Plant-Pathogenic Oomycetes, Escherichia coli Strains, and Salmonella spp. Frequently Found in Surface Water Used for Irrigation of Fruit and Vegetable Crops in New York State

While rain and irrigation events have been associated with an increased prevalence of foodborne pathogens in produce production environments, quantitative data are needed to determine the effects of various spatial and temporal factors on the risk of produce contamination following these events. This study was performed to quantify these effects and to determine the impact of rain and irrigation events on the detection frequency and diversity of Listeria species (including L. monocytogenes) and L. monocytogenes in produce fields. Two spinach fields, with high and low predicted risks of L. monocytogenes isolation, were sampled 24, 48, 72, and 144 to 192 h following irrigation and rain events. Predicted risk was a function of the field's proximity to water and roads. Factors were evaluated for their association with Listeria species and L. monocytogenes isolation by using generalized linear mixed models (GLMMs). In total, 1,492 (1,092 soil, 334 leaf, 14 fecal, and 52 water) samples were collected. According to the GLMM, the likelihood of Listeria species and L. monocytogenes isolation from soil samples was highest during the 24 h immediately following an event (odds ratios [ORs] of 7.7 and 25, respectively). Additionally, Listeria species and L. monocytogenes isolates associated with irrigation events showed significantly lower sigB allele type diversity than did isolates associated with precipitation events (P ‫؍‬ <0.001), suggesting that irrigation water may be a point source of L. monocytogenes contamination. Small changes in management practices (e.g., not irrigating fields before harvest) may therefore reduce the risk of L. monocytogenes contamination of fresh produce. Foodborne outbreaks have been increasingly linked to fresh produce in the United States (1-6). In fact, the proportion of foodborne outbreaks that were attributed to produce between 1998 and 2008, 46%, was over twice that attributed to meat, 22% (6). Similarly, between 2002 and 2011, produce-associated outbreaks caused, on average, more illnesses per outbreak than any other food (1). As a result, the safety of fresh produce has come into question, negatively affecting produce growers, the food industry, and local economies (7,8). For example, as a consequence of a 2011 listeriosis outbreak linked to fresh cantaloupes in the United States (9), cantaloupe consumption dropped nationwide by 53% (10). The instability of the cantaloupe market following the 2011 outbreak is indicative of a larger trend of wide-scale consumer avoidance of products associated with outbreaks, even when the outbreak is associated with point source events (7,8). Thus, prevention of produce-associated outbreaks is a key concern of the produce industry. Although most listeriosis outbreaks associated with fresh produce are traced back to processing environments, the prevention of produce contamination in production environments is crucial. In fact, previous studies have shown that low-level sporadic contamination of produce in production environments can result in pathogen pr...

Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 54%

Spatial and Temporal Factors Associated with an Increased Prevalence of Listeria monocytogenes in Spinach Fields in New York State

Weller

Wiedmann

Strawn

2015

“…Use of poultry litter which has been heat treated and pelletized (heat-treated poultry pellets [HTPP]) as a BSAAO may provide sufficient nutrients to leafy green vegetables while minimizing the risk of enteric bacterial contamination associated with untreated manure in the preharvest environment. However, introduction of pathogens through the use of contaminated irrigation water (14,15), scat from wild animals (16), bird droppings (17,18), and runoff from nearby livestock operations (19)(20)(21) are all potential routes that may introduce bacterial pathogens to soils in crop fields, and the presence of HTPP in soil may aid survival, as evidenced by increased growth in soil extracts prepared with HTPP-amended soil (22).…”

mentioning

confidence: 99%

Salmonella enterica in Soils Amended with Heat-Treated Poultry Pellets Survived Longer than Bacteria in Unamended Soils and More Readily Transferred to and Persisted on Spinach

