Control of Salmonella in food related environments by chemical disinfection

Light-Based Anti-Biofilm and Antibacterial Strategies

Biofilm formation and antimicrobial resistance pose significant challenges not only in clinical settings (i.e., implant-associated infections, endocarditis, and urinary tract infections) but also in industrial settings and in the environment, where the spreading of antibiotic-resistant bacteria is on the rise. Indeed, developing effective strategies to prevent biofilm formation and treat infections will be one of the major global challenges in the next few years. As traditional pharmacological treatments are becoming inadequate to curb this problem, a constant commitment to the exploration of novel therapeutic strategies is necessary. Light-triggered therapies have emerged as promising alternatives to traditional approaches due to their non-invasive nature, precise spatial and temporal control, and potential multifunctional properties. Here, we provide a comprehensive overview of the different biofilm formation stages and the molecular mechanism of biofilm disruption, with a major focus on the quorum sensing machinery. Moreover, we highlight the principal guidelines for the development of light-responsive materials and photosensitive compounds. The synergistic effects of combining light-triggered therapies with conventional treatments are also discussed. Through elegant molecular and material design solutions, remarkable results have been achieved in the fight against biofilm formation and antibacterial resistance. However, further research and development in this field are essential to optimize therapeutic strategies and translate them into clinical and industrial applications, ultimately addressing the global challenges posed by biofilm and antimicrobial resistance.

Comparison of the Efficiency of Selected Disinfectants against Planktonic and Biofilm Populations of Escherichia coli and Staphylococcus aureus

The aim of this study is to compare the efficacy of selected food disinfectants on planktonic populations of Staphylococcus aureus and Escherichia coli and on the same microorganisms (MOs) incorporated in a biofilm. Two disinfectants were used for treatment: peracetic acid-based disinfectant (P) and benzalkonium chloride-based disinfectant (D). Testing of their efficacy on the selected MO populations was performed using a quantitative suspension test. The standard colony counting procedure was used to determine their efficacy on bacterial suspensions in tryptone soy agar (TSA). The germicidal effect (GE) of the disinfectants was determined based on the decimal reduction ratio. For both MOs, 100% GE was achieved at the lowest concentration (0.1%) and after the shortest exposure time (5 min). Biofilm production was confirmed with a crystal violet test on microtitre plates. Both E. coli and S. aureus showed strong biofilm production at 25 °C with E. coli showing significantly higher adherence capacity. Both disinfectants show a significantly weaker GE on 48 h biofilms compared to the GE observed after application of the same concentrations on planktonic cells of the same MOs. Complete destruction of the viable cells of the biofilms was observed after 5 min of exposure to the highest concentration tested (2%) for both disinfectants and MOs tested. The anti-quorum sensing activity (anti-QS) of disinfectants P and D was determined via a qualitative disc diffusion method applied to the biosensor bacterial strain Chromobacterium violaceum CV026. The results obtained indicate that the disinfectants studied have no anti-QS effect. The inhibition zones around the disc therefore only represent their antimicrobial effect.

Multidrug-Resistant Biofilms (MDR): Main Mechanisms of Tolerance and Resistance in the Food Supply Chain

Biofilms are mono- or multispecies microbial communities enclosed in an extracellular matrix (EPS). They have high potential for dissemination and are difficult to remove. In addition, biofilms formed by multidrug-resistant strains (MDRs) are even more aggravated if we consider antimicrobial resistance (AMR) as an important public health issue. Quorum sensing (QS) and horizontal gene transfer (HGT) are mechanisms that significantly contribute to the recalcitrance (resistance and tolerance) of biofilms, making them more robust and resistant to conventional sanitation methods. These mechanisms coordinate different strategies involved in AMR, such as activation of a quiescent state of the cells, moderate increase in the expression of the efflux pump, decrease in the membrane potential, antimicrobial inactivation, and modification of the antimicrobial target and the architecture of the EPS matrix itself. There are few studies investigating the impact of the use of inhibitors on the mechanisms of recalcitrance and its impact on the microbiome. Therefore, more studies to elucidate the effect and applications of these methods in the food production chain and the possible combination with antimicrobials to establish new strategies to control MDR biofilms are needed.

Use of Cocktail of Bacteriophage for Salmonella Typhimurium Control in Chicken Meat

Foodborne diseases are extremely relevant and constitute an area of alert for public health authorities due to the high impact and number of people affected each year. The food industry has implemented microbiological control plans that ensure the quality and safety of its products; however, due to the high prevalence of foodborne diseases, the industry requires new microbiological control systems. One of the main causative agents of diseases transmitted by poultry meat is the bacterium Salmonella enterica. Disinfectants, antibiotics, and vaccines are used to control this pathogen. However, they have not been efficient in the total elimination of these bacteria, with numerous outbreaks caused by this bacterium observed today, in addition to the increase in antibiotic-resistant bacteria. The search for new technologies to reduce microbial contamination in the poultry industry continues to be a necessity and the use of lytic bacteriophages is one of the new solutions. In this study, 20 bacteriophages were isolated for Salmonella spp. obtained from natural environments and cocktails composed of five of them were designed, where three belonged to the Siphoviridae family and two to the Microviridae family. This cocktail was tested on chicken meat infected with Salmonella Typhimurium at 10 °C, where it was found that this cocktail was capable of decreasing 1.4 logarithmic units at 48 h compared to the control.

Determination of an effective agent combination using nisin against Salmonella biofilm

This present study aims to determine the lowest concentration effects of the assayed different antibiotics; antimicrobial agents alone and their combinations with nisin were investigated to prevent the biofilm formation and break down the biofilm structure of Salmonella. While the combination of nisin and EDTA showed a synergistic effect against Salmonella strain, chlorhexidine digluconate and streptomycin with nisin showed a partial synergetic effect; citric acid and sulfonamides with nisin showed an indifferent effect. The use of citric acid and chlorhexidine digluconate alone was very effective in Salmonella inhibition. While the citric acid combined with other agents had not much effect, the use of chlorhexidine digluconate combined with nisin and EDTA inactivated the total initial count within 24 h. Significantly, when citric acid and sulfonamides are used alone, they reduce by 64% and 44%, respectively. When they used nisin + EDTA, this ratio increased to 83% and 84%, respectively. For the prevention of biofilm, the most suitable conditions were determined as 97% biofilm inhibition. The results of this study can be used as a guide for the emergence of new approaches to ensure the food safety and quality of the food industry.

