Practical Preventive Considerations for Reducing the Public Health Burden of Poultry-Related Salmonellosis.

With poultry products as one of the leading reservoirs for the pathogen, in a typical year in the United States, it is estimated that over one million individuals contract non-typhoidal Salmonella infections. Foodborne outbreaks associated with Salmonella infections in poultry, thus, continue to remain a significant risk to public health. Moreover, the further emergence of antimicrobial resistance among various serovars of Salmonella is an additional public health concern. Feeding-based strategies (such as use of prebiotics, probiotics, and/or phytobiotics as well as essential oils), non-feeding-based strategies (such as use of bacteriophages, vaccinations, and in ovo strategies), omics tools and surveillance for identifying antibiotic-resistance genes, post-harvest application of antimicrobials, and biosecurity measures at poultry facilities are practical interventions that could reduce the public health burden of salmonellosis and antibiotic resistance associated with poultry products. With the escalating consumption of poultry products around the globe, the fate, prevalence, and transmission of Salmonella in agricultural settings and various poultry-processing facilities are major public health challenges demanding integrated control measures throughout the food chain. Implementation of practical preventive measures discussed in the current study could appreciably reduce the public health burden of foodborne salmonellosis associated with poultry products.

Synergistic Effects of Nisin, Lysozyme, Lactic Acid, and CitricidalTM for Enhancing Pressure-Based Inactivation of Bacillus amyloliquefaciens, Geobacillus stearothermophilus, and Bacillus atrophaeus Endospores.

The inactivation of bacterial endospores continues to be the main curtailment for further adoption of high-pressure processing in intrastate, interstate, and global food commerce. The current study investigated the effects of elevated hydrostatic pressure for the inactivation of endospore suspension of three indicator spore-forming bacteria of concern to the food industry. Additionally, the effects of four bacteriocin/bactericidal compounds were studied for augmenting the decontamination efficacy of the treatment. Elevated hydrostatic pressure at 650 MPa and at 50 °C was applied for 0 min (untreated control) and for 3, 7, and 11 min with and without 50K IU of nisin, 224 mg/L lysozyme, 1% lactic acid, and 1% CitricidalTM. The results were statistically analyzed using Tukey- and Dunnett's-adjusted ANOVA. Under the condition of our experiments, we observed that a well-designed pressure treatment synergized with mild heat and bacteriocin/bactericidal compounds could reduce up to >4 logs CFU/mL (i.e., >99.99%) of bacterial endospores. Additions of nisin and lysozyme were able, to a great extent, to augment (p < 0.05) the decontamination efficacy of pressure-based treatments against Bacillus amyloliquefaciens and Bacillus atrophaeus, while exhibiting no added benefit (p ≥ 0.05) for reducing endospores of Geobacillus stearothermophilus. The addition of lactic acid, however, was efficacious for augmenting the pressure-based reduction of bacterial endospores of the three microorganisms.

Sensitivity of wild-type and rifampicin-resistant O157 and non-O157 Shiga toxin-producing Escherichia coli to elevated hydrostatic pressure and lactic acid in ground meat and meat homogenate.

Various serogroups of Shiga toxin-producing Escherichia coli have been epidemiologically associated with foodborne disease episodes in the United States and around the globe, with E. coli O157: H7 as the dominant serogroup of public health concern. Serogroups other than O157 are currently associated with about 60% of Shiga toxin-producing E. coli related foodborne illness episodes. Current study evaluated sensitivity of the O157 and epidemiologically important non-O157 serogroups of the pathogen to elevated hydrostatic pressure and 1% lactic acid. Pressure intensity of 250 to 650 MPa were applied for 0 to 7 min for inactivation of strain mixtures of wild-type and rifampicin-resistant E. coli O157, as well as O26, O45, O103, O111, O121, and O145 serogroups and ATCC® 43895™ strain in ground meat and 10% meat homogenate. E. coli O157 were reduced (p < 0.05) from 6.86 ± 0.2 to 4.56 ± 0.1 log CFU/g when exposed to pressure of 650 MPa for 7 min. Corresponding reductions (p < 0.05) for non-O157 E. coli were from 6.98 ± 0.3 to 4.72 ± 0.1. The D-values at 650 MPa were 3.71 and 3.47 min for O157 and non-O157 serogroups, respectively. Presence of 1% lactic acid to a great extent augmented (p < 0.05) decontamination efficacy of the treatment in meat homogenate resulting in up to 5.6 and 6.0 log CFU/mL reductions for O157 and non-O157 serogroups, respectively. Among the tested serogroups, the wild-type and rifampicin-resistant phenotypes exhibited (p ≥ 0.05) comparable pressure sensitivity. Thus, these two phenotypes could be used interchangeably in validation studies. Our results also illustrate that, application of elevated hydrostatic pressure could be utilized for assuring safety of ground and non-intact meat products against various serogroups of Shiga toxin-producing E. coli. Addition of 1% lactic acid additionally provided industrially appreciable augmentation in efficacy of the pressure-based treatments.

