Foodborne Bacterial, Viral, and Protozoan Pathogens in Field and Market Strawberries and Environment of Strawberry Farms

Abstract

Field-grown strawberries, the environment of strawberry farms and fresh strawberries from marketplaces were examined for bacterial, viral, and protozoan pathogens. The presence of bacteria was determined using culture and real-time PCR (qPCR), presence of protozoa and viruses using qPCR and reverse transcription qPCR, respectively. The highest proportion of positivity was observed for Escherichia coli both in field and purchased strawberries (up to 48.6%). Finding of Cronobacter ranged from 0.6% to 9% both for field and market strawberries. The prevalence of other pathogens (Listeria monocytogenes, Giardia intestinalis, Cryptosporidium sp., and Norovirus) in strawberries was below 4.5%; HAV was not detected at all. Positivity of the environment was determined to be lower than 2.1% for all microorganisms, except for E. coli. The concentration of pathogens in most samples did not exceed 100 CFU/g using culture and 1.8 × 10 2 GE/g of strawberries or swabbing area 6.1 × 10 2 GE/mL or swabbing area of environmental samples using qPCR. All studied farms applied preventive measures such as drip irrigation, avoidance of organic fertilizers, and use of mulch foils or gloves for workers to decrease contamination of strawberries. Despite this, certain pathogens were found in fresh strawberries. Even at low concentrations, these pathogens can be a source of infection for consumers. Thus, their presence in strawberries is of particular significance as these are mostly consumed fresh and without any thermal processing.

Microbiological quality of raw berries and their products: A focus on foodborne pathogens

“…(2017) reported no L. monocytogenes in the fresh-cut strawberries studied. Similar results were found by Dziedzinska et al. (2018), where L. monocytogenes detection was reported as sporadic with only one positive sample from all field strawberries (0.6%) and one positive sample of purchased strawberries (1.4%).…”

“…Blackberry was the only fruit found positive for E. coli which was detected in just two out of 75 berry samples. However, in another study a high proportion of positive samples was observed for E. coli both in field and purchased strawberries (up to 48.6%) but with counts less than 100 cfu g −1 (Dziedzinska et al., 2018). Levels of fecal organisms, such as E. coli are a better indicator of contamination (Nguyen-The and Carlin, 1994) and this could explain why this organism has been included as a hygienic criterion in the EU regulation (No 2073/2005) (Anonymous, 2005).…”

Occurrence of selected viral and bacterial pathogens and microbiological quality of fresh and frozen strawberries sold in Spain

“…(2015) found generic E. coli on only 2 of 72 (2.8 %) of strawberry samples from primary production in Belgium, at concentrations of 1.0 log 10 CFU/g and 3.0 Log 10 CFU/g and Dziedzinska et al (2018) found 9.0 % (14 of 156) of strawberry field samples contaminated with E. coli in the Czech Republic, and 1.4% from marketplaces (1 of 70).…”

“…The incidence of NoV in strawberry matrix can be explained because viral contamination can occur in all parts of food chain (Dziedzinska et al, 2018)…”

MOL-PCR and xMAP Technology

“…Subsequently, 1200 mL of the mixture was applied to the spin column, and the manufacturer's protocol followed. Water samples were processed as previously described in Dziedzinska et al 37 Briefly, water samples (10 L) with pH lowered to 3.5 were passed through negatively charged filters (cellulose nitrate HA Millipore membrane, 0.45-mm pore size; Merck, Darmstadt, Germany). Elution of viral particles by beef extract solution (3% w/v; pH 9.5) in glycine buffer (0.05 mol/L) followed.…”