Microbial dynamics of indicator microorganisms on fresh tomatoes in the supply chain from Mexico to the USA.

Quality and safety of fresh produce are important to public health and maintaining commerce between Mexico and USA. While preventive practices can reduce risks of contamination and are generally successful, the variable environment of the supply chain of fresh produce can be suitable for introduction or proliferation of pathogenic microorganisms. As routine surveillance of these pathogens is not practical, indicator microorganisms are used to assess the sanitary conditions of production and handling environments. An opportunity exists to use indicators on fresh produce to measure how handling and transport from field to market may affect microbial populations that contribute to their quality or safety. The objective was to quantify indicator microorganisms on tomatoes sampled along the supply chain during the harvest year, in order to observe the levels and changes of populations at different locations. Roma tomatoes (n=475) were taken from the same lots (n=28) at four locations of the postharvest supply chain over five months: at arrival to and departure from the packinghouse in México, at the distribution center in Texas, and at retail in USA. Samples were analyzed individually for four microbial populations: aerobic plate count (APC), total coliforms (TC), generic Escherichia coli, and yeasts and molds (YM). APC population differed (p<0.05) from 1.9±1.1, 1.7±1.1, 2.3±1.1 and 3.5±1.4logCFU/g at postharvest, packing, distribution center and supermarket, respectively. TC populations were <1logCFU/g at postharvest, increased at packing (0.7±1.0logCFU/g), decreased in distribution (0.4±0.8logCFU/g) and increased in supermarkets (1.4±1.5logCFU/g). Generic E. coli was not identified from coliform populations in this supply chain. YM populations remained <1logCFU/g, with the exception of 1.1±1.3logCFU/g at supermarkets and tomatoes were not visibly spoiled. The levels reported from this pilot study demonstrated the dynamics within populations as influenced by time and conditions in one supply chain during a harvest year, while the large variances in some locations indicate opportunities for improvement. Overall, packinghouse and supermarket locations were identified as crucial points to control microbial safety risks.

Ability of Hand Hygiene Interventions Using Alcohol-Based Hand Sanitizers and Soap To Reduce Microbial Load on Farmworker Hands Soiled during Harvest.

Effective hand hygiene is essential to prevent the spread of pathogens on produce farms and reduce foodborne illness. The U.S. Food and Drug Administration Food Safety Modernization Act Proposed Rule for Produce Safety recommends the use of soap and running water for hand hygiene of produce handlers. The use of alcohol-based hand sanitizer (ABHS) may be an effective alternative hygiene intervention where access to water is limited. There are no published data on the efficacy of either soap or ABHS-based interventions to reduce microbial contamination in agricultural settings. The goal of this study was to assess the ability of two soap-based (traditional or pumice) and two ABHS-based (label-use or two-step) hygiene interventions to reduce microbes (coliforms, Escherichia coli, and Enterococcus spp.) and soil (absorbance of hand rinsate at 600 nm [A600]) on farmworker hands after harvesting produce, compared with the results for a no-hand-hygiene control. With no hand hygiene, farmworker hands were soiled (median A600, 0.48) and had high concentrations of coliforms (geometric mean, 3.4 log CFU per hand) and Enterococcus spp. (geometric mean, 5.3 log CFU per hand) after 1 to 2 h of harvesting tomatoes. Differences in microbial loads in comparison to the loads in the control group varied by indicator organism and hygiene intervention (0 to 2.3 log CFU per hand). All interventions yielded lower concentrations of Enterococcus spp. and E. coli (P < 0.05), but not of coliforms, than were found in the control group. The two-step ABHS intervention led to significantly lower concentrations of coliforms and Enterococcus spp. than the pumice soap and label-use ABHS interventions (P < 0.05) and was the only intervention to yield significantly fewer samples with E. coli than were found in the control group (P < 0.05). All interventions removed soil from hands (P < 0.05), soap-based interventions more so than ABHS-based interventions (P < 0.05). ABHS-based interventions were equally as effective as hand washing with soap at reducing indicator organisms on farmworker hands. Based on these results, ABHS is an efficacious hand hygiene solution for produce handlers, even on soiled hands.

Validation of a novel rinse and filtration method for efficient processing of fresh produce samples for microbiological indicator enumeration.

