Master of Science, The Ohio State University, 2024, Animal Sciences
Listeria monocytogenes is an invasive, zoonotic, foodborne pathogen that causes human listeriosis. L. monocytogenes is a resilient pathogen capable of surviving and even proliferating under various environmental conditions. Its capacity to persist in soil, manure, water, and various farm environments necessitates an investigation to safeguard consumers and maintain the reputation of small specialty crop farms. Small specialty crop farms (SSCFs) are an important and growing sector for crop production in the USA. Currently, there is little information on the prevalence and genetic landscape of the L. monocytogenes from SSCFs. Bridging this knowledge gap would help understand potential public health risks associated with the L. monocytogenes coming from these farms. The goal of our study is to understand the prevalence and genomic diversity among the isolates in the SSCF niche by characterizing pangenome, serogroups, antimicrobial resistance genes, and virulence genes. We collected, tested, and processed dairy and poultry manure, soil, water, and produce samples (n = 1842) for L. monocytogenes from 15 SSCF between 2016 to 2020. Isolates were analyzed through Whole Genome Sequencing (WGS). The overall prevalence of L. monocytogenes on SSCF was 7.17% (132/1842 samples). Based on positive samples, the prevalence of L. monocytogenes was 23.2% (n=53/228) in dairy manure, 11.0% (n=14/127) in water, 6.2% (n=31/500) in produce, 3.6% (n=28/777) in soil, 2.9% (n=6/210) in poultry manure. From these 132 positive samples, 347 isolates were obtained and were subjected to whole genome sequencing (WGS). Pangenome analysis detected the presence of 2,036 core genes. In silico serotyping of L. monocytogenes detected the presence of four serotypes 1/2a, 1/2b, 1/2c, and 4b, implicated in human infections. Analysis of antimicrobial resistance (AMR) genes identified the presence of 10 genes: abc-f, fos(X), mecA, vanZ, mprF, mprB, vga(G), ampC, group_1242, and tetR. In addition, an arsenic- (open full item for complete abstract)
Committee: Gireesh Rajashekara (Advisor); Joy Scaria (Committee Chair); Greg Habing (Committee Chair)
Subjects: Animal Sciences; Microbiology; Public Health