Comparative Microbial Analysis: Standard Plate Count & IMViC Tests

This practical assignment involves a microbial analysis of both fresh and abused minced chicken. The standard plate count method was used to quantify the total number of microorganisms present, revealing a significantly higher count (250 CFU/g) in the abused sample compared to the fresh sample (below 30 CFU/g). IMViC tests were conducted to identify coliform group bacteria and gram-negative contamination. The Indole test, Methyl Red test, Voges-Proskauer test, and Citrate test each yielded positive results for the abused minced chicken, indicating bacterial contamination, while the fresh minced chicken showed negative results across all tests. These findings underscore the importance of proper handling and storage to prevent microbial growth in minced chicken. Desklib provides access to similar solved assignments and study tools for students.

Discussion
Standard plate count was conducted to calculate the number of plates present per
gram of meat (Ahmad et al., 2013). For the abused minced chicken the microorganism count
was significantly higher at 250 CFU/g while for the fresh minced chicken it was negligible
and lower than 30 CFU/g.
To identify presence of coliform group and gram negative contamination in the fresh
minced chicken and abused minced chicken sample IMViC tests were conducted (Chishimba
et al., 2016).
Indole test was conducted where two samples were kept in the broth of peptone water
containing tryptophan. Enzyme tryptophanase react with tryptophan to produce pyruvate,
ammonium and indole molecule. Kovac’s reagent is added to indole. Red layer is seen on the
top of liquid in case of abused minced chicken but not in case of fresh minced chicken.
MRVP broth is used in methyl red test which detects acid production using pyruvate.
Methyl Red is used as a pH indicator. Red colour appeared in abused minced chicken and
gave positive result for bacterial contamination while in case of fresh minced chicken it
remained yellow reflecting negative result.
MRVP broth is also used in Voges-Proskauer test. Alpha-naphthol and potassium
hydroxide is used to identify the presence of acetylmethylcarbinol. Positive result was
reflected in abused chicken as pinkish red colour was seen and negative in fresh minced
chicken.
Simmon's citrate agar is used in citrate test. Agar contains ammonium ions, citrate and
bromothymol blue. After the abused chicken was added the citrate agar became blue while

remained green for fresh chicken. So positive result was reflected for the abused minced
chicken and negative in fresh minced chicken.
References
Ahmad, M. U. D., Sarwar, A., Najeeb, M. I., Nawaz, M., Anjum, A. A., Ali, M. A., &
Mansur, N. (2013). Assessment of microbial load of raw meat at abattoirs and retail
outlets. J. Anim. Plant Sci, 23(3), 745-748.
Chishimba, K., Hang’Ombe, B. M., Muzandu, K., Mshana, S. E., Matee, M. I., Nakajima, C.,
& Suzuki, Y. (2016). Detection of extended-spectrum beta-lactamase-producing
Escherichia coli in market-ready chickens in Zambia. International journal of
microbiology, 2016.