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Log Reduction (log + reduction)
Selected AbstractsHCV796: A selective nonstructural protein 5B polymerase inhibitor with potent anti-hepatitis C virus activity In Vitro, in mice with chimeric human livers, and in humans infected with hepatitis C virus,HEPATOLOGY, Issue 3 2009Norman M. Kneteman Anti-hepatitis C virus (HCV) drug development has been challenged by a lack of experience with inhibitors inclusive of in vitro, animal model, and clinical study. This manuscript outlines activity and correlation across such a spectrum of models and into clinical trials with a novel selective nonstructural protein 5B (NS5B) polymerase inhibitor, HCV796. Enzyme assays yielded median inhibitory concentration (IC50) values of 0.01 to 0.14 ,M for genotype 1, with half maximal effective concentration (EC50s) of 5 nM and 9 nM against genotype 1a and 1b replicons. In the chimeric mouse model, a 2.02 ± 0.55 log reduction in HCV titer was seen with monotherapy, whereas a suboptimal dose of 30 mg/kg three times per day in combination with interferon demonstrated a 2.44 log reduction (P = 0.001 versus interferon alone) Clinical outcomes in combination with pegylated interferon and ribavirin have revealed additive efficacy in treatment naïve patients. Abnormal liver function test results were observed in 8% of HCV-796 patients treated for over 8 weeks, resulting in suspension of further trial activity. Conclusion: The RNA-dependent RNA polymerase inhibitor HCV796 demonstrated potent anti-HCV activity consistently through enzyme inhibition assays, subgenomic replicon, and chimeric mouse studies. Strong correlations of outcomes in the mouse model were seen with subsequent clinical trials, including a plateau in dose-related antiviral activity and additive impact from combination therapy with interferon. These outcomes demonstrate the utility of the range of in vitro and in vivo models now available for anti-HCV drug development and support the potential utility of polymerase inhibitors in future combination therapies for HCV treatment. (HEPATOLOGY 2009.) [source] Antimicrobial efficiency of titanium dioxide-coated surfacesJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2010P. Muranyi Abstract Aims:, Development and evaluation of an antimicrobially active titanium dioxide coating. Methods and results:, For this purpose, titanium dioxide coatings were applied to glass slides by using a sol-gel method and then exposed to a light source. The antimicrobial efficiency was determined by a count reduction test for selected test strains (Aspergillus niger, Bacillus atrophaeus, Kocuria rhizophila), which were homogenously sprayed onto surface. The bacterial count of K. rhizophila was reduced by up to 3·3 log10 on titanium dioxide samples within 4 h of UV-A light exposure. Experiments with spore formers did not lead to any significant log reduction. A further aspect of this work was to evaluate the effect of selected parameters (relative humidity, inoculation density, radiation intensity) on the antimicrobial efficiency to gain knowledge for further optimization procedures. At a high relative humidity (85% r.h.), increased inactivation was observed for K. rhizophila (up to 5·2 log10). Furthermore, a dependency of the antimicrobial effect on the radiation intensity and the inoculation density was identified. Conclusions:, Antimicrobial surfaces and coatings based on titanium dioxide have the potential to effectively inactivate vegetative micro-organisms. Significance and impact of the study:, Knowledge about the antimicrobial efficiency of titanium dioxide was gained. This is a prerequisite for industrial applications to improve hygiene, food quality and safety. [source] Proposed mechanism of inactivating Escherichia coli O157:H7 by ultra-high pressure in combination with tert -butylhydroquinoneJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008A.S. Malone Abstract Aims:, Investigating mechanisms of lethality enhancement when Escherichia coli O157:H7, and selected E. coli mutants, were exposed to tert -butylhydroquinone (TBHQ) during ultra-high pressure (UHP) treatment. Methods and Results:,Escherichia coli O157:H7 EDL-933, and 14 E. coli K12 strains with mutations in selected genes, were treated with dimethyl sulfoxide solution of TBHQ (15,30 ppm), and processed with UHP (400 MPa, 23 ± 2°C for 5 min). Treatment of wild-type E. coli strains with UHP alone inactivated 2·4,3·7 log CFU ml,1, whereas presence of TBHQ increased UHP lethality by 1·1,6·2 log CFU ml,1; TBHQ without pressure was