Inactivation of Shiga toxin-producing Escherichia coli O157: H7 and mesophilic background microbiota of meat homogenate using elevated hydrostatic pressure, mild heat, and thymol.

A six-strain mixture of E. coli O157:H7 was exposed to 0 to 9 min of six treatments: (i) hydrostatic pressure (400 MPa) at 4 °C; (ii) hydrostatic pressure and thymol at 4 °C; (iii) thymol at 4 °C; (iv) heat at 40 °C; (v) hydrostatic pressure at 40 °C; and (vi) hydrostatic pressure and thymol at 40 °C. Pressure intensity level of 400 MPa and thymol concentration of 0.15% (w/v) were used for the experiments of inoculated pathogen (4.0 to 5.0 log CFU/mL) in a homogenate (10% nonsterilized beef in 90% sterilized distilled water). Temperature was precisely monitored by stainless steel water jacket surrounding pressure chamber (16 mL volume), mechanically linked to a refrigerated circulating water bath. Analyses of variance were conducted followed by Tukey- and Dunnett's-adjusted mean separations. Pathogen counts before treatment were 4.08 ± 0.7 log CFU/mL and were reduced (P < 0.05) to 0.67 ± 0.2 log CFU/mL after 6 min of pressure treatment. Thymol and mild heat (40 °C) further augmented decontamination efficacy of pressure treatments where in their presence, the mesophilic background microbiota counts of pressure-treated samples after 3, 6, and 9 min were reduced (P < 0.05) by 2.1, 2.5, and 3.1 log CFU/mL, respectively. Results of the current study indicate that thymol and mild heat could enhance decontamination efficacy of elevated hydrostatic pressure for pasteurization of food commodities. This could be of great significance for industry practitioners to assure microbiological safety of a product and cost optimization by benefiting from synergism of antimicrobials, mild heat, and elevated hydrostatic pressure. PRACTICAL APPLICATION: Thymol and mild heat could enhance decontamination efficacy of pressure-based pasteurizer that could be of great significance for practitioners. Application of pressure coupled with antimicrobial and mild heat could assure microbiological safety of a product, lead to cost optimization, and assist in meeting regulatory requirements of food commerce such as Hazard Analysis and Critical Control Point and Preventive Control for Human Food rule of Food Safety Modernization Act. Addition of an antimicrobial could have further co-benefits for the product due to residual protective effects during shelf-life and minimizing potential undesirable organoleptic changes associated with pressure treatments of >400 MPa.

Sensitivity of Planktonic Cells of Staphylococcus aureus to Elevated Hydrostatic Pressure as Affected by Mild Heat, Carvacrol, Nisin, and Caprylic Acid.

