Characterization of pig saliva as the major natural habitat of Streptococcus suis by analyzing oral, fecal, vaginal, and environmental microbiota

Abstract

It is generally difficult to specify the sources of infection by which domestic animals may acquire pathogens. Through 16S rRNA gene amplicon sequencing, we compared the composition of microbiota in the saliva, vaginal mucus, and feces of pigs, and in swabs of feeder troughs and water dispensers collected from pig farms in Vietnam. The composition of the microbiota differed between samples in each sample group. Streptococcus , Actinobacillus , Moraxella , and Rothia were the most abundant genera and significantly discriminative in saliva samples, regardless of the plasticity and changeability of the composition of microbiota in saliva. Moreover, species assignment of the genus Streptococcus revealed that Streptococcus suis was exceptional in the salivary microbiota, due to being most abundant among the streptococcal species and sharing estimated proportions of 5.7%–9.4% of the total bacteria in saliva. Thus, pig oral microbiota showed unique characteristics in which the major species was the pig pathogen. On the other hand, β-diversity analysis showed that the microbiota in saliva was distinct from those in the others. From the above results, pig saliva was shown to be the major natural habitat of S . suis , and is suggested to be the most probable source of S . suis infection.

Relationships among Fecal, Air, Oral, and Tracheal Microbial Communities in Pigs in a Respiratory Infection Disease Model

“…Streptococcus is part of the core tonsillar microbiome in newborn piglets [ 26 ], and is also part of the core oropharyngeal microbiome in piglets, together with Lactobacillus and Actinobacillus [ 20 ]. Streptococcus is one of the most abundant genera in pig saliva, along with Actinobacillus, Moraxella , and Rothia [ 24 ], and was reported as the major bacterial genus in aerosols from pig confinement buildings [ 33 ]. Additionally, Clostridium and Escherichia were documented to be among the most abundant genera in feces during the preweaning phase, while Megasphaera and Lactobacillus seem to be more abundant during the postweaning phase in pigs [ 12 , 13 , 14 , 15 ].…”

“…The majority of contact pigs were confirmed infected at least one month prior to sampling. Therefore, they were considered to be at a late infection stage [ 24 ]. Pigs were not exposed to antimicrobials known to be effective against Mycoplasma species during the study.…”

“…In fact, oral fluids, saliva, and oral mucosal transudate [ 21 ] collected in ropes gnawed on by pigs in pens, are widely used for the detection of respiratory viruses in swine herds [ 22 , 23 ]. Although Murase, et al [ 24 ] described the microbiome in pig saliva, the microbiome associated with oral fluids was not described.…”

Analysis of Porcine Pro- and Anti-Inflammatory Cytokine Induction by S. suis In Vivo and In Vitro

“…Weaning piglets are commonly asymptomatically colonized with S. suis at mucosal surfaces [4,5]. Bacteria can be found shortly after birth in several locations, including the saliva [6], palatine and nasopharyngeal tonsils and mandibular lymph nodes [7,8]. However, when S. suis becomes invasive, it can induce severe diseases associated with meningitis, endocarditis, arthritis or septicemia [9].…”

Culture-Negative Streptococcus suis Infection Diagnosed by Metagenomic Next-Generation Sequencing

“…Streptococcus suis is a major swine pathogen, and typically colonizes the nasal cavities, tonsils, and upper respiratory, genital, and gastrointestinal tracts (1,2). Streptococcus suis has recently been recognized as a zoonotic pathogen that may cause infections in humans in occupational contact with pigs or pork (3,4).…”