Effect of dietary fish-oil on survival of experimental animals after infection with Streptococcus pneumoniae or Klebsiella pneumoniae.

Dietary fish-oil has beneficial effect in infections and in autoimmune disorders. This effect is thought to be associated with alterations in the immune system. The Gram negative organism Klebsiella pneumoniae has been used as an infective agent in most studies investigating the effect of dietary fish-oil on infection. The immune response against Gram positive bacteria is somewhat different to the response to Gram negative oeganisms. Moreover, the Gram positive bacteria Streptococcus pneumoniae is a very common pathogen, particularly in children. To investigate whether dietary fish-oil has different effect in infections by Gram positive or Gram negative bacteria, we studied the survival of mice fed with fish-oil or corn-oil supplemented diets and infected in the lungs with either Klebsiella pneumoniae or Streptococcus pneumoniae. 120 NMRI mice were divided into four groups and fed diets supplemented with fish-oil (two groups, 30 mice in each group) or corn-oil (two groups, 30 mice in each group). After six weeks, the mice were infected with Klebsiella pneumoniae (fish-oil group and corn-oil group) or with Streptococcus pneumoniae serotype 3 (fish-oil group and corn-oil group). The survival was monitored. The experiment was performed twice. The survival of the mice infected with Klebsiella pneumoniae was significantly better in the groups receiving the fish-oil enriched diet as compared to the groups fed the corn-oil enriched diet (p=0.0001 and 0.0013). There was no difference in the survival of mice infected with Streptococcus pneumoniae serotype 3, receiving the fish-oil or corn-oil enriched diets (p=0.74 and p=0.15). These results indicate that dietary fish-oil has beneficial effect on survival of mice after experimental infection with the Gram negative bacteria Klebsiella pneumoniae but not on experimental infections with the Gram positive bacteria Streptococcus pneumoniae serotype 3.