The efficacy of different sanitizers against MS2 bacteriophage introduced onto plastic or stainless steel surfaces

The virucidal activities of 11 prepared disinfectant solutions (active ingredients of household sanitizers) and 10 household sanitizers against bacteriophage MS2 on plastic and stainless steel surfaces were studied. Among the prepared sanitizers, 70-90% ethanol and ethanol-based disinfectants resulted in 1-2.5 log PFU/mL reductions on both surfaces. The 70% isopropanol and isopropanol-based formula reduced MS2 by 0.7-1.5 log PFU/mL on both surfaces. Other disinfectants, containing 0.1% benzalkonium chloride (BAC), 0.5% hydrogen peroxide, or 4% acetic acid, showed significant (P < 0.05) lower log reductions (-0.17-0.55 log PFU/mL) compared with other treatments. At room temperature, the virucidal activities of 70% ethanol on plastic (1.46-1.64 log PFU/mL reductions) and stainless steel (0.84-0.93 log PFU/mL reductions) surfaces were not significantly (P > 0.05) affected by the treatment time (30-600 s). However, 85% ethanol-treated groups showed significant (P < 0.05) higher log reductions in 60 and 600 s treated groups (1.69-2.24 log PFU/mL) compared with those in 30 s treated groups (0.92-1.32 log PFU/mL). Their virucidal activities were further examined at low temperatures (4 and 8 °C). We observed that the surface inactivation efficacies were not affected by the low temperatures. In addition, the virucidal activities of household sanitizers revealed that sanitizers with 1.84% (pH = 12.5, ∼17,500 ppm free-chlorine concentrations) or 3% (pH = 13.1, ∼38,100 ppm free-chlorine concentrations) sodium hypochlorite (NaClO) reduced 4.15-6.23 log PFU/mL MS2 on hard surfaces after 60 s contact time. Furthermore, an approximately 1.5 log PFU/mL reduction was observed in groups treated by sanitizer H (active ingredients: 58% ethanol + 0.1% quaternary ammonium compound). Household products with BAC or organic acid resulted in -0.28-0.33 log reductions on two surfaces after 30 or 60 s treatment. Therefore, the use of ethanol and NaClO-based products should be considered as a potential surface decontamination strategy in the food industry.

Advances in emerging technologies for the decontamination of the food contact surfaces

Foodborne pathogens could be transferred to food from food contact surfaces contaminated by poor hygiene or biofilm formation. The food processing industry has various conditions favouring microbes' adherence, such as moisture, nutrients, and the microbial inoculums obtained from the raw material. The function of the ideal antimicrobial surface is preventing initial attachment of the microbes, killing the microbes or/and removing the dead bacteria. This review article provides detail about the challenges food industries are facing with respect to food contact materials. It also summarises the merits and demerits of several sanitizing methods developed for industrial use. Furthermore, it reviews the new and emerging techniques that enhance the efficiency of reducing microbial contamination. Techniques such as surface functionalisation, high-intensity ultrasound, cold plasma technologies etc. which have high potential to be used for the decontamination of food contact surfaces are discussed. The emerging designs of antibacterial surfaces provide the opportunity to reduce or eradicate the adhesion of microorganisms. The most important purpose of these surfaces is to prevent the attachment of bacteria and to kill the bacteria that come in contact. These emerging technologies have a high potential for developing safe and inert food contact materials for the food industry.

Combination treatment of peroxyacetic acid or lactic acid with UV-C to control Salmonella Enteritidis biofilms on food contact surface and chicken skin

The risk of salmonellosis is expected to increase with the rise in the consumption of poultry meat. The aim of this study was to investigate the combination treatment of peroxyacetic acid (PAA) or lactic acid (LA) with UV-C against Salmonella Enteritidis biofilms formed on food contact surface (stainless steel [SS], silicone rubber [SR], and ultra-high molecular weight polyethylene [UHMWPE]) and chicken skin. The biofilm on food contact surface and chicken skin was significantly decreased (P < 0.05) by combination treatment of PAA or LA with UV-C. Combination treatment of PAA (50-500 μg/mL) with UV-C (5 and 10 min) reduced 3.10-6.41 log CFU/cm² and LA (0.5-2.0%) with UV-C (5 and 10 min) reduced 3.35-6.41 log CFU/cm² of S. Enteritidis biofilms on food contact surface. Salmonella Enteritidis biofilms on chicken skin was reduced around 2 log CFU/g with minor quality changes in color and texture by combination treatment of PAA (500 μg/mL) or LA (2.0%) with UV-C (10 min). Additional reduction occurred on SS and UHMWPE by PAA or LA with UV-C, while only LA with UV-C caused additional reduction on chicken skin. Also, it was visualized that the biofilm on food contact surface and chicken skin was removed through field emission scanning electron microscopy (FESEM) and death of cells constituting the biofilm was confirmed through confocal laser scanning microscopy (CLSM). These results indicating that the combination treatment of PAA or LA with UV-C could be used for S. Enteritidis biofilm control strategy in poultry industry.

Simultaneous annihilation of microorganisms and volatile organic compounds from municipal solid waste storage rooms with slightly acidic electrolyzed water

Great deal pathogenic bacteria and malodorous gases are hidden in municipal solid waste (MSW), which poses excellent environmental sanitation risks for sanitation workers and residents, and preventive measures should be implemented. In this study, the simultaneous annihilation of microorganisms and volatile organic compounds (VOCs) with slightly acidic electrolyzed water (SAEW) was investigated in an MSW storage room of a residential community in Shanghai, China. The microbial population of airborne, surfaces and handles of waste bins, hands of sanitation workers and the main components of VOCs were measured. The results indicated that the bacterial reduction efficiencies of SAEW with an available chlorine concentration (ACC) of 50-100 mg/L on surfaces and handles of waste bins and sanitation workers' hands were 22.7%-84.1%. Also, SAEW effectively reduced the average population of airborne bacteria and fungi by 358 and 378 colony-forming units (CFU)/m³ and decreased the detection rates of coliforms by 14.2%-51.9%. The concentrations of most VOCs were reduced by 21.4%-88.3% after spraying SAEW. And the accumulated values of carcinogenic and noncarcinogenic risks also tended to decrease with spraying SAEW. These findings imply that SAEW has significant application potential to control environmental sanitation risks in MSW storage rooms.