minimally lethal (0,0·6 log reduction). Response of E. coli K12 mutants to these treatments suggests that iron,sulfur cluster-containing proteins ([Fe,S]-proteins), particularly those related to the sulfur mobilization (SUF system), nitrate metabolism, and intracellular redox potential, are critical to the UHP,TBHQ synergy against E. coli. Mutations in genes maintaining redox homeostasis and anaerobic metabolism were associated with UHP,TBHQ resistance. Conclusions:, The redox cycling activity of cellular [Fe,S]-proteins may oxidize TBHQ, potentially leading to the generation of bactericidal reactive oxygen species. Significance and Impact of the Study:, A mechanism is proposed for the enhanced lethality of UHP by TBHQ against E. coli O157:H7. The results may benefit food processors using UHP,based preservation, and biologists interested in piezophilic micro-organisms. [source] Use of the modified Robbins device to study the in vitro biofilm removal efficacy of NitrAdineÔ, a novel disinfecting formula for the maintenance of oral medical devicesJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2008T. Coenye Abstract Aims:, To evaluate the use of the modified Robbins device (MRD) to test disinfection strategies against biofilms that form on oral medical devices and to test the biofilm removal efficacy of NitrAdineTM, a disinfectant for the maintenance of oral medical devices. Methods and Results:, Biofilms were grown on discs using the MRD and biofilms formed in this system were used to evaluate the efficacy of NitrAdineTM and to determine the optimal disinfection conditions. Our data indicate that the use of the MRD allows for the rapid and reproducible formation of high-density biofilms. Determination of the efficacy of NitrAdineTM revealed high activity against biofilms tested (e.g. >3 log reduction for Candida albicans and Staphylococcus aureus) and allowed the determination of the optimal conditions for its use. Conclusion:, The high reproducibility and flexibility of the MRD make it an excellent candidate for standardized testing of disinfectants aimed at reducing biofilms on oral medical devices. Using this system, we were able to demonstrate that NitrAdineTM exhibits high activity against biofilms formed by the micro-organisms tested. Significance and Impact of the Study:, Our data suggest that our procedure is appropriate for standardized testing of disinfectants aimed at reducing biofilms on oral medical devices. [source] Possible mechanisms for the relative efficacies of ortho -phthalaldehyde and glutaraldehyde against glutaraldehyde-resistant Mycobacterium chelonaeJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2001S.E. Walsh Aims: This investigation compared glutaraldehyde (GTA)-sensitive and -resistant strains of Mycobacterium chelonae and examined the effects of pretreatment of GTA-sensitive and -resistant strains of Myco. chelonae with chemical agents that interfere with cell wall synthesis. Methods and Results: When exposed to 2% (v/v) GTA at 25°C, GTA-resistant strains of Myco. chelonae dried on to glass carriers were not inactivated to any significant extent. By contrast, GTA-sensitive strains of Myco. chelonae and a strain of Myco. terrae suffered a > 6 log reduction in viability in 5 min. However, ortho -phthalaldehyde (OPA; 0·5% w/v) achieved a corresponding inactivation against two GTA-resistant strains within 5,10 and 10,20 min, respectively. Electron microscopy, using a non-aldehyde fixation process and also negative staining, failed to detect any extensive changes in GTA-sensitive and -resistant cultures exposed to GTA or OPA. Thin-layer chromatography was unsuccessful in detecting differences between GTA-resistant and -sensitive strains of Myco. chelonae. However, pretreatment of GTA-resistant cells with mycobacterial cell wall synthesis inhibitors increased their subsequent susceptibility further to OPA but not to GTA. Conclusions:Ortho -phthalaldehyde is an effective new biocidal agent that, at its in-use concentration, is rapidly bactericidal to non-sporulating bacteria, including GTA-sensitive and -resistant mycobacteria. Significance and Impact of the Study: Pretreatment of GTA-resistant cells with mycobacterial cell wall synthesis inhibitors increased their subsequent susceptibility to OPA but not to GTA. [source] INACTIVATION OF STAPHYLOCOCCUS AUREUS EXPOSED TO DENSE-PHASE CARBON DIOXIDE IN A BATCH SYSTEMJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2009HUACHUN HUANG ABSTRACT The inactivation of Staphylococcus aureus exposed to dense-phase carbon dioxide (DPCD) was