Current study investigated effects of elevated hydrostatic pressure exposure in the presence of mild heat and natural antimicrobials against Staphylococcus aureus. Hydrostatic pressure of 350 to 550 MPa with nisin (5000 IU/mL), carvacrol, or caprylic acid (0.5% v/v) were applied for the reduction in four-strain mixture of S. aureus in HEPES buffer at 4 and 40 °C for up to 7 min. Results were statistically analyzed by ANOVA and D-values were additionally calculated using best-fitted linear model. Prior to exposure to treatments at 4 °C, counts of the pathogen were 7.95 ± 0.4 log CFU/mL and were reduced (p < 0.05) to 6.44 ± 0.3 log CFU/mL after 7 min of treatment at 450 MPa. D-value associated with this treatment was 5.34 min (R2 = 0.72). At 40 °C, counts were 8.21 ± 0.7 and 5.77 ± 0.3 log CFU/mL before and after the 7-min treatments, respectively. D-value associated with 40 °C treatment was 3.30 min (R2 = 0.62). Application of the antimicrobials provided additional pathogen reduction augmentation for treatments < 5 min. The results of the current study could be incorporated for meeting regulatory requirements such as Food Code, HACCP, and Preventive Control for Human Food of Food Safety Modernization Act for assuring microbiological safety of products against this prevalent pathogen of public health concern.

The Threat of Antibiotic Resistance in Changing Climate.

As the earliest form of life, microorganisms have elaborate. [...].

Fate and Biofilm Formation of Wild-Type and Pressure-Stressed Pathogens of Public Health Concern in Surface Water and on Abiotic Surfaces.

Since the historic outbreak near Broad Street in London, which serves as cornerstone of modern epidemiology, infectious diseases spread in surface and sub-surface water has been a persisting public health challenge. The current study investigated persistence of wild-type and pressure-stressed Listeria monocytogenes, Escherichia coli O157:H7, and non-typhoidal Salmonella enterica serovars in surface water stored aerobically for up to 28 days at 5, 25, and 37 °C. Additionally, biofilm formation of wild-type and pressure-stressed non-typhoidal Salmonella serovars were monitored on surface of stainless steel and rubber coupons for 28 days at 25 and 37 °C. While L. monocytogenes exhibited a lower (p < 0.05) survival rate at 5 °C, relative to the two Gram-negative pathogens, at higher temperatures of 25 and 37 °C, all three pathogens exhibited similar (p ≥ 0.05) trends for survival in surface water. Both wild-type and pressure-stressed Salmonella serovars in the vast majority of tested times, temperatures, and surfaces exhibited comparable (p ≥ 0.05) persistence and biofilm formation capability. Our study thus indicates the occurrence of contamination could lead to prolonged survival of these microorganisms in low-nutrient environments and highlights the need for preventive measures such as those articulated under Produce Safety Rule of the U.S. Food Safety Modernization Act.

Augmenting the Pressure-Based Pasteurization of Listeria monocytogenes by Synergism with Nisin and Mild Heat.

The current study investigated Listeria monocytogenes inactivation using mild heat with elevated hydrostatic pressure and nisin under buffered condition. A four-strain pathogen mixture was exposed to 0 (control) and up to 9 min of (1) 4 °C elevated pressure; (2) 4 °C elevated pressure and nisin; (3) 4 °C nisin; (4) heat at 40 °C; (5) 40 °C elevated pressure; (6) 40 °C elevated pressure and nisin; and (7) 40 °C nisin. Elevated hydrostatic pressure at 400 MPa (Hub880 Explorer, Pressure BioScience Inc., Easton, MA, USA) and nisin concentration of 5000 IU/mL were used in the trials. Analyses of variance were conducted, followed by Dunnett's- and Tukey-adjusted means separations. Under conditions of these experiments, nisin augmented (p < 0.05) decontamination efficacy of 40 °C heat and elevated hydrostatic pressure treatments, particularly at treatment interval of 3 min. This synergism with nisin faded away (p ≥ 0.05) as the treatment time for thermal, high-pressure, and thermal-assisted pressure processing increased. The results of our study, thus, exhibit that practitioners and stakeholders of pressure-based technologies could benefit from synergism of mild heat and nisin for short-term, high-pressure pasteurization treatments to achieve microbial safety and economic feasibility comparable to traditional heat-treated products.

Safety of Food and Water Supplies in the Landscape of Changing Climate.

In response to evolving environmental, production, and processing conditions, microbial communities have tremendous abilities to move toward increased diversity and fitness by various pathways such as vertical and horizontal gene transfer mechanisms, biofilm formation, and quorum sensing [...].

