Figure 2. The effects of stroke and age on bacterial translocation 72 hours after 90 minute MCAO and on MLN bacterial burden 7 days after 60 minute MCAO.

(A) Representative image of intestinal and MLN fluorescence in a non-GFP transfected aged sham (“Control”) and in an aged stroke (90min MCAO, 72hr reperfusion) mouse transplanted with GFP+ E. coli (“GFP+ ve”). Average fluorescence of controls was subtracted as background from GFP+ aged sham and stroke values. (B) While there was no difference in intestinal fluorescence 72 hours after 90 minute stroke or sham surgery (p=0.51, n=4/group) there was a (C) significant increase in aged MLN fluorescence following stroke compared to sham values (p<0.01, n=4/group). (D) Species of Staphylococcus and Enterococcus colonized organs from both young and aged mice 72 hours after 90 minute MCAO, bacteria of the genera Escherichia and Enterobacter were only found in organs from young and aged mice, respectively (n=12-16/group). (E) There was a significant effect of age on MLN bacterial burden a week after 60 minute MCAO or sham surgery as measured by a 2-way ANOVA performed on the logarithmically transformed CFU/mL data (F(1,19)=p<0.01, n=4-7/group). Aged mice had significantly greater MLN bacterial burden compared to young at this timepoint following stroke (p<0.05). Data are presented as raw untransformed CFU/mL values. (F) Representative image of CFUs grown on blood agar from young and aged stroke MLN homogenates. Values in (D) are expressed as the percentage of the total number of successfully identified bacteria that were matched with a particular genus and values in (B, C, and E) are expressed as mean ± SEM. Abbreviations: MLN, mesenteric lymph node; CFU, colony-forming unit; GFP+ ve, microbiome transplanted with GFP-tagged E. coli; ASH,aged sham; AST, aged stroke; n.s., not significant; a.u., arbitrary units. *, p≤0.05; **, p<0.01.