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 \u3c 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

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 \u3e4 logs CFU/mL (i.e., \u3e99.99%) of bacterial endospores. Additions of nisin and lysozyme were able, to a great extent, to augment (p \u3c 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 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 \u3c 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 \u3c 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

Prevention of Foodborne Pathogens and Industrially Relevant Spoilage Microorganisms: Synergism of an Emerging Technology with Traditional Preservation Methods

The current project investigated the effect of mild heat and elevated hydrostatic pressure of 380 MPa, and nisin on the inactivation of L. monocytogenes, L. innocua, and spoilage microorganisms. The pathogen mixture was exposed to three different treatments: application of pressure in the presence of mild heat, a combination of mild heat with nisin, and the last treatment included the combination of mild heat, pressure, and nisin. The treatments were carried out for 0, 3, and 5 min. The project also studied the effect of two different temperatures (4.4 °C and 60.0 °C) and their combination on two different pressure parameters (380 and 650 MPa) along with malic acid. The results showed that nisin augmented the decontamination efficacy of elevated hydrostatic pressure at a treatment interval of 3 min when used in synergism with hydrostatic pressure. The study also showed that high temperature of 60.0 °C and high hydrostatic pressure along with malic acid have better decontamination effect against Shiga toxinproducing E. coli O157:H7. The current study additionally compared biofilm formation of six-strain mixtures of Shiga toxin-producing E. coli O157:H7 (STEC) and non-O157 Shiga toxin-producing E. coli (nSTEC). The experiment compared biofilm formation of two sets where one set included the comparison of wild-type STEC and nSTEC and the other included comparison of both serogroups for rifampicin-resistant strains. The log reductions for treatment with sodium hypochlorite treatments for STEC and nSTEC were 2.9 and 3.5, respectively, which accounted for greater than 99% inactivation of bacterial biofilms. On day 21, the treatment with quaternary ammonium compounds resulted in a 2.9 log reduction for nSTEC. These results showed the industrial importance of bacterial biofilm and exhibited resistance to commonly available commercial treatments validated in the past against planktonic cells. These results could be incorporated as part of food safety management systems, such as those articulated in Hazard Analysis and Critical Control Point and Food Safety Modernization Act regulations to ensure the microbiological safety of the food products and to improve public health

Public Health Importance of Preventive Measures for Salmonella Tennessee and Salmonella Typhimurium Strain LT2 Biofilms

Various serovars of Salmonella had been the subject of research for over 150 years; nonetheless, the bacterium has remained an important pathogen of public health concern to date. The tremendous ability of Salmonella to form biofilms on biotic and abiotic surfaces is an important underlying reason for the prevalence of this opportunistic pathogen in healthcare, manufacturing, and the food chain. The current study illustrates that using very common industrial antimicrobial treatments at the highest concentrations suggested by the manufacturers is only efficacious against planktonic and one-day mature biofilms of the pathogen while exhibiting a lack of efficacy for complete removal of bacterial biofilms formed for longer than 2 days. This exhibits the importance of preventive measures against Salmonella biofilm formation in healthcare and manufacturing facilities, schools, nursing homes, and domestic environments. Additionally, our study illustrates the importance of including both planktonic and sessile cells of the pathogen in microbiology validation studies, especially for niche and hard-to-reach surfaces. The current study additionally investigated the suitability of an avirulent strain of the pathogen as a surrogate for pathogenic Salmonella serovars for public health microbiology validation studies when the use of virulent strains is not economically feasible or not possible due to safety concerns