Microbial communities, resistomes, and virulomes of veal calves and dairy animals with a side-note on Salmonella Kentucky

Authors: Haley, Bradd; SALAHEEN, SERAJUS - University Of Maryland; KIM, SEON WOO - University Of Maryland; Van Kessel, Jo Ann

Submitted to: Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: 12/6/2018
Publication Date: 12/6/2018
Citation: Haley, B.J., Salaheen, S., Kim, S., Van Kessel, J.S. 2018. Microbial communities, resistomes, and virulomes of veal calves and dairy animals with a side-note on Salmonella Kentucky. Microbiology. p. 1.

Interpretive Summary:

Technical Abstract: The extent to which carriage of antibiotic resistant bacteria in food animals is responsible for the burden of antibiotic resistance in human infections is currently not well known. Thus, there is a need to further evaluate the genomic diversity of multidrug resistant (MDR) bacteria and the microbial communities in which they are found within these animals. To further evaluate the prevalence of antibiotic resistance in the feces of dairy animals, we shotgun sequenced the metagenomes of 34 fecal samples collected from lactating dairy cows and pre-weaned calves, and 24 samples from veal calves in two different age groups. Metagenomic analyses indicated that there was a high level of diversity among the samples and that antibiotic resistance genes were abundant in all samples, with tetracycline, aminoglycoside, and multidrug efflux resistance genes being the most frequently found. A comparison of the microbial communities and resistomes in lactating cow samples and pre-weaned calf samples indicated that community structures and resistome structures were significantly different between the two age groups. In veal calf samples there was no identifiable difference in the community structures, but a moderate difference in the resistome structures between the age groups. We further evaluated potential associations between Salmonella Kentucky, one of the most frequently isolated S. enterica serovars from dairy cows, and the microbial communities of these animals using 16S rRNA sequencing. There were no significant differences in community structures between S. Kentucky shedding cows and non-shedding cows, nor were there any differences in the abundance of any taxa between the two groups. Our concurrent work on individual S. Kentucky genomes indicated that isolates collected from poultry are phylogenetically distinct from those collected from dairy cows and isolates collected from North America were distinct from those isolated abroad. These phylogenetic data were used to identify the potential sources of S. Kentucky infections in Maryland. Results of these analyses indicated that a significant portion of S. Kentucky infections in this state were associated with travel abroad indicating that authochthonous S. Kentucky in the US may be responsible for a relatively low number of salmonellosis cases. Future work will determine the drivers of antibiotic resistance in dairy animals and the mechanisms of S. Kentucky host-specificity in dairy animals.