In Situ Evaluation of Paenibacillus alvei in Reducing Carriage of Salmonella enterica Serovar Newport on Whole Tomato Plants

Abstract

dRecently, tomatoes have been implicated as a primary vehicle in food-borne outbreaks of Salmonella enterica serovar Newport and other Salmonella serovars. Long-term intervention measures to reduce Salmonella prevalence on tomatoes remain elusive for growing and postharvest environments. A naturally occurring bacterium identified by 16S rRNA gene sequencing as Paenibacillus alvei was isolated epiphytically from plants native to the Virginia Eastern Shore tomato-growing region. After initial antimicrobial activity screening against Salmonella and 10 other bacterial pathogens associated with the human food supply, strain TS-15 was further used to challenge an attenuated strain of S. Newport on inoculated fruits, leaves, and blossoms of tomato plants in an insect-screened high tunnel with a split-plot design. Survival of Salmonella after inoculation was measured for groups with and those without the antagonist at days 0, 1, 2, and 3 and either day 5 for blossoms or day 6 for fruits and leaves. Strain TS-15 exhibited broad-range antimicrobial activity against both major food-borne pathogens and major bacterial phytopathogens of tomato. After P. alvei strain TS-15 was applied onto the fruits, leaves, and blossoms of tomato plants, the concentration of S. Newport declined significantly (P < 0.05) compared with controls. Astonishingly, >90% of the plants had no detectable levels of Salmonella by day 5 for blossoms. The naturally occurring antagonist strain TS-15 is highly effective in reducing the carriage of Salmonella Newport on whole tomato plants. The application of P. alvei strain TS-15 is a promising approach for reducing the risk of Salmonella contamination during tomato production.

Transmission and Retention of Salmonella enterica by Phytophagous Hemipteran Insects

“…Similarly, infestation and feeding by some phytophagous insects enhanced the persistence of S. enterica on lettuce leaves (13). Persistence and growth of human bacterial pathogens on crop plants increase the chance that an infectious dose would survive until harvest, posing a public health threat (14,15). Thus, the risk of a food-borne illness outbreak due to consumption of contaminated crop plants can be influenced by biotic factors, including phytophagous insects.…”

Identification and Structural Characterization of Naturally-Occurring Broad-Spectrum Cyclic Antibiotics Isolated from Paenibacillus

“…Of particular interest is biocontrol of crop production for food safety applications, where pathogens, including fungal and bacterial growth, can be minimized or prevented by using a bacterial strain or compounds produced by bacteria that are native to the environment and exhibit antibiotic properties [3,4]. Previously, two naturally-occurring gram-positive bacteria identified as Paenibacillus alvei were isolated from plants native to the Virginia Eastern Shore tomato growing region [5,6]. Both strains showed broad-spectrum antimicrobial activity against gram-negative and gram-positive foodborne pathogens.…”

“…Here, we present the detection and identification of broadspectrum antimicrobial compounds produced by an environmentally isolated Paenibacillus alvei strain from plants native in the U.S. to the Virginia Eastern Shore tomato growing region [5,6]. Compounds were first fractionated by off-line ultra-performance liquid chromatography (UPLC), and the bioactivity of each fraction was assessed against gramnegative and -positive bacteria.…”

Effects of nitrogen and potassium fertilization on the susceptibility of tomatoes to post-harvest proliferation of Salmonella enterica

“…Potential routes by which S. enterica and enterovirulent E. coli colonize edible plant parts in the field and under greenhouse conditions have been investigated (Fletcher et al, 2013;Islam et al, 2004;Moyne et al, 2011;Park et al, 2012). Pre-harvest, microbiological quality of fresh produce is affected by the presence of native epiphytic microbiota (including phytopathogens), the types and levels of irrigation, and the use of soil amendments (Allard et al, 2014;Brandl, 2006Brandl, , 2008Brandl and Amundson, 2008;Franz and van Bruggen, 2008;Gu et al, 2013;GutierrezRodriguez et al, 2012;Moyne et al, 2011;Park et al, 2012;PozaCarrion et al, 2013). However, relatively little remains known about the impact of crop production practices on post-harvest susceptibility of raw fruits and vegetables to human pathogens.…”