investigated, and the kinetics of come-up time (CUT) in pressurization was monitored with come-down time (CDT) and temperature fluctuation in depressurization. CUT was about 2.5, 3.5, 4.0 and 4.0 min; CDT was 3.4, 3.7, 4.5 and 4.5 min; lowest temperature of samples in depressurization was 4, ,1, ,15 and ,22C, corresponding to 10, 20, 30 and 40 MPa at 37C. The inactivation behavior of S. aureus was closely related to the variables of process pressure, holding-pressure time (HPT), process temperature and process cycling. The log reduction of S. aureus at 40 MPa for 30-min HPT was significantly greater (P < 0.05), but the inactivation effect at 10, 20 and 30 MPa was similar. The log reduction of S. aureus at 30 and 40 MPa for 60-min HPT was similar and significantly greater (P < 0.05), while the inactivation effect at 10 and 20 MPa was similar. The inactivation of S. aureus against HPT conformed to a fast,slow biphase kinetics; the two stages were well fitted to a first-order model with higher regression coefficients R2 = 1.000 and 0.9238; their respective D values (decimal reduction time) were 16.52 and 70.42 min. As the process temperature increased, the log reduction of S. aureus increased significantly (P < 0.05); the inactivation kinetics of S. aureus versus process temperature was characterized with a fast inactivation rate from 32 to 45C and a slow inactivation rate from 45 to 55C. As compared to one-process cycling for a total of 60-min HPT, four-process cycling resulted in a significant reduction of S. aureus, and its maximal reduction was near to 5 log cycles, indicating that more process cycling caused more inactivation of S. aureus under identical pressure and temperature with equal HPT. However, the maximal reduction was 0.09 and 0.12 log cycles for two- and four-process cyclings with 0-min HPT, indicating that pressurization and depressurization had a lesser effect on the inactivation of S. aureus, while HPT was significant in DPCD to inactivate S. aureus. PRACTICAL APPLICATIONS Dense-phase carbon dioxide (DPCD) is a novel technology to achieve cold pasteurization and/or sterilization of liquid and solid materials, and is likely to replace or partially substitute currently and widely applied thermal processes. This study showed that DPCD effectively inactivated Staphylococcus aureus inoculated in 7.5% sodium chloride broth, and the inactivation behavior of S. aureus was closely related to the pressure, holding-pressure time, temperature and process cycling. Based on this observation, the technology of DPCD can be applied in the pasteurization of foods such as milk and various fruit juices, especially thermal-sensitive materials. [source] VALIDATION OF PATHOGEN DESTRUCTION DURING MANUFACTURE OF A MEAT-BASED POTATO SNACK (CHIPAROO)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2003S. J. KIERAS ABSTRACT A Chiparoo is a comminuted rabbit and sweet potato dehydrated snack chip manufactured using a process suitable for underdeveloped regions of the world. The purpose of this study was to evaluate the ability of the Chiparoo manufacturing process to adequately deliver 5 log reductions in Listeria monocytogenes, Escherichia coli O157:H7, Salmonella typhimurium, and Staphylococcus aureus per gram of food product. These four pathogens were inoculated into regular (pH , 6.0) and lime juice added (pH , 5.0) formulations of rabbit and sweet potato Chiparoos. They were inoculated as a cocktail of four microorganisms at concentrations of approximately 106/g of each pathogen. Individual inoculations of each pathogen at the same concentration (106/g) were also prepared. After inoculation, the product was held for 5 h at 37C, to simulate the maximum hold time in a sub-Saharan Africa manufacturing facility, then dehydrated at 55C (+/- 5C) for 9 h. Samples of the product were taken during the hold and dehydration steps, decimally diluted and plated on the appropriate enumeration medium. The regular formulation (pH , 6.0) did not achieve the required 5 log reduction of each of the four pathogens, while the lime juice added formulation (pH , 5.0) achieved the desired minimum 5 log reduction for each of the four foodborne pathogens tested. [source] WATER ACTIVITY AND THE INACTIVATION OF ENTEROBACTER CLOACAE INOCULATED IN CHOCOLATE LIQUOR AND A MODEL SYSTEM BY PULSED ELECTRIC FIELD TREATMENTJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2002S. MI Effects of water activity (aw) on the inactivation of Enterobacter cloacae inoculated in chocolate liquor and in a model system of 0.1% (w/v) peptone water and glycerol by pulsed electric field (PEF) treatment were investigated. An electric field strength of 24.5 kV/cm, a total treatment time of 320 ,s, a pulse duration time of 4 ,s, a pulse delay time of 15 ,s, and a pulse cycle time of 15 s were selected for PEF treatment. The inactivation ofE. cloacae by PEF increased significantly as aw increased (P < 0. 