Several methods have been described to prepare fresh produce samples for microbiological analysis, each with its own advantages and disadvantages. The aim of this study was to compare the performance of a novel combined rinse and membrane filtration method to two alternative sample preparation methods for the quantification of indicator microorganisms from fresh produce. Decontaminated cantaloupe melons and jalapeño peppers were surface inoculated with a cocktail containing 10(6) CFU/ml Escherichia coli, Salmonella Typhimurium, and Enterococcus faecalis. Samples were processed using a rinse and filtration method, homogenization by stomacher, or a sponge-rubbing method, followed by quantification of bacterial load using culture methods. Recovery efficiencies of the three methods were compared. On inoculated cantaloupes, the rinse and filtration method had higher recovery of coliforms (0.95 log CFU/ml higher recovery, P = 0.0193) than the sponge-rubbing method. Similarly, on inoculated jalapeños, the rinse and filtration method had higher recovery for coliforms (0.84 log CFU/ml higher, P = 0.0130) and E. coli (1.46 log CFU/ml higher, P < 0.0001) than the sponge-rubbing method. For jalapeños, the rinse and filtration method outperformed the homogenization method for all three indicators (0.79 to 1.71 log CFU/ml higher, P values ranging from 0.0075 to 0.0002). The precision of the three methods was also compared. The precision of the rinse and filtration method was similar to that of the other methods for recovery of two of three indicators from cantaloupe (E. coli P = 0.7685, E. faecalis P = 0.1545) and was more precise for recovery of two of three indicators from jalapeño (coliforms P = 0.0026, E. coli P = 0.0243). Overall, the rinse and filtration method performed equivalent to, and sometimes better than, either of the compared methods. The rinse and filtration method may have logistical advantages when processing large numbers of samples, improving sampling efficiency and facilitating microbial detection.

Endothelial epithelial sodium channel inhibition activates endothelial nitric oxide synthase via phosphoinositide 3-kinase/Akt in small-diameter mesenteric arteries.

Recent studies have shown that the epithelial sodium channel (ENaC) is expressed in vascular tissue. However, the role that ENaC may play in the responses to vasoconstrictors and NO production has yet to be addressed. In this study, the contractile responses of perfused pressurized small-diameter rat mesenteric arteries to phenylephrine and serotonin were reduced by ENaC blockade with amiloride (75.1+/-3.2% and 16.9+/-2.3% of control values, respectively; P<0.01) that was dose dependent (EC(50)=88.9+/-1.6 nmol/L). Incubation with benzamil, another ENaC blocker, had similar effects. alpha, beta, and gamma ENaC were identified in small-diameter rat mesenteric arteries using RT-PCR and Western blot with specific antibodies. In situ hybridization and immunohistochemistry localized ENaC expression to the tunica media and endothelium of small-diameter rat mesenteric arteries. Patch-clamp experiments demonstrated that primary cultures of mesenteric artery endothelial cells expressed amiloride-sensitive sodium currents. Mechanical ablation of the endothelium or inhibition of eNOS with N(omega)-nitro-L-arginine inhibited the reduction in contractility caused by ENaC blockers. ENaC inhibitors increased eNOS phosphorylation (Ser 1177) and Akt phosphorylation (Ser 473). The presence of the phosphoinositide 3-kinase inhibitor LY294002 blunted Akt phosphorylation and eNOS phosphorylation and the decrease in the response to phenylephrine caused by blockers of ENaC, indicating that the phosphoinositide 3-kinase/Akt pathway was activated after ENaC inhibition. Finally, we observed that the effects of blockers of ENaC were flow dependent and that the vasodilatory response to shear stress was enhanced by ENaC blockade. Our results identify a previously unappreciated role for ENaC as a negative modulator of eNOS and NO production in resistance arteries.

Stycholysin II, a cytolysin from the sea anemone Stichodactyla helianthus promotes higher hemolysis in aged red blood cells.

We have investigated the relationship between the status of red blood cells (RBCs) and their susceptibility to toxin sticholysin II (StII) hemolytic activity; we have evaluated this effect in different RBC ensembles, comprising young and old cells, and in cells partially damaged by their pre-exposition to a free radical source. Upon action of StII, young cell populations are less prone to hemolysis than the whole population, while old cell populations and peroxyl-oxidized red cells are lysed faster than the whole population. Cell K(+) content was higher in young cells and lower in both senescent cells and in peroxyl-damaged cells relative to whole cell population. The relevance of cell K(+) content in St II-induced lysis was shown when external Na(+) was partially replaced by K(+); under this condition, RBC lysed faster in the presence of St II but no difference was observed among young cells, whole cells population and peroxyl-damaged cells; only old cells lysed faster that the whole population, response that can be due to an enhanced St II-induced pore formation as supported by evaluation of St II irreversible binding to RBC. It is concluded that this factor and the amount of intracellular K(+) are the dominant parameters that modulate the resistance of RBC to St II-induced lysis.