Comparison of Peracetic Acid and Chlorine Effectiveness during Fresh-Cut Vegetable Processing at Industrial Scale

ABSTRACT

This study was conducted to compare the efficacy of two sanitizing agents, chlorine and peracetic acid (PAA), in reducing spoilage and pathogenic microorganisms and disinfection by-products in the washing stage of three types of minimally processed vegetables: iceberg lettuce, carrots, and baby leaves. These fresh-cut products are consumed uncooked; thus, proper sanitation is essential in preventing foodborne illness outbreaks. The comparison was done at industrial scale with equipment already used in the fresh-cut industry and with washers designed and manufactured for this purpose. Results showed that for washing water hygiene and final product microbial quality, the use of PAA or chlorine had similar efficacy. Different scenarios combining PAA, chlorine, and water were tested, simulating the current industrial processes for each of the tested vegetables. Overall, results confirmed that the use of a sanitizer, PAA or chlorine, in the washing water is effective for the prevention of cross-contamination during the washing process and hence for produce food safety. For final product microbiological quality and shelf life, the use of chlorine or PAA showed no significant differences in lettuce or baby leaves. Chlorinated disinfection by-products in processing water were not formed in significant amounts when washing water was treated with PAA in all scenarios and for all tested vegetables, whereas washing with chlorine (80 mg/L) generated important amounts of trihalomethanes, chlorates, and chlorites. Although chlorates and chlorites were always below the recommended levels or legal limits established for drinking water, trihalomethanes exceeded the legal limits. For perchlorates, values were below the quantification limit in all scenarios. Our results show that PAA is a reliable alternative to chlorine disinfection strategies in the fresh-cut industry.

HIGHLIGHTS

[Preliminary results of the Spanish Society of Nephrology multicenter study of quality performance measures: hemodialysis outcomes can be improved]

INTRODUCTION

The Spanish Society of Nephrology "Quality in Nephrology Working Group" (QNWG) was created in 2002. The aims of this group are the identification, diffusion, implementation and consolidation of a systematic, objective and comprehensive set of quality performance measures (QPMs) to help along the improvement of patient care and outcomes on hemodialysis, by means of strategies of feedback and benchmarking, and the design of quality improvement projects. The objective of this study is to present the preliminary results of a set of quality performance measures obtained in a group of Spanish hemodialysis centers, as well as to evaluate the repercussion of the application of the aforementioned thecniques on the observed results.

METHODS

During 2007 a total of 28 hemodialysis units participated in the study; 2516 patients were evaluated. A specific software was designed and used to facilitate the calculation of CPMs in each unit. The clinical indicators used refered to dialysis adequacy; anemia; mineral metabolisme; nutrition; viral infections; vascular access; mortality, morbidity (number and days of hospital admissions); and renal transplant. Every three months each center received its own data and its comparison with the rest of the group.

RESULTS

Except for hemoglobin levels we observed a global improvement. The percentage of centers reaching the stablished standards defined by the QNWG passed from 65% to 90,9% for Kt/V Daugirdas II (> 1,3 in > that 80% of the patients); from 71,4 % to 77,2 % for PTH (> 30 % of patients with serum PTH between 150 and 300 pg/ml); and from 42,8 % to 63,5 % for phosphate (> 75 % of patients with a serum phsphate < 5,5 mg/dl). More than 50% of centers showed an improvement in their final results as compared with their own initial results in all analyzed CPMs. Those centers that did not obtained an improvement in their results started the study with better percentages of acomplishment than those that showed a significant improvement in QPMs. (80,6+/-15,4 versus 71,8+/-16,6 respectively; p<0,001)

CONCLUSIONS

We are starting to make progresses in our knowledge of clinical results in our hemodialysis units, although there is still a long way to go over. To monitor and share CPMs results within hemodialysis centers might help to improve their results as well as to reduce intecenters variability.