05). As aw of chocolate liquor increased from 0.48 to 0.89, the log reduction of E. cloacae increased from 0.1 to 1.3. The measured temperature change inside the PEF treatment chamber was 0.4C when the log reduction was 1. 3. Similarly, as aw increased from 0. 51 to 0.91 in the model system, the log reduction increased from 0.4 to 1.3. E. cloacae surviving a low aw environment had high resistance to PEF. PEF inactivated E. cloacae in the chocolate liquor with aw of 0.85 by 1 log at O h incubation. However, the log reduction was only 0.1 when PEF treatment was applied to E. cloacae which was incubated for 2 h in the chocolate liquor with aw of 0.85 before PEF treatment. E. cloacae surviving the low aw environment might have resistance not only to the low aw but also to PEF. The resistance to low aw environment may need to be considered when the inactivation of microorganisms by PEF is evaluated. [source] Pasteurization of Beer by a Continuous Dense-phase CO2 SystemJOURNAL OF FOOD SCIENCE, Issue 3 2006Gillian F. Dagan ABSTRACT: Effects on beer quality were studied after pasteurization by a continuous dense-phase carbon dioxide (DPCD) system. Changes in haze formation, foaming capacity and stability, and objective and subjective aroma and flavor were evaluated, after validation of a 5-log reduction in yeast populations. A maximum log reduction in yeast populations of 7.38 logs was predicted at 26.5 MPa, 21°C, 9.6% CO2, and 4.77 min residence time. Haze was reduced by DPCD pasteurization from 146 nephelometric turbidity units (NTU) to 95 NTU. At this same treatment combination, aroma and flavor of beer sample means were not considered significantly different (P= 0.3415) from fresh beer sample means when evaluated in a difference from control test, using fresh beer as the reference. Foam capacity and stability were affected minimally by CO2 processing; however, changes would most likely be unnoticed by consumers. [source] Wine is Bactericidal to Foodborne PathogensJOURNAL OF FOOD SCIENCE, Issue 9 2004T. Møretrø ABSTRACT: Red and white wines without added sulfite were tested for antibacterial activity against stationary-phase grown cells of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus. The wines had bactericidal activity against all strains, with the red wine being most potent. S. Typhimurium was most sensitive, with 6 log reduction after 10 min exposure to wine, whereas S. aureus appeared least sensitive to the wines. Mutants having the gene encoding the alternative sigma factor disrupted were generally more sensitive to wine than their wild-type counterparts. When different combinations of ethanol, organic acids, and acidity were tested against the pathogens, it was found that a composition of 0.15% malic acid, 0.6% tartaric acid, 15% ethanol, and pH 3.0 had a strong bactericidal effect. The compounds in the mixture seemed to act synergistically against the pathogens. The pathogens grew in 25% to 40% white wine diluted in brain hearth infusion broth, with S. aureus being able to grow at the highest concentration of wine. Preincubation of the bacteria in sublethal concentrations of wine and ethanol and pH 4.5 did not increase their tolerance against wine or against the mixture of organic acids and ethanol. In conclusion, wine had an antibacterial effect against the pathogens tested. The synergistic effect of organic acids, ethanol, and low pH seems to be responsible for a major part of the antibacterial effect of wine. The alternative sigma factors seemed to be involved in protection of the bacteria against wine. [source] Response Surface Modeling for the Inactivation of Escherichia coli O157:H7 on Green Peppers (Capsicum annuum) by Ozone Gas TreatmentJOURNAL OF FOOD SCIENCE, Issue 3 2002Y. Han ABSTRACT: : The effects of ozone gas concentration (2 to 8 mg/l), relative humidity (RH) (60 to 90%), and treatment time (10 to 40 min) on inactivation of E. coli O157:H7 on green peppers were studied using response surface methodology. A 3-factor Box-Behnken experimental plan was designed and microbial log reduction was measured as a response. The statistical analysis of developed predictive model suggested that ozone gas concentration, RH, and treatment time all significantly (P < 0.01) increased the rate of log reduction of E. coli O157:H7. Among the 3 factors, the effect of ozone gas concentration on bacterial inactivation was the greatest, while the effect of RH was the least. The interaction between ozone gas concentration and RH exhibited a significant and synergistic effect (P < 0.05). [source] Treatment of Helicobacter pylori infection with intra-gastric violet light phototherapy: A pilot clinical trial,LASERS IN SURGERY AND MEDICINE, Issue 5 2009Anthony J. Lembo MD Abstract Background and Objective Helicobacter pylori infects the mucus layer of the human stomach and causes peptic ulcers and adenocarcinoma. We have previously shown that H. pylori accumulates photoactive porphyrins making the organism susceptible to inactivation by light, and that small spot endoscopic illumination with violet light reduced bacterial load in human stomachs. This study assessed the feasibility and safety of whole-stomach intra-gastric violet phototherapy for the treatment of H. pylori infection. Study Design/Materials and Methods A controlled, prospective pilot trial was conducted using a novel light source consisting of laser diodes and diffusing fibers to deliver 408-nm illumination at escalating total fluences to the whole stomach. Eighteen adults (10 female) with H. pylori infection were treated at three U.S. academic endoscopy centers. Quantitative bacterial counts were obtained from biopsies taken from the antrum, body, and fundus, and serial urea breath tests. Results The largest reduction in bacterial load was in the antrum (>97%), followed by body (>95%) and fundus (>86%). There was a correlation between log reduction and initial bacterial load in the antrum. There was no dose,response seen with increasing illumination times. The urea breath test results indicated that the bacteria repopulated in days following illumination. Conclusion Intra-gastric violet light phototherapy is feasible and safe and may represent a novel approach to eradication of H. pylori, particularly in patients who have failed standard antibiotic treatment. This was a pilot study involving a small number of patients. Further research is needed to determine if phototherapy can be effective for eradicating H. pylori. Lasers Surg. Med. 41:337,344, 2009. © 2009 Wiley-Liss, Inc. [source] Inactivation of Vibrio parahaemolyticus in pure culture, whole live and half shell oysters (Crassostrea virginica) by X-rayLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2009B.S.M. Mahmoud Abstract Aims:, To study the inactivation effect of different doses of X-ray on Vibrio parahaemolyticus in pure culture, inoculated whole live and half shell oysters and to evaluate the efficacy of X-ray doses on reduction of inherent microflora on oysters. Methods and Results:, X-ray was produced using RS 2400 generator system (Rad Source Technologies Inc.). Pure culture of V. parahaemolyticus, inoculated half and whole shell oysters with V. parahaemolyticus were treated with 0·0, 0·1, 0·5, 0·75, 1·0, 1·5, 2·0, 3·0 and 5·0 kGy X-ray. Surviving bacteria in the pure culture and inoculated oysters, before and after treatment, were enumerated using overlay plating (in TSA then TCBS) and most probable number (MPN) methods. A greater than 6·0 log reduction of V. parahaemolyticus was observed with 0·75, 2·0 and 5·0 kGy X-ray for pure culture, half shell and whole shell oysters, respectively. Treatment with 0·75, 2·0 and 5·0 kGy X-ray reduced the MPN to <3 for pure culture, half and whole shell oysters, respectively. Treatment with 1·0 kGy X-ray significantly (P < 0·05) reduced the inherent micro-organisms on whole shell oysters from 4·7 ± 0·1 to less than the detectable limit (<1·0 log CFU g,1). Conclusions:, X-ray (1,5 kGy) significantly (P < 0·05) reduced V. parahaemolyticus and inherent microflora on oysters to less than detectable limit (<1·0 log CFU g,1). Significance and Impact of the Study:, Treatment with X-ray could control pathogenic bacteria and extend the shelf life of oysters. [source] Sterilization of ginseng using a high pressure CO2 at moderate temperaturesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Fariba Dehghani Abstract The aim of this study was to determine the feasibility of using high pressure CO2 for sterilization of Ginseng powder, as an alternative method to conventional techniques such as ,-irradiation and ethylene oxide. The Ginseng sample used in this study was originally contaminated with fungi and 5,×,107 bacteria/g that was not suitable for oral use. This is the first time that high pressure CO2 has been used