The Persistence of Bacterial Pathogens in Surface Water and Its Impact on Global Food Safety

Water is vital to agriculture. It is essential that the water used for the production of fresh produce commodities be safe. Microbial pathogens are able to survive for extended periods of time in water. It is critical to understand their biology and ecology in this ecosystem in order to develop better mitigation strategies for farmers who grow these food crops. In this review the prevalence, persistence and ecology of four major foodborne pathogens, Shiga toxin-producing Escherichia coli (STEC), Salmonella, Campylobacter and closely related Arcobacter, and Listeria monocytogenes, in water are discussed. These pathogens have been linked to fresh produce outbreaks, some with devastating consequences, where, in a few cases, the contamination event has been traced to water used for crop production or post-harvest activities. In addition, antimicrobial resistance, methods improvements, including the role of genomics in aiding in the understanding of these pathogens, are discussed. Finally, global initiatives to improve our knowledge base of these pathogens around the world are touched upon.

Processing environment monitoring in low moisture food production facilities: Are we looking for the right microorganisms?

Processing environment monitoring is gaining increasing importance in the context of food safety management plans/HACCP programs, since past outbreaks have shown the relevance of the environment as contamination pathway, therefore requiring to ensure the safety of products. However, there are still many open questions and a lack of clarity on how to set up a meaningful program, which would provide early warnings of potential product contamination. Therefore, the current paper aims to summarize and evaluate existing scientific information on outbreaks, relevant pathogens in low moisture foods, and knowledge on indicators, including their contribution to a "clean" environment capable of limiting the spread of pathogens in dry production environments. This paper also outlines the essential elements of a processing environment monitoring program thereby supporting the design and implementation of better programs focusing on the relevant microorganisms. This guidance document is intended to help industry and regulators focus and set up targeted processing environment monitoring programs depending on their purpose, and therefore provide the essential elements needed to improve food safety.

Incorporation of Antimicrobial Bio-Based Carriers onto Poly(vinyl alcohol-co-ethylene) Surface for Enhanced Antimicrobial Activity

A biobased rechargeable antimicrobial modification approach was developed using a covalent immobilization of food grade yeast cell wall particles on a model plastic film. We demonstrate the applications of this modification approach on poly(vinyl alcohol-co-ethylene) surface to inactivate inoculated bacteria with or without the presence of organic content, reducing the cross-contamination between food contact surface and model fresh produce, and inhibiting the growth of biofilms on the film surface. These biobased cell wall particle modified plastic films can enhance the binding of chlorine to the plastic surface in the form of N-halamine, extend the stability of chlorine against high organic content and ambient storage, and improve the rechargeability of the plastic films. Upon charging with chlorine, these modified plastic films inactivated 5 log of model Gram-negative bacteria (Escherichia coli O157:H7) and Gram-positive bacteria (Listeria innocua used as a surrogate of pathogenic Listeria monocytogenes) within 2 min of surface inoculation in water and within 20 min in an organic-rich aqueous environment. The modified plastic films prevented the transfer of bacteria and eliminated cross-contamination from the contaminated films to a spinach leaf surface, while 3 log CFU/leaf of bacteria were transferred from a contaminated native film to a noninoculated spinach surface. In addition, these modified plastic films reduced the adhesion of L. innocua cells by 2.7-3.6 log CFU/cm² compared with control films during extended incubation for biofilm formation. Overall, this study demonstrates the feasibility of this biobased food grade modification approach to reduce microbial contamination and improve produce safety in the food processing industry.

Isolation and characterization of Salmonella spp. from food and food contact surfaces in a chicken processing factory

The presence of Salmonella serotypes is a major safety concern of the food industry and poultry farmers. This study aimed to isolate and identify Salmonella spp. from a chicken processing facility by PCR and pulsed-field gel electrophoresis (PFGE). In addition, the biofilm-forming abilities of the isolated bacteria on stainless steel, silicone rubber, plastic, and chicken skin were also investigated. PCR was used for the confirmation of Salmonella serotypes, and then gene similarity within the same serotype was analyzed by PFGE. As a result, 26 S. Enteritidis isolates were detected at a high rate from both food contact surfaces and chicken products during processing. All of them were 100% genetically identical to the same bacteria. The results indicated that the virulence factors and effective biofilm-forming ability of S. Enteritidis isolates could affect human health and economic revenue. It was also suggested that the visual observation of food and food contact surfaces could be a great concern in the future. The continuous monitoring of S. Enteritidis molecular and biofilm characteristics is needed to increase food safety.

Cupric ion in combination with hydrogen peroxide and hydroxylamine applied to inactivation of different microorganisms

The microbial inactivation by cupric ion (Cu(II)) in combination with hydrogen peroxide (H₂O₂) and hydroxylamine (HA) was investigated for twelve different microorganisms (five Gram-negative bacteria, three Gram-positive bacteria, and four bacteriophages). The inactivation efficacy, protein oxidation, and RNA (or DNA) damage were monitored during and after treatment by Cu(II), Cu(II)/HA, Cu(II)/H₂O₂ and Cu(II)/HA/H₂O₂. The rate of microbial inactivation by the (combined) microbicides generally increased in the order of Cu(II) < Cu(II)/H₂O₂ < Cu(II)/HA < Cu(II)/HA/H₂O₂; Cu(II)/HA/H₂O₂ resulted in 0.18-0.31, 0.10-0.18, and 0.55-3.83 log inactivation/min for Gram-negative bacteria, Gram-positive bacteria, and bacteriophages, respectively. The degrees of protein oxidation and RNA (or DNA) damage increased in the order of Cu(II) < Cu(II)/HA < Cu(II)/H₂O₂ < Cu(II)/HA/H₂O₂. In particular, Cu(II)/HA/H₂O₂ led to exceptionally fast inactivation of the viruses. Gram-positive bacteria tended to show higher resistance to microbicides than other microbial species. The microbicidal effects of the combined microbicides on the target microorganisms were explained by the roles of Cu(I) and Cu(III) generated by the redox reactions of Cu(II) with H₂O₂, HA, and oxygen. Major findings of this study indicate that Cu(II)-based combined microbicides are promising disinfectants for different waters contaminated by pathogenic microorganisms.