Inactivation of Salmonella Senftenberg 775W by ultrasonic waves under pressure at different water activities

The inactivation of Salmonella Senftenberg 775W by ultrasonic waves (20 kHz, 117 microm) under pressure (175 kPa) treatments at sublethal (manosonication; MS) and lethal temperatures (manothermosonication; MTS) in media of different water activities has been investigated. Heat decimal reduction time values increased up to eighteen fold when the water activity was decreased from >0.99 to 0.93 at 65 degrees C, but hardly increased the MS resistance. In reduced water activity media (a(w) of 0.96 and 0.93) a synergistic lethal effect was observed between heat and ultrasound under pressure, being the inactivation rate of Salmonella Senftenberg 775W three times faster than the expected additive rate considering an effect of both bacterial lethal processes. An empirical mathematical equation enabled to predict the D(MS) and D(MTS) values obtained at different temperatures and a(w) in the ranges investigated of Salmonella serovars and also the microbial level of inactivation due to the synergistic lethal effect of MTS treatments in media of reduced a(w). This work could be useful for improving sanitation and preservation treatments of foods, especially those in which components protect microorganisms to heat.

[Late nephrology referral influences on morbidity and mortality of hemodialysis patients. A provincial study]

OBJECTIVE

To evaluate the influence of late referral to nephrology of the patients with chronic renal failure in the morbimortality of the patients who start hemodialysis. SUBJETS AND METHODS: There were included in the study the patients who started hemodialysis (HD) as first form of treatment, and that survived at least three months in both hospitals of reference of the province of Huesca from january 1990 to december 2001. Patients who started HD after acute renal failure were excluded. Clinical and analytical data were determined for each patient at the start of HD and during the follow-up. Early (ER) and late referral (LR) were defined by the time of first nephrology encounter greather than or less than 4 months respectively, before HD initiation. Morbidity analysis (using multiple linear regression with rate of days of hospitalization as dependent variable) and global and anual during the first three years of follow-up survival analysis (using Cox proportional hazards regression) were carried out.

RESULTS

A total of 139 patients (78%) started HD in the ER group and 39 (22%) in LR group. Mean follow-up was similar in both (ER = 34.43 +/- 25.5 months; LR = 34.42 +/- 28.37 months). At the start of dialysis LR was associated to higher proportion of temporary catheters, lower level of hematocrit and albumin, higher comorbidity and higher levels of urea and creatinine. Risk factors selected by the model in the morbidity analysis were index of comorbidity (CI), late referral, serum albumin, urea reduction ratio (URR) and hematocrit (R2 = 0.334, F = 16.97, p < 0.005). The final equation of regression was: Rate of hospitalization's days = 101.12 + (2.45 x CI) - (12. 11 x LR) - (11.57 x Alb.) - (0.43 x PRU) - (0.83 x Hto). Variables selected by Cox's regression model that were associated with survival throughout complete follow-up were hematocrit (RR = -0,207, CI 95% 0.726-0.910, p < 0.0005), index of comorbidity (RR = 0,265, CI 95% 1.066-1.594, p = 0.007), PRU (RR = - 0,059, CI 95% 0.893-0.996, p = 0.038) and type of dialysis membrane (RR = 0,771, Cl 95% 0.260-0.822, p = 0.007). Nevertheless, in successive models fitting after 12, 24 and 36 months of follow-up the variable LR influenced in an independent way survival first two years, losing his significance later.

CONCLUSION

In our study patients of the group LR presented a worse clinical and metabolic situation at the beginning of the HD. Later there was demonstrated in this group a higher long-term morbidity and a lower survival the first two years.

Inactivation kinetics of Yersinia enterocolitica by citric and lactic acid at different temperatures

Inactivation of Yersinia enterocolitica by citric (1--20% w/v) and lactic (0.3--4.0% v/v) acids at different temperatures (4, 20, 40 degrees C) has been investigated. Inactivation effect of citric and lactic acids was dependent on time and temperature of exposure and acid concentration. Survival curves of Y. enterocolitica suspended in citric acid solutions at 4 and 20 degrees C displayed a shoulder followed by an exponential inactivation, but at 40 degrees C a shoulder was not observed. At all temperatures investigated, survival curves of Y. enterocolitica suspended in lactic acid solutions were linear or slightly concave upwards. A mathematical model based on the Weibull distribution accurately described the kinetics of inactivation of Y. enterocolitica by both acids. The influence of the citric acid concentration on Y. enterocolitica resistance was independent of the treatment temperature. However for lactic acid, the influence of the acid concentration on microbial inactivation depended on the temperature. At any temperature investigated, lactic acid was significantly more effective than citric acid.

