High diversity of viable bacteria isolated from lymph nodes of slaughter pigs and its possible impacts for food safety

• Published in: Journal of applied microbiology Vol. 119; no. 5; pp. 1420 - 1432
• Main Authors: Mann, E, Dzieciol, M, Pinior, B, Neubauer, V, Metzler‐Zebeli, B.U, Wagner, M, Schmitz‐Esser, S
• Format: Journal Article
• Language: English
• Published: England Published for the Society for Applied Bacteriology by Blackwell Science 01.11.2015; Oxford University Press
• Subjects: Abattoirs; Acinetobacter; Actinobacteria; Animals; Bacteria; Bacteria - classification; Bacteria - genetics; Bacteria - isolation & purification; Bacteria - metabolism; Biodiversity; Carnobacterium; cultivation; data collection; DNA; enlarged; Escherichia coli; Firmicutes; Food Safety; gastrointestinal system; gastrointestinal tract; Gastrointestinal Tract - microbiology; genes; Genetic Variation; granulomatous; high-throughput nucleotide sequencing; Hogs; hyperplasia; Lactobacillus; lymph node; lymph nodes; Lymph Nodes - microbiology; Lymphatic system; Microbiology; microbiota; Molecular Sequence Data; pathogens; Phylogeny; phylotype; pig; Proteobacteria; purulent; Random Amplified Polymorphic DNA Technique; ribosomal RNA; RNA, Ribosomal, 16S - genetics; Salmonella enterica; slaughter; Staphylococcus; Streptococcus suis; Swine; microbiota; gastrointestinal tract; bacteria; pathogens; lymph node; enlarged; granulomatous; cultivation; pig; purulent
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/jam.12933

AIMS: Ileocaecal lymph nodes (ICLNs) of pigs, the key immune inductive site for bacterial systemic invasion, were examined in this study with emphasis on viable and cultivable bacteria. METHODS AND RESULTS: Asymptomatic and pathologically altered ICLNs of slaughter pigs (n = 16) with hyperplasia, purulence or granulomatous formations were aerobically and anaerobically cultivated. In total, 209 isolates were collected and the near full‐length 16S rRNA gene from each isolate was sequenced. Taxonomic classification revealed that 68% of the isolates belonged to Proteobacteria, 27% to Firmicutes and 5% to Actinobacteria. Purulent and granulomatous ICLNs generally tended to contain more Proteobacteria than asymptomatic and enlarged ICLNs (P = 0·061). The isolates could be assigned to 25 species belonging to 17 genera including Escherichia, Carnobacterium, Lactobacillus, Staphylococcus and Acinetobacter. Furthermore, pathogens such as Streptococcus suis and Salmonella enterica were detected. The most abundant isolate (57%) was most similar (>99%) to Escherichia coli. Random amplified polymorphic DNA (RAPD) profiling revealed a high genetic diversity among E. coli isolates and 24% of these isolates were positive for at least one gene associated with enterohemorrhagic disease (eae, fliC, stx₁ or hlyA). Compared with a recently published DNA‐based high‐throughput sequencing data set including the same ICLNs, 4% of species detected were cultivable. CONCLUSIONS: The presence of viable, commensal and pathogenic bacterial phylotypes could be proven in ICLNs with Proteobacteria being dominant. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that broadly characterizes viable bacteria from ICLNs of pigs. The presence of bacteria in lymph nodes of farm animals has practical relevance for host colonization and possible chronic infection. It is also of great interest for basic research investigating translocation of bacteria from the gastrointestinal tract to ICLNs.