Occurrence of Aliarcobacter spp. in fresh and pre-cut vegetables of common use in San José, Costa Rica.

Aliarcobacter is a Gram-negative rod that can cause disease in both animals and humans. Several studies have evidenced its presence in a wide variety of foods. Given that the number of foodborne illness outbreaks linked to the consumption of vegetables has increased worldwide and that there is a lack of information about the occurrence of Aliarcobacter spp. in these, the aim of this study was to evaluate its presence and the occurrence of virulence factors in both fresh and ready-to-eat vegetable samples. 180 vegetable samples from Costa Rica were analyzed for the presence of Aliarcobacter spp., including 90 pre-cut vegetable packages and 90 fresh vegetables. Two (2.2%) of the isolates from pre-cut vegetables and 19 (21.1%) of the isolates obtained from fresh vegetables were confirmed as Aliarcobacter spp. One of the isolates from the pre-cut vegetable samples was identified as A. butzleri. For the fresh vegetables, 11 isolates were identified as A. skirrowii, one as A. butzleri, and the 7 remaining isolates could not be identified at a species level. There is an 87.5% positivity for hecA and 93.8% for pldA, virulence genes in strains isolated from fresh produce, contrasting with an absolute absence from pre-cut vegetable-isolated strains. These results evidence the presence of Aliarcobacter on fresh and pre-cut vegetables from Costa Rica and the potential hazard it might represent for public health.

Modelling the Effect of Salt Concentration on the Fate of Listeria monocytogenes Isolated from Costa Rican Fresh Cheeses.

"Turrialba cheese" is a Costa Rican fresh cheese highly appreciated due to its sensory characteristics and artisanal production. As a ready-to-eat dairy product, its formulation could support Listeria monocytogenes growth. L. monocytogenes was isolated from 14.06% of the samples and the pathogen was able to grow under all tested conditions. Due to the increasing demand for low-salt products, the objective of this study was to determine the effect of salt concentration on the growth of pathogen isolates obtained from local cheese. Products from retail outlets in Costa Rica were analyzed for L. monocytogenes. These isolates were used to determine growth at 4 °C for different salt concentration (0.5-5.2%). Kinetic curves were built and primary and secondary models developed. Finally, a validation study was performed using literature data. The R2 and Standard Error of fit of primary models were ranked from 0.964-0.993, and 0.197-0.443, respectively. An inverse relationship was observed between growth rate and salt concentration. A secondary model was obtained, with R2 = 0.962. The model was validated, and all values were Bf > 1, thus providing fail-safe estimations. These data were added to the free and easy-to-use predictive microbiology software "microHibro" which is used by food producers and regulators to assist in decision-making.

Presence of Listeria monocytogenes in Ready-to-Eat Meat Products Sold at Retail Stores in Costa Rica and Analysis of Contributing Factors.

ABSTRACT: Listeria monocytogenes is a pathogenic bacterium associated with ready-to-eat (RTE) meat products sold at the retail level. The objective of this research was to determine the prevalence of L. monocytogenes in RTE meat products sold at retail in Costa Rica and to study the factors associated with the levels of contamination; analyzed factors include hygienic practices within stores (cutting techniques and microbial contamination of products) and the behavior of the isolates (persistence against antimicrobials and transfer potential). A total of 190 samples of RTE meat products were collected and analyzed for the presence of coliforms and Listeria spp. Isolates of L. monocytogenes were then evaluated in terms of resistance to disinfectants (quaternary ammonium compound [QAC] and chlorine) and their transfer potential from food contact surfaces (knife and cutting boards). Overall Listeria spp. prevalence was 37.4% (71 of 190); Listeria innocua was present in 32.1% (61 of 190) of the products, and L. monocytogenes was found in just 2.6% (5 of 190) of the samples. Most contaminated samples were cut with a knife at the moment of purchase (44.2%). When analyzing practices within the stores, it was observed that L. monocytogenes transfer from inoculated knife to salchichón was higher for samples cut at the beginning of the experiment. In addition, L. monocytogenes transfer from inoculated cutting boards was independent of the number of slices but contamination from plastic was higher than wood. Regarding L. monocytogenes resistance to disinfectants, average reductions of 2.6 ± 1.1 log CFU/mL were detected after 6 min of exposure to 200 ppm of chlorine; however, chlorine resistance varied among the strains. Prevalence of L. monocytogenes in RTE meat products sold at retail could be associated with handling practices within the stores; further studies are necessary to estimate the impact of these practices on the overall risk for consumers.

Effects of oxytetracycline on the performance and activity of biomixtures: Removal of herbicides and mineralization of chlorpyrifos.

Biopurification systems (BPS) are design to remove pesticides from agricultural wastewater. This work assays for the first time the potential effect of an antibiotic of agricultural use (oxytetracycline, OTC) on the performance of a biomixture (biologically active core of BPS), considering that antibiotic-containing wastewaters are also produced in agricultural labors. The respiration of the biomixture was stimulated in the presence of increasing doses of OTC (≥100mgkg-1), and only slightly increased with lower doses (≤10mgkg-1). When co-applied during the removal of chlorpyrifos, OTC increased chlorpyrifos mineralization rates at low doses, resembling a hormetic effect. The biomixture was also able to remove three herbicides (atrazine, ametryn and linuron) with half-lives of 24.3 d, 43.9 d and 30.7 d; during co-application of OTC at a biomixture-relevant concentration, only the removal of ametryn was significantly inhibited, increasing its half-life to 92.4 d. Ecotoxicological assays revealed that detoxification takes place in the biomixture during the removal of herbicides in the presence of OTC. Overall results suggest that co-application of OTC in a biomixture does not negatively affect the performance of the matrix in every case; moreover, the co-application of this antibiotic could improve the mineralization of some pesticides.

Simultaneous removal of structurally different pesticides in a biomixture: Detoxification and effect of oxytetracycline.

The biopurification systems (BPS) used for the treatment of pesticide-containing wastewater must present a versatile degrading ability, in order to remove different active ingredients according to the crop protection programs. This work aimed to assay the simultaneous removal of several pesticides (combinations of herbicides/insecticides/fungicides, or insecticides/fungicides) in a biomixture used in a BPS over a period of 115 d, and in the presence of oxytetracycline (OTC), an antibiotic of agricultural use that could be present in wastewater from agricultural pesticide application practices. The biomixture was able to mostly remove the herbicides during the treatment (removal rates: atrazine ≈ linuron > ametryn), and suffered no inhibition by OTC (only slightly for ametryn). Two fungicides (carbendazim and metalaxyl) were removed, nonetheless, in the systems containing only fungicides and insecticides, a clear increase in their half-lives was obtained in the treatments containing OTC. The neonicotinoid insecticides (imidacloprid and thiamethoxam) and the triazole fungicides (tebuconazole and triadimenol) were not significantly eliminated in the biomixture. Globally, the total removal of active ingredients ranged from 40.9% to 61.2% depending on the system, following the pattern: herbicides > fungicides > insecticides. The ecotoxicological analysis of the process revealed no detoxification towards the microcrustacean Daphnia magna, but a significant decay in the phytotoxicity towards Lactuca sativa in some cases, according to seed germination tests; in this case, OTC proved to be partially responsible for the phytotoxicity. The patterns of pesticide removal and detoxification provide inputs for the improvement of BPS use and their relevance as devices for wastewater treatment according to specific pesticide application programs.