Application of probiotic strains as feed additives in poultry against Campylobacter jejuni

Campylobacteriosis is the most frequent zoonotic disease in the EU in recent years (Hugas et al., 2009) and the bacterial species most frequently implicated is Campylobacter jejuni. Epidemiological data obtained by the European Food Safety Authority have concluded that poultry meat is the major source of campylobacteriosis in humans. An alternative and effective approach to antibiotic administration to livestock to reduce bacterial contamination is the use of probiotics. The aim of the present work is to select probiotics to be used as additives in feed for livestock poultry in order to reduce C. jejuni contamination and therefore enhance the safety of poultry meat. Methods 55 lactic acid bacteria and bifidobacteria were screened for desirable properties for their use as probiotics: anti-microbial activity against three C. jejuni strains was studied using the spot agar test and the well diffusion assay using neutralized culture supernatants; survival in simulated gastro intestinal tract (pH 2.5 and 1% bile salts) and food/feed processing conditions (50 and 55 °C) was determined and susceptibility to the most diffused antibiotics was checked. The two most interesting strains were separately administered to poultry by oral gavages to evaluate their capability to colonize the GI tract and to estimate their effect on C. jejuni population. Quantification of both administered probiotics and C.jejuni was done via real time PCR. Results 16 strains out of the 55 tested showed anti-microbial activity against all the three C. jejuni strains. After the well diffusion agar assay, the number of strains showing interesting antimicrobial activity was reduced to 11. These strains were used for further studies: they were found to be sensitive to low pH, whereas the majority of them survived well to exposure to bile salts and well tolerated heat shock at both 50 °C and 55 °C. Most of the strains were sensitive to several antibiotics, including some of the most common compounds used in poultry therapy. On the basis of these activities, two strains, namely Lactobacillus plantarum PCS 20 and Bifidobacterium longum PCB 133, were chosen for the in vivo trial in poultry. The results evidenced that L. plantarum PCS 20 was not present in poultry feces at detectable concentration after two weeks of daily administration, whereas B. longum PCB 133 significantly increased in the feces after administration and its amount was still high after a wash-out period of 6 days. In the same period, C. jejuni concentration in poultry feces was significantly reduced in chickens administered with B. longum PCB 133. Discussion A B. longum strain possessing interesting probiotic properties and capable of surviving in the chicken GI tract has been selected in this work. Its marked anti-microbial activity against Campylobacter both in vitro and in vivo make it an excellent candidate for being employed as additives to feed for poultry for the reduction of food-borne campylobacteriosis in humans. Studies are currently being performed in order to develop suitable ways of administering the selected probiotic strain in the feed. References Hugas et al. 2009 Trends Food Sci. Technol. 20, 188.