Molecular Analysis of the Composition ofLactobacillusPopulations Inhabiting the Stomach and Caecum of Pigs

The strain composition of Lactobacillus populations inhabiting the stomach and caecal contents of piglets aged 6-150 days was determined using ribotyping and pulsed field gel electrophoresis of DNA digests. These genetic fingerprinting methods proved effective in demonstrating transitions occurring in the Lactobacillus microflora of the pigs raised on a commercial farm. The composition of the Lactobacillus microflora showed periods of stability in which animals of the same age harboured similar collections of predominant strains. Periods of instability were also detected: post-weaning (stomach and caecum) and in grower accommodation (caecum). The majority of the lactobacillus isolates were resistant to erythromycin and tetracycline, presumably reflecting the use of antibiotics as prophylactic agents on the farm. A strain of Lactobacillus acidophilus, used to inoculate the piglets at 5 days old, was detected in the stomach contents of only the two pigs examined at 18 days old. Antibodies reactive with whole cells of lactobacilli were detected in serum samples obtained from the pigs.