Comparison of the chlorine inactivation of Yersinia enterocolitica in chlorine demand and demand-free systems

Inactivation of Yersinia enterocolitica by chlorine (0.6 to 20 ppm) was investigated in distilled water and in tryptic soy broth (TSB, 0.015%) at different temperatures (4, 20, and 40 degrees C). In distilled water, chlorine inactivation of Y. enterocolitica was enhanced by increasing the temperature from 4 to 20 degrees C, and survival curves were described by a model that assumed first-order kinetics followed by tailing in which the microbial concentration remained constant. The presence of TSB increased chlorine resistance of Y. enterocolitica, and survival curves were concave downward. These survival curves were described by a model based on the Weibull distribution. Chlorine decay in distilled water was independent of temperature and of the initial concentration of available chlorine and was modeled by first-order reaction kinetics. Chlorine decay in TSB was independent of the initial chlorine concentration but depended on the treatment temperature and was modeled by the addition of two first-order decay equations. The increased resistance of Y. enterocolitica to chlorine in TSB was not due only to the chlorine demand by the TSB components. These components protected Y. enterocolitica cells from the antimicrobial effect of chlorine.

Membrane damage and microbial inactivation by chlorine in the absence and presence of a chlorine-demanding substrate

The relationship between cell inactivation and membrane damage was studied in two gram-positive organisms, Listeria monocytogenes and Bacillus subtilis, and two gram-negative organisms, Yersinia enterocolitica and Escherichia coli, exposed to chlorine in the absence and presence of 150 ppm of organic matter (Trypticase soy broth). L. monocytogenes and B. subtilis were more resistant to chlorine in distilled water. The addition of small amounts of organic matter to the chlorination medium drastically increased the resistance of both types of microorganisms, but this effect was more marked in Y. enterocolitica and E. coli. In addition, the survival curves for these microorganisms in the presence of organic matter had a prolonged shoulder. Sublethal injury was not detected under most experimental conditions, and only gram-positive cells treated in distilled water showed a relevant degree of injury. The exposure of bacterial cells to chlorine in distilled water caused extensive permeabilization of the cytoplasmic membrane, but the concentrations required were much higher than those needed to inactivate cells. Therefore, there was no relationship between the occurrence of membrane permeabilization and cell death. The addition of organic matter to the treatment medium stabilized the cytoplasmic membrane against permeabilization in both the gram-positive and gram-negative bacteria investigated. Exposure of E. coli cells to the outer membrane-permeabilizing agent EDTA increased their sensitivity to chlorine and caused the shoulders in the survival curves to disappear. Based on these observations, we propose that bacterial envelopes could play a role in cell inactivation by modulating the access of chlorine to the key targets within the cell.

[Huesca and Teruel survey on hemodialysis management]

A cross sectional study was performed in order to evaluate the treatment conditions and medical outcomes among 131 prevalent hemodialysis patients (57% males; mean age 66 +/- 12 years) in Huesca and Teruel. Data were collected at 5 hemodialysis units in Huesca and Teruel. Diabetes mellitus, at 30 percent, was the most common cause of renal insufficiency. The mean (+/- SD) urea-reduction ratio (URR) was 66.0 +/- 8.8%. We observed that 56.5% of the population reached an URR higher than 65%. The duration of dialysis session was 220 +/- 24 minutes, with a rate of blood flow 297 +/- 47 ml/min. 36% of patients used high-flux membranes. The patterns of vascular access were: 69% arteriovenous fistula, 5% synthetic graft and 26% catheter. Eighty nine percent of patients were treated with erythropoietin. The mean dose of erythropoietin was 109 +/- 62 UI/Kg weight/week. Thirty nine percent of patients had haemoglobin below 11.0 g/dl (mean 11.2 +/- 1.4 g/dl). Ferritin levels were below 100 ng/ml in 24% of the patients and 25% showed a transferrin saturation index below 20%. Fifty percent of patients were receiving vitamin D. Serum calcium 9.3 +/- 0.8 mg/dl; phosphorous 5.5 +/- 1.5 mg/dl; calcium-phosphorous product 51.5 +/- 14.3 mg/dl; PTHi 433 +/- 459 pg/ml; and aluminium 26.8 +/- 14.5 mcg/l were the mean of main biochemical markers of mineral metabolism. Sixty eight percent of patients had phosphorous levels below 6.0 mg/dl. Thirty seven percent of patients had aluminium levels lower than 20 mcg/l. The mean serum albumin was 3.4 +/- 0.4 g/dl. Forty five percent of patients had albumin below 3.5 g/dl.

