Effect of preventive application of <I>Enterococcus faecium</I> EF55 on intestinal mucosa during salmonellosis in chickens

In the present study the effect of preventive application of <I>Enterococcus faecium</I> EF 55 on the intestinal mucosa was evaluated in experimentally infected chickens with <I>Salmonella enterica</I> subsp. <I>Enteritidis</I>. A total of 120, one-day-old <I>Salmonella</I>-free chickens of Isa Brown hybrid were divided into 4 groups. The chickens in groups E and ES were perorally inoculated with <I>E. faecium</I> EF55 in a dose of 1 × 109 CFU/ml for 7 consecutive days. Placebo was applied to birds in control group C and group S during the first 7 days of life. At the age of 8 days chickens in groups ES and S were perorally infected with <I>S. enterica</I> subsp.<I> Enteritidis</I> phage type 4 in a dose of 1 × 108 CFU/ml. In birds treated with <I>E. faecium</I> EF 55 (group ES) a decreased number of <I>Salmonella</I> spp. positive individuals was recorded from 28.5% 2 days post infection (p.i.) to 10% 14 days p.i. when the difference between group ES and group with the application of <I>Salmonella</I> Enteritidis alone (group S) was significant (<I>P</I> < 0.01). On the contrary, in birds of group S the percentage of <I>Salmonella</I> spp. positive animals showed no constant changes. It increased from 12.5% 2 days p.i. to 37.5% 4 days p.i. The maximum of positive samples 83.3% was found 14 days p.i. The application of <I>E. faecium</I> EF55 reduced colonisation of caeca and minimized translocation of salmonellae into the liver and spleen. Two days p.i. the shortest villi in the jejunum were observed in group S – 1 266.2 µm, when compared to group E with the highest jejunal villi – 1 605 µm (<I>P</I> < 0.05). The growth of the villi was observed 14 days p.i. in all groups except group S. The early exposition of chickens to <I>E. faecium</I> EF55 led to more rapid development of intestinal villi when compared to the untreated control (P < 0.05). Reduced colonisation of the intestinal tract by salmonellae in birds treated with <I>E. faecium</I> EF 55 also preserved the microenvironment of the intestine from harmful effects of the pathogen.