for the sterilization of herbal medicine to decrease the total aerobic microbial count (TAMC) and fungi. The effect of the process duration, operating pressure, temperature, and amount of additives on the sterilization efficiency of high pressure CO2 were investigated. The process duration was varied over 15 h; the pressure between 100 and 200 bar and the temperature between 25 and 75°C. A 2.67-log reduction of bacteria in the Ginseng sample was achieved after long treatment time of 15 h at 60°C and 100 bar, when using neat carbon dioxide. However, the addition of a small quantity of water/ethanol/H2O2 mixture, as low as 0.02 mL of each additive/g Ginseng powder, was sufficient for complete inactivation of fungi within 6 h at 60°C and 100 bar. At these conditions the bacterial count was decreased from 5,×,107 to 2.0,×,103 TAMC/g complying with the TGA standard for orally ingested products. A 4.3 log reduction in bacteria was achieved at 150 bar and 30°C, decreasing the TAMC in Ginseng sample to 2,000, below the allowable limit. However, fungi still remained in the sample. The complete inactivation of both bacteria and fungi was achieved within 2 h at 30°C and 170 bar using 0.1 mL of each additive/g Ginseng. Microbial inactivation at this low temperature opens an avenue for the sterilization of many thermally labile pharmaceutical and food products that may involve sensitive compounds to ,-radiation and chemically reactive antiseptic agents. Biotechnol. Bioeng. 2009;102: 569,576. © 2008 Wiley Periodicals, Inc. [source] VALIDATION OF PATHOGEN DESTRUCTION DURING MANUFACTURE OF A MEAT-BASED POTATO SNACK (CHIPAROO)JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2003S. J. KIERAS ABSTRACT A Chiparoo is a comminuted rabbit and sweet potato dehydrated snack chip manufactured using a process suitable for underdeveloped regions of the world. The purpose of this study was to evaluate the ability of the Chiparoo manufacturing process to adequately deliver 5 log reductions in Listeria monocytogenes, Escherichia coli O157:H7, Salmonella typhimurium, and Staphylococcus aureus per gram of food product. These four pathogens were inoculated into regular (pH , 6.0) and lime juice added (pH , 5.0) formulations of rabbit and sweet potato Chiparoos. They were inoculated as a cocktail of four microorganisms at concentrations of approximately 106/g of each pathogen. Individual inoculations of each pathogen at the same concentration (106/g) were also prepared. After inoculation, the product was held for 5 h at 37C, to simulate the maximum hold time in a sub-Saharan Africa manufacturing facility, then dehydrated at 55C (+/- 5C) for 9 h. Samples of the product were taken during the hold and dehydration steps, decimally diluted and plated on the appropriate enumeration medium. The regular formulation (pH , 6.0) did not achieve the required 5 log reduction of each of the four pathogens, while the lime juice added formulation (pH , 5.0) achieved the desired minimum 5 log reduction for each of the four foodborne pathogens tested. [source] Effect of Combined Ozone and Organic Acid Treatment for Control of Escherichia coli O157:H7 and Listeria monocytogenes on LettuceJOURNAL OF FOOD SCIENCE, Issue 3 2006Hyun-Gyun Yuk ABSTRACT: This study was conducted to determine the effects of ozonated water (1, 3, and 5 ppm) alone with different exposure times (0.5,1,3, or5min), and combinations of 3 ppm ozone with 1% organic acids (acetic, citric, or lactic acids) during 1-min exposure for inactivating Escherichia coli O157:H7 and Listeria monocytogenes on lettuce and to observe the regrowth of these pathogenic bacteria on treated lettuce during storage for 10 d at 15°C. Results showed that 5 ppm ozone treatment for 5 min gave 1.09-log and 0.94-log reductions of E. coli O157:H7 and L. monocytogenes, respectively, indicating insignificant reductions compared with 3 ppm ozone treatment for 5 min. Treatment with 3 ppm ozone combined with 1 % citric acid for 1 min immersing resulted in 2.31 - and 1.84-log reductions (P < 0.05), respectively. During storage at 15°C for 10 d after combined treatment and packaging, populations of E. coli O157:H7 and L. monocytogenes increased to approximately 9.0-log colony forming unit (CFU) /g, indicating that this treatment did not have a residual antimicrobial effect during storage. Although the storage study did not show control of these pathogens, the combined ozone-organic acid treatment was more effective in reducing population levels of these pathogens on lettuce than individual treatments. [source] | ||||||||||||||||