Abstract
Background: Gram-positive and Gram-negative bacteria and their associated toxins, especially lipopolysaccharide (LPS), elicit distinct immunological responses that may modulate vitamin D3 and C-reactive protein (CRP) levels. Aim: This study aimed to determine the physiological effects of different bacterial agents and two doses of endotoxin (LPS) on serum vitamin D3 and CRP levels in male albino rats. Methods: Eighty-four male albino rats were randomly assigned to seven groups (n=12/group): negative control (G1), Staphylococcus aureus (G2), Streptococcus pyogenes (G3), Salmonella typhi (G4), Klebsiella pneumoniae (G5), diluted LPS 2.5 µg/kg (G6), and concentrated LPS 5 µg/kg (G7). Serum vitamin D3 and CRP were measured by ELISA on days 2, 4, and 6. Results: Vitamin D3 levels showed significant inter-group differences on all days (P≤0.05), with the highest early value in G6 (66.4±9.72 ng/mL on day 2) and the lowest in G7 (45.0±0.64 ng/mL on day 4). CRP showed significant differences only on day 2 (P=0.00283), with G3 recording the highest value (41.45±1.78 mg/L). Conclusion: Gram-negative bacteria and LPS had the greatest influence on vitamin D3 dynamics, with a clear dose-dependent effect. CRP was an early-phase acute-response marker with significant differences limited to the early stage of infection.