The protective effect of Enterococcus faecium EF 55 against Salmonella enterica serovar Enteritidis phage type 4 (SE PT4) was studied in 1-day-old chicks. The EF 55 strain (isolated and characterised by the authors earlier) was applied daily (1.10 9 CFU/0.2 ml PBS) for 7 days. Oral inoculation of the SE PT4 strain was performed on day 8 in a single dose of 5.10 8 CFU/0.2 ml PBS. The experiment lasted for 21 days. Samples were collected on day 1 of the experiment to verify the absence of Salmonella, on day 8 to check colonisation of EF 55 and immunological status in experimental birds, and on days 2, 4, 6, 8 and 14 after SE PT4 infection of chicks. Strain EF 55 sufficiently colonised the digestive tract of chicks after 7 days of application. The highest numbers of EF 55 in the faeces of chicks were observed before SE infection and persisted to day 6 post infection (p.i.) in both the EF and EF+SE groups. PCR confirmed the identity of the EF 55 strain. The counts of SE PT4 strain in faeces of the EF+SE group were significantly reduced in comparison to those in the SE group on days 2 and 14 p.i. (P < 0.01). The significant reduction of salmonellae in the caecum was recorded at the end of the experiment (day 14 p.i.) in the EF+SE group in comparison to the SE group (P < 0.01). At day 4 p.i., colonies of S. Enteritidis PT4 were found in the liver of chicks of the SE group in a higher concentration than in chicks of the EF+SE group (P < 0.001). Salmonellae were isolated from the liver until days 8 and 6 p.i. in the SE and EF+SE groups, respectively. The mean values of actual lymphocyte subpopulations in the blood and the relative percentage of caecal intraepithelial lymphocyte subpopulations (CD4, CD8, CD44, TCR, MHC II and IgM) were not influenced at a statistically significant level by the application of the EF 55 and/or the SE PT4 strain. The results demonstrate the antimicrobial effect of E. faecium EF 55 against S. Enteritidis PT4.
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.
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