Development of Salmonellosis as Affected by Bioactive Food Compounds.

Infections caused by Salmonella serovars are the leading cause of foodborne hospitalizations and deaths in Americans, extensively prevalent worldwide, and pose a considerable financial burden on public health infrastructure and private manufacturing. While a comprehensive review is lacking for delineating the role of dietary components on prevention of Salmonellosis, evidence for the role of diet for preventing the infection and management of Salmonellosis symptoms is increasing. The current study is an evaluation of preclinical and clinical studies and their underlying mechanisms to elaborate the efficacy of bioactive dietary components for augmenting the prevention of Salmonella infection. Studies investigating dietary components such as fibers, fatty acids, amino acids, vitamins, minerals, phenolic compounds, and probiotics exhibited efficacy of dietary compounds against Salmonellosis through manipulation of host bile acids, mucin, epithelial barrier, innate and adaptive immunity and gut microbiota as well as impacting the cellular signaling cascades of the pathogen. Pre-clinical studies investigating synergism and/or antagonistic activities of various bioactive compounds, additional randomized clinical trials, if not curtailed by lack of equipoise and ethical concerns, and well-planned epidemiological studies could augment the development of a validated and evidence-based guideline for mitigating the public health burden of human Salmonellosis through dietary compounds.

Interactions of Carvacrol, Caprylic Acid, Habituation, and Mild Heat for Pressure-Based Inactivation of O157 and Non-O157 Serogroups of Shiga Toxin-Producing Escherichia coli in Acidic Environment.

The current study investigated synergism of elevated hydrostatic pressure, habituation, mild heat, and antimicrobials for inactivation of O157 and non-O157 serogroups of Shiga toxin-producing Escherichia coli. Various times at a pressure intensity level of 450 MPa were investigated at 4 and 45 °C with and without carvacrol, and caprylic acid before and after three-day aerobic habituation in blueberry juice. Experiments were conducted in three biologically independent repetitions each consist of two replications and were statistically analyzed as a randomized complete block design study using ANOVA followed by Tukey- and Dunnett's-adjusted mean separations. Under the condition of this experiment, habituation of the microbial pathogen played an influential (p < 0.05) role on inactivation rate of the pathogen. As an example, O157 and non-O157 serogroups were reduced (p < 0.05) by 1.4 and 1.6 Log CFU/mL after a 450 MPa treatment at 4 °C for seven min, respectively, before habituation. The corresponding log reductions (p < 0.05) after three-day aerobic habituation were: 2.6, and 3.3, respectively at 4 °C. Carvacrol and caprylic acid addition both augmented the pressure-based decontamination efficacy. As an example, Escherichia coli O157 were reduced (p < 0.05) by 2.6 and 4.2 log CFU/mL after a seven-min treatment at 450 MPa without, and with presence of 0.5% carvacrol, respectively, at 4 °C.

Outbreak History, Biofilm Formation, and Preventive Measures for Control of Cronobacter sakazakii in Infant Formula and Infant Care Settings.

Previously known as Enterobacter sakazakii from 1980 to 2007, Cronobacter sakazakii is an opportunistic bacterium that survives and persists in dry and low-moisture environments, such as powdered infant formula. Although C. sakazakii causes disease in all age groups, infections caused by this pathogen are particularly fatal in infants born premature and those younger than two months. The pathogen has been isolated from various environments such as powdered infant formula manufacturing facilities, healthcare settings, and domestic environments, increasing the chance of infection through cross-contamination. The current study discusses the outbreak history of C. sakazakii and the ability of the microorganism to produce biofilms on biotic and abiotic surfaces. The study further discusses the fate of the pathogen in low-moisture environments, articulates preventive measures for healthcare providers and nursing parents, and delineates interventions that could be utilized in infant formula manufacturing to minimize the risk of contamination with Cronobacter sakazakii.

Synergism of Mild Heat and High-Pressure Pasteurization Against Listeria monocytogenes and Natural Microflora in Phosphate-Buffered Saline and Raw Milk.