The Effect of Disinfectants on Quinolone Resistant E. coli (QREC) in Biofilm

The aim of disinfection is to reduce the number of microorganisms on surfaces which is a challenge due to biofilms. In the present study, six quinolone resistant Escherichia coli (QREC) strains with three different biofilm matrix compositions were included to assess the log₁₀ colony forming units (CFU) reduction effect of three disinfectants at various exposure times on biofilm of different ages and morphotypes. Biofilm was formed on stainless steel coupons for two and five days before transferred to tubes with Virocid 0, 25%, VirkonS 1%, and TP990 1% and left for various exposure times. The biofilms were scraped off and serial dilutions were spread on blood agar plates where colony forming units (CFU) were counted. A mean log₁₀ CFU reduction ≥4 was seen on two-day-old biofilm with VirkonS and Virocid (30 min) but not on five-day old biofilm. TP990 did not display sufficient effect under the conditions tested. The bactericidal effect was inferior to that reported on planktonic bacteria. The findings of this study should be considered when establishing both disinfectant routines and standard susceptibility tests, which further should accommodate E. coli biofilms and not only Pseudomonas as is the case today.

Disinfection efficiency of hospital infectious disease wards with chlorine dioxide and hypochlorous acid

The disinfection efficiencies of two chemical disinfectants, chlorine dioxide and weak acid hypochlorous water (WAHW), were examined in the soiled room and dishwashing room of a hospital infectious disease ward in Taiwan. The investigations were conducted in two seasons, namely winter and summer, in order to examine the correlation between the bioaerosol concentration and the environmental factors. In addition, a single-daily disinfection mode (SM) and a twice-daily disinfection mode (TM) were applied in this study. The results showed that the bacteria and fungi colony counts were strongly correlated with the temperature. Both disinfectants reduced the bacteria and fungi concentrations in the considered rooms. However, of the two disinfectants, the ClO₂ showed a stronger disinfection effect than the WAHW. It means that when using ClO₂ as the disinfectant, the disinfection efficiency of the TM treatment mode is significantly better than that of the SM treatment mode. But, when using WAHW as the disinfectant, no significant difference is found between the disinfection efficiencies of the two methods. Overall, the results showed that the application of ClO₂ twice daily provided the most effective means of satisfying the Taiwan EPA guidelines for the indoor air quality of hospital medical wards.

Effects of subzero saline chilling on broiler chilling efficiency, meat quality, and microbial safety

The poultry industry has attempted to improve carcass chilling efficiency, meat quality, and product safety. The purpose of this research was to investigate the effects of subzero saline chilling on carcass chilling, breast fillet tenderness, and microbial safety. After evisceration, broiler carcasses were chilled using ice slurry control (0% NaCl/0.5°C) or subzero saline solutions (3% NaCl/-1.8°C and 4% NaCl/-2.41°C). Broiler carcasses in the subzero saline solutions were chilled efficiently and reduced the chilling time by 11% in 3% NaCl/-1.8°C and 37% in 4% NaCl/-2.41°C over the ice slurry chilling. The breast fillets of broiler carcasses in 4% NaCl/-2.41°C were significantly tenderized than those in water control (P < 0.05), with an intermediate value observed in 3% NaCl/-1.8°C. Before chilling, broiler carcasses possessed mesophilic aerobic bacteria, Escherichia coli, and total coliforms for 3.81, 0.78, and 1.86 log cfu/g, respectively, which were significantly reduced after chilling in 3% NaCl/-1.8°C or 4% NaCl/-2.41°C solution over the water control (P < 0.05), except the mesophilic aerobic bacteria. Based on these results, chilling of boiler carcass in 4% NaCl/-1.8°C solution appears to improve carcass chilling efficiency, meat tenderness, and bacterial reduction for E. coli and total coliforms.

Antimicrobial resistance associated with the use of antimicrobial processing aids during poultry processing operations: cause for concern?

Antimicrobial resistance has become a global issue and a threat to human and animal health. Contamination of poultry carcasses with meat-borne pathogens represents both an economic and a public health concern. The use of antimicrobial processing aids (APA) during poultry processing has contributed to an improvement in the microbiological quality of poultry carcasses. However, the extensive use of these decontaminants has raised concerns about their possible role in the co-selection of antibiotic-resistant bacteria. This topic is presented in the current review to provide an update on the information related to bacterial adaptation to APA used in poultry processing establishments, and to discuss the relationship between APA bacterial adaptation and the acquisition of a new resistance phenotype to therapeutic antimicrobials by bacteria. Common mechanisms such as active efflux and changes in membrane fluidity are the most documented mechanisms responsible for bacterial cross-resistance to APA and antimicrobials. Although most studies reported a bacterial resistance to antibiotics not reaching a clinical level, the under-exposure of bacteria to APA remains a concern in the poultry industry. Further research is needed to determine if APA used during poultry processing and therapeutic antimicrobials share common sites of action in bacteria and encounter similar mechanisms of resistance.

