Background
One of the central tasks of microbiological analysis is the identification of unknown microorganisms. The application of this need, namely the ability to qualitatively identify pathogens to select a plan for further clinical risk management activities, dictates the need for in-depth, detailed, and correct investigation of the strain and even serotype of microorganisms (Tortora et al., 2020). In addition, accurate knowledge of the pathogen strain simplifies drug selection and makes antibiotic selection more sensitive. Using a stepwise microbiological assay technique, this study aimed to identify an unknown bacterium, later revealed to be Micrococcus luteus.
Results
Discussion
Almost all tests performed showed the absence of any positive reaction to the laboratory intervention, which allows us to sharply narrow down the range of candidates for the role of an unknown pathogen. After Gram staining unequivocally, the residual purple staining of the bacteria indicates their Gram-positivity, which means that any prokaryotes with a thick layer of lipopolysaccharides in the cell wall must be excluded (CDC n.d.). Then, it was seen that the shape of the bacteria was not bacilliform but spherical (cocci), which means that all bacillus candidates were excluded: only Staphylococcus epidermidis and Micrococcus luteus were relevant for this step. However, Staphylococcus epidermidis showed positive results on two of the three hydrocarbon fermentation tests; the absence of any response to the hydrocarbon fermentation test, as well as negative results on the VP, MR, citrate, and KIA tests, were reliable evidence of Micrococcus luteus as a candidate unknown pathogen. In addition, the catalysis test was predicted to be positive, which means that the bacterium is capable of releasing oxygen from peroxide. Micrococcus luteus is a species of fixed globular bacteria that collects in tetrads (Wickham Laboratories, 2019). For humans with normal immune system function, Micrococcus luteus is not thought to be dangerous. The bacterium naturally inhabits soils, air, and water bodies and lives in human mucous membranes. Thus, the bacterium detected is not pathogenic in the literal sense and does not pose a severe clinical danger.
References
CDC. (n.d.). Gram stain [PDF document]. Web.
Tortora, G. J., Funke, B. R., Case, C. L., Weber, D., & Bair III, W. B. (2020). Microbiology: An introduction, eBook. Pearson Higher Ed.
Wickham Laboratories. (2019). Fact sheet Micrococcus luteus [PDF document]. Web.