As many as 99% of illnesses caused by Listeria monocytogenes are foodborne in nature, leading to 94% hospitalizations, and are responsible for the collective annual deaths of 266 American adults. The current study is a summary of microbiological hurdle validation studies to investigate synergism of mild heat (up to 55 °C) and elevated hydrostatic pressure (up to 380 MPa) for decontamination of Listeria monocytogenes and natural background microflora in raw milk and phosphate-buffered saline. At 380 MPa, for treatments of 0 to 12 min, d-values of 3.47, 3.15, and 2.94 were observed for inactivation of the pathogen at 4, 25, and 50 °C. Up to 3.73 and >4.26 log CFU/mL reductions (p < 0.05) of habituated Listeria monocytogenes were achieved using pressure at 380 MPa for 3 and 12 min, respectively. Similarly, background microflora counts were reduced (p < 0.05) by 1.3 and >2.4 log CFU/mL after treatments at 380 MPa for 3 and 12 min, respectively. Treatments below three min were less efficacious (p ≥ 0.05) against the pathogen and background microflora, in the vast majority of time and pressure combinations. Results of this study could be incorporated as part of a risk-based food safety management system and risk assessment analyses for mitigating the public health burden of listeriosis.

Sensitivity of Salmonella serovars and natural microflora to high-pressure pasteurization: Open access data for risk assessment and practitioners.

Industrial adoption of high-pressure processing is gaining importance and momentum as an alternative method to traditional utilization of antimicrobials and heat-based pasteurization. This indicates the need for extensive validation studies and available data for feasible and efficacious adoption of the technology by practitioners and the private industry. Current dataset is obtained utilizing elevated hydrostatic pressure of 35 to 380 MPa for time intervals of 0 (untreated controls) to 10 min, for decontamination of mesophilic background microflora and inoculated Salmonella in orange juice [1]. This open accessed data could be incorporated as part of risk assessment analyses for mitigating the risk of non-typhoidal foodborne salmonellosis by public health practitioners. It could also be utilized to validate the efficacy of elevated hydrostatic pressure against Salmonella serovars and background microflora in food manufacturing.

Effects of Elevated Hydrostatic Pressure against Mesophilic Background Microflora and Habituated Salmonella Serovars in Orange Juice.

With recent improvements in the commercial feasibility of high pressure pasteurization units, the technology is gaining rapid acceptability across various sectors of food manufacturing, thus requiring extensive validation studies for effective adoption. Various times (1 min to 10 min) and intensity levels (0 MPa to 380 MPa) of elevated hydrostatic pressure were investigated for decontamination of mesophilic background microflora and inoculated Salmonella in orange juice. Results were analyzed by GLM procedure of SAS using Tukey- and Dunnett-adjusted ANOVA, additionally the Kmax and D-values were calculated using best-fitted (maximum R²) model obtained by GInaFit software. At 380 MPa, for treatments of 1 min to 10 min, D-value of 1.35, and inactivation Kmax of 3.34 were observed for Salmonella serovars. D-values were 5.90 and 14.68 for treatments of 241 MPa and 103 MPa, respectively. Up to 1.01 and >7.22 log CFU/mL reductions (p < 0.05) of habituated Salmonella serovars at planktonic stages were achieved using application of pressure at 380 MPa for 1 min and 10 min, respectively. Mesophilic background microflora counts were reduced (p < 0.05) by 1.68 to 5.29 log CFU/mL after treatment at 380 MPa for 1 min and 10 min, respectively. Treatments below two minutes were less efficacious (p ≥ 0.05) against the pathogen and background microflora, in vast majority of time and pressure combinations.

Adoptable Interventions, Human Health, and Food Safety Considerations for Reducing Sodium Content of Processed Food Products.

