Comparative Sterilization of Escherichia coli

Jonathan So

Department of Biological Sciences

Saddleback college

Mission Viejo, CA 92692

Because of the danger of pathogenic contamination in food production, medical and laboratory research it is important to determine if microwave irradiation or submersion in 100°C hot water bath is more efficient in regards to inactivation of E. coli. Inoculates of Escherichia coli were subjected to submersion in 100°C hot water bath heating and microwaves at 2450 MHz for 30s and 60s spell out numbers and seconds. Samples of the treated inoculates were then streak plated and allowed to incubate for 96 hours after which colonies were counted, recorded and analyzed via an ANOVA test. Post Hoc analysis indicated there was no statistically significant difference between microwave irradiation at 2450 MHz and submersion in 100°C hot water bath.

Efficient sterilization of pathogens is of interest to many fields; why? the food industry, medical/hospital, and waste and bio-hazard treatment, because of its relative low cost microwave irradiation is particularly appealing (Celandroni et al. 2004; Górny et al. 2007; Latimer and Matsen 1977). Other studies have focused on the cellular effects, structural or metabolic of microwave irradiation compared to those of conventional heating (Celandroni et al. 2004; Dreyfuss and Chipley 1980; Woo, Rhee and Park 2000 *names need to be in same order as on citation),*go in to detail about their findings the aim of this project is to compare the efficiency of inactivation of E. coli by microwave irradiation and by submersion in 100°C water.

Materials and Methods

The microwave oven used in the experiment was a consumer grade Sears Roebuck, Model No. 5678701080 2,450MHz microwave oven manufactured 1986. E. coli was used throughout the experiment. Fifty two glass 13x100mm test tubes containing 5ml of Nutrient Broth were inoculated with E. coli using an aseptic technique which is. Inoculates were then incubated at 37°C for 24hours.

Inoculates were then exposed to irradiation in the microwave by placing one test tube at a time in the center of the microwave oven and irradiating for 30s or 60s (numbers need to be spelled out along with units), n=10 per interval. Hot water bath inoculates were subjected to submersion in a 100°C water bath for 30s or 60s (numbers need to be spelled out along with units). Microwave irradiated and 100°C water bath samples were then streak plated on Nutrient Agar plates, and incubated for 96 hours at 37°C. Colonies produced by/of viable E. coli on plates were counted and recorded. Data were then analyzed with ANOVA followed by Boneferri post hoc correction.*missing date and location as well as where E.coli was obtained.

Results

Microwave irradiation did not result in a statistically significantly greater inactivation of E. coli than those treated in hot water bath. (Figures 1, 2 and Table 1)* needs to be expanded… i.e.: test(s) used, standard error, p values, actual data means etc.

Figure 1. Effect of exposure on E. coli colonies produced. Needs more description

Table 1. effect of exposure Effects of exposure upon number of colonies of E. coli produced
30s / Number of colonies
Hot water bath / 0 / 1 / 74 / 82 / 77 / 23 / 40 / 0 / 49 / 150+
Irradiated / 0 / 0 / 1 / 0 / 36 / 150+ / 0 / 0 / 0 / 0
60s
Hot water bath / 64 / 43 / 13 / 0 / 67 / 14 / 18 / 4 / 3 / 0
Irradiated / 0 / 0 / 0 / 0 / 0 / 0 / 3 / 0 / 0 / 0
0s
Control / 150+ / 150+ / 150+ / 150+ / 150+ / 150+ / 150+ / 150+ / 150+ / 150+
*Needs a caption, or more explanation in results paragraph.

Figure 2. Bar graph of Effects of exposure upon mean colonies of E. coli produced

*Missing standard error bars and needs to explain more, what is the data trend showing?

Discussion

The results showed no statistically significant difference between the test tubes that underwent microwave irradiation at 2450MHz and submersion in 100°C hot water bath. They did however differ from previous findings by Gee and So (2009) Which were?, the overall inactivation at 60s (numbers need to be spelled out along with units) of irradiation reflected those found by Latimer and Matsen (1977) which were? . The difference in findings between this experiment and that of Gee and So(2008) are most likely attributed to greater number of intervals ran as well as different statistical analysis.

Literature Cited

*need to use at least 5 sources!

Celadroni F., Giannessi F., Ghelardi E., Longo I., Tosoratti N., Baggiani A., Salvetti S.,

and Senesi S. 2004. Effect of microwave radiation on Bacillus subtilis spores.

Applied and Environmental Microbiology, 97: 1220-1227

Chipley J.R., Dreyfuss M.S. (1980) Comparison of effects of sublethal microwave radiation and conventional heating on the metabolic activity of Staphylococcus aureus. Applied and Environmental Microbiology, 39: 13-16

Gee B. and So J. (2009) The Comparative Efficiency of Sterilization by conventional Heating And Microwave Irradiation On E. coli. Saddleback Journal of Biology 7,119

Górny R., Harkawy A., Kasznia-Kocot J., Lis D., Łudzeń-Izbińska B., Mainelis G., Marzec S., Niesler A., Siwińska E., Wlazło A.(2007) Viability of fungal and Actinomycetal spores after microwave radiation of building materials. Ann agric Environ Med 14: 313-324

Latimer J, Matsen M. (1977) Microwave oven irradiation as a method for bacterial decontamination in a clinical microbiology laboratory. J Clinical Microbiology, 6: 340-342

Park H-D., Rhee I-K, Woo I-S. (2000) Differential damage in bacterial cells by microwave radiation on the basis of cell wall structure. Applied and Environmental Microbiology, 66: 2243-2247

Review Form

Department of Biological Sciences

Saddleback College, Mission Viejo, CA 92692

Author (s): Jonathan So__

Title: Comparative Sterilization of Escheria Coli

Summary

Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you understood the paper.

  • He took tubes of E.coli and tried two different ways to kill the bacteria (a microwave, and a hot water bath). And agar plated the tubes afterward to see if it worked. There seened to be n significant difference between the two methods.

General Comments

Generally explain the paper’s strengths and weaknesses and whether they are serious, or important to our current state of knowledge.

  • The paper had some grammatical errors along with a lot of missing information. The author should have used more explanation of the topic and of the figures as well as the data over all. Because of the amount of information that is missing, I do not think that this paper should be published.

Technical Criticism

Review technical issues, organization and clarity. Provide a table of typographical errors, grammatical errors, and minor textual problems. It's not the reviewer's job to copy Edit the paper, mark the manuscript.

  • See red words in paper above

This paper was a final version This paper was a rough draft