Understanding Antimicrobial Resistance (AMR) Profiles of Salmonella Biofilm and Planktonic Bacteria Challenged with Disinfectants Commonly Used During Poultry Processing

Sublethal sanitizers exposure differentially affects biofilm formation in three adapted Salmonella strains: A phenotypic-transcriptomic analysis of increased biofilm formed by ATCC 14028

PURPOSE

Using sanitizer in food industry is an important mean of sterilization and biofilm eradication, but inappropriate operation may lead to resistance, posing a concealed risk to food safety. The purpose of this study was to assess the impact of sub-lethal sanitizers on the biofilm formed by adaptive Salmonella and to explore the variations in transcription within adaptive Salmonella biofilms when co-incubated with sublethal concentrations of sanitizers.

METHODS

The microbroth dilution method was determined to measure the MIC of three sanitizers on Salmonella, and adaptation induction was conducted with steadily increasing sanitizer concentrations. The effect of sub-MIC sanitizers on the biofilm of Salmonella was investigated by crystal violet method, confocal laser scanning microscopy and transcriptomics.

RESULTS

The results indicated that the maximum growth concentration of the adapted strains was 1.69-43.25 times that of the original MIC, and the number of bacteria and matrix content were increased when re-exposed to sub-MIC benzalkonium chloride (BZK), and the expression of regulatory factors and various amino acid biosynthesis and metabolism-related genes showed an up-regulation trend.

SIGNIFICANCE

This will be beneficial to clarify the correlation and mechanism between the sanitizer adaptation of salmonellae caused by improper sanitization and increased biofilm formation resulting from this adaptation. And it helps to adjust the appropriate dosage of sanitizer and optimize sanitation standard operating procedures (SSOP) in the foodstuff industry, thereby effectively promoting the bactericidal effect and eliminating foodborne pathogens' biofilm.

Effectiveness of sanitizers on different biofilm-forming microorganisms associated with the poultry drinking water system

The sanitation of the poultry drinking water system (DWS) is essential to controlling pathogens and biofilms in the DWS. Intervention approaches including several sanitizers have been developed, but there is limited information on the efficacy of some of these sanitizers. The aim of this study was to evaluate the effectiveness of peracid-based (PAB), peroxide-based (PB), and hypochlorite-based (HB) sanitizers against field-isolated Salmonella (10), E. coli (2) and Bacillus (2), along with their antibiofilm effects on six of these bacterial strains on polyvinylchloride (PVC), a common DWS pipe material. The minimum inhibitory and bactericidal concentrations (MIC and MBC) were determined using the microdilution broth method. For biofilm production, PVC rings were inoculated (5-6 Log10 CFU/mL) in buffered peptone water, incubated at 30°C for 48 h, and detached with cotton swabs for quantification. The antibiofilm effect of the sanitizers was further assessed at MIC, 2X-MIC, 4X-MIC, and water (control). Data was analyzed using ANOVA and Least squares in JMP Pro 18. The MIC and MBC of PAB for all isolates ranged from 11.36 to 28.42 ppm, PB from 15.26 to 71.21 ppm, and HB was 106.67 to 350 ppm. Bacillus licheniformis formed the most biofilm (5.39 Log10 CFU/mL) as single-species bacteria while Salmonella attached more (6.36 Log10 CFU/mL) than E. coli (5.41 Log10 CFU/mL) and Bacillus (2.08 Log10 CFU/mL) when grown together in mixed cultures. PAB and HB eliminated the biofilms of all strains tested at MIC in mixed-species cultures while PB had no significant effect. Overall, PAB demonstrated the greatest potential as a DWS sanitizer, showing superior efficacy against planktonic and biofilm cells compared to PB and HB. This research highlights the importance of targeted microbial profiling and sanitizer efficacy testing for pre-harvest pathogen control, providing valuable insights for enhancing food safety in poultry production systems.

Probiotics/prebiotics effect on chicken gut microbiota and immunity in relation to heat-stress and climate-change mitigation

Heat stress is a serious hazard that threatens world poultry production. The avian gut microbiome plays a critical role in improving nutrient utilization, competing with pathogens, stimulating an immune response, and reducing inflammatory reactions. Hence, the gut microbiome has a positive impact on the host's health which appears in the shape of improved body weight, feed conversion rate, and increased birds' productivity (meat or eggs). Accordingly, this review shed light on the chicken gut microbiome, its correlation with the immunity of chicken, and how this affects the general health condition of the bird as well as, the role of prebiotics and probiotics in improving the gut health and increasing birds' productivity, especially under climate change and heat stress condition. The review aims to focus on the significance of maintaining healthy chickens in order to increase the production of poultry meat to satisfy human needs. A robust microbiota and a well-functioning immune system synergistically contribute to the optimal health and productivity of chickens.

Trans-cinnamaldehyde nanoemulsion reduces Salmonella Enteritidis biofilm on steel and plastic surfaces and downregulates expression of biofilm associated genes

Salmonella Enteritidis is a major poultry-associated foodborne pathogen that can form sanitizer-tolerant biofilms on various surfaces. The biofilm-forming capability of S. Enteritidis facilitates its survival on farm and food processing equipment. Conventional sanitization methods are not completely effective in killing S. Enteritidis biofilms. This study investigated the efficacy of a Generally Recognized as Safe phytochemical Trans-cinnamaldehyde (TC), and in its nanoemulsion form (TCNE), for inhibiting S. Enteritidis biofilm formation and inactivating mature biofilms developed on polystyrene and stainless-steel surfaces. Moreover, the effect of TC on Salmonella genes critical for biofilm formation was studied. TCNE was prepared using a high energy sonication method with Tween 80. For biofilm inhibition assay, S. Enteritidis was allowed to form biofilms either in the presence or absence of sub-inhibitory concentration (SIC; 0.01 %) of TCNE at 25°C and the biofilm formed was quantified at 24-h intervals for 48 h. For the inactivation assay, S. Enteritidis biofilms developed at 25°C for 48 h were exposed to TCNE (0.5, 1 %) for 1, 5, and 15 min, and surviving S. Enteritidis in the biofilm were enumerated. SIC of TCNE inhibited S. Enteritidis biofilm by 45 % on polystyrene and 75 % on steel surface after 48 h at 25°C compared to control (P < 0.05). All TCNE treatments rapidly inactivated S. Enteritidis mature biofilm on polystyrene and steel surfaces (P < 0.05). The lower concentration of TCNE (0.5 %) reduced S. Enteritidis counts by 1.5 log CFU/ml as early as 1 min of exposure on both polystyrene and stainless-steel surfaces. After 15 min of exposure, TCNE at concentration of 0.5 or 1 % reduced S. Enteritidis count significantly by 4.5 log CFU or 6 log CFU/ml on polystyrene or stainless-steel surfaces. TC downregulated the expression of S. Enteritidis genes (hilA, hilC, flhD, csgA, csgD, sdiA) responsible for biofilm formation (P < 0.05). Results suggest that TCNE has potential as a natural disinfectant for controlling S. Enteritidis biofilms on common farm and food processing surfaces, such as plastic and steel.

The Trade-Off Between Sanitizer Resistance and Virulence Genes: Genomic Insights into E. coli Adaptation

BACKGROUND

Escherichia coli is one of the most studied bacteria worldwide due to its genetic plasticity. Recently, in addition to characterizing its pathogenic potential, research has focused on understanding its resistance profile to inhibitory agents, whether these be antibiotics or sanitizers.

OBJECTIVES

The present study aimed to investigate six of the main serogroups of foodborne infection (O26, O45, O103, O111, O121, and O157) and to understand the dynamics of heterogeneity in resistance to sanitizers derived from quaternary ammonium compounds (QACs) and peracetic acid (PAA) using whole-genome sequencing (WGS).

METHODS

Twenty-four E. coli strains with varied resistance profiles to QACs and PAA were analyzed by WGS using NovaSeq6000 (150 bp Paired End reads). Bioinformatic analyses included genome assembly (Shovill), annotation via Prokka, antimicrobial resistance gene identification using Abricate, and core-genome analysis using Roary. A multifactorial multiple correspondence analysis (MCA) was conducted to explore gene-sanitizer relationships. In addition, a large-scale analysis utilizing the NCBI Pathogen Detection database involved a 2 × 2 chi-square test to examine associations between the presence of qac and stx genes.

RESULTS

The isolates exhibited varying antimicrobial resistance profiles, with O45 and O157 being the most resistant serogroups. In addition, the qac gene was identified in only one strain (S22), while four other strains carried the stx gene. Through multifactorial multiple correspondence analysis, the results obtained indicated that strains harboring genes encoding Shiga toxin (stx) presented profiles that were more likely to be sensitive to QACs. To further confirm these results, we analyzed 393,216 E. coli genomes from the NCBI Pathogen Detection database. Our results revealed a significant association (p < 0.001) between the presence of qac genes and the absence of stx1, stx2, or both toxin genes.

CONCLUSION

Our findings highlight the complexity of bacterial resistance mechanisms and suggest that non-pathogenic strains may exhibit greater tolerance to QAC sanitizer than those carrying pathogenicity genes, particularly Shiga toxin genes.

