The genetic diversity of commensal Escherichia coli strains isolated from non-antimicrobial treated pigs varies according to age group

• Published in: PloS one 2017-05, Vol.12 (5), p.e0178623-e0178623
• Main Authors: Ahmed, Shahana, Olsen, John E, Herrero-Fresno, Ana
• Format: Article
• Language: English
• Subjects: Age; Age Factors; Age groups; Analysis; Animal sciences; Animals; Anti-Bacterial Agents - administration & dosage; Antibiotics; Antiinfectives and antibacterials; Antimicrobial agents; Antimicrobial resistance; Bacteria; Biodiversity; Biology and Life Sciences; Computer and Information Sciences; Denmark; Deoxyribonucleic acid; DNA; Drug resistance; E coli; Electrophoresis, Gel, Pulsed-Field; Escherichia coli; Escherichia coli - genetics; Escherichia coli - isolation & purification; Feces; Genes; Genes, Bacterial; Genetic aspects; Genetic diversity; Genetic Variation; Genomes; Genotypes; Hogs; Laboratories; Lactose; Medicine and Health Sciences; Nucleotide sequence; People and Places; Phylogeny; Physiological aspects; Polymerase Chain Reaction; Research and Analysis Methods; Single-nucleotide polymorphism; Strains (organisms); Studies; Suidae; Swine; Swine - microbiology; Virulence; Weaning
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0178623

This is the first report on the genetic diversity of commensal E. coli from pigs reared in an antibiotic free production system and belonging to different age groups. The study investigated the genetic diversity and relationship of 900 randomly collected commensal E. coli strains from non-antimicrobial treated pigs assigned to five different age groups in a Danish farm. Fifty-two unique REP profiles were detected suggesting a high degree of diversity. The number of strains per pig ranged from two to 13. The highest and the lowest degree of diversity were found in the early weaners group (Shannon diversity index, H' of 2.22) and piglets (H' of 1.46) respectively. The REP profiles, R1, R7 and R28, were the most frequently observed in all age groups. E. coli strains representing each REP profile and additional strains associated with the dominant profiles were subjected to PFGE and were assigned to 67 different genotypes. Whole genome sequence analysis of 52 isolates leading to unique REP profiles identified a high level of sequence variation. Six and six strains were assigned to sequence type ST10 and sequence type ST58, respectively. Virulence and antimicrobial resistance genes, as well as, genes associated with mobile genetic elements were commonly found among these commensal E. coli strains. Interestingly, strains yielding the three most common REP profiles clustered together in the SNPs phylogenetic tree, and such strains may represent the archetypal commensal E. coli in Danish pigs.