Although vital for maintaining health when consumed in moderation, various epidemiological studies in recent years have shown a strong association between excess dietary sodium with an array of health complications. These associations are robust and clinically significant for development of hypertension and prehypertension, two of the leading causes of preventable mortality worldwide, in adults with a high-sodium diet. Data from developed nations and transition economies show worldwide sodium intake of higher than recommended amounts in various nations. While natural foods typically contain a moderate amount of sodium, manufactured food products are the main contributor to dietary sodium intake, up to 75% of sodium in diet of American adults, as an example. Lower cost in formulation, positive effects on organoleptic properties of food products, effects on food quality during shelf-life, and microbiological food safety, make sodium chloride a notable candidate and an indispensable part of formulation of various products. Although low-sodium formulation of each product possesses a unique set of challenges, review of literature shows an abundance of successful experiences for products of many categories. The current study discusses adoptable interventions for product development and reformulation of products to achieve a modest amount of final sodium content while maintaining taste, quality, shelf-stability, and microbiological food safety.

Lactic acid resistance of Shiga toxin-producing Escherichia coli and multidrug-resistant and susceptible Salmonella Typhimurium and Salmonella Newport in meat homogenate.

This study compared lactic acid resistance of individual strains of wild-type and rifampicin-resistant non-O157 Shiga toxin-producing Escherichia coli (STEC) and of susceptible and multidrug-resistant (MDR) and/or MDR with acquired ampC gene (MDR-AmpC) Salmonella against E. coli O157:H7. After inoculation of sterile 10% beef homogenate, lactic acid was added to a target concentration of 5%. Before acid addition (control), after acid addition (within 2 s, i.e. time-0), and 2, 4, 6 and 8 min after addition of acid, aliquots were removed, neutralized, and analyzed for survivors. Of wild-type and of rifampicin-resistant non-O157 STEC strains, irrespective of serogroup, 85.7% (30 out of 35 strains) and 82.9% (29 out of 35 strains), respectively, reached the detection limit within 0-6 min. Of Salmonella strains, 87.9% (29 out of 33 isolates) reached the detection limit within 0-4 min, irrespective of antibiotic resistance phenotype. Analysis of non-log-linear microbial survivor curves indicated that non-O157 STEC serogroups and MDR and susceptible Salmonella strains required less time for 4D-reduction compared to E. coli O157:H7. Overall, for nearly all strains and time intervals, individual strains of wild-type and rifampicin-resistant non-O157 STEC and Salmonella were less (P < 0.05) acid tolerant than E. coli O157:H7.

Biofilm formation of O157 and non-O157 Shiga toxin-producing Escherichia coli and multidrug-resistant and susceptible Salmonella typhimurium and newport and their inactivation by sanitizers.

This study compared biofilm formation by 7 serogroups of pathogenic Escherichia coli and 2 or 3 phenotypes of Salmonella (susceptible, multidrug-resistant [MDR], and/or multidrug resistant with ampC gene [MDR-AmpC]). One-week mature biofilms were also exposed to water, quaternary ammonium compound-based (QAC), and acid-based (AB) sanitizers. Seven groups (strain mixture) of above-mentioned pathogens were separately spot-inoculated onto stainless steel coupons surfaces for target inoculation of 2 log CFU/cm2, then stored statically, partially submerged in 10% nonsterilized meat homogenate at 4, 15, and 25 °C. Biofilm cells were enumerated on days 0, 1, 4, and 7 following submersion in 30 mL for 1 min in water, QAC, and AB. Counts on inoculation day ranged from 1.6 ± 0.4 to 2.4 ± 0.6 log CFU/cm2 and changed to 1.2 ± 0.8 to 1.9 ± 0.8 on day 7 at 4 °C with no appreciable difference among the 7 pathogen groups. After treatment with QAC and AB on day 7, counts were reduced (P < 0.05) to less than 0.7 ± 0.6 and 1.2 ± 0.5, respectively, with similar trends among pathogens. Biofilm formation at higher temperatures was more enhanced; E. coli O157:H7, as an example, increased (P < 0.05) from 1.4 ± 0.6 and 2.0 ± 0.3 on day 0 to 4.8 ± 0.6 and 6.5 ± 0.2 on day 7 at 15 and 25 °C, respectively. As compared to 4 °C, after sanitation, more survivors were observed for 15 and 25 °C treatments with no appreciable differences among pathogens. Overall, we observed similar patterns of growth and susceptibility to QAC and AB sanitizers of the 7 tested pathogen groups with enhanced biofilm formation capability and higher numbers of treatment survivors at higher temperatures.

