Assessment of Lactobacillus acidophilus (L. acidophilus) therapeutic and prophylactic role in rats experimentally infected with Blastocystis subtype 3 (ST3).

Blastocystis, an eukaryote, inhabits the intestinal tract of humans and animals worldwide. Lactobacillus acidophilus (L. acidophilus), a probiotic, has been reported to be effective against blastocystosis. The present study evaluated the therapeutic and prophylactic effectiveness of L. acidophilus compared to metronidazole (MTZ) in rats experimentally infected with Blastocystis subtype 3 (ST3). Four groups of Blastocystis ST3-infected rats received MTZ, L. acidophilus, both MTZ and L. acidophilus, or prophylactic L. acidophilus. Non-infected and infected control groups were included. The effectiveness of treatment and prevention was evaluated using parasitological monitoring, histopathological examination, immunohistochemical staining for TNF-α and IgA expression, and immunological testing for TNF-α and IL-10. In the L. acidophilus-treated group, a 76% reduction in the mean fecal parasitic count and a 67% clearance in the intestinal wash were achieved aligning closely with outcomes observed in the MTZ-treated group. An immunomodulatory impact via upregulation of the anti-inflammatory cytokine IL-10 and downregulation of the pro-inflammatory cytokine TNF-α was demonstrated as well. Combined administration of MTZ and L. acidophilus exhibited superior efficacy with a 99% decrease in the mean fecal parasitic count and a 98% decrease in the intestinal fluid parasitic count. Additionally, the lowest TNF-α and the highest IL-10 serum levels. Prophylactic use of L. acidophilus for 7 days neither prevented infection nor reduced its severity. Furthermore, no significant differences were detected in serum levels of TNF-α and IL-10 following post-prophylaxis and post-treatment with L. acidophilus. Accordingly, L. acidophilus might be recommended as an adjuvant treatment alongside MTZ for improved efficacy against blastocystosis.