title: Diversity, distribution and antibiotic resistance of Enterococcus spp. recovered from tomatoes, leaves, water and soil on U.S. Mid-Atlantic farms.
abstract: Antibiotic-resistant enterococci are important opportunistic pathogens and have been recovered from retail tomatoes. However, it is unclear where and how tomatoes are contaminated along the farm-to-fork continuum. Specifically, the degree of pre-harvest contamination with enterococci is unknown. We evaluated the prevalence, diversity and antimicrobial susceptibilities of enterococci collected from tomato farms in the Mid-Atlantic United States. Tomatoes, leaves, groundwater, pond water, irrigation ditch water, and soil were sampled and tested for enterococci using standard methods. Antimicrobial susceptibility testing was performed using the Sensititre microbroth dilution system. Enterococcus faecalis isolates were characterized using amplified fragment length polymorphism to assess dispersal potential. Enterococci (n = 307) occurred in all habitats and colonization of tomatoes was common. Seven species were identified: Enterococcus casseliflavus, E. faecalis, Enterococcus gallinarum, Enterococcus faecium, Enterococcus avis, Enterococcus hirae and Enterococcus raffinosus. E. casseliflavus predominated in soil and on tomatoes and leaves, and E. faecalis predominated in pond water. On plants, distance from the ground influenced presence of enterococci. E. faecalis from samples within a farm were more closely related than those from samples between farms. Resistance to rifampicin, quinupristin/dalfopristin, ciprofloxacin and levofloxacin was prevalent. Consumption of raw tomatoes as a potential exposure risk for antibiotic-resistant Enterococcus spp. deserves further attention.
authors.affiliation: Maryland Institute for Applied Environmental Health, School of Public Health, University of Maryland, College Park, MD 20742, USA.
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Micallef
authors.forename: Rachel E Rosenberg
authors.initials: RE
authors.lastname: Goldstein
authors.forename: Ashish
authors.initials: A
authors.lastname: George
authors.forename: Laura
authors.initials: L
authors.lastname: Ewing
authors.forename: Ben D
authors.initials: BD
authors.lastname: Tall
authors.forename: Marc S
authors.initials: MS
authors.lastname: Boyer
authors.forename: Sam W
authors.initials: SW
authors.lastname: Joseph
authors.forename: Amy R
authors.initials: AR
authors.lastname: Sapkota
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D044822:Biodiversity; D016983:Enterococcus / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D005638:Fruit / Q000382:microbiology*; D060587:Groundwater / Q000382:microbiology*; D018551:Solanum lycopersicum / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008873:Mid-Atlantic Region; D018515:Plant Leaves / Q000382:microbiology*; D012988:Soil Microbiology
chemical_list: D000900:Anti-Bacterial Agents
keywords: Amplified fragment length polymorphism; Antibiotic resistance; Enterococcus faecalis; Enterococcus spp.; Food safety; Pre-harvest tomatoes; Soil; Water