Normal intestinal bacteria can initiate systemic disease by translocating out of the intestinal lumen to extraintestinal sites such as the mesenteric lymph nodes (MLN), liver, and spleen. To determine whether dietary essential fatty acids can affect the incidence of bacterial translocation, separate groups of mice were fed one of two diets for 8 days: an essential fatty acid-replete diet (EFA-R) containing a basal formula supplemented with arginine, yeast RNA, menhaden oil, and safflower oil, or an essential fatty acid-deficient diet (EFA-D) containing the same ingredients with the safflower oil replaced by menhaden oil. Mice were given either diet alone, diet plus 50 Î¼ g of intraperitoneal lipopolysaccharide (LPS), or diet plus 3 days of 4 mg of intramuscular metronidazole (MET) three times a day. (Both LPS and MET have been shown to increase the incidence of bacterial translocation to the MLN.) Within treatment groups there were no significant differences in the total numbers of viable ileal bacteria (separate quantitation of strict anaerobes, aerobic, and facultative Gram-positive results, and aerobic and facultative Gram-negative results). The incidence of bacterial translocation to the MLN was increased in mice fed EFA-D as compared with EFA-R in mice treated with diet alone (17% us 0%; p <.005) and in mice treated with diet plus LPS (71% us 48%; p =.027). There was no difference in the incidence of bacterial translocation in mice fed EFA-D or EFA-R and treated with MET (83% us 81%). (Journal of Parenteral and Enteral Nutrition16:122-128, 1992).