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


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.


CONCLUSIONS
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.
Department for Farm Animals and Veterinary Public Health, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.|Department for Farm Animals and Veterinary Public Health, Research Cluster 'Animal Gut Health', University of Veterinary Medicine, Vienna, Austria.
E
E
Mann
Department for Farm Animals and Veterinary Public Health, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.
M
M
Dzieciol
Department for Farm Animals and Veterinary Public Health, Institute for Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
B
B
Pinior
Department for Farm Animals and Veterinary Public Health, Research Cluster 'Animal Gut Health', University of Veterinary Medicine, Vienna, Austria.|Department for Farm Animals and Veterinary Public Health, Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine, Vienna, Austria.
V
V
Neubauer
Department for Farm Animals and Veterinary Public Health, Research Cluster 'Animal Gut Health', University of Veterinary Medicine, Vienna, Austria.|University Clinic for Swine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
B U
BU
Metzler-Zebeli
Department for Farm Animals and Veterinary Public Health, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.|Department for Farm Animals and Veterinary Public Health, Research Cluster 'Animal Gut Health', University of Veterinary Medicine, Vienna, Austria.
M
M
Wagner
Department for Farm Animals and Veterinary Public Health, Institute of Milk Hygiene, Milk Technology and Food Science, University of Veterinary Medicine, Vienna, Austria.|Department for Farm Animals and Veterinary Public Health, Research Cluster 'Animal Gut Health', University of Veterinary Medicine, Vienna, Austria.
S
S
Schmitz-Esser
D000003:Abattoirs; D000818:Animals; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D044822:Biodiversity; D059022:Food Safety; D041981:Gastrointestinal Tract / Q000382:microbiology; D014644:Genetic Variation; D008198:Lymph Nodes / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D019105:Random Amplified Polymorphic DNA Technique; D013552:Swine
D012336:RNA, Ribosomal, 16S
bacteria; cultivation; enlarged; gastrointestinal tract; granulomatous; lymph node; microbiota; pathogens; pig; purulent