Food Microbiology Results Sampleapa

Running Head: FOOD MICROBIOLOGY 1

Food Microbiology: Results

Name

Course

Date

FOOD MICROBIOLOGY 2

Summary of results

Data obtained in the PCR tests for the bacterial detection as treated in the green and the

yellow diagenode dyes were as follow:

Raw data for cycling A. Green

Raw data for cycling A.Yellow

FOOD MICROBIOLOGY 3

Summary of the possible outcome

Amplification of

internal control

Amplification of

sample

Result

Positive

Negative

Pathogen is negative

Positive

Pathogen is positive

The green channel contained the food samples while the yellow channel contained the

internal control. The result for the pathogen in the samples was positive for the tested pathogen as

the food sample curves in the green channel were above the above the preset threshold (Qiagen,

mericon™ DNA Bacteria Handbook, 2016). The internal control in the yellow channel indicated

that there was the presence of salmonella in the internal control samples to act as a positive control

for the samples in the green channel (Qiagen, 2013).

The PCR was successful as the test was able to indicate the presence of the pathogen DNA

in the samples. The cycling of the DNA samples in the green channel amplified the DNA strands

and allowed for the monitoring and the detection of the DNA where cycle though fluorescence in

the PCR (Tomás, A, & Ferrús, 2009). The green dye improved the sensitivity of the PCR through

the application of the polymerase chain reaction and the fluorescent reporter molecules to enable

the detection of Salmonella DNA in the food sample (Qiagen, 2013).

Discussion

The determination of the presence of the salmonella DNA was based on the amplification

of the samples target sequence and the real time visualization of through the generated plot in the

FOOD MICROBIOLOGY 4

PCR. The test was able to show that the Salmonella was existent in the patient’s feces and the meat

in the hamburger (Anna & Wioleta, 2005).

The internal control was the sample that contained the Salmonella DNA that was used to

test for the presence of the same in the food samples prepared in the laboratory. The internal control

also provided the reference plot that was used to compare with the extracted DNA from the food

samples. The green channel and the yellow channel plots had similarity, where the samples were

above the baseline preset for the threshold hence indicating the presence of the salmonella DNA.

Questions

What extra step could be added to the PCR assay you used, so that it is more likely to

detect genetic material from viable bacterial cells?

The extra step that should be included in the PCR assay would be the Nucleic acid

hybridization as the method is fast and sensitive and it is used to detect the bacteria in the pre-

enrichment medium. The process involves the hybridization of DNA or RNA through the

employment of radioactive and fluorescent probes for the hybridization of the nucleic acids in the

samples (Aleksandra, Hilde, & Siv, 2011).

Presuming that viable, Salmonella was isolated by the AS5013.10 method; does a positive

result for the presence of Salmonella by this real-time PCR assay prove that the strain of

Salmonella identified was the outbreak strain?

The result from the PCR plot showed the presence of the salmonella DNA in the food

samples and the faeces of the patients. The salmonella bacteria have two genera with more than

2500 serovars and often foodborne. The salmonella strains discovered in the samples are those of

the Typhi species and can cause the typhoid fever, and due to the quick development of the

symptoms, they are presumed to be the outbreak-causing strain (Hendriksen, 2003).

FOOD MICROBIOLOGY 5

What method that you have studied could be added to improve the sensitivity and

specificity of the total method you did, and to decrease the time for the total assay to get a

result? At what step would you add this method?

The method that would be added to increase the sensitivity of the process and decrease the

time used for the test would be the nucleic acid hybridization and would be added pre-enriching

the assay hence; it will reduce the time for enriching the samples (Biomerieux, 2016).

Conclusion

Finally, the laboratory test of the samples was able to show the presence of the salmonella

in the food sample taken by the patients. The PCR method used the amplification of the target

sequence in the bacteria to visualize the presence of the bacteria in the food samples. More test

should be done to explore the nature of the strain and take the relevant measures.

References

Aleksandra, M., Hilde, M. Ø., & Siv, B. S. (2011). Novel Food Pathogen Testing Technologies:

Molecular Biology Methods.

Anna, Z., & Wioleta, C. (2005). Detection of Salmonella spp. Presence in Food. Poland: University

of Warmia and Mazury in Olsztyn, Faculty of Food Sciences.

Biomerieux. (2016). Salmonella Detection and Identification Methods. Rapidmicrobiology.

Hendriksen, R. S. (2003). A global Salmonella surveillance and laboratory support project of the

World Health Organization. Global Salm-Surv.

Qiagen. (2013). Product Insert for the AOAC-RI PTM-certified and NF VALIDATION certified

mericon®Automated and Manual Salmonella Detection Workflows. Qiagen.

Qiagen. (2016). mericon™ DNA Bacteria Handbook. Qiagen.

FOOD MICROBIOLOGY 6

Tomás, D. R., A, H. M., & Ferrús, M. A. (2009). Validation of Real-Time PCR and Enzyme-

Linked Fluorescent Assay-Based Methods for Detection of Salmonella spp. in Chicken

Feces Samples. Food Analytical Methods. 180–189.

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