Interspecies Interactions in Dual-Species Biofilms Formed by Psychrotrophic Bacteria and the Tolerance of Sessile Communities to Disinfectants

ABSTRACT

Biofilms on the surface of food processing equipment act as potential reservoirs of microbial contamination. Bacterial interactions are believed to play key roles in both biofilm formation and antimicrobial tolerance. In this study, Aeromonas hydrophila, Chryseobacterium oncorhynchi, and Pseudomonas libanensis, which were previously isolated from Chinese raw milk samples, were selected to establish two dual-species biofilm models (P. libanensis plus A. hydrophila and P. libanensis plus C. oncorhynchi) on stainless steel at 7°C. Subsequently, three disinfectants, hydrogen peroxide (100 ppm), peracetic acid (100 ppm), and sodium hypochlorite (100 ppm), were used to treat the developed sessile communities for 10 min. Structural changes after exposure to disinfectants were analyzed with confocal laser scanning microscopy. The cell numbers of both A. hydrophila and C. oncorhynchi recovered from surfaces increased when grown as dual species biofilms with P. libanensis. Dual-species biofilms were more tolerant of disinfectants than were each single-species biofilm. Peracetic acid was the most effective disinfectant for removing biofilms, followed by hydrogen peroxide and sodium hypochlorite. The results expand the knowledge of mixed-species biofilms formed by psychrotrophic bacteria and will be helpful for developing effective strategies to eliminate bacterial mixed-species biofilms.

HIGHLIGHTS

Inhibitory effect of ethanol and thiamine dilaurylsulfate against loosely, intermediately, and tightly attached mesophilic aerobic bacteria, coliforms, and Salmonella Typhimurium in chicken skin

The effects of 3 ethanol levels (30, 50, and 70%) with and without thiamine dilaurylsulfate (TDS; 1,000 ppm) were evaluated for the reduction of natural mesophilic aerobic bacteria (MAB), coliforms, and inoculated Salmonella Typhimurium (S. Typhimurium) in chicken skin. The chicken skin was inoculated with a 7 log cfu/mL suspension of S. Typhimurium. Loosely, intermediately, and tightly attached cells were recovered from chicken skin through shaking at 200 rpm for 5 min, stomaching for 1 min, and blending for 1 min, respectively. Increasing the ethanol concentration reduced the number of MAB, coliforms, and S. Typhimurium on the chicken skin, whereas TDS treatment without ethanol was not effective. Intermediately and tightly attached microorganisms (total MAB, coliforms, and S. Typhimurium) were more resistant to chemical disinfectants than loosely attached microorganisms. The combination of 70% ethanol with TDS was most effective than the combination of TDS with lower concentrations of ethanol in reducing populations of loosely, intermediately, and tightly attached MAB (by 1.88 log cfu/g, 1.21 log cfu/g, and 0.84 log cfu/g, respectively), coliforms (by 1.14 log cfu/g, 1.04 log cfu/g, and 0.67 log cfu/g, respectively), and S. Typhimurium (by 1.62 log cfu/g, 1.72 log cfu/g, and 1.27 log cfu/g, respectively). However, the chicken skin treated with higher concentrations of ethanol was tougher (P < 0.05) and more yellow and less red (P < 0.05) than that treated with lower concentrations of ethanol or with water (control). On the other hand, a combination of 30% ethanol and TDS yielded the best results, showing the reduction greater than 0.5 log cfu/g in S. Typhimurium, with no negative effect on chicken skin color or texture. Thus, a combination of 30% ethanol and TDS appears to be the optimal treatment for reducing microbial contamination of skin-on chicken products to enhance poultry safety without decreasing food quality, and this treatment could be applied in the poultry industry.

Conhecimento dos consumidores e eficiência dos métodos de lavagem e desinfecção de alface (Lactuca sativa) comercializada em supermercados em uma cidade do sul do Brasil

Resumo A alface é um vegetal mundialmente consumido. Porém, quando mal higienizada pode ser a causa de doenças transmitidas por alimentos. Esse trabalho teve como objetivo verificar o conhecimento dos manipuladores referente à lavagem e desinfecção de vegetais e avaliar a eficiência de diferentes processos de lavagem e desinfecção de alface (Lactuca sativa) comercializada em supermercados. Foi aplicado um questionário aos consumidores para conhecer as práticas de lavagem e desinfecção dos vegetais. Foram adquiridas 100 amostras de alfaces em diferentes supermercados. Para avaliar a qualidade microbiológica das alfaces, foram usados: alface sem tratamento (T0); lavagem com água tratada corrente (T1); imersão em água tratada por 30 minutos (T2); imersão em hipoclorito de sódio a 200 ppm por 15 minutos (T3); e 30 minutos (T4); imersão em solução de vinagre a 2% (T5); imersão em solução de vinagre a 20% (T6); imersão em hipoclorito de sódio a 50 ppm por 30 minutos (T7); e 15 minutos (T8). Após a realização dos tratamentos, foi realizada contagem total de bactérias heterotróficas e coliformes termotolerantes. A contagem média de bactérias heterotróficas encontradas antes da higienização (T0) foi de 5,54 log UFC/g. A maioria dos consumidores afirmou que faz a lavagem das alfaces apenas com água; somente 7,50% fazem a desinfecção; e 56,3% afirmam não ter conhecimento da maneira correta da higienização dos vegetais. Todos os métodos utilizados foram capazes de reduzir as contagens de bactérias heterotróficas, sendo que as melhores reduções foram apresentadas respectivamente pelos tratamentos T4 (2,27 log UFC/g) e T3 (2,09 log UFC/g). Nenhuma das amostras apresentou contaminação por coliformes antes e depois da higienização. Esses resultados permitem concluir que métodos de lavagem e desinfecção de alfaces são necessários para reduzir a contaminação microbiana nesse alimento antes do consumo e que se torna necessário orientar os consumidores da importância dessa prática.

Exploitation of plant extracts and phytochemicals against resistant Salmonella spp. in biofilms

Salmonella is one of the most frequent causes of foodborne outbreaks throughout the world. In the last years, the resistance of this and other pathogenic bacteria to antimicrobials has become a prime concern towards their successful control. In addition, the tolerance and virulence of pathogenic bacteria, such as Salmonella, are commonly related to their ability to form biofilms, which are sessile structures encountered on various surfaces and whose development is considered as a universal stress response mechanism. Indeed, the ability of Salmonella to form a biofilm seems to significantly contribute to its persistence in food production areas and clinical settings. Plant extracts and phytochemicals appear as promising sources of novel antimicrobials due to their cost-effectiveness, eco-friendliness, great structural diversity, and lower possibility of antimicrobial resistance development in comparison to synthetic chemicals. Research on these agents mainly attributes their antimicrobial activity to a diverse array of secondary metabolites. Bacterial cells are usually killed by the rupture of their cell envelope and in parallel the disruption of their energy metabolism when treated with such molecules, while their use at sub-inhibitory concentrations may also disrupt intracellular communication. The purpose of this article is to review the current available knowledge related to antimicrobial resistance of Salmonella in biofilms, together with the antibiofilm properties of plant extracts and phytochemicals against these detrimental bacteria towards their future application to control these in food production and clinical environments.

