Efficacy of Combination Treatment with Sodium Metasilicate and Sodium Hypochlorite for Inactivation of Norovirus on Fresh Vegetables.

In recent years, fresh vegetables have frequently been associated with the foodborne transmission of enteric viruses, such as human norovirus (NoV). Therefore, several studies have focused on developing methods to inactivate foodborne viruses for preventing outbreaks of foodborne illnesses. Sodium hypochlorite (NaOCl) is commonly used as a disinfectant, but results in undesirable effects on the appearance and taste of foods and can generate toxic byproducts when it exceeds the allowable concentration. Here, we evaluated the efficacy of a range of NaOCl concentrations (50-1000 ppm) for reducing the amounts of human NoV (NoV GII.4) on lettuce (Lactuca sativa), celery (Apium graveolens L.), and white cabbage (Brassica oleracea ssp. capitata). In addition, the combination treatment of NaOCl and sodium metasilicate (SMS, 0.1-0.5%) pentahydrate was evaluated for its ability to decrease the populations of NoV GII.4 in the three food samples. An immunomagnetic separation procedure combined with reverse transcription quantitative polymerase chain reaction was used for virus detection. For lettuce, celery, and cabbage, the NoV GII.4 recovery rates were 57.3% ± 6.5%, 52.5% ± 1.7%, and 60.3% ± 3.9%, respectively, using a glycine/NaCl elution buffer (0.25 M glycine/0.14 M NaCl, pH 9.5). The reductions of NoV GII.4 were 3.17, 3.06, and 3.27 log10 genomic copies/µL for lettuce, celery, and cabbage, respectively, at 1000 ppm NaOCl, while a reduction of ∼3 log10 genomic copies/µL was obtained when the samples were treated with a combination of 100 ppm NaOCl and 0.4% SMS pentahydrate. Taken together, these results demonstrated that combined treatment with NaOCl and SMS pentahydrate was an efficient strategy to reduce the concentration of NaOCl for control of NoV GII.4 contamination in fresh vegetables.

Enrichment Broth for the Detection of Campylobacter jejuni and Campylobacter coli in Fresh Produce and Poultry.

Although campylobacteriosis caused by Campylobacter jejuni and Campylobacter coli has been increasingly reported worldwide owing to the consumption of contaminated poultry and fresh produce, the current detection protocols are not selective enough to inhibit unspecific microbes other than these pathogens. Five antibiotics were separately added to Bolton broth, and the survival rates of 18 Campylobacter spp. and 79 non-Campylobacter spp. were evaluated. The survival rate of the non-Campylobacter spp. was the lowest in Bolton broth with rifampin (6.3%), followed by cefsulodin (12.7%), novobiocin (16.5%), and potassium tellurite and sulfamethozaxole (both 17.7%). Also the most effective concentration of rifampin was found to be 12.5 mg/L, which markedly inhibited non-Campylobacter strains while not affecting the survival of Campylobacter strains. After the Campylobacter spp. were enriched in Bolton broth supplemented with 12.5 mg/L rifampin (R-Bolton broth), CampyFood Agar (CFA) was found to be better in selectively isolating the pathogens in the enrichment broth than the International Organization for Standardization method of using modified charcoal cefoperazone deoxycholate agar (mCCDA) for this step. When applied to natural food samples-here, romaine lettuce, pepper, cherry tomato, Korean leek, and chicken-the R-Bolton broth-CFA combination decreased the number of false-positive results by 50.0, 4.2, 20.8, 50.0, and 94.4%, respectively, compared with the International Organization for Standardization method (Bolton broth-mCCDA combination). These results demonstrate that the combination of R-Bolton broth and CFA is more efficient in detecting C. jejuni and C. coli in poultry and fresh produce and thus should replace the Bolton broth-mCCDA combination.