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Three litters of healthy neonatal piglets (10-11 piglets in each litter) from a commercial maternal line herd (Landrace-Yorkshire-Duroc) were used. All piglets were weaned at 21 days of age. On the day of weaning, sows were removed from the piglets, while piglets remained in the nursing pens. Piglets were fed ad libitum with a diet that did not contain any antibiotics. Piglets had free access to water. On days 7, 14, 21, 24 and 35 (of age), one piglet from each litter was euthanized. Fresh digesta from the stomach, jejunum and ileum (approximate middle segments) were collected and stored at -20 ºC for molecular analysis. To analyse the microbiota intimately attached to jejunum mucosa, the luminal fluid was drained, middle segments of the jejunum (3-4 cm) were excised, washed with sterile phosphate buffered saline (PBS) (pH 7.0), and immediately frozen in liquid nitrogen and stored at -20 ºC. Mucosal samples were collected from the frozen tissue after defrosting by scraping the luminal surface with a sterile glass slide.
Denaturing gradient gel electrophoresis analysis showed that, after weaning, predominant bands related to Lactobacillus spp. disappeared and were replaced by potential pathogenic species, such as Peptostreptococcus anaerobius, Moraxella cuniculi, S. suis and Porphyromonas catoniae. Real-time PCR revealed that the abundances of lactobacilli and Lactobacillus sobrius as a proportion of total bacterial abundance were significantly lower (P<0.05) in the stomach, jejunum and ileum of weaned piglets than in 21-day-old piglets. A specific and sensitive real-time PCR assay was developed for quantification of the important pathogen S. suis within gastrointestinal microbiota. The assay showed that S. suis predominated in the stomach samples of weaned piglets with population levels up to 107 copies g-1 digesta, while it was not detected in the stomach before weaning. Streptococcus suis was not dominant in the jejunum and ileum digesta before weaning, but became dominant after weaning, with population levels up to 107 copies g-1 digesta.
The results demonstrated for the first time the post-weaning dominance of the potentially harmful S. suis in piglet intestine. The results also suggest that the defensive barrier of the stomach can be impaired as S. suis became dominant while the proportion of Lactobacillus populations decreased after weaning, which may further result in an increase of S. suis abundance in the intestine.
Y Su, W Yao, ON. Perez-Gutierrez, H Smidt and WY Zhu 2008 Federation of European Microbiological Societies. 66: 546-555.
