). Samples from Source C and D were also contaminated and showed comparable levels of bacterial contamination in the spread plates as well as pour plates as is evident in Fig. I1. Variations in the level of bacterial contamination measured in terms of CFUs/ml from the spread and the pour plates in samples from Source A & D could have been due to methodological errors while culturing the bacteria or due to extraneous factors such as maintenance of incubation temperature and difference in the period after which the cultures were examined for colony counting. Samples from source B either yielded results which were considered nonnot statistically significant, so these results were not included in our conclusions. statistically for comparison and were this ignored.
This particular experiment employed the viable colony counting technique which is appropriate from an academic point of view but more rigorous methods like spectrophotometry, Coulter counting and more advanced techniques need to be used by authorities to determine contamination level in such products, so that appropriate advisories could be issued to the food producers, handlers as well as consumers.
As stated earlier, the research as done in this experiment is crucial as the first step in looking at the greater picture of potential threats to health of inhabitants of the area. Future research can look into the possible causes of bacterial contamination, discrepancies variations in such levels of contamination, the correlation between the potential diseases caused by such bacteria, and the available health expenditures as recorded by the hospitals of the area. This correlation, if found, can help the city government implement better food preservation and storage measures in order to minimize potential threats to the inhabitants of the area. Various researches studies have found comparative advantageimplementation of policies and strategies implemented tocan reduce the contamination threats (Carpenter & Broadbent, 2010). , andThese strategies can possibly be implemented in consultation with the local Chamber of Commerce and the business community.
(Carpenter & Broadbent, 2010).
This particular experiment employed the viable colony counting technique which is appropriate from an academic point of view but more rigorous methods like spectrophotometry, Coulter counting and more advanced techniques need to be used by authorities to determine contamination level in such products, so that appropriate advisories could be issued to the food producers, handlers as well as consumers.
REFRENCES
Mangalassary, S. (2012). In-package Pasteurization of Ready to Eat (RTE) Meat Products-an Effective Way to Control Post-processing Contamination,. Journal of Food Processing Technology, 3:e 110.
Mousa, M.M., Ibrahim, H.A.A., Somaia, A. (2011). Occurrence of Staphylococci and Escherichia coli in ground beef and some processed meat,. Alexandria J.of Veterinary Sciences, 32 (1), 47-55.
Shand, R. F. (2012). Nau microbiology lab manual bio 205. Englewood, CO: Morton Publishing Company.
Waters, A.E., Contente-Cuomo, T., Buchhagen, J. et al. (2011) Multidrug-Resistant Staphylococcus aureus in US Meat and Poultry,. Clinical Infectious Diseases, 52 (10), 1227-1230.
