A wide range of bacterial and viral porcine pathogens are routinely isolated from the tonsils [1]. In this study, we identified large numbers of sequences whose closest affiliate in the database were Haemophilus parasuis and Pasteurella multocida (on average 12.8% and 9.3%, respectively, of reads identified at the 97% cutoff), as well as small numbers of sequences closest Daporinad solubility dmso to Streptococcus suis (on average 0.4% of reads identified) from almost all

samples. However, we did not find sequences affiliated with Actinobacillus pleuropneumoniae or A. suis, which have been reported to be found in most swine herds in Ontario, Canada [7]. Small numbers of sequences closest to Mycoplasma were found in a few pigs, but these were not identified beyond the Classifier function

of the RDP. Herd 1 has been regularly tested and found to be free of A. pleuropneumoniae, A. suis, and Mycoplasma, which is substantiated by these results. We were surprised not to find sequences consistent with the presence of pathogenic Actinobacillus species in Herd 2, which has had a history of chronic but undefined selleckchem respiratory problems. It is possible that these chronic problems are related to the higher numbers of Pasteurella sequences found in Herd 2, or to the presence of another known respiratory pathogen, Arcanobacterium, found in Herd 2 but not Herd 1. In addition to porcine pathogens, many bacterial agents of foodborne infections of humans have been isolated from pig tonsils, including members of the Enterobacteriaceae such as Salmonella species, Escherichia

Amisulpride coli, and Yersinia enterocolitica as well as Campylobacter species and Listeria monocytogenes [9–13]. We found low numbers of Campylobacter (0.17% of total reads) and Escherichia (0.59% of total reads) in most of the pig tonsils in this study. In addition, we found other Enterobacteriaceae (1.9% of the total) that are rarely associated with human foodborne illness, including Citrobacter, Enterobacter, Morganella, Proteus, and Providencia, in one or more pigs. We did not find Salmonella, Yersinia, or Listeria in these tonsil samples from healthy pigs. The only other mammalian system where the tonsillar microbiota has been reported is in humans. Culture-based studies of human tonsils have identified Streptococcus pyogenes; S. pneumoniae; Group C, F, and G β-hemolytic streptococci; several α-hemolytic and non-hemolytic streptococci; Staphylococcus aureus; Haemophilus influenzae; H. parainfluenzae; and Moraxella catarrhalis in aerobic cultures [25–31]. Many species of the Bacteroides-Prevotella-Porphyromonas group, Fusobacterium, Lactobacillus, Peptostreptococcus, and Veillonella have also been isolated using anaerobic cultures.