Safety Assessment of Pseudomonas fluorescens DS17R Chloroform Extract: Low Acute But Dose-Dependent Subacute Oral Toxicity in Rats

The present study evaluated the acute and subacute oral toxicities of a chloroform extract from Pseudomonas fluorescens DS17R in Wistar rats to support its safe application as a biocontrol agent. For acute toxicity assessment following OECD Guideline 423, female Wistar rats (n = 3 per step) received single oral doses of 300, 2000, or 5000 mg/kg body weight (bw) and were observed for 14 days. For subacute toxicity, female rats (n = 5 per group) received daily oral doses of 0 (control), 57.5, 115, 230, or 460 mg/kg bw for 28 days, after which hematological, biochemical, and histopathological analyses were performed. Acute toxicity testing revealed no mortality at 300 or 2000 mg/kg bw, but 50% mortality at 5000 mg/kg bw, yielding a median lethal dose (LD50) of 4574 mg/kg bw, classifying the extract as practically nontoxic (OECD Category 5). Subacute 28-day oral exposure induced dose- and time-dependent physiological and biochemical responses. Body weight showed a biphasic pattern, with a significant increase at 57.5 mg/kg bw and reductions at ≥ 115 mg/kg bw, while feed intake was transiently suppressed. Hepatic enlargement was observed at 115–460 mg/kg bw, accompanied by elevated alkaline phosphatase and mild AST increase; histology revealed sinusoidal dilation and leukocyte infiltration. Splenomegaly, lymphopenia at 230 and 460 mg/kg bw, microcytosis, anisocytosis, and thrombocytosis reflected hematopoietic and immune modulation. Renal stress was evidenced by hyponatremia, hypokalemia, hypochloremia, hypercalcemia, and decreased phosphate at doses ≥ 57.5 mg/kg bw, with mild tubular alterations. Lipid remodeling included increased triglycerides and HDL, with decreased LDL at doses ≥ 115 mg/kg bw. Overall, the extract induced adaptive metabolic and redox-mediated responses without irreversible organ damage, supporting its potential safe use as a microbial biocontrol agent under the tested conditions.