Efficacy of disinfectant-impregnated wipes used for surface disinfection in hospitals: a review

Background

"Ready-to-use" disinfecting wipes (also known as pre-impregnated disinfecting wipe) are broadly used in food industry and domestic situations. Their application in hospitals and healthcare centres for decontamination of medical devices and surfaces is steadily increasing because of their convenient implementation in practice and reliable performance. Beside their acceptable compliance and easy application, literature reported the disinfection failure due to the interaction between textile substrate and active ingredients, which can highly increase the risk of an infection outbreak. This review aims to call attention to the wide range of variables affecting the disinfectant-impregnated wipes' (DIWs) disinfection performances in hospitals.

Methods

A systematic literature search based on the five categories i. wipes, ii. disinfectants, iii. Application methods, iv. interaction between wipes and active ingredients and v. wiping strategy which can possibly influence the disinfection effectiveness of DIWs was conducted by Google scholar. Studies regarding the efficacy evaluation of DIWs in clinical applications were also reviewed from the National Centre for Biotechnology Information database.

Results

Variables that impact on the disinfection performance of disinfectant-impregnated wipes in surface disinfection in hospitals were summarised and critically discussed. In addition to the information, current disinfectant-impregnated wipes' decontamination efficacy test standards were reviewed, and different standards exposed some disadvantage in their testing design.

Conclusion

Various parameters contribute to the impact of DIWs disinfection performance in practice. The interaction between disinfectant active ingredients and the wiping materials barricades their broad application in hospitals. More studies of the DIWs' disinfection efficacy in clinical practice are in need. Current standards evaluating the DIWs' efficacy are required to improve for more realistic condition simulation and differentiating between mechanical removal of inoculum from a surface and chemical inactivation of the test microbe.

Transcriptome Analysis of Salmonella Heidelberg after Exposure to Cetylpyridinium Chloride, Acidified Calcium Hypochlorite, and Peroxyacetic Acid

The application of RNA sequencing in commercial poultry could facilitate a novel approach toward food safety with respect to identifying conditions in food production that mitigate transcription of genes associated with virulence and survivability. In this study, we evaluated the effects of disinfectant exposure on the transcriptomes of two field isolates of Salmonella Heidelberg (SH) isolated from a commercial broiler processing plant in 1992 and 2014. The isolates were each exposed separately to the following disinfectants commonly used in poultry processing: cetylpyridinium chloride (CPC), acidified calcium hypochlorite (aCH), and peroxyacetic acid (PAA). Exposure times were 8 s with CPC to simulate a poultry processing dipping station or 90 min with aCH and PAA to simulate the chiller tank in a poultry processing plant at 4°C. Based on comparison with a publicly available annotated SH reference genome with 5,088 genes, 90 genes were identified as associated with virulence, pathogenicity, and resistance (VPR). Of these 90 VPR genes, 9 (10.0%), 28 (31.1%), and 1 (1.1%) gene were upregulated in SH 2014 and 21 (23.3%), 26 (28.9%), and 2 (2.2%) genes were upregulated in SH 2014 challenged with CPC, aCH, and PAA, respectively. This information and previously reported MICs for the three disinfectants with both SH isolates allow researchers to make more accurate recommendations regarding control methods of SH and public health considerations related to SH in food production facilities where SH has been isolated. For example, the MICs revealed that aCH is ineffective for SH inhibition at regulatory levels allowed for poultry processing and that aCH was ineffective for inhibiting SH growth and caused an upregulation of VPR genes.

An assay for determining the susceptibility of Salmonella isolates to commercial and household biocides

Poultry and meat products contaminated with Salmonella enterica are a major cause of foodborne illness in the United States. The food industries use a wide variety of antimicrobial interventions to reduce bacterial contamination. However, little is known about Salmonella susceptibility to these compounds and some studies have shown a concerning link between biocide resistance and antibiotic resistance. To investigate this, a 96 well panel of 17 common household and commercially used biocides was designed to determine the minimum inhibitory concentrations (MIC) of these compounds for Salmonella. The panel contained two-fold serial dilutions of chemicals including Dodecyltrimethylammonium chloride (DC), Benzalkonium chloride (BKC), Cetylpyridinium chloride (CPC), Hexadecyltrimethylammonium bromide (HB), Hexadecyltrimethylammonium chloride (HC), Acetic acid (AA), Lactic acid (LA), Citric acid (CA), Peroxyacetic acid (PXA), Acidified sodium chlorite (ASC), Sodium hypochlorite (SHB), 1,3 dibromo, 5,5 dimethylhydantoin (DBH), Chlorhexidine (CHX), Sodium metasilicate (SM), Trisodium phosphate (TSP), Arsenite (ARI), and Arsenate (ARA). The assay was used to test the susceptibility of 88 multidrug resistant (MDR) Salmonella isolates from animal sources. Bacteria are defined as multidrug resistant (MDR) if it exhibited non-susceptibility to at least one agent in three or more antimicrobial categories. The concentration of biocide at which ≥50% of the isolates could not grow was designated as the minimum inhibitory concentration or MIC50 and was used as the breakpoint in this study. The MIC50 (μg ml-1) for the tested MDR Salmonella was 256 for DC, 40 for BKC, 80 for CPC. HB and HC, 1,640 for AA, 5664 for LA, 3,156 for CA, 880 for PXA, 320 for ASC, 3.0 for CHX, 1,248 for DBH, 3,152 (6%) for SHB, 60,320 for SM, 37,712 for TSP, 56 for ARI and 832 for ARA. A few isolates were not susceptible at the MIC50 breakpoint to some chemicals indicating possible resistance. Isolates with MICs of two 2-fold dilutions above the MIC50 were considered resistant. Biocides for which resistant isolates were detected included CPC (n = 1 isolate), HB (1), CA (18), ASC (7), CHX (22), ARA (16), and ARI (4). There was no correlation detected between the biocide susceptibility of Salmonella isolates and antibiotic resistance. This assay can determine the MICs of bacteria to 17 biocides in a single test and will be useful in evaluating the efficacy of biocides and to detect the development of resistance to them.