Antimicrobial resistance patterns and biofilms resurgence ability of Escherichia coli associated with commercial layer chicken farms in Sri Lanka

This study aims to understand antimicrobial resistance (AMR) associated with planktonic and biofilm-forming bacteria in Sri Lankan chicken industry. Planktonic or biofilm-forming Escherichia coli were isolated from different sources in layer chicken farms and their AMR profiles were determined. Minimum inhibitory concentrations (MICs) of selected antibiotics were quantified against planktonic E. coli isolated from water. Minimum biofilm inhibitory/eradication concentrations (MBIC/MBEC) of tetracycline were determined for biofilm E. coli. Faecal E. coli demonstrated highest resistance to tetracycline (64 % of isolates). Biofilm-derived planktonic E. coli showed greater resistance to antibiotics than planktonic E. coli (75 % vs 62.5 %). The MBIC and MBEC of tetracycline in E. coli biofilm phenotype were significantly greater than MIC of planktonic phenotype of the same isolate (P < 0.05). This study highlights the importance of eliminating biofilms in chicken industry as biofilm-forming bacteria isolated from drinkers demonstrated a significantly greater AMR and can act as a source of AMR dissemination.

Salmonella Infantis Adhesion to Various Surfaces and In Vitro Antimicrobial Efficacy of Commercial Disinfectants

Salmonella Infantis poses a significant challenge in poultry production due to its persistence and resistance to disinfectants. This study investigated the survival of the S. Infantis strain on different surfaces and evaluated the efficacy of disinfectants in both preventing and treating biofilms. The survival of the tested S. Infantis strain was assessed on plastic and stainless steel surfaces after 24 and 48 h. The minimum inhibitory concentrations (MICs) of five disinfectants were determined, and their antiadhesion effectiveness was evaluated using crystal violet. The efficacy of biofilm treatment was evaluated by cell culturability. The results showed that the adhesion of S. Infantis was significantly higher on the plastic surface. The disinfectants were effective at reducing biofilm formation only within the first 24 h. Fresh solutions of disinfectants based on quaternary ammonium compounds exhibited the highest antimicrobial efficacy, while chlorocresol was the most effective for both the prevention and treatment of biofilms. The study results suggest that the presence of plastic surfaces may contribute to the dissemination of Salmonella. Additionally, the effectiveness of disinfectants varied based on storage conditions and contact time, while biofilms demonstrated reduced susceptibility compared to planktonic cells. However, given the laboratory scale of this study, further validation on a commercial scale is necessary to confirm these findings.

Simultaneous Effects of Food-related Stresses on the Antibiotic Resistance of Foodborne Salmonella Serotypes

Antibiotic resistance has become one of the most critical issues in the field of public health in recent years. Exposure to food environment stresses may result in the development of antibiotic resistance in Salmonella. The present study aimed to investigate the simultaneous effects of food-related stresses (osmotic pressure, acid, heat, cold, and freezing stresses) on the antibiotic resistance changes in Salmonella Enteritidis and Salmonella Typhimurium. A factorial design with five factors at two levels was used to evaluate the main and interactive effects of stress factors on the antibiotic resistance of Salmonella serotypes. The changes in the antibiotic resistance of Salmonella serotypes were evaluated using the disc diffusion assay. The results showed that the different stresses had different effects on the antibiotic resistance of Salmonella serotypes. The freezing time and osmotic stresses had the most significant effects on the antibiotic resistance (P < 0.05). S. Enteritidis showed the slightest changes after exposure to stresses. The results also showed that a low level (24 h) of freezing time decreased the antibiotic resistance, but at a high level (96 h) increased it. The results emphasized that food processing and storage conditions should be considered as crucial factors in developing antibiotic resistance in Salmonella.

Defense mechanisms of Salmonella against antibiotics: a review

Salmonella is a foodborne pathogenic bacterium that causes salmonellosis worldwide. Also, Salmonella is considered a serious problem for food safety and public health. Several antimicrobial classes including aminoglycosides, tetracyclines, phenols, and β-Lactams are used to treat Salmonella infections. Antibiotics have been prescribed for decades to treat infections caused by bacteria in human and animal healthcare. However, intensive use of antibiotics resulted in antibiotic resistance (AR) among several foodborne bacteria including Salmonella. Furthermore, multi-drug resistance (MDR) of Salmonella has increased dramatically. In addition to MDR Salmonella, extensively drug resistant (XDR) as well as pan drug resistant (PDR) Salmonella were reported globally. Therefore, increasing AR is becoming a serious universal public health crisis. Salmonella developed many mechanisms to ensure its survival against antimicrobials. The most prominent defense mechanisms against these antibiotics include enzymatic inactivation, expelling drugs from the cell through efflux pumps, altering the structure of drugs, and changing or protecting the targets of drugs. Additionally, the formation of biofilms and plasmid-mediated AR by Salmonella, enhancing its resistance to various antibiotics, making it a challenging pathogen in both healthcare and food industry settings. This review focuses exclusively on providing a detailed overview of the mechanisms of AR in Salmonella.

Salmonella Prevalence and antibiotic resistance profile in raw poultry meat sold in North Lebanon: Insights from the COVID-19 pandemic and economic crisis

Salmonella-related foodborne illness is a significant public health concern, with the primary source of human infection being animal-based food products, particularly chicken meat. Lebanon is currently experiencing a dual crisis: the COVID-19 pandemic and an unprecedented economic crisis, which has resulted in substantial challenges to the public health system and food safety. This study aims to assess the prevalence and antibiotic resistance profile of Salmonella in raw poultry meat sold in North Lebanon during this dual crisis. A cross-sectional study was carried out between May 2021 and April 2022 across six different districts in North Lebanon. A total of 288 whole, unprocessed chickens were examined. The isolation and identification of Salmonella isolates were done based on cultural and biochemical properties. All isolates were subjected to antimicrobial susceptibility testing and phenotypic assays for Extended-Spectrum Beta-lactamase (ESBL) detection. The prevalence of Salmonella in raw poultry meat purchased in North Lebanon reached 18.05 % (52/288). The dry season and chilled chicken were significantly associated with an increased risk of Salmonella contamination (P < 0.05). Additionally, 34.61 % of the isolates were potential ESBL producers, and 57.69 % exhibited multidrug resistance (MDR). This study highlights the existence of MDR in chicken meat in North Lebanon, posing a potential health risk if undercooked chicken meat is consumed. This emphasizes the importance of the implementation of preventive strategies and hygienic procedures throughout the food chain to reduce the risk of Salmonella spp. contamination in chicken meats and its potential transmission to humans.

A Single Base Change in the csgD Promoter Resulted in Enhanced Biofilm in Swine-Derived Salmonella Typhimurium

Pathogenic Salmonella strains causing gastroenteritis typically can colonize and proliferate in the intestines of multiple host species. They retain the ability to form red dry and rough (rdar) biofilms, as seen in Salmonella enterica serovar Typhimurium. Conversely, Salmonella serovar like Typhi, which can cause systemic infections and exhibit host restriction, are rdar-negative. In this study, duck-derived strains and swine-derived strains of S. Typhimurium locate on independent phylogenetic clades and display relative genomic specificity. The duck isolates appear more closely related to human blood isolates and invasive non-typhoidal Salmonella (iNTS), whereas the swine isolates were more distinct. Phenotypically, compared to duck isolates, swine isolates exhibited enhanced biofilm formation that was unaffected by the temperature. The transcriptomic analysis revealed the upregulation of csgDEFG transcription as the direct cause. This upregulation may be mainly attributed to the enhanced promoter activity caused by the G-to-T substitution at position -44 of the csgD promoter. Swine isolates have created biofilm polymorphisms by altering a conserved base present in Salmonella Typhi, iNTS, and most Salmonella Typhimurium (such as duck isolates). This provides a genomic characteristics perspective for understanding Salmonella transmission cycles and evolution.

Fighting Salmonella Infantis: bacteriophage-driven cleaning and disinfection strategies for broiler farms

Introduction

Salmonella is a bacterium that can cause food-borne infections and is responsible for the most common gastrointestinal illnesses. The emergence of multi-drug resistant (MDR) strains worldwide is a major threat, representing a major challenge in public health. To reduce its incidence, the One Health approach is required, and the development of new biocontrol protocols will help prevent or eliminate the spread of Salmonella. Prevention measures, such as on-farm cleaning and disinfection protocols, are a crucial step in reducing infection to new flocks and eliminating bacteria that remain in the facilities. However, MDR Salmonella species, such as S. Infantis, are highly resistant to conventional cleaning and disinfection protocols, with an increased ability to persist in the broiler farm environment. The need for alternative biocontrol methods has led to the use of bacteriophages or phages, viruses that target bacteria, as promising tools. Thus, the aim of this study was to evaluate the efficacy of phages as a biocide against S. Infantis isolates in combination with cleaning and disinfection protocols in 10 commercial poultry farms.

Methods

All commercial farms selected in this study had persistent Salmonella, even after the routinely used cleaning and disinfection procedures. In addition, Salmonella isolated before treatment were phenotypically characterized by antimicrobial resistance patterns.

Results

The results showed that 100% of S. Infantis were resistant to at least one antibiotic, and > 70% were MDR. Phages were then isolated against the in-farm bacteria, purified, and multiplied for each poultry farm. The cleaning and disinfection protocols included the application of the lytic phages (vB_Si_CECAV_FGS009; vB_Si_CECAV_FGS017; vB_Si_CECAV_FGS029 and vB_Si_CECAV _FGS030) twice at 24-h intervals between cleaning and disinfection. Following the cleaning and disinfection procedures, Salmonella detection was reduced from 100% after cleaning to 36% after applying the phages and dropped to 0% after the final step of disinfection, thus eliminating Salmonella from the farm facilities.