Antilisterial properties of marinades during refrigerated storage and microwave oven reheating against post-cooking inoculated chicken breast meat.

This study evaluated growth of Listeria monocytogenes inoculated on cooked chicken meat with different marinades and survival of the pathogen as affected by microwave oven reheating. During aerobic storage at 7 °C, on days 0, 1, 2, 4, and 7, samples were reheated by microwave oven (1100 W) for 45 or 90 s and analyzed microbiologically. L. monocytogenes counts on nonmarinated (control) samples increased (P < 0.05) from 2.7 ± 0.1 (day-0) to 6.9 ± 0.1 (day-7) log CFU/g during storage. Initial (day-0) pathogen counts of marinated samples were <0.5 log CFU/g lower than those of the control, irrespective of marinating treatment. At 7 d of storage, pathogen levels on samples marinated with tomato juice were not different (P ≥ 0.05; 6.9 ± 0.1 log CFU/g) from those of the control, whereas for samples treated with the remaining marinades, pathogen counts were 0.7 (soy sauce) to 2.0 (lemon juice) log CFU/g lower (P < 0.05) than those of the control. Microwave oven reheating reduced L. monocytogenes counts by 1.9 to 4.1 (45 s) and >2.4 to 5.0 (90 s) log CFU/g. With similar trends across different marinates, the high levels of L. monocytogenes survivors found after microwave reheating, especially after storage for more than 2 d, indicate that length of storage and reheating time need to be considered for safe consumption of leftover cooked chicken.

Sensitivity of Shiga toxin-producing Escherichia coli, multidrug-resistant Salmonella, and antibiotic-susceptible Salmonella to lactic acid on inoculated beef trimmings.

Studies were performed to determine whether lactic acid treatments used to reduce Escherichia coli O157:H7 on beef trimmings are also effective in controlling non-O157 Shiga toxin-producing E. coli (nSTEC), and multidrug-resistant and antibiotic-susceptible Salmonella. Beef trimming pieces (10 by 5 by 1 cm) were inoculated (3 log CFU/cm(2)) separately with four-strain mixtures of rifampin-resistant E. coli O157:H7, O26, O45, O103, O111, O121, and O145. Similarly, in a second study, trimmings were separately inoculated with rifampin-resistant E. coli O157:H7, and antibiotic-susceptible or multidrug-resistant (MDR and/or MDR-AmpC) Salmonella Newport and Salmonella Typhimurium. Inoculated trimmings were left untreated (control) or were immersed for 30 s in 5% lactic acid solutions (25 or 55°C). No differences (P ≥ 0.05) were obtained among surviving counts of E. coli O157:H7 and those of the tested nSTEC serogroups on lactic acid-treated (25 or 55°C) samples. Counts (3.1 to 3.3 log CFU/cm(2)) of E. coli O157:H7 and nSTEC were reduced (P < 0.05) by 0.5 to 0.9 (25°C lactic acid) and 1.0 to 1.4 (55°C lactic acid) log CFU/cm(2). Surviving counts of Salmonella on treated trimmings were not influenced by serotype or antibiotic resistance phenotype and were similar (P ≥ 0.05) or lower (P < 0.05) than surviving counts of E. coli O157:H7. Counts (3.0 to 3.3 log CFU/cm(2)) were reduced (P < 0.05) by 0.5 to 0.8 (E. coli O157:H7) and 1.3 to 1.5 (Salmonella) log CFU/cm(2) after treatment of samples with 25°C lactic acid. Corresponding reductions following treatment with lactic acid at 55°C were 1.2 to 1.5 (E. coli O157:H7) and 1.6 to 1.9 (Salmonella) log CFU/cm(2). Overall, the results indicated that lactic acid treatments used against E. coli O157:H7 on beef trimmings should be similarly or more effective against the six nSTEC serogroups and against multidrug-resistant and antibiotic-susceptible Salmonella Newport and Salmonella Typhimurium.