Bactericidal efficacy of a quaternary ammonium compound with food additive grade calcium hydroxide toward Salmonella Infantis and Escherichia coli on abiotic carriers

The bactericidal efficacies of 0.2% food additive grade calcium hydroxide (FdCa(OH)2) solution, a quaternary ammonium compound (QAC) diluted at 1:500 (QACx500) and their mixture-Mix500 (FdCa(OH)2 powder added at final concentration 0.2% to QACx500)-were investigated at two different temperatures (room temperature (RT) (25 ± 2°C) and 2°C), using varying contact time, with or without presence of organic materials (5% fetal bovine serum: FBS), either in suspension or on abiotic carrier (steel, rubber and plastic). In the suspension test, QACx500 could inactivate Salmonella Infantis at effective level (≥3 log reductions), within 30 sec and 5 sec, respectively, with or without 5% FBS at RT; however, at 2°C it required 30 min and 1 min, respectively. Mix500 revealed the same efficacy as QACx500 at RT, but, at 2°C it required 1 min and 30 sec, respectively with or without FBS. Whereas, 0.2% FdCa(OH)2 solution alone could inactivate S. Infantis within 1 min and 3 min, respectively at RT and 2°C, even with 5% FBS. In the carrier test, single disinfectant required bit more (3 or 5 min) contact time to reduce bacterial load (S. Infantis or Escherichia coli) down to the effective level on rubber surface than that on steel and plastic surface. However, Mix500 could inactivate both bacteria on carrier surfaces within 1 min, even at 2°C. Thus, synergistic effects were observed in the suspension test and the carrier test at both temperatures toward both bacteria.

Application of calcium oxide (CaO, heated scallop-shell powder) for the reduction of Listeria monocytogenes biofilms on eggshell surfaces

This study investigated bactericidal activity of 0.05 to 0.50% calcium oxide (CaO) against planktonic cells in tryptic soy broth (TSB) and biofilms of Listeria monocytogenes on eggshell surfaces. The bactericidal activity of CaO against planktonic cells and biofilms of L. monocytogens significantly (P < 0.05) increased log reductions with increasing concentrations of CaO. Exposure to 0.05 to 0.50% CaO for one min reduced planktonic cells in TSB cell suspensions by 0.47 to 3.86 log10CFU/mL and biofilm cells on the shell surfaces by 0.14 to 2.32 log10CFU/cm2. The Hunter colors of eggshells ("L" for lightness, "a" for redness, and "b" for yellowness), shell thickness (puncture force), and sensory quality (egg taste and yolk color) were not changed by 0.05 to 0.50% CaO treatment. The nonlinear Weibull model was used to calculate CR = 3 values as the CaO concentration of 3 log (99.9%) reduction for planktonic cells (R2 = 0.96, RMSE = 0.26) and biofilms (R2 = 0.95, RMSE = 0.18) of L. monocytogens. The CR = 3 value, 0.31% CaO for planktonic cells, was significantly (P < 0.05) lower than 0.57% CaO for biofilms. CaO could be an alternative disinfectant to reduce planktonic cells and biofilms L. monocytogenes on eggshell surface in egg processing plants.

Proteomic analysis of antimicrobial effects of pegylated silver coated carbon nanotubes in Salmonella enterica serovar Typhimurium

BACKGROUND

Synthesis of silver nano-compounds with enhanced antimicrobial effects is of great interest for the development of new antibacterial agents. Previous studies have reported the antibacterial properties of pegylated silver-coated carbon nanotubes (pSWCNT-Ag) showing less toxicity in human cell lines. However, the mechanism underlining the pSWCNT-Ag as a bactericidal agent remained unfolded. Here we assessed the pSWCNT-Ag effects against foodborne pathogenic bacteria growth and proteome profile changes.

RESULTS

Measurements of bioluminescent imaging, optical density, and bacteria colony forming units revealed dose-dependent and stronger bactericidal activity of pSWCNT-Ag than their non-pegylated counterparts (SWCNT-Ag). In ovo administration of pSWCNT-Ag or phosphate-buffered saline resulted in comparable chicken embryo development and growth. The proteomic analysis, using two-dimensional electrophoresis combined with matrix assisted laser desorption/ionization time of flight/time of flight mass spectrometry, was performed on control and surviving Salmonella enterica serovar Typhimurium to pSWCNT-Ag. A total of 15 proteins (ten up-regulated and five down-regulated) differentially expressed proteins were identified. Functional analyses showed significant reduction of proteins associated with biofilm formation, nutrient and energy metabolism, quorum sensing and maintenance of cell structure and cell motility in surviving S. Typhimurium. In contrast, proteins associated with oxygen stress, DNA protection, starvation, membrane rebuilding, and alternative nutrient formation were induced as the compensatory reaction.

CONCLUSIONS

This study provides further evidence of the antibacterial effects of pSWCNT-Ag nanocomposites and knowledge of their mechanism of action through various protein changes. The findings may lead to the development of more effective and safe antimicrobial agents.