Discussion

This study demonstrates that bacteriophage application after cleaning and before disinfection enhances the removal of MDR Salmonella Infantis in commercial broiler farms, suggesting their use as biocontrol agents to reduce Salmonella, a major public health concern.

Effective elimination of bacteria on hard surfaces by the combined use of bacteriophages and chemical disinfectants

Hospital-acquired infections (HAIs) represent one of the significant causes of morbidity and mortality worldwide, and controlling pathogens in the hospital environment is of great importance. Currently, the standard disinfection method in the hospital environment is chemical disinfection. However, disinfectants are usually not used strictly according to the label, making them less effective in disinfection. Therefore, there is an emergent need to find a better approach that can be used in hospitals to control pathogenic bacteria in the clinical environment. Bacteriophages (phages) are effective in killing bacteria and have been applied in the treatment of bacterial infections but have not received enough attention regarding the control of contamination in the clinical environment. In this study, we found that various phages remain active in the presence of chemical disinfectants. Moreover, the combined use of specific phages and chemical disinfectants is more effective in removing bacterial biofilms and eliminating bacteria on hard surfaces. Thus, this proof-of-concept study indicates that adding phages directly to chemical disinfectants might be an effective and economical approach to enhance clinical environment disinfection.

IMPORTANCE

In this study, we investigated whether the combination of bacteriophages and chemical disinfectants can enhance the efficacy of reducing bacterial contamination on hard surfaces in the clinical setting. We found that specific phages are active in chemical disinfectants and that the combined use of phages and chemical disinfectants was highly effective in reducing bacterial presence on hard surfaces. As a proof-of-concept, we demonstrated that adding specific phages directly to chemical disinfectants is an effective and cost-efficient strategy for clinical environment disinfection.

Prevalence of Antimicrobial Resistance Among the Hydrogen Sulfide Producing Bacteria Isolated on XLD Agar from the Poultry Fecal Samples

Poultry products remain as one of the most popular and extensively consumed foods in the world and the introduction of hydrogen sulfide (H2S) producing antibiotic resistant bacterial species into it is an emerging challenge. The current study has been designed to analyze the distribution of antibiotic resistance among the H2S producing bacteria isolated from the fecal samples of chickens from different poultry farms. Here, twenty bacterial isolates were selected based on their ability to produce H2S on XLD agar, and the16S rDNA sequencing was carried out for their molecular identification. The results showed the isolates as belong to Salmonella spp. and Citrobacter spp. and in the antibiotic susceptibility test (AST), three of the Salmonella strains were found to be resistant to antibiotics such as tetracycline, doxycycline, nalidixic acid, and amikacin. Also, fourteen Citrobacter strains showed resistance towards azithromycin, and furthermore, eleven of them were also resistant to streptomycin. Resistance towards tetracycline was observed among five of the Citrobacter strains, and seven were resistant to doxycycline. Further molecular screening by the PCR has showed three of the Salmonella strains along with eight Citrobacter isolates to have tetA gene along with four of the Citrobacter strains to have co-harbored blaTEM gene. The results on biofilm formation have also demonstrated three Salmonella strains along with nine Citrobacter strains to have the ability to form moderate biofilm. The study thus describes the occurrence of H2S producing multidrug-resistant bacteria in poultry feces, which might contribute towards the dissemination of antibiotic resistance genes to other microorganisms including human pathogens with likely risk to treat disease conditions.

Comparative Assessment of the Antibacterial and Antibiofilm Actions of Benzalkonium Chloride, Erythromycin, and L(+)-Lactic Acid against Raw Chicken Meat Campylobacter spp. Isolates

Campylobacter spp. are significant zoonotic agents, which cause annually millions of human cases of foodborne gastroenteritis worldwide. Their inclusion in biofilms on abiotic surfaces seems to play a pivotal role in their survival outside of the host, growth, and spread. To successfully mitigate the risks that arise with these bacteria, it is crucial to decrease their prevalence within the food production chain (from farm to the table), alongside the successful treatment of the resulting illness, known as campylobacteriosis. For this, the use of various antimicrobial agents remains actively in the foreground. A general-purpose biocide and cationic surfactant (benzalkonium chloride; BAC), a widely used macrolide antibiotic (erythromycin; ERY), and a naturally occurring organic acid (L(+)-lactic acid; LA) were comparatively evaluated in this work for their potential to inhibit both the planktonic and biofilm growth of 12 selected Campylobacter spp. (of which, seven were C. jejuni and five were C. coli) raw chicken meat isolates, all grown in vitro as monocultures. The inhibitory action of LA was also studied against four mixed-culture Campylobacter biofilms (each composed of three different isolates). The results showed that the individual effectiveness of the agents varied significantly depending on the isolate, growth mode (planktonic, biofilm), intercellular interactions (monocultures, mixed cultures), and the growth medium used (with special focus on blood presence). Thus, BAC exhibited minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and minimum biofilm inhibitory concentrations (MBICs) that ranged from 0.5 to 16 μg/mL. Interestingly enough, these values varied widely from 0.25 to 1024 μg/mL for ERY. Concerning LA, the MICs, MBCs, and MBICs varied from 1024 to 4096 μg/mL, with mixed-culture biofilm formation always being more difficult to suppress when compared to biofilm monocultures. In addition, it was evident that intercellular interactions encountered within mixed-culture Campylobacter biofilms significantly influenced both the population dynamics and the tolerance of each consortium member to acid exposure. Overall, the findings of this study provide useful information on the comparative effectiveness of three well-known antimicrobial agents for the control of Campylobacter spp. under various growth modes (i.e., planktonic, biofilm, monocultures, mixed cultures) that could potentially be encountered in food production and clinical settings.

The quorum sensing molecule C12-HSL promotes biofilm formation and increases adrA expression in Salmonella Enteritidis under anaerobic conditions

Acyl-homoserine lactones (AHLs) are quorum-sensing signaling molecules in Gram-negative bacteria and positively regulate biofilm formation in Salmonella under specific conditions. In this study, biofilm formation in Salmonella enterica was evaluated at 28 and 37 °C, under aerobic and anaerobic conditions. Additionally, the influence of the N-dodecanoyl-DL-homoserine lactone (C12-HSL) on biofilm formation and the expression of genes related to the synthesis of structural components, regulation, and quorum sensing was assessed under anaerobiosis at 28 and 37 °C. Biofilm formation was found not to be influenced by the atmospheric conditions at 28 °C. However, it was reduced at 37 °C under anaerobiosis. C12-HSL enhanced biofilm formation at 37 °C under anaerobiosis and increased the expression of the adrA and luxS genes, suggesting an increase in c-di-GMP, a second messenger that controls essential physiological functions in bacteria. These results provide new insights into the regulation of biofilm formation in Salmonella under anaerobic conditions.

Biofilm formation in food processing plants and novel control strategies to combat resistant biofilms: the case of Salmonella spp

Salmonella is one of the pathogens that cause many foodborne outbreaks throughout the world, representing an important global public health problem. Salmonella strains with biofilm-forming abilities have been frequently isolated from different food processing plants, especially in poultry industry. Biofilm formation of Salmonella on various surfaces can increase their viability, contributing to their persistence in food processing environments and cross-contamination of food products. In recent years, increasing concerns arise about the antimicrobial resistant and disinfectant tolerant Salmonella, while adaptation of Salmonella in biofilms to disinfectants exacerbate this problem. Facing difficulties to inhibit or remove Salmonella biofilms in food industry, eco-friendly and effective strategies based on chemical, biotechnological and physical methods are in urgent need. This review discusses biofilm formation of Salmonella in food industries, with emphasis on the current available knowledge related to antimicrobial resistance, together with an overview of promising antibiofilm strategies for controlling Salmonella in food production environments.

Exposing Salmonella Senftenberg and Escherichia coli Strains Isolated from Poultry Farms to Formaldehyde and Lingonberry Extract at Low Concentrations

European Union (EU) countries strive to improve the quality and safety of food of animal origin. Food production depends on a good microbiological quality of fodder. However, feed can be a reservoir or vector of pathogenic microorganisms, including Salmonella or Escherichia coli bacteria. Salmonella spp. and E. coli are the two most important food-borne pathogens of public health concern. Contamination with these pathogens, mainly in the poultry sector, can lead to serious food-borne diseases. Both microorganisms can form biofilms on abiotic and biotic surfaces. The cells that form biofilms are less sensitive to disinfectants, which in turn makes it difficult to eliminate them from various surfaces. Because the usage of formaldehyde in animal feed is prohibited in European countries, the replacement of this antibacterial with natural plant products seems very promising. This study aimed to assess the inhibitory effectiveness of Vaccinium vitis-idaea extract against biofilm produced by model Salmonella enterica and E. coli strains. We found that formaldehyde could effectively kill both species of bacterial cells in biofilm, while the lingonberry extract showed some antibiofilm effect on S. enterica serovar Senftenberg. In conclusion, finding natural plant products that are effective against biofilms formed by Gram-negative bacteria is still challenging.