Shah

Bradshaw

Nyarko

et al. 2019

Untreated biological soil amendments of animal origin (BSAAO) are commonly used as biological fertilizers but can harbor foodborne pathogens like Salmonella enterica, leading to potential transfer from soils to fruits and vegetables intended for human consumption. Heat-treated poultry pellets (HTPP) can provide produce growers with a slow-release fertilizer with a minimized risk of pathogen contamination. Little is known about the impact of HTPP-amended soil on the survival of Salmonella enterica. The contributions of RpoS and formation of viable but nonculturable cells to Salmonella survival in soils are also inadequately understood. We quantified the survival of Salmonella enterica subsp. enterica serovar Newport wild-type (WT) and rpoS-deficient (ΔrpoS mutant) strains in HTPP-amended and unamended soil with or without spinach plants over 91 days using culture and quantitative PCR methods with propidium monoazide (PMA-qPCR). Simulated “splash” transfer of S. Newport from soil to spinach was evaluated at 35 and 63 days postinoculation (dpi). The S. Newport WT and ΔrpoS mutant reached the limit of detection, 1.0 log CFU/g (dry weight), in unamended soil after 35 days, whereas 2 to 4 log CFU/g (dry weight) was observed for both WT and ΔrpoS mutant strains at 91 dpi in HTPP-amended soil. S. Newport levels in soils determined by PMA-qPCR and plate count methods were similar (P > 0.05). HTPP-amended soils supported higher levels of S. Newport transfer to and survival on spinach leaves for longer periods of time than did unamended soils (P < 0.05). Salmonella Newport introduced to HTPP-amended soils survived for longer periods and was more likely to transfer to and persist on spinach plants than was S. Newport introduced to unamended soils. IMPORTANCE Heat-treated poultry pellets (HTPP) often are used by fruit and vegetable growers as a slow-release fertilizer. However, contamination of soil on farms may occur through contaminated irrigation water or scat from wild animals. Here, we show that the presence of HTPP in soil led to increased S. Newport survival in soil and to greater likelihood of its transfer to and survival on spinach plants. There were no significant differences in survival durations of WT and ΔrpoS mutant isolates of S. Newport. The statistically similar populations recovered by plate count and estimated by PMA-qPCR for both strains in the amended and unamended soils in this study indicate that all viable populations of S. Newport in soils were culturable.

“…Recent investigations have focused on irrigation water as a potential environmental source of Salmonella for preharvest contamination of produce (8)(9)(10)(11)12). Furthermore, the static nature of some irrigation ponds may sustain persistent populations of Salmonella (13,14).…”

mentioning

confidence: 99%

Distribution and Characterization of Salmonella enterica Isolates from Irrigation Ponds in the Southeastern United States

Luo

Ginn

et al. 2015

f Irrigation water has been implicated as a likely source of produce contamination by Salmonella enterica. Therefore, the distribution of S. enterica was surveyed monthly in irrigation ponds (n ‫؍‬ 10) located within a prime agricultural region in southern Georgia and northern Florida. All ponds and 28.2% of all samples (n ‫؍‬ 635) were positive for Salmonella, with an overall geometric mean concentration (0.26 most probable number [MPN]/liter) that was relatively low compared to prior reports for rivers in this region. Salmonella peaks were seasonal; the levels correlated with increased temperature and rainfall (P < 0.05). The numbers and occurrence were significantly higher in water (0.32 MPN/liter and 37% of samples) than in sediment (0.22 MPN/ liter and 17% of samples) but did not vary with depth. Representative isolates (n ‫؍‬ 185) from different ponds, sample types, and seasons were examined for resistance to 15 different antibiotics; most strains were resistant to streptomycin (98.9%), while 20% were multidrug resistant (MDR) for 2 to 6 antibiotics. DiversiLab repetitive extragenic palindromic-element sequence-based PCR (rep-PCR) revealed genetic diversity and showed 43 genotypes among 191 isolates, as defined by >95% similarity. The genotypes did not partition by pond, season, or sample type. Genetic similarity to known serotypes indicated Hadar, Montevideo, and Newport as the most prevalent. All ponds achieved the current safety standards for generic Escherichia coli in agricultural water, and regression modeling showed that the E. coli level was a significant predictor for the probability of Salmonella occurrence. However, persistent populations of Salmonella were widely distributed in irrigation ponds, and the associated risks for produce contamination and subsequent human exposure are unknown, supporting continued surveillance of this pathogen in agricultural settings.