Correlations among Resistances to Different Antimicrobial Compounds in Salmonella Strains from Hen Eggshells

Persistence of antibiotic-resistant Salmonella in the food chain may depend on strain tolerance to other antimicrobials and also on biofilm formation capacity. Yet, there is limited information on sensitivity of antibiotic-resistant Salmonella to other antimicrobials, such as phenolic compounds, chemical preservatives, or antimicrobial peptides. This study aimed at correlating antimicrobial resistance and biofilm formation capacity in antibiotic-resistant, biocide-tolerant Salmonella strains from hen eggshells. A collection of 21 strains previously selected according to their antibiotic resistance and biocide tolerance phenotypes were used for the present study. Strains were inspected for their biofilm formation capacity and for their sensitivity to (i) phenolic compounds (carvacrol, thymol), (ii) chemical preservatives (sodium lactate, trisodium phosphate), and (iii) cationic antimicrobials (polymyxin B, lysozyme-EDTA). Biofilm formation capacity was not correlated with antimicrobial resistances of the planktonic Salmonella. Polymyxin B and the lysozyme-EDTA combinations showed significant ( P < 0.05) positive correlations to each other and to sodium lactate. Significant ( P < 0.05) positive correlations were also observed for benzalkonium chloride and cetrimide with carvacrol, thymol, and trisodium phosphate, or between hexadecylpyridinium chloride and carvacrol. Antibiotic resistance also correlated positively with a higher tolerance to other antimicrobials (cefotaxime, ceftazidime, and ciprofloxacin with carvacrol, thymol, and trisodium phosphate; netilmicin with thymol and trisodium phosphate; tetracycline with carvacrol and thymol). These results must be taken into consideration to ensure a proper use of antimicrobials in the poultry industry, at concentrations that do not allow coselection of biocide-tolerant, antibiotic-resistant Salmonella.

Efficacy evaluation of commercial disinfectants by using Salmonella enterica serovar Typhimurium as a test organism

The efficacies of six commercial disinfectants were evaluated by using Salmonella enterica serovar Typhimurium under simulated natural conditions such as sub-zero temperature, short disinfecting time, and surface type (uneven or smooth). We used a suspensionmodel test to determine the disinfecting efficacy under varying contact times (1, 5, 10, and 30 min) and temperatures (25°C, 4°C, 0°C, and -10°C). The bactericidal effect according to surface structure was measured by using a carriermodel test at 25°C and -10°C. The effective concentrations of each disinfectant were fixed to give a disinfecting effect within a short time (< 1 min) at 25°C and -10°C. The suspension model results revealed that bactericidal efficacy significantly dropped at low temperature for most of the disinfectants used; a sodium dichloroisocyanurate product showed the strongest efficacy. In the carrier test, bacterial load on a wooden surface was more difficult to remove than that on a stainless-steel surface. The results show that commercial disinfectant products vary in their disinfecting efficacy, which is affected by several field factors including temperature, contact time, and carrier material. Environmental conditions and surface type for disinfection should be considered prior to selecting an optimal disinfectant in the field.

Recovery of Salmonella isolated from eggs and the commercial layer farms

BACKGROUND

Salmonella is recognized as a common bacterial cause of foodborne diarrheal illness worldwide, and animal or its food products have been the most common vehicles of the Salmonella infections. This study aimed to investigate the distribution of Salmonella in two commercial layer farms and to determine the genetic relatedness between these strains. The Salmonella isolates were serotyped by slide agglutination using commercial antisera and analyzed for genetic relatedness using pulsed-field gel electrophoresis (PFGE).

RESULTS

The internal environment had the highest prevalence of Salmonella (14/15, 93.3%), followed by external environment (60/96, 62.5%) and egg samples (23/84, 27.3%). The prevalence of Salmonella in the environment was significantly higher than that in egg samples (p < 0.05). The occurrence of Salmonella in the internal environment (93.3%) was relatively higher than in the external environment (55.6-77.2%). The 111 isolates were distributed among 15 PFGE types, and the PFGE results suggested that there existed cross-contamination between these strains not only from eggs, but also from the environments.

CONCLUSIONS

The findings indicated ongoing Salmonella cross-contamination inside or outside of the layer farms, and that Salmonella could also spread along the egg production line.

Using Photocatalyst Metal Oxides as Antimicrobial Surface Coatings to Ensure Food Safety-Opportunities and Challenges

Cross-contamination of foods with pathogenic microorganisms such as bacteria, viruses, and parasites may occur at any point in the farm to fork continuum. Food contact and nonfood contact surfaces are the most frequent source of microbial cross-contamination. In the wake of new and emerging food safety challenges, including antibiotic-resistant human pathogens, conventional sanitation and disinfection practices may not be sufficient to ensure safe food processing, proper preparation, and also not be environmentally friendly. Nanotechnology-enabled novel food safety interventions have a great potential to mitigate the risk of microbial cross-contamination in the food chain. Especially engineered nanoparticles (ENPs) are increasingly finding novel applications as antimicrobial agents. Among various ENPs, photocatalyst metal oxides have shown great promise as effective nontargeted disinfectants over a wide range of microorganisms. The present review provides an overview of antimicrobial properties of various photocatalyst metal oxides and their potential applications as surface coatings. Further, this review discusses the most common approaches to developing antimicrobial coatings, methods to characterize, test, and evaluate antimicrobial efficacy as well as the physical stability of the coatings. Finally, regulations and challenges concerning the use of these novel photocatalytic antimicrobial coatings are also discussed.

Effect of ethanol perturbation on viscosity and permeability of an inner membrane in Bacillus subtilis spores

In this work, we investigated how a combination of ethanol and high temperature (70°C), affect the properties of the inner membrane of Bacillus subtilis spores. We observed membrane permeabilization for ethanol concentrations ≥50%, as indicated by the staining of the spores' DNA by the cell impermeable dye Propidium Iodide. The loss of membrane integrity was also confirmed by a decrease in the peak corresponding to dipicolinic acid using infrared spectroscopy. Finally, the spore refractivity (as measured by phase contrast microscopy) was decreased after the ethanol-heat treatment, suggesting a partial rehydration of the protoplast. Previously we have used fluorescent lifetime imaging microscopy (FLIM) combined with the fluorescent molecular rotor Bodipy-C12 to study the microscopic viscosity in the inner membrane of B. subtilis spores, and showed that at normal conditions it is characterized by a very high viscosity. Here we demonstrate that the ethanol/high temperature treatment led to a decrease of the viscosity of the inner membrane, from 1000cP to 860cP for wild type spores at 50% of ethanol. Altogether, our present work confirms the deleterious effect of ethanol on the structure of B. subtilis spores, as well as demonstrates the ability of FLIM - Bodipy-C12 to measure changes in the microviscosity of the spores upon perturbation.