Zingerone inhibits biofilm formation and enhances antibiotic efficacy against Salmonella biofilm

Salmonella enterica serovar Typhi is a significant cause of typhoid fever and a major public health problem. The ability of S. Typhi to form biofilms on living and non-living surfaces results in antibiotic resistance and poses a major challenge in health care. In this study, we assessed the ability of zingerone alone and in combination with antibiotics against the motility phenotypes and biofilm-forming ability of S. Typhi. Results showed that zingerone effectively reduced the swimming, swarming, and twitching phenotypes and exhibited biofilm inhibition potential. Moreover, zingerone enhanced the antibiofilm activity of ciprofloxacin and kanamycin. Microscopic analysis revealed a thinner biofilm in the presence of zingerone, which may have enhanced the antibiofilm efficacy of the antibiotics. The microscopic analysis showed that the presence of zingerone resulted in a reduction in the thickness of the biofilm, potentially increasing the antibiofilm efficacy of the antibiotics. In silico molecular docking and simulation studies further indicated that zingerone may bind to the fimbriae subunits (FimA, FimC, FimH, and FimY) of S. Typhi and form stable interactions. These findings provide important insights into the potential of zingerone to target biofilm-associated Salmonella infections. Further research is considered a promising option for designing innovative approaches to prevent infections associated with biofilms. Schematic representation of the role of zingerone in biofilm, motility inhibition and molecular interactions with biofilm associated proteins.

Estimation by flow cytometry of percentages of survival of Listeria monocytogenes cells treated with tetracycline, with or without prior exposure to several biocides

In certain circumstances, disinfectants are used at sublethal concentrations. The aim of this research work was to determine whether contact of Listeria monocytogenes NCTC 11994 with subinhibitory concentrations of three disinfectants widely used in food processing environments and in the health-care system, benzalkonium chloride (BZK), sodium hypochlorite (SHY) and peracetic acid (PAA), can cause the adaptation of the strain to the biocides and increase its resistance to tetracycline (TE). The minimum inhibitory concentrations (MIC; ppm) were 2.0 (BZK), 3500.0 (SHY) and 1050.0 (PAA). On exposure to increasing subinhibitory concentrations of the biocides, the maximum concentrations (ppm) of the compounds that allowed the strain to grow were (ppm) 8.5 (BZK), 3935.5 (SHY) and 1125.0 (PAA). Both the control cells (non-exposed) and the cells that had been in contact with low doses of biocides were treated with different concentrations of TE (0 ppm, 250 ppm, 500 ppm, 750 ppm, 1000 ppm and 1250 ppm) for 24, 48 and 72 h, and the survival percentages determined using flow cytometry, following dying with SYTO 9 and propidium iodide. The cells previously exposed to PAA presented higher survival percentages (P < 0.05) than the rest of the cells for most of the concentrations of TE and treatment times trialled. These results are worrying because TE is sometimes used to treat listeriosis, highlighting the importance of avoiding the use of disinfectant at subinhibitory doses. Furthermore, the findings suggest that flow cytometry is a fast and simple technique to obtain quantitative data on bacterial resistance to antibiotics.

Phytochemicals: potential alternative strategy to fight Salmonella enterica serovar Typhimurium

The rise of multidrug resistant (MDR) microorganisms is a great hazard worldwide and has made it difficult to treat many infectious diseases adequately. One of the most prevalent causes of outbreaks of foodborne illness worldwide is Salmonella. The ability of this and other harmful bacteria to withstand antibiotics has recently proven crucial to their effective control. Since the beginning of time, herbal medicines and phytochemicals have been employed for their potent antibacterial action and there is a growing trend toward the production of plant based natural products for the prevention and treatment of pathogenic infections. Numerous phytochemicals have been proven effective against the molecular determinants responsible for attaining drug resistance in pathogens like efflux pumps, membrane proteins, bacterial cell communications and biofilms. The medicinal plants having antibacterial activity and antibiotics combination with phytochemicals have shown synergetic activity against Salmonella enterica serovar Typhimurium. The inhibitory effects of tannins on rumen proteolytic bacteria can be exploited in ruminant nutrition. Improved control of the rumen ecology and practical use of this feed additive technology in livestock production will be made possible by a better knowledge of the modulatory effects of phytochemicals on the rumen microbial populations in combination with fermentation. This review focuses on the development of antibacterial resistance in Salmonella, the mechanism of action of phytochemicals and the use of phytochemicals against S. enterica serovar Typhimurium. The advances and potential future applications of phytochemicals in the fight against resistant are also discussed.

Application of encapsulated and dry-plated food acidulants to control Salmonella enterica in raw meat-based diets for dogs

There is an increasing demand for raw meat-based diets (RMBDs) for dogs, but these foods cannot be heat-pasteurized. Thus, the objective of this study was to evaluate the antimicrobial efficacy of encapsulated and dry-plated glucono delta lactone (GDL), citric acid (CA), and lactic acid (LA) when challenged against Salmonella enterica inoculated in a model raw meat-based diet (RMBDs) for dogs. Nutritionally complete, raw diets were formulated with different levels (1.0, 2.0 and 3.0% (w/w)) of both encapsulated and dry-plated GDL, CA, and LA with both the positive (PC) and the negative controls (NC) without acidulants. The diets were formed into patties of ∼100 g and inoculated with 3-cocktail mixtures of Salmonella enterica serovars, excluding the NC to achieve a final concentration of ∼6.0 Log CFU/patty. Microbial analyses were performed on the inoculated diets and survivors of S. enterica enumerated. Both encapsulated and dry-plated CA and LA had higher log reductions compared to GDL (P < 0.05). However, encapsulated CA and LA at 1.0% (w/w) exhibited higher log reductions (P > 0.05) and preserved product quality compared to the dry-plated acidulants at 1.0%. We concluded that 1.0% (w/w) of encapsulated citric or lactic acids could be successfully applied as an antimicrobial intervention in raw diets for dogs.

Current and future interventions for improving poultry health and poultry food safety and security: A comprehensive review

Poultry is thriving across the globe. Chicken meat is the most preferred poultry worldwide, and its popularity is increasing. However, poultry also threatens human hygiene, especially as a fomite of infectious diseases caused by the major foodborne pathogens (Campylobacter, Salmonella, and Listeria). Preventing pathogenic bacterial biofilm is crucial in the chicken industry due to increasing food safety hazards caused by recurring contamination and the rapid degradation of meat, as well as the increased resistance of bacteria to cleaning and disinfection procedures commonly used in chicken processing plants. To address this, various innovative and promising strategies to combat bacterial resistance and biofilm are emerging to improve food safety and quality and extend shelf-life. In particular, natural compounds are attractive because of their potential antimicrobial activities. Natural compounds can also boost the immune system and improve poultry health and performance. In addition to phytochemicals, bacteriophages, nanoparticles, coatings, enzymes, and probiotics represent unique and environmentally friendly strategies in the poultry processing industry to prevent foodborne pathogens from reaching the consumer. Lactoferrin, bacteriocin, antimicrobial peptides, cell-free supernatants, and biosurfactants are also of considerable interest for their prospective application as natural antimicrobials for improving the safety of raw poultry meat. This review aims to describe the feasibility of these proposed strategies and provide an overview of recent published evidences to control microorganisms in the poultry industry, considering the human health, food safety, and economic aspects of poultry production.

Applications of water activated by ozone, electrolysis, or gas plasma for microbial decontamination of raw and processed meat

A raw or processed meat product can be a breeding ground for spoilage bacteria (Enterobacteriaceae, Lactobacillus spp., Pseudomonas spp., etc.). Failure of decontamination results in food quality loss and foodborne illnesses caused by pathogens such as Salmonella, Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes. Often, meat processors decontaminate the carcass using cheap chemicals or artificial antimicrobial agents not listed on the ingredient list, which is discouraged by health-conscious consumers. Foods with clean labels became more popular during the COVID-19 pandemic, which led consumers to choose healthier ingredients. Novel methods of controlling or improving meat safety are constantly being discovered. This review focuses on novel means of electrochemically activate water that is being investigated as a sanitizing agent for carcasses and processing area decontamination during production or at the end. Water can be activated by using non-thermal techniques such as ozonation, electrolysis, and cold plasma technologies. Recent studies showed that these activated liquids are powerful tools for reducing microbial activity in raw and processed meat. For instance, plasma-activated water can be used to enhance microbiological safety and avoid the negative effects of direct gaseous plasma on the organoleptic aspects of food products. In addition, electrolyzed water technology offers hurdle enhancement by combining with non-thermal strategies that have great potential. Ozonation is another way of activating water which provides a very convenient way to control microbiological safety and finds several recent applications as aqueous ozone for meat decontamination. These solutions are highly reactive and convenient for non-conventional applications in the meat industry related to food safety because of their antimicrobial or antiviral impact. The present review highlights the efficacy of activated-water decontamination of raw and processed meat via non-thermal solutions.

