Impact on the mutagenicity of strain TA102 of Salmonella Typhimurium by chlorpyrifos in high concentration together with Lacticaseibacillus rhamnosus GG

ABSTRACT Chlorpyrifos is a widely used organophosphate pesticide with significant environmental impact. Lacticaseiobacillus rhamnosus GG has shown potential for degrading such pesticides. This study assessed its ability to neutralize high concentrations of chlorpyrifos in a medium containing Salmonella Typhimurium tester strain, in triplicate, with metabolic activation (S9+). Toxicity tests using strain TA100 of Salmonella Typhimurium at various concentrations determined 20 mg/plate for further assays. Mutagenicity was evaluated with TA97a, TA98, TA100, and TA102 strains of Salmonella Typhimurium, using dimethyl sulfoxide (DMSO) as a negative control and 2-anthramine as a positive control. L. rhamnosus GG (5 mg/plate) was pre-incubated with chlorpyrifos at 37 ºC for 48 h or added at experiment time (00 h). A mutagenic index (MI) ≥ 2 indicated a significant two-fold mutation increase (p<0.05). Toxicity followed TA102 > TA100 = TA97a, with TA98 being non-toxic. After 48 h and 00 h pre-incubation, MI values were: 0.6 and 1.4 (TA97a), 1.6 and 1.9 (TA98), 0.4 and 0.8 (TA100), and 2.3 and 1.9 (TA102). The probiotic restored bacterial viability, including TA98, which became mutagenic at 00h. L. rhamnosus GG facilitated organophosphate bioremediation in TA97a and TA100 but was ineffective against TA102.