Abstract
Background:
Raoultella planticola is a developing pathogen that can infect both humans and animals. Raoultella spp. commonly colonize the gastrointestinal and upper respiratory systems. It usually causes pneumonia, bile tract infections, and bacteremia.

Aim:
In this study, the anticancer activity of an isolated brown pigment of a Raoultella planticola isolate was tested in vitro.

Methods:
The laboratory examination included culturing in brain-heart infusion broth, conducting biochemical tests, using the automatic VITEK2 Compact for bacterial isolate identification, performing the MTT assay to evaluate the cytotoxic effect on both the mammary cancer cell line (AMN3) and normal rat fibroblast (REF), and utilizing enzyme-linked immunosorbent assay to measure cytokine levels.

Results:
R. planticola was found in cow nasal swabs with respiratory problems. The extracted pigment had a significant cytotoxic effect (decreased cell viability) at doses of 2067.5 μg/mL (p < 0.0001 and 0.0001, respectively) and 1033.5 μg/mL (p < 0.0001 and 0.003, respectively). However, the lowest dose (516.875 μg/mL, p > 0.43 and p > 0.18) could not inhibit the growth of malignant or healthy cells. The first and second highest pigment concentrations reduce IL-1β and TNF-α and increase Fas in the AMN3 cell supernatant (p < 0.05). In the AMN3 cell supernatant, the lowest concentration significantly increased IL-1β levels (p < 0.0472) and Fas levels (p < 0.0146), but did not affect TNF-α levels (p < 0.1274). Pigment concentrations at the first and second highest levels significantly reduced IL-1β and TNF-α levels in the REF cell supernatant (p < 0.05), whereas the lowest concentration did not. All pigment doses did not affect the Fas levels in the REF cell supernatant (p > 0.05).

Conclusion:
In a concentration-dependent manner, the extracted pigment may exert cytotoxic effects and impact cytokine secretion levels in cancerous and normal cell types.

Key words: Raoultella planticola; VITEK2; MTT assay; AMN3; Enzyme-linked immunosorbent assay.