Exploring Possible Ways to Enhance the Potential and Use of Natural Products through Nanotechnology in the Battle against Biofilms of Foodborne Bacterial Pathogens

Biofilms enable pathogenic bacteria to survive in unfavorable environments. As biofilm-forming pathogens can cause rapid food spoilage and recurrent infections in humans, especially their presence in the food industry is problematic. Using chemical disinfectants in the food industry to prevent biofilm formation raises serious health concerns. Further, the ability of biofilm-forming bacterial pathogens to tolerate disinfection procedures questions the traditional treatment methods. Thus, there is a dire need for alternative treatment options targeting bacterial pathogens, especially biofilms. As clean-label products without carcinogenic and hazardous potential, natural compounds with growth and biofilm-inhibiting and biofilm-eradicating potentials have gained popularity as natural preservatives in the food industry. However, the use of these natural preservatives in the food industry is restricted by their poor availability, stability during food processing and storage. Also there is a lack of standardization, and unattractive organoleptic qualities. Nanotechnology is one way to get around these limitations and as well as the use of underutilized bioactives. The use of nanotechnology has several advantages including traversing the biofilm matrix, targeted drug delivery, controlled release, and enhanced bioavailability, bioactivity, and stability. The nanoparticles used in fabricating or encapsulating natural products are considered as an appealing antibiofilm strategy since the nanoparticles enhance the activity of the natural products against biofilms of foodborne bacterial pathogens. Hence, this literature review is intended to provide a comprehensive analysis of the current methods in nanotechnology used for natural products delivery (biofabrication, encapsulation, and nanoemulsion) and also discuss the different promising strategies employed in the recent and past to enhance the inhibition and eradication of foodborne bacterial biofilms.

Towards a Harmonized Terminology: A Glossary for Biocide Susceptibility Testing

Disinfection is a key strategy to reduce the burden of infections. The contact of bacteria to biocides-the active substances of disinfectants-has been linked to bacterial adaptation and the development of antimicrobial resistance. Currently, there is no scientific consensus on whether the excessive use of biocides contributes to the emergence and spread of multidrug resistant bacteria. The comprehensive analysis of available data remains a challenge because neither uniform test procedures nor standardized interpretive criteria nor harmonized terms are available to describe altered bacterial susceptibility to biocides. In our review, we investigated the variety of criteria and the diversity of terms applied to interpret findings in original studies performing biocide susceptibility testing (BST) of field isolates. An additional analysis of reviews summarizing the knowledge of individual studies on altered biocide susceptibility provided insights into currently available broader concepts for data interpretation. Both approaches pointed out the urgent need for standardization. We, therefore, propose that the well-established and approved concepts for interpretation of antimicrobial susceptibility testing data should serve as a role model to evaluate biocide resistance mechanisms on a single cell level. Furthermore, we emphasize the adaptations necessary to acknowledge the specific needs for the evaluation of BST data. Our approach might help to increase scientific awareness and acceptance.

Acute stress of the typical disinfectant glutaraldehyde-didecyldimethylammonium bromide (GD) on sludge microecology in livestock wastewater treatment plants: Effect and its mechanisms

Glutaraldehyde and didecyldimethylammonium bromide (GD) is a disinfectant widely used to prevent African swine fever (ASF) in livestock farms. However, the effect of residual GD on the activated sludge microbial ecology of receiving wastewater treatment plants (WWTPs) remains largely unknown. In this study, seven simulated systems were established to research the effects of GD on WWTPs and reveal the underlying mechanisms of microecological responses to GD at different concentrations. Both the nitrogen and carbon removal rates decreased with increasing GD concentrations, and nitrogen metabolism was inhibited more obviously, but the inhibition weakened with increasing stress duration. Microorganisms activated their SoxRS systems to promote ATP synthesis and electron transfer to support the hydrolysis and efflux of GD by producing a small number of ROS when exposed to GD at less than 1 mg/L. The overproduction of ROS led to a decrease of antioxidant and nitrogen removal enzyme activities, and upregulation of the porin gene increased the risk of GD entering the intracellular space upon exposure to GD at concentrations higher than 1 mg/L. Some denitrifiers survived via resistance and their basic capabilities of sugar metabolism and nitrogen assimilation. Notably, low concentrations of disinfectants could promote vertical and horizontal transfer of multiple resistance genes, especially aminoglycosides, among microorganisms, which might increase not only the adaptation capability of denitrifiers but also the risk to ecological systems. Therefore, the risks of disinfectants targeting ASF on ecology and health as well as the effects of disinfectant residuals from the COVID-19 epidemic should receive more attention.

Disinfectant resistance of Salmonella in in vitro contaminated poultry house models and investigation of efficient disinfection methods using these models

Salmonellaenterica subsp. enterica (Salmonella) shows disinfectant resistance by forming biofilms on solid surfaces. However, efficient disinfection methods to eliminate Salmonella biofilms from farms have not yet been examined in detail. In this study, more than 80% of Salmonella strains from farms in Yamagata prefecture, Japan, were biofilm producers. Regardless of the extent of their biofilm formation ability, their biofilms were highly resistant to hypochlorous acid on plastic surfaces. To establish efficient disinfection methods in farms, we developed in vitro Salmonella-contaminated poultry house models by depositing dust on ceramic and stainless-steel carriers in poultry houses for one month and culturing a representative Salmonella strain on the carriers. Biofilm-like structures, including Salmonella-like cells, were observed on the models by scanning electron microscopy. Salmonella was not efficiently removed from the models even by cleaning with a surfactant at 25/65°C and disinfection with quaternary ammonium compound or hypochlorous acid at 25°C; on the contrary, viable Salmonella cells increased in some tests under these conditions, suggesting that these models successfully simulate the highly persistent characteristics of Salmonella in farms. However, the persistent bacterial cells were markedly decreased by soaking in 65°C surfactant followed by rinsing with 80°C water, additional cleaning using chlorine dioxide or disinfection with dolomitic lime, suggesting the effectiveness of these methods against Salmonella in farms. Since many different disinfection conditions may be easily tested in laboratories, our models will be useful tools for establishing effective and practical disinfection methods in farms.

Natural products from traditional medicine as promising agents targeting at different stages of oral biofilm development

Oral cavity is an ideal habitat for more than 1,000 species of microorganisms. The diverse oral microbes form biofilms over the hard and soft tissues in the oral cavity, affecting the oral ecological balance and the development of oral diseases, such as caries, apical periodontitis, and periodontitis. Currently, antibiotics are the primary agents against infectious diseases; however, the emergence of drug resistance and the disruption of oral microecology have challenged their applications. The discovery of new antibiotic-independent agents is a promising strategy against biofilm-induced infections. Natural products from traditional medicine have shown potential antibiofilm activities in the oral cavity with high safety, cost-effectiveness, and minimal adverse drug reactions. Aiming to highlight the importance and functions of natural products from traditional medicine against oral biofilms, here we summarized and discussed the antibiofilm effects of natural products targeting at different stages of the biofilm formation process, including adhesion, proliferation, maturation, and dispersion, and their effects on multi-species biofilms. The perspective of antibiofilm agents for oral infectious diseases to restore the balance of oral microecology is also discussed.

Retail Chicken Carcasses as a Reservoir of Multidrug-Resistant Salmonella

Salmonella is a major cause of foodborne disease outbreaks worldwide, mainly through poultry. Recently, there has been an increase in multidrug-resistant (MDR) Salmonella infections globally. The increased drug resistance results in increased costs and poorer health outcomes due to unavailability or delayed treatment. This study aims to determine the prevalence of Salmonella in retail raw chicken meat and identify their antimicrobial resistance profiles. A total of 270 retail raw chicken carcasses (local and imported) were collected from three hypermarket chains in Qatar between November 2017 and April 2018. Thirty carcasses were contaminated with Salmonella (11.11%). The prevalence of Salmonella in locally produced chicken was higher than in imported chicken (OR = 2.56, 95% CI: 1.18-5.53, p = 0.016). No significant differences were found between the prevalence and storage temperature or hypermarket chain. The highest resistance rates in the isolates were reported to tetracycline (73.7%) followed by nitrofurantoin (53.3%), ampicillin (50%), amoxicillin-clavulanic acid, ceftriaxone (26.7%), and ciprofloxacin (23.3%). Eight isolates were potential extended-spectrum β-lactamase-producers, all in imported frozen chicken (p < 0.0001). Additionally, 43.3% of the isolates were MDR and associated with frozen chicken (OR = 16.88, 95% CI: 2.55-111.47, p = 0.002). The findings indicate that while the prevalence of Salmonella in retail chicken in Qatar is moderate, a large proportion of them are MDR.

Untargeted Metabolomics Approach of Cross-Adaptation in Salmonella Enterica Induced by Major Compounds of Essential Oils

Cross-adaptation phenomena in bacterial populations, induced by sublethal doses of antibacterial solutions, are a major problem in the field of food safety. In this regard, essential oils and their major compounds appear as an effective alternative to common sanitizers in food industry environments. The present study aimed to evaluate the untargeted metabolomics perturbations of Salmonella enterica serovar Enteritidis that has been previously exposed to the sublethal doses of the major components of essential oils: cinnamaldehyde, citral, and linalool (CIN, CIT, and LIN, respectively). Cinnamaldehyde appeared to be the most efficient compound in the assays evaluating the inhibitory effects [0.06% (v/v) as MBC]. Also, preliminary tests exhibited a phenotype of adaptation in planktonic and sessile cells of S. Enteritidis when exposed to sublethal doses of linalool, resulting in tolerance to previously lethal concentrations of citral. A metabolomics approach on S. Enteritidis provided an important insight into the phenomenon of cross-adaptation induced by sublethal doses of major compounds of some essential oils. In addition, according to the results obtained, when single molecules were used, many pathways may be involved in bacterial tolerance, which could be different from the findings revealed in previous studies regarding the use of phytocomplex of essential oils. Orthogonal projection to latent structures (OPLS) proved to be an interesting predictive model to demonstrate the adaptation events in pathogenic bacteria because of the global engagement to prevent and control foodborne outbreaks.

