The gram-positive tonsillar and nasal flora of piglets before and after weaning

AIMS: To investigate gram-positive nasal and tonsillar microbial flora of piglets before and after weaning. METHODS AND RESULTS: The nasal and tonsillar gram-positive bacterial flora of 20 non-weaned piglets (2 weeks of age) and 20 weaned piglets (6 weeks of age), obtained from four different piggeries, was quantified by culture and identified by tDNA-PCR. The most widely occurring species from nasal conchae before as well as after weaning in the different piglets investigated were Streptococcus suis and Rothia nasimurium. After weaning a wide variety of Lactobacillus species appeared but in low numbers. In the tonsils, Strep. suis, Strep. dysgalactiae, S. hyicus, S. aureus, Arcanobacterium pyogenes and Actinomyces hyovaginalis were the species isolated from the largest number of pigs before and after weaning. S. aureus and most lactobacilli became more prevalent after weaning. Bacteria not known to be associated with pigs found in the present study included R. nasimurium, Strep. gallolyticus, Pediococcus pentosaceus and some Lactobacillus species. CONCLUSIONS: Over 30 different gram-positive bacterial species may occur in nasal conchae and tonsils of unweaned piglets at 2 weeks of age and of 6-week-old weaned piglets. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated that weaning is associated with changes in prevalence of only a small minority of the highly diversified bacterial flora of the nares and tonsils of pigs.