Location: Meat Safety & Quality ResearchTitle: Genomic-based identification of environmental and clinical Listeria monocytogenes strains associated with an abortion outbreak in beef heifers
|WHITMAN, KATHERINE - University Of Nebraska|
|Bono, James - Jim|
|Clawson, Michael - Mike|
|LOY, JOHN - University Of Nebraska|
|Bosilevac, Joseph - Mick|
|ONDRAK, JEFFREY - University Of Nebraska|
Submitted to: BMC Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2020
Publication Date: 2/22/2020
Citation: Whitman, K.J., Bono, J.L., Clawson, M.L., Loy, J.D., Bosilevac, J.M., Arthur, T.M., Ondrak, J.D. 2020. Genomic-based identification of environmental and clinical Listeria monocytogenes strains associated with an abortion outbreak in beef heifers. BMC Veterinary Research. 16:70. https://doi.org/10.1186/s12917-020-2276-z.
Interpretive Summary: Listeria monocytogenes is a bacterial pathogen that is ubiquitous in the environment and can cause a number of diseases in mammals, including gastritis, septicemia, meningitis and miscarriage or premature birth. Many L. monocytogenes infections can be linked to the consumption of contaminated food. In this study, we report on our investigation into an abortion outbreak that took place in a beef cattle operation that was caused by L. monocytogenes. The abortions occurred over a 36-day period, with samples taken from two aborted fetuses and 21 cows who aborted their fetuses. Of those samples, 19 were positive for L. monocytogenes. Subsequent culturing of L. monocytogenes from water and feed samples identified both as potential origins of infection. We sequenced the genomes of all 19 L. monocytogenes strains isolated from the case samples, as well as the genomes of strains isolated from feed and water samples, and found that many were either completely or closely identical to each other. Three genetically distinct strain types of L. monocytogenes caused the outbreak. One distinct strain type was isolated from 11 of the abortion cases and from all of the water and feed samples that were culture positive for L. monocytogenes. Due to animal, feed, and water movement at the beef cattle operation, this finding indicates that water and/or feed contaminated with L. monocytogenes was the source of infection for the 11 abortion cases. The source of the two other strain types that also caused abortions could not be determined. Because of these findings, the contaminated feed source was discontinued from use, and the water tanks were sanitized. These interventions coincided with abortions ceasing several days later with one exception. This study is the first of its kind in the investigation of a cattle abortion outbreak, and demonstrates the utility of using whole genome sequencing as a component of outbreak investigations.
Technical Abstract: Background: In a beef cattle facility an outbreak of abortions occurred over a 36-day period and included samples from two aborted (non-viable) fetuses and 21 post-abortion clinical cases. There are numerous etiologies, including clinical listeriosis. At the species level, Listeria monocytogenes is ubiquitous in cattle production environments, including soil, feed, and occasionally water sources, and is a common enteric resident of cattle and other mammals. There are four genetically distinct lineages of L. monocytogenes (I-IV), with most lineage III and IV isolates obtained from ruminants. Definitive diagnosis of L. monocytogenes as a causative agent in disease outbreaks relies upon case identification, appropriate sample collection, and laboratory confirmation. Furthermore, clearly establishing a relationship between a pathogen source and clinical disease is difficult. Results: Of the two fetal and 21 clinical case submissions, 19 were positive for L. monocytogenes. Subsequent culture for L. monocytogenes from water and silage sources identified both as potential origins of infection. Using whole-genome sequencing and phylogenetic analyses, clinical, water and silage L. monocytogenes strains grouped into two of four lineages. All water and silage strains, plus 11 clinical strains placed in lineage III, with identical or nearly identical genomic sequences. The remaining eight clinical strains placed in lineage I, with seven having nearly identical sequences and one distinctly different. Conclusion: Three genetically distinct strains within two lineages of L. monocytogenes caused the abortion outbreak. The etiology of abortion in 11 cases was directly linked to water and silage contamination from a lineage III L. monocytogenes strain. The source of infection for the remaining abortion cases with two different strains from lineage I is unknown. This is the first report of L. monocytogenes genomics being used as part of an outbreak investigation of cattle abortion.