Effect of pH and Salinity on the Ability of Salmonella Serotypes to Form Biofilm

Salmonella is a major cause of food-borne infections in Europe, and the majority of human infections are caused by only a few serotypes, among them are Salmonella enterica subsp. enterica serotype Enteritidis (hereafter Salmonella Enteritidis), Salmonella Typhimurium, and the monophasic variant of S. Typhimurium. The reason for this is not fully understood, but could include virulence factors as well as increased ability to transfer via the external environment. Formation of biofilm is considered an adaptation strategy used by bacteria to overcome environmental stresses. In order to assess the capability of different Salmonella serotypes to produce biofilm and establish whether this is affected by pH and salinity, 88 Salmonella isolates collected from animal, food, and human sources and belonging to 15 serotypes, including those most frequently responsible for human infections, were tested. Strains were grown in tryptic soy broth (TSB), TSB with 4% NaCl pH 4.5, TSB with 10% NaCl pH 4.5, TSB with 4% NaCl pH 7, or TSB with 10% NaCl pH 7, and biofilm production was assessed after 24 h at 37°C using crystal violet staining. A linear mixed effect model was applied to compare results from the different experimental conditions. Among the tested serotypes, S. Dublin showed the greatest ability to form biofilm even at pH 4.5, which inhibited biofilm production in the other tested serotypes. Salmonella Senftenberg and the monophasic variant of S. Typhimurium showed the highest biofilm production in TSB with 10% NaCl pH 7. In general, pH had a high influence on the ability to form biofilm, and most of the tested strains were not able to produce biofilm at pH 4.5. In contrast, salinity only had a limited influence on biofilm production. In general, serotypes causing the highest number of human infections showed a limited ability to produce biofilm in the tested conditions, indicating that biofilm formation is not a crucial factor in the success of these clones.

Assessing antimicrobial resistance occurrence in the Portuguese food system: Poultry, pigs and derived food, 2014-2018

Antimicrobial resistance (AMR) spread in the food system is a major threat to public and animal health. We describe AMR trends in zoonotic bacteria and identify risk factors associated with AMR occurrence in animals and derived food in Portugal. Data from the Portuguese AMR surveillance programme on food-producing animals, 2014-2018, were used. AMR frequencies were calculated for Escherichia coli, Campylobacter and Salmonella in broilers, turkeys, pig populations and their derived food products. AMR-associated factors were studied for Salmonella isolates: population, sampling stage (farm, slaughterhouse and processing plant), sample type (environmental, carcase and food), sampler (HACCP, industry, official and official and industry), sample context (control and eradication programmes and monitoring), year (2014-2018) and season. Logistic regression was applied to estimate crude odds ratio and adjusted odds ratio (aOR) with 95% confidence intervals (95% CI). The final models were obtained using a backward stepwise method. This study included 2,157 Escherichia coli, 561 Campylobacter and 1,071 Salmonella isolates. The highest prevalence estimates amongst tested antimicrobials for each bacterial species in 2014-2018 had the following ranges: (i) (fluoro)quinolones: E. coli: 84%-93%, Campylobacter: 94%-98%; (ii) tetracyclines: E. coli: 68%-91%, Campylobacter: 87%-91%, Salmonella: 72%; (iii) penicillins: E. coli: 82%-100%; (iv) sulphonamides: E. coli: 68%-82%. Compared with the reference categories for host (broiler), year (2014), season (winter) and sampler (HACCP own checks), resistance to at least one antimicrobial in Salmonella was significantly less likely in laying hens (aOR 0.28; 95% CI: 0.18-0.42), 2016 (aOR 0.56; 95% CI: 0.33-0.93), 2017 (aOR 0.29; 95% CI: 0.17-0.51) and 2018 (aOR 0.35; 95% CI: 0.20-0.61), autumn (aOR 0.63; 95% CI: 0.40-0.97) and more likely to occur in broiler products (aOR 5.14; 95% CI: 2.61-10.54), pork products (aOR 6.84; 95% CI: 3.74-12.98) and official and industry combined sampling (aOR 2.16; 95% CI: 1.06-4.47). This study reveals a high prevalence of Salmonella resistance, especially during the summer and in post-farm stages of the Portuguese food system to nearly all antimicrobials and in the summer in farms to (fluoro)quinolones. Measures to tackle resistance are required.

Water-Soluble Ruthenium (II) Complex Derived From Optically Pure Limonene and Its Microencapsulation Are Efficient Tools Against Bacterial Food Pathogen Biofilms: Escherichia coli, Staphylococcus aureus, Enteroccocus faecalis, and Listeria monocytogenes

Bioactive aminooxime ligands based on optically pure (R)-limonene have been synthesized in two steps. Their ruthenium (II) cationic water-soluble complex was prepared by a reaction between dichloro (para-cymene) ruthenium (II) dimers and aminooxime ligands in a 1:2 molar ratio. Antibacterial and antibiofilm activities of the synthetized complex were assessed against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Enterococcus faecalis. The results revealed that the ruthenium (II) complex has higher antibacterial and antibiofilm activities in comparison with free ligands or the enantiopure (R)-limonene. Moreover, microencapsulation of this complex reduced its cytotoxicity and improved their minimum inhibitory concentration and antibiofilm activity toward the considered bacteria. The ruthenium (II) complex targets the bacterial cell membrane, which leads to rapid leakage of intracellular potassium. Our study suggests that the developed ruthenium (II) complexes could be useful as an alternative to conventional disinfectants.

Differences in biofilm formation of Salmonella serovars on two surfaces under two temperature conditions

AIMS

Salmonella is extremely diverse, with >2500 serovars that are genetically and phenotypically diverse. The aim of this study was to build a collection of Salmonella isolates that are genetically diverse and to evaluate their ability to form biofilm under different conditions relevant to a processing environment.

METHODS AND RESULTS

Twenty Salmonella isolates representative of 10 serovars were subtyped using Clustered regularly interspaced short palindromic repeats (CRISPR)-typing to assess the genetic diversity between isolates of each serovar. Biofilm formation of the isolates on both plastic and stainless-steel surfaces at 25 and 15°C was assessed. At 25°C, 8/20 isolates each produced strong and moderate biofilm on plastic surface compared to stainless-steel (3/20 and 13/20 respectively). At 15°C, 5/20 produced strong biofilm on plastic surface and none on stainless-steel. Several isolates produced weak biofilm on plastic (11/20) and stainless-steel (16/20) surfaces. Serovar Schwarzengrund consistently produced strong biofilm while serovars Heidelberg and Newport produced weak biofilm.

CONCLUSION

These results suggest that Salmonellae differ in their attachment depending on the surface and temperature conditions encountered, which may influence persistence in the processing environment.

SIGNIFICANCE AND IMPACT OF STUDY

These differences in biofilm formation could provide useful information for mitigation of Salmonella in processing environments.

Disinfectant and Antimicrobial Susceptibility Studies of Staphylococcus aureus Strains and ST398-MRSA and ST5-MRSA Strains from Swine Mandibular Lymph Node Tissue, Commercial Pork Sausage Meat and Swine Feces

Staphylococcus aureus (S. aureus) causes gastrointestinal illness worldwide. Disinfectants are used throughout the food chain for pathogenic bacteria control. We investigated S. aureus bioavailability in swine Mandibular lymph node tissue (MLT) and pork sausage meat (PSM), established susceptibility values for S. aureus to disinfectants, and determined the multilocus sequence type of MRSA strains. Antimicrobial and disinfectant susceptibility profiles were determined for 164 S. aureus strains isolated from swine feces (n = 63), MLT (n = 49) and PSM (n = 52). No antimicrobial resistance (AMR) was detected to daptomycin, nitrofurantoin, linezolid, and tigecycline, while high AMR prevalence was determined to erythromycin (50.6%), tylosin tartrate (42.7%), penicillin (72%), and tetracycline (68.9%). Methicillin-resistant S. aureus (MRSA) strains, ST398 (n = 6) and ST5 (n = 1), were found in the MLT and PSM, 4 MRSA in MLT and 3 MRSA strains in the PSM. About 17.5% of feces strains and 41.6% of MLT and PSM strains were resistant to chlorhexidine. All strains were susceptible to triclosan and benzalkonium chloride, with no cross-resistance between antimicrobials and disinfectants. Six MRSA strains had elevated susceptibilities to 18 disinfectants. The use of formaldehyde and tris(hydroxylmethyl)nitromethane in DC&R was not effective, which can add chemicals to the environment. Didecyldimethylammonium chloride and benzyldimethylhexadecylammonium chloride were equally effective disinfectants. ST398 and ST5 MRSA strains had elevated susceptibilities to 75% of the disinfectants tested. This study establishes susceptibility values for S. aureus strains from swine feces, mandibular lymph node tissue, and commercial pork sausage against 24 disinfectants. Since it was demonstrated that S. aureus and MRSA strains can be found deep within swine lymph node tissue, it may be beneficial for the consumer if raw swine lymph node tissue is not used in uncooked food products and pork sausage.

