Effectiveness of a peracetic acid solution on Escherichia coli reduction during fresh-cut lettuce processing at the laboratory and industrial scales.

Fresh leafy greens like lettuce can be consumed raw and are susceptible to foodborne pathogens if they become contaminated. Recently, the number of reported pathogenic foodborne outbreaks related to leafy greens has increased. Therefore, it is important to try to alleviate the human health burden associated with these outbreaks. Processing of fresh-cut lettuce, including washing, is a step in the supply chain that needs to be well controlled to avoid cross-contamination. Current measures to control the quality of lettuce during washing include the use of chemicals like chlorine; however, questions regarding the safety of chlorine have prompted research for alternative solutions with peracetic acid (PAA). This study evaluates the effectiveness of a PAA (c.a. 75 mg/L) solution on the reduction of a commensal E. coli strain during the washing of fresh-cut lettuce. Experiments were performed at the laboratory scale and validated at the industrial scale. We observed that the use of PAA was not adversely affected by the organic load in the water. The contact time and dose of the PAA showed to be relevant factors, as observed by the approximately 5-log reduction of E. coli in the water. Results showed that once introduced during washing, E. coli remained attached to the lettuce, thus supporting the need to control for pathogenic bacteria earlier in the supply chain (e.g., during primary production) as well as during washing. Moreover, our results showed that the use of PAA during washing did not have an apparent effect on the levels of fluorescent pseudomonads (FP) and total heterotrophic bacteria (THB) in lettuce. Overall, our results at the laboratory and industrial scales confirmed that during the processing of fresh-cut produce, where the accumulation of soil, debris, and other plant exudates can negatively affect washing, the use of a PAA (c.a. 75 mg/L) solution was an effective and safe wash water disinfectant that can potentially be used at the industrial scale.

Efficacy of chlorine dioxide on Escherichia coli inactivation during pilot-scale fresh-cut lettuce processing.

Controlling water quality is critical in preventing cross-contamination during fresh produce washing. Process wash water (PWW) quality can be controlled by implementing chemical disinfection strategies. The aim of this study was to evaluate the pilot-scale efficacy of chlorine dioxide (ClO2) during processing on the reduction of Escherichia coli in the PWW and on processed fresh-cut 'Lollo Rossa' lettuce. The objective was to have a residual target concentration of either 5 or 3 mg/L ClO2 in the washing tank (3.5 m3) before and during 800 kg of lettuce processing (90 min). After 90 min., a nonpathogenic, non-Extended Spectrum Beta-Lactamase (ESBL) E. coli inoculum from an overnight culture broth (37 °C) was added to the tank resulting in an approximate final level of 106 CFU/mL. PWW and lettuce samples for microbiological and chemical analyses were taken before and after the input and supply halted. ClO2 concentrations quickly decreased after ClO2 input halted, yet a residual concentration of ≥2.5 mg/L and ≥2.1 mg/L ClO2, respectively for 5 and 3 mg/L pilots, was present 12 min after the supply halted. No detectable levels of E. coli (limit of detection 5 log) were determined in the water within 1 min after E. coli was added to the ClO2 containing wash water. Results demonstrated that ClO2 use at the semi-commercial pilot scale was able to reduce the E. coli peak contamination in the PWW. After storage (5 days, 4 °C), background microbial communities (i.e., fluorescent Pseudomonads and total heterotrophic bacteria) grew out on lettuce. Overall, ClO2 decreased the potential for cross-contamination between batches compared to when no sanitizer was used. Chlorate levels of the lettuce sampled before entering the wash water ranged from 7.3-11.6 µg/kg. The chlorate levels of the lettuce sampled after being washed in the ClO2 containing wash water, as well as after rinsing and centrifugation, ranged from 22.8-60.4 µg/kg; chlorite levels ranged from 1.3-1.6 mg/kg, while perchlorate levels were below the limit of quantification (LOQ, <5 ng/g). In this study, we report the semi-commercial pilot-scale evaluation of ClO2, for its ability to maintain the PWW quality and to prevent cross-contamination in the washing tank during fresh-cut lettuce processing. Furthermore, we provide quantitative values of ClO2 disinfection by-products chlorate and chlorite as well as of perchlorate from PWW and/or lettuce samples.

Bacterial Canker (Clavibacter michiganensis subsp. michiganensis) of Tomato in Commercial Seed Produced in Indonesia.

In 2002, Clavibacter michiganensis subsp. michiganensis (Smith) Davis, the causal organism of bacterial canker of tomato (Lycopersicon esculentum), was isolated from two of six commercial asymptomatic tomato seed lots produced on Java in Indonesia. C. michiganensis subsp. michiganensis has not been reported in Indonesia previously. Methods based on the protocol of the International Seed Health Initiative were used to extract and identify the presence of C. michiganensis subsp. michiganensis in tomato seed. C. michiganensis subsp. michiganensis was isolated with dilution plating on the semiselective media D2ANX and mSCM. The identity of the colonies was confirmed by immunofluorescence microscopy, polymerase chain reaction (2), fatty methyl ester analysis, enzyme-linked immunosorbent assay based on monoclonal antibody 103 (1), and a pathogenicity test in which three replicate tomato plants were stem inoculated with 108 cells ml-1. Within 2 weeks, stripes on stems developed that split and exposed reddish brown cavities (stem cankers). The presence of C. michiganensis subsp. michiganensis poses a direct threat on tomato production, which is one of five economically most important vegetable crops in Indonesia. References: (1) A. Alvarez et al. Phytopathology 83:1405, 1993. (2) M. S. Santos et al. Seed Sci. Technol. 25:581, 1997.

[Acute kidney insufficiency in the treatment of psoriasis using fumaric esters]. / Akute Niereninsuffizienz bei der Behandlung der Psoriasis mit Fumarsäure-Estern.

We describe two patients who developed acute renal failure during therapy with fumaric acid-esters. Histologic findings after renal biopsy in one patient were compatible with the diagnosis of acute tubular necrosis (ATN), and renal function was restored after cessation of the medication. The histologic diagnosis in the other patient was tubulo-interstitial nephritis (TIN), possibly reactive to ATN. The recovery of renal function was incomplete after 9 months. Two other patients had deterioration of renal function and proteinuria during therapy with fumaric acid-esters. The symptoms were completely reversible in one patient after discontinuation of the medication, and incompletely reversible in the other. The literature is reviewed and a comparison is drawn with the maleic acid model in the rat.

Occurrence of vascular IgA deposits in clinically normal skin of patients with renal disease.

Skin and kidney biopsies were performed on 262 patients with various nephropathies. In 45 skin biopsy specimens finely granular deposits of predominantly IgA and late-acting complement factors were detected in the walls of superficial capillaries, sometimes concomitantly with IgM, IgG, C4 or a combination of these proteins. Twelve of the 45 patients presented with anaphylactoid purpura and the majority of the other 33 patients had either recurrent macroscopic or microscopic hematuria. The renal lesions in 32 of these 45 patients consisted of focal segmental intracapillary proliferation. In 35 the kidney biopsy specimen showed mesangial deposits of IgA; in one case IgA was deposited along the glomerular basement membrane. In only three of the remaining 217 patients without cutaneous IgA deposits were typical mesangial IgA deposits found. The close correlation between IgA deposits in cutaneous vessels and focal segmental intracapillary proliferation with mesangial IgA deposits suggests that immunofluorescence examination of skin biopsy specimens could prove of diagnostic value. The results provide additional evidence for a close pathogenic relationship between IgA-associated glomerulonephritis and anaphylactoid purpura.