Search

Bacterial biofilms are highly difficult to control, hence significant economic resources have been allocated to develop strategies to eradicate them. This study evaluated the effect of an enzymatic treatment to be used as a cleaning product to control the presence of biofilms. Two different materials used in the food industry, polystyrene and stainless steel, were tested using Salmonella Typhimuirum and Cronobacter sakazakii. Biofilm formation was carried out by inoculating the surfaces with a standardized concentration of 4 log (CFU cm−2) and incubated for 48 hr with renewal of nutrients. The biofilm formation and subsequent enzymatic treatment were quantified using fluorescence microscopy and the conventional culture method. The enzymatic treatment showed significant reductions of 2–3 log (CFU cm−2) in biofilm cells, which was attributed to the degradation of the extracellular matrix and the further detachment of both microorganisms. The maximum biofilm detachment obtained with the preventive formula was 46.67%; however, this percentage could be increased by applying an aggressive treatment or by adding a subsequent disinfection step that would eliminate adhered microbial cells. Further, the enzymatic cleaning treatment could be exploited as a potent technology to control bacterial adherence and biofilm formation in the food industry. [ABSTRACT FROM AUTHOR]

Two different TiO2 nanoparticles, NM101 and NM105, were evaluated against a range of Gram-positive (Staphylococcus aureus, Bacillus cereus, Lactobacillus casei, Lactobacillus bulgaricus, Lactobacillus acidophilus and Lactobacillus lactis) and Gram-negative (Salmonella enterica var. Enteridis and Escherichia coli) bacteria. Both NM101 and NM105 TiO2 nanoparticles (UV-exposed or none) had a significant antibacterial activity when the concentration of TiO2 suspension was 100 µg mL−1. The activation of the TiO2 NPs led, in all cases, to a shift in the growth curve, revealing lower counts as the concentration increased. E. coli was the most significantly affected pathogen by both TiO2 nanoparticles reaching among 2–3 log CFU.mL−1 reduction. In addition, in the case of the probiotic bacteria, NM105 TiO2 nanoparticles had similar effects as the bacterial density was reduced by 2–3 log CFU.mL−1. These results may be applied as a potent technology to be included in the formulation of new disinfectants. [ABSTRACT FROM AUTHOR]

Detection of biofilms on food-contact surfaces is essential for establishing sanitization procedures and avoiding microbial contamination of food products. The objective of our study was to develop a peroxide biodetector, to detect and reveal the presence of biofilms. A positive reaction was observed when biodetector bubbles were formed on stainless steel and polypropylene surfaces. A range of microorganisms able to form biofilms was evaluated. Catalase-positive bacteria: Staphylococcus aureus, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enterica ser. Typhimurium and Cronobacter sakazakii were employed as well as the catalase-negative bacterium: Lactobacillus brevis. With the exception of C. sakazakii, all catalase-positive foodborne pathogens forming the biofilms showed a positive detection by the biodetector, being 104 CFU cm−2 the minimum microbial load detected. The strongest positive reaction was for P. aeruginosa. Results demonstrated the potential of this biodetector to detect biofilms, particularly when used as a tool in the food industry. [ABSTRACT FROM AUTHOR]

This study evaluated the capacity of real-time PCR and conventional culture methods to detect Salmonella enterica serovar Typhimurium and Listeria monocytogenes adhered to stainless steel surfaces used as food contact surfaces. The adhesion of the microorganisms to the surfaces was performed under dry conditions to represent the stress to which these pathogens can be subjected in the food processing environment. The samples were analyzed with various pre-enrichment times: S. Typhymurium (0, 6, and 18 h) and L. monocytogenes (0, 6, and 25 h) and with procedures concentrating or not concentrating the samples after the pre-enrichments. The results showed that real-time PCR obtained increased capacity than the conventional method to detect a low number of both pathogens, and real-time PCR even detected samples without pre-enrichment. However, pre-enrichment is recommended to avoid the detection of false positives from dead cells during adhesion and to ensure the absence of false negatives due to low initial concentrations. The concentration of the adhering bacteria increased the frequency in the detection of positive results for S. Typhimurium, but this effect was not observed in the case of L. monocytogenes. • Detection of Salmonella Typhimurium and Listeria monocytogenes adhered to surfaces under dry conditions. • High capacity of real-time PCR detection compared to conventional culture method. • Pre-enrichment is recommended to avoid false positives. • Concentration of samples increases S. Typhymurium detection. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes continues to be one of the most important public health challenges for the meat sector. Many attempts have been made to establish the most efficient cleaning and disinfection protocols, but there is still the need for the sector to develop plans with different lines of action. In this regard, an interesting strategy could be based on the control of this type of foodborne pathogen through the resident microbiota naturally established on the surfaces. A potential inhibitor, Bacillus safensis, was found in a previous study that screened the interaction between the resident microbiota and L. monocytogenes in an Iberian pig processing plant. The aim of the present study was to evaluate the effect of preformed biofilms of Bacillus safensis on the adhesion and implantation of 22 strains of L. monocytogenes. Mature preformed B. safensis biofilms can inhibit adhesion and the biofilm formation of multiple L. monocytogenes strains, eliminating the pathogen by a currently unidentified mechanism. Due to the non-enterotoxigenic properties of B. safensis, its presence on certain meat industry surfaces should be favored and it could represent a new way to fight against the persistence of L. monocytogenes in accordance with other bacterial inhibitors and hygiene operations. [ABSTRACT FROM AUTHOR]