Genetic Characterization of Salmonella Infantis with Multiple Drug Resistance Profiles Isolated from a Poultry-Farm in Chile

Salmonella comprises over 2500 serotypes and foodborne contamination associated with this pathogen remains an important health concern worldwide. During the last decade, a shift in serotype prevalence has occurred as traditionally less prevalent serotypes are increasing in frequency of infections, especially those related to poultry meat contamination. S. Infantis is one of the major emerging serotypes, and these strains commonly display antimicrobial resistance and can persist despite cleaning protocols. Thus, this work aimed to isolate S. Infantis strains from a poultry meat farm in Santiago, Chile and to characterize genetic variations present in them. We determined their genomic and phenotypic profiles at different points along the production line. The results indicate that the strains encompass 853 polymorphic sites (core-SNPs) with isolates differing from one another by 0-347 core SNPs, suggesting variation among them; however, we found discrete correlations with the source of the sample in the production line. Furthermore, the pan-genome was composed of 4854 total gene clusters of which 2618 (53.9%) corresponds to the core-genome and only 181 (3.7%) are unique genes (those present in one particular strain). This preliminary analysis will enrich the surveillance of Salmonella, yet further studies are required to assess their evolution and phylogeny.

Promising strategies to control persistent enemies: Some new technologies to combat biofilm in the food industry-A review

Biofilm is an advanced form of protection that allows bacterial cells to withstand adverse environmental conditions. The complex structure of biofilm results from genetic-related mechanisms besides other factors such as bacterial morphology or substratum properties. Inhibition of biofilm formation of harmful bacteria (spoilage and pathogenic bacteria) is a critical task in the food industry because of the enhanced resistance of biofilm bacteria to stress, such as cleaning and disinfection methods traditionally used in food processing plants, and the increased food safety risks threatening consumer health caused by recurrent contamination and rapid deterioration of food by biofilm cells. Therefore, it is urgent to find methods and strategies for effectively combating bacterial biofilm formation and eradicating mature biofilms. Innovative and promising approaches to control bacteria and their biofilms are emerging. These new approaches range from methods based on natural ingredients to the use of nanoparticles. This literature review aims to describe the efficacy of these strategies and provide an overview of recent promising biofilm control technologies in the food processing sector.

A systematic review from basics to omics on bacteriophage applications in poultry production and processing

The growing human population is currently facing an unprecedented challenge on global food production and sustainability. Despite recognizing poultry as one of the most successful and rapidly growing food industries to address this challenge; poultry health and safety remain major issues that entail immediate attention. Bacterial diseases including colibacillosis, salmonellosis, and necrotic enteritis have become increasingly prevalent during poultry production. Likewise, outbreaks caused by consumption of undercooked poultry products contaminated with zoonotic bacterial pathogens such as Salmonella, Campylobacter and Listeria, are a serious public health concern. With antimicrobial resistance problem and restricted use of antibiotics in food producing animals, bacteriophages are increasingly recognized as an attractive natural antibacterial alternative. Bacteriophages have recently shown promising results to treat diseases in poultry, reduce contamination of carcasses, and enhance the safety of poultry products. Omics technologies have been successfully employed to accurately characterize bacteriophages and their genes/proteins important for interaction with bacterial hosts. In this review, the potential of using lytic bacteriophages to mitigate the risk of major poultry-associated bacterial pathogens are explored. This study also explores challenges associated with the adoption of this technology by industries. Furthermore, the impact of omics approaches on studying bacteriophages, their host interaction and applications is discussed.

Bacteriophage treatment before chemical disinfection can enhance removal of plastic surface-associated Pseudomonas aeruginosa

Opportunistic pathogens can linger on surfaces in hospital and building plumbing environments, leading to infections in at-risk populations. Further, biofilm-associated bacteria are protected from removal and inactivation protocols, such as disinfection. Bacteriophages show promise as tools to treat antibiotic resistant infections. As such, phages may also be useful in environmental applications to prevent newly acquired infections. In the current study, the potential of synergies between bacteriophage and chemical disinfection of the opportunistic pathogen Pseudomonas aeruginosa was assessed under various conditions. Specifically, surface-associated P. aeruginosa was treated with various concentrations of phages (P1 or JG004), chemical disinfectant (sodium hypochlorite or benzalkonium chloride), or combined sequential treatments under three distinct attachment models (spot inoculations, dry biofilms, and wet biofilms). Phages were very effective at removing bacteria in spot inoculation (>3.2 log₁₀ removal) and wet biofilms (up to 2.6 log₁₀ removal), while phages prevented regrowth of dry biofilms in the application time. In addition, phage treatment followed by chemical disinfection inactivated more P. aeruginosa under wet biofilm conditions better than either treatment alone. This effect was hindered when chemical disinfection was applied first, followed by phage treatment, suggesting additive benefits of combination treatments are lost when phage is applied last. Further, we confirm prior evidence of greater phage tolerance to benzalkonium chloride relative to sodium hypochlorite, informing choices for combination phage-disinfectant approaches. Overall, this paper further supports the potential of using combination phage and chemical disinfectant treatments to improve inactivation of surface-associated P. aeruginosa. Importance Phages are already utilized in the healthcare industry to treat antibiotic resistant infections, such as on implant-associated biofilms and in compassionate care cases. Phage treatment could also be a promising new tool to control pathogens in the built environment, preventing infections from occurring. This study shows that phage can be combined effectively with chemical disinfectants to improve removal of wet biofilms and bacteria spotted onto surfaces while preventing regrowth in dry biofilms. This has the potential to improve pathogen containment within the built environment and drinking water infrastructure to prevent infections of opportunistic pathogens.

Reduction of Salmonella Infantis on skin-on, bone-in chicken thighs by cetylpyridinium chloride application and the impact on the skin microbiota

Salmonella Infantis has been the etiological agent of numerous foodborne outbreaks of nontyphoidal Salmonella. Consequently, there is an emergent need to mitigate Salmonella Infantis among poultry. Thus, this study evaluated the efficacy of cetylpyridinium chloride (CPC) versus peroxyacetic acid (PAA), on bone-in, skin-on chicken thighs for the reduction of Salmonella and changes in the microbiota. Exactly 100 skin-on, bone-in chicken thighs (2 trials, 0 and 24 h, k = 5, n = 5, N = 50) were inoculated with 10⁸ CFU/mL of a nalidixic acid resistant strain of S. Infantis for an attachment of 10⁶ CFU/g. Thighs were treated with 20 s part dips (350 mL): a no inoculum, no treatment control (NINTC); no treatment control (NTC); tap water (TW); TW+CPC; TW+PAA. Following treatment, thighs were rinsed in 150 mL of nBPW, and rinsates were collected. Rinsates were spot plated for Salmonella and aerobic bacteria (APC). Log₁₀ transformed counts were analyzed using a mixed-effects model (random effect = trial) with means separated using Tukey's HSD (P ≤ 0.05). The genomic DNA of rinsates was extracted, and the 16S rDNA was sequenced on an Illumina MiSeq. Microbiota data were analyzed using QIIME2, with data considered significant at P ≤ 0.05 (main effects) and Q≤0.05 (pairwise differences). Treatment × time interactions were observed for both Salmonella and APC (P < 0.05). The treatment of thighs with PAA and CPC reduced Salmonella and APC in respect to the controls. Numerically, thighs treated with CPC had less Salmonella (4.29 log₁₀CFU/g) and less APC (4.56 log₁₀CFU/g) at 24 h than all other treatments (P > 0.05). Differences in diversity metrics were not consistently observed between treatments; however, in trial 2, the NTC treated thighs were different than those treated with CPC (P < 0.05; Q < 0.05). In both trials, ANCOM, the analysis of microbiome compositional profiles, revealed shifts at both the phylum and order levels with thighs being different in the relative abundances of Proteobacteria (P < 0.05). In conclusion, treatment of skin-on poultry parts with CPC may reduce the risk of foodborne outbreaks caused by Salmonella Infantis.

Combination of Natural Compounds With Novel Non-thermal Technologies for Poultry Products: A Review

Ensuring safe, fresh, and healthy food across the shelf life of a commodity is an ongoing challenge, with the driver to minimize chemical additives and their residues in the food processing chain. High-value fresh protein products such as poultry meat are very susceptible to spoilage due to oxidation and bacterial contamination. The combination of non-thermal processing interventions with nature-based alternatives is emerging as a useful tool for potential adoption for safe poultry meat products. Natural compounds are produced by living organisms that are extracted from nature and can be used as antioxidant, antimicrobial, and bioactive agents and are often employed for other existing purposes in food systems. Non-thermal technology interventions such as high-pressure processing, pulsed electric field, ultrasound, irradiation, and cold plasma technology are gaining increasing importance due to the advantages of retaining low temperatures, nutrition profiles, and short treatment times. The non-thermal unit process can act as an initial obstacle promoting the reduction of microflora, while natural compounds can provide an active obstacle either in addition to processing or during storage time to maintain quality and inhibit and control growth of residual contaminants. This review presents the application of natural compounds along with emerging non-thermal technologies to address risks in fresh poultry meat.

