The intestinal microbiota and parasitic helminths have coevolved inside their host to reach a balance. Any alteration of this equilibrium may affect the parasite survival. This study aims to evaluate the influence of the microbiota modification on intestinal settlement of the nematode Trichinella spiralis by long term treatment prior to experimental infection with two antibiotics of different profiles, the aminoglycoside (streptomycin) and the beta-lactam (penicillin). As expected, the experiment showed that antibiotic treatment changes the parasite environment so that makes your establishment less effective.