This study tested multiple methods for assessing microbial populations and identified bacteria detected on supermarket food-contact surfaces. The results for culture medium–based conventional methods, i.e., swabbing, direct count, sampling discs, and Petrifilm, showed that surface cleaning was satisfactory. However, direct epifluorescence microscopy (DEM) and bioluminescence detection of adenosine triphosphate (ATP) showed that surface cleaning was unsatisfactory. The surfaces of the fruit and vegetables section were the most contaminated, followed by the sections for cured meats and cheeses, fresh seafood, the aisles of the sections tested, meat, and yogurts and desserts. Likewise, significantly higher microbiological counts were observed on painted wood than on stainless steel, plastic, and painted epoxy surfaces (p < 0.05). Room-temperature food storage areas had higher bacterial counts than refrigerated areas (p < 0.05). Although no Salmonella spp., Listeria monocytogenes , or Staphylococcus aureus were detected, opportunistic pathogenic bacteria such as coagulase-negative staphylococci, Listeria grayi , and Pseudomonas spp. were isolated. Furthermore, the identification of the opportunistic and emerging foodborne pathogen Cronobacter sakazakii and the indicator of bacterial contamination Escherichia coli demonstrates potential risks to consumer health. Moreover, the Enterobacteriaceae count was low; however, the high total microbiological count detected by DEM indicates that cleaning and disinfection procedures should be improved. Compared to conventional methods, the use of DEM with stainless-steel disc surfaces as sampling support could increase the accuracy of detecting and enumerating microbial populations on surfaces by identifying residual bacteria after inadequate disinfection procedures. • Bacterial culture methods, DEM, and ATP detection. • Food section, temperature, and surface type affected counts. • DEM showed higher counts than culture methods. • Cronobacter sakazakii and Escherichia coli were detected. [ABSTRACT FROM AUTHOR]

This study evaluated the organic residues of milk fouling using fluorescence and confocal laser scanning microscopy. The inorganic content was analyzed with energy-dispersive X-ray spectroscopy, complemented with inductively coupled plasma optical emission spectrometry. These techniques were applied to evaluate milk fouling cleanliness using an alkaline product and an enzymatic formulation based on protease and amylase. The results showed that the efficiency of enzymatic cleaning was 87.1% when it was evaluated at 55°C for 30 min, and with a medium of pH 8.5. No difference was found from the efficacy in eliminating dairy fouling observed for the chemical cleaning (86.9%). The fluorescence microscopy proved useful for determining the organic solid components in the outer layer of the dairy fouling. The fouling spatial disposition in 3 dimensions, obtained by confocal laser scanning microscopy, showed that it was formed of 51.3% sugars, 9.3% fats, and 39.4% proteins, with the enzymatic cleaning of these compounds being homogeneous, compared with chemical cleaning. The protein and lipid contents were in the surface layer, whereas sugars were located in the innermost part that contributes to the Maillard reaction during fouling formation. After enzymatic cleaning, the reduction in the concentration of Ca and P was 71.61 and 74.67%, respectively, compared with fouling intact. Thus, enzymatic cleaning, without the accumulation of Na from chemical cleaning, leaves 1.5 times less mineral than chemical cleaning. Knowing the content and structure of fouling in the industry helps to formulate better products to achieve proper levels of cleanliness. Additionally, studying the cleaning residues helps to avoid problems of cross-contamination between batches or subsequent microbial growths (biofilms) on surfaces with residues. [ABSTRACT FROM AUTHOR]

Conventional cleaning with chemical products uses a substantial amount of water and energy to clean the fouling related to dairy production, resulting in significant economic costs. We evaluated an enzymatic treatment based on the use of protease and amylase to clean dairy fouling generated in an indirect plate heat exchanger and the spray dryer equipment of a pilot plant, representing real cleaning conditions in the dairy industry. The efficacy of the enzymatic treatment in removing fouling at 50 °C was comparable to that of the clean-in-place method, with alkaline–acid cleaning performed at a maximum temperature of 80 °C. Microbiological analysis showed that the cleaning treatments guaranteed adequate hygienic conditions of the dairy products manufactured. Monitoring fluorescence markers, such as tryptophan, riboflavin, Maillard compounds, and dityrosine could help improve the effectiveness of both alkaline and enzymatic cleaning. The enzymatic treatment fulfills dairy industry objectives, saving water and energy during washing by reducing chemical product use. Considering that enzymatic cleaning is biodegradable after use and that its economic cost is competitive compared to chemical cleaning, it represents a viable alternative to the chemical cleaning of dairy fouling. • Effectiveness of enzymatic treatment to clean dairy fouling on a dairy pilot plant. • Efficacy of the enzymatic treatment comparable to clean-in-place cleaning method. • Microbiological counts showed that enzymatic cleaning ensured hygienic conditions. • Fluorescence marker monitoring improves the effectiveness of cleaning. • Enzymatic cleaning saves water and energy reducing the use of chemical products. [ABSTRACT FROM AUTHOR]