[Study of immutable variables determining rHuEPO dose requirements on hemodialysis patients]

Patients receiving recombinant human erythropoietin (rHuEPO) therapy show wide variability in their responsiveness to the drug. Variables that affect rHuEPO dose requirements can be broadly divided into modificable and immutable characteristics. Most of the scientific research on rHuEPO hyporesponsiveness has focused on modificable variables (iron status, dialysis adequacy), while immutable variables such as gender, etiology of chronic renal failure (CRF) and age have been insufficiently explored. A cross sectional study was performed in order to evaluate if immutable patient characteristics determine rHuEPO dose requirements among 215 patients (52% males; mean age 66 +/- 14 years) on hemodialysis (HD) for more than twelve months. Data were collected at 10 hemodialysis units in Aragon. Patients were divided into three groups according to their gender, their cause of CRF (diabetic nephropathy, vascular nephropathy, tubulointerstitial nephropathy and primary glomerulonephritis) and their age (younger than 60 years, from 60 to 75 years, older than 75 years). Despite a similar dose of rHuEPO, women had lower mean hemoglobin (11.1 +/- 1.5 versus 11.6 +/- 1.7 g/dl; p = 0.0258) than men. The greater hemoglobin in men than women may be attributed to greater serum albumin in men (3.5 +/- 0.3 versus 3.7 +/- 0.3 mg/dl; p = 0.0001). Requirements of rHuEPO were higher in the patients with etiology of primary glomerulonephritis compared with those with the other etiologies, even those with diabetic nephropathy (p = 0.0374). The rHuE-PO doses required to obtain similar hemoglobin levels were higher in patients younger than 60 years (p = 0.0249). We conclude that women, patients with primary glomerulonephritis as cause of CRF, and patients younger than 60 years showed the highest requirements of rHuEPO doses.

Relationship between inactivation kinetics of a Listeria monocytogenes suspension by chlorine and its chlorine demand

AIMS

Chlorine demand by Listeria monocytogenes cells and inactivation of L. monocytogenes by chlorine (0.6-1.0 mg l(-1)) at different temperatures (4, 20 and 30 degrees C) have been investigated in a batch reactor.

METHODS AND RESULTS

Chlorine demand depended on the microbial concentration and was independent on the initial chlorine concentration and temperature. Chlorine decay was modelled by the addition of two first-order decay equations. Inactivation of L. monocytogenes by chlorine depended on the initial microbial concentration, initial chlorine concentration and temperature. A mathematical model based on a biphasic inactivation properly described survival curves of L. monocytogenes and a tertiary model was developed that satisfactorily predicted the inactivation of L. monocytogenes by different concentrations of initial chlorine at different temperatures.

CONCLUSIONS

Both available chlorine decay and inactivation of L. monocytogenes by chlorine were biphasic and can be modelled by a two-term exponential model.

SIGNIFICANCE AND IMPACT OF THE STUDY

The biphasic nature of survival curves of L. monocytogenes did not reflect the effect of a change of available chlorine concentration during the treatment. The microbial inactivation was caused by successive reactions that occur after the consumption of the chlorine by the bacterial cell components.

Kidney allograft biopsy: a valuable tool in assessing the diagnosis of acute rejection

In order to determine the value of an isolated renal percutaneous biopsy in renal allografts with acute rejection, we studied 17 allograft nephrectomies, in which the histological degree of acute rejection of each of 30 Tru-cut cylinders, were compared with the histological degree of acute rejection diagnosed in 6 large fragments of each kidney considered as a whole. An accurate histological degree of acute rejection was made in 366 cylinders (71.8%). One hundred twenty-nine kidney cylinders (25.3%) were considered of a minor histological degree of acute rejection and 15 cylinders (2.9%) of a higher histological degree. We conclude that percutaneous renal allograft biopsy provides a representative picture of acute rejection histopathology but must be evaluated with other clinical and biochemical data for a correct clinical management.

Ureteral fistula after renal transplantation: the significance of delayed images

Urinary leakage after renal transplantation is a serious complication that can lead to diagnostic difficulties. A case is reported of urinoma secondary to ureteral fistula characterized in the routine study by a photon-deficient area. Only the image obtained at 6 h allowed a correct diagnosis. The causes for this are discussed and the need to include a delayed study in the follow-up protocol of these patients is emphasized.