Role played by the environment in the emergence and spread of antimicrobial resistance (AMR) through the food chain

The role of food-producing environments in the emergence and spread of antimicrobial resistance (AMR) in EU plant-based food production, terrestrial animals (poultry, cattle and pigs) and aquaculture was assessed. Among the various sources and transmission routes identified, fertilisers of faecal origin, irrigation and surface water for plant-based food and water for aquaculture were considered of major importance. For terrestrial animal production, potential sources consist of feed, humans, water, air/dust, soil, wildlife, rodents, arthropods and equipment. Among those, evidence was found for introduction with feed and humans, for the other sources, the importance could not be assessed. Several ARB of highest priority for public health, such as carbapenem or extended-spectrum cephalosporin and/or fluoroquinolone-resistant Enterobacterales (including Salmonella enterica), fluoroquinolone-resistant Campylobacter spp., methicillin-resistant Staphylococcus aureus and glycopeptide-resistant Enterococcus faecium and E. faecalis were identified. Among highest priority ARGs bla CTX -M, bla VIM, bla NDM, bla OXA -48-like, bla OXA -23, mcr, armA, vanA, cfr and optrA were reported. These highest priority bacteria and genes were identified in different sources, at primary and post-harvest level, particularly faeces/manure, soil and water. For all sectors, reducing the occurrence of faecal microbial contamination of fertilisers, water, feed and the production environment and minimising persistence/recycling of ARB within animal production facilities is a priority. Proper implementation of good hygiene practices, biosecurity and food safety management systems is very important. Potential AMR-specific interventions are in the early stages of development. Many data gaps relating to sources and relevance of transmission routes, diversity of ARB and ARGs, effectiveness of mitigation measures were identified. Representative epidemiological and attribution studies on AMR and its effective control in food production environments at EU level, linked to One Health and environmental initiatives, are urgently required.

Biocidal Resistance in Clinically Relevant Microbial Species: A Major Public Health Risk

Antimicrobial resistance is one of the greatest dangers to public health of the 21st century, threatening the treatment and prevention of infectious diseases globally. Disinfection, the elimination of microbial species via the application of biocidal chemicals, is essential to control infectious diseases and safeguard animal and human health. In an era of antimicrobial resistance and emerging disease, the effective application of biocidal control measures is vital to protect public health. The COVID-19 pandemic is an example of the increasing demand for effective biocidal solutions to reduce and eliminate disease transmission. However, there is increasing recognition into the relationship between biocide use and the proliferation of Antimicrobial Resistance species, particularly multidrug-resistant pathogens. The One Health approach and WHO action plan to combat AMR require active surveillance and monitoring of AMR species; however, biocidal resistance is often overlooked. ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens and numerous fungal species have demonstrated drug and biocidal resistance where increased patient mortality is a risk. Currently, there is a lack of information on the impact of biocide application on environmental habitats and ecosystems. Undoubtedly, the excessive application of disinfectants and AMR will merge to result in secondary disasters relating to soil infertility, loss of biodiversity and destruction of ecosystems.

Contamination of Retail Meat Samples with Multidrug-Resistant Organisms in Relation to Organic and Conventional Production and Processing: A Cross-Sectional Analysis of Data from the United States National Antimicrobial Resistance Monitoring System, 2012-2017

BACKGROUND

During food animal production, animals are exposed to, colonized by, and sometimes infected with bacteria that may contaminate animal products with susceptible and multidrug-resistant organisms (MDRO). The United States' Organic Foods Production Act resulted in decreased antibiotic use in some animal production operations. Some studies have reported that decreased antibiotic use is associated with reduced MDRO on meat.

OBJECTIVES

The aim of this study was to investigate associations of meat production and processing methods with MDRO and overall bacterial contamination of retail meats.

METHODS

Bacterial contamination data from 2012 to 2017 for chicken breast, ground beef, ground turkey, and pork chops were downloaded from the National Antimicrobial Resistance Monitoring System. Poisson regression models with robust variance were used to estimate associations with MDRO contamination and any contamination (adjusted for year and meat type) overall, and according to bacteria genus (Salmonella, Campylobacter, Enterococcus, Escherichia coli) and meat type.

RESULTS

A total of 39,349 retail meat samples were linked to 216 conventional, 123 split (conventional and organic), and three organic processing facilities. MDRO contamination was similar in conventionally produced meats processed at split vs. conventional facilities but was significantly lower in organically produced meats processed at split facilities [adjusted prevalance ratio (aPR)=0.43; 95% CI: 0.30, 0.63]. Meat processed by split vs. conventional processors had higher or similar MDRO contamination for all tested bacterial genera except Campylobacter (aPR=0.29; 95% CI: 0.13, 0.64). The prevalence of any contamination was lower in samples processed at split vs. conventional facilities for aggregated samples (aPR=0.70; 95% CI: 0.68, 0.73) and all meat types and bacterial genera.

DISCUSSION

Organically produced and processed retail meat samples had a significantly lower prevalence of MDRO than conventionally produced and processed samples had, whereas meat from split processors had a lower prevalence of any contamination than samples from conventional processors had. Additional studies are needed to confirm findings and clarify specific production and processing practices that might explain them. https://doi.org/10.1289/EHP7327.

Occurrence of disinfectant-resistant bacteria in a fresh-cut vegetables processing facility and their role in protecting Salmonella enteritidis

Chemical disinfectants are widely used to control foodborne pathogen contamination in fresh-cut vegetables (FVs) processing facilities. In this study, we investigated the disinfectant-resistant bacteria in a FVs processing facility and evaluate the effects of these bacteria on Salmonella enteritidis biofilm formation and disinfectant resistance. The disinfectant-resistance profiles were determined using 0.02% sodium hypochlorite (NaClO), 0.2% benzalkonium bromide (BAB) and 2% hydrogen peroxide (H₂O₂) solutions. The results showed the high occurrence of disinfectant resistant bacteria in the FVs processing environment, especially in the clean area. All isolates showed planktonic susceptibility to H₂O₂ and BAB, while the Gram-positive isolates were specifically resistant to NaClO. Isolates with biofilm-forming ability showed resistance to tested disinfectants. Disinfectant resistance of S. enteritidis was not significantly enhanced in most of the mixed-species biofilms, except for Bacillus paramycoides B5 which not only increased the biomass but also enhanced the survival ability of the Salmonella under NaClO treatment. Increased biomass and compact biofilm structures were observed in mixed-species biofilms by scanning electron microscopy (SEM). This study provides new insights into the disinfectant-resistant bacteria from food processing facilities and highlights their relevance for foodborne pathogen contamination.

The occurrence of disinfectant-resistant bacteria in a fresh-cut vegetables processing facility was observed, and Bacillus paramycoides B5 enhanced S. enteritidis survival under NaClO treatment.

Microbial biofilm: A matter of grave concern for human health and food industry

Pathogenic microorganisms have adapted different strategies during the course of time to invade host defense mechanisms and overcome the effect of potent antibiotics. The formation of biofilm on both biotic and abiotic surfaces by microorganisms is one such strategy to resist and survive even in presence of antibiotics and other adverse environmental conditions. Biofilm is a safe home of microorganisms embedded within self-produced extracellular polymeric substances comprising of polysaccharides, extracellular proteins, nucleic acid, and water. It is because of this adaptation strategy that pathogenic microorganisms are taking a heavy toll on the health and life of organisms. In this review, we discuss the colonization of pathogenic microorganisms on tissues and medically implanted devices in human beings. We also focus on food spoilage, disease outbreaks, biofilm-associated deaths, burden on economy, and other major concerns of biofilm-forming pathogenic microorganisms in food industries like dairy, poultry, ready-to-eat food, meat, and aquaculture.

Thyme Oil Enhances the Inactivation of Salmonella enterica on Raw Chicken Breast Meat During Marination in Lemon Juice With Added Yucca schidigera Extract

Enteric pathogens such as Salmonella enterica can survive in low pH conditions and pose a food safety threat during marinating of raw poultry meat. A study was conducted to investigate the effectiveness of thyme oil for killing S. enterica on raw chicken during marination in lemon juice containing yucca extract. Samples of raw chicken breast were inoculated with a five-serovar mixture of S. enterica (~10⁸ CFU/mL) and immersed for 2, 4, 6, and 8 h in four lemon-based marinades at 22°C: lemon juice alone (L), L with added 0.5% yucca extract (L + Y), L + Y and 0.5% thyme oil (L + Y + 0.5% TO) and L + Y + 1.0% TO. The L and L + Y served as controls. Survivors were determined by surface plating chicken homogenates on xylose-lysine tergitol-4 (XLT4) agar and XLT4 agar overlaid with non-selective agar (TAL) and counting bacterial colonies after 48 h of incubation (35°C). Marinades containing Y and TO significantly reduced initial viable populations of S. enterica compared to control (L and L + Y) solutions (P < 0.05). Based on S. enterica survivors on TAL medium, the L and L + Y reduced initial populations by 1.12 and 1.42 Log CFU/sample, respectively, after 8 h whereas, Log reductions caused by L + Y + 0.5% TO and L + Y + 1.0% TO, respectively, were 2.62 and 3.91 (P < 0.05). Numbers of survivors were higher on TAL compared to XLT4 agar (P < 0.05); however, the extent of sub-lethal injury caused by the marinades was not statistically significant (P > 0.05). The death rate of S. enterica increased significantly (P < 0.05) in the marinades containing TO (0.5 or 1.0%) compared to control (L + Y). Based on these results, thyme oil has good potential to increase the antimicrobial efficacy of lemon juice marinade against Salmonella on raw chicken breast and enhance the microbial safety of this popular poultry product.