Co-exposure to polyethylene fiber and
Salmonella enterica
serovar Typhimurium alters microbiome and metabolome of
in vitro
chicken cecal mesocosms
Authors: Chatman Chamia C. , Olson Elena G. , Freedman Allison J. , Dittoe Dana K. , Ricke Steven C. , Majumder Erica L-W. 
Published: July 2024

ABSTRACT

Humans and animals encounter a summation of exposures during their lifetime (the exposome). In recent years, the scope of the exposome has begun to include microplastics. Microplastics (MPs) have increasingly been found in locations, including in animal gastrointestinal tracts, where there could be an interaction with
Salmonella enterica serovar
Typhimurium, one of the commonly isolated serovars from processed chicken. However, there is limited knowledge on how gut microbiomes are affected by microplastics and if an effect would be exacerbated by the presence of a pathogen. In this study, we aimed to determine if acute exposure to microplastics
in vitro
altered the gut microbiome membership and activity. The microbiota response to a 24 h co-exposure to
Salmonella enterica
serovar Typhimurium and/or low-density polyethylene (PE) microplastics in an
in vitro
broiler cecal model was determined using 16S rRNA amplicon sequencing (Illumina) and untargeted metabolomics. Community sequencing results indicated that PE fiber with and without
S
. Typhimurium yielded a lower
Firmicutes/Bacteroides
ratio compared with other treatment groups, which is associated with poor gut health, and overall had greater changes to the cecal microbial community composition. However, changes in the total metabolome were primarily driven by the presence of
S
. Typhimurium. Additionally, the co-exposure to PE fiber and
S
. Typhimurium caused greater cecal microbial community and metabolome changes than either exposure alone. Our results indicate that polymer shape is an important factor in effects resulting from exposure. It also demonstrates that microplastic-pathogen interactions cause metabolic alterations to the chicken cecal microbiome in an
in vitro
chicken cecal mesocosm.

IMPORTANCE

Researching the exposome, a summation of exposure to one’s lifespan, will aid in determining the environmental factors that contribute to disease states. There is an emerging concern that microplastic-pathogen interactions in the gastrointestinal tract of broiler chickens may lead to an increase in
Salmonella
infection across flocks and eventually increased incidence of human salmonellosis cases. In this research article, we elucidated the effects of acute co-exposure to polyethylene microplastics and
Salmonella enterica
serovar Typhimurium on the ceca microbial community
in vitro
.
Salmonella
presence caused strong shifts in the cecal metabolome but not the microbiome. The inverse was true for polyethylene fiber. Polyethylene powder had almost no effect. The co-exposure had worse effects than either alone. This demonstrates that exposure effects to the gut microbial community are contaminant-specific. When combined, the interactions between exposures exacerbate changes to the gut environment, necessitating future experiments studying low-dose chronic exposure effects with
in vivo
model systems.