Bacterial diversity on stainless steel surfaces of egg processing companies and potential of selected isolates to spoil liquid whole egg products

AimsTo assess the bacterial diversity in the French egg processing industry and to explore the adhesion and spoilage potential of selected bacteria.Methods and ResultsSterile stainless steel chips were suspended for 2 months inside the pipelines of seven egg processing companies, before and after the pasteurizer, at warm and cold seasons. After exposure, the bacterial diversity was assessed by 16S rDNA sequencing. The 231 collected isolates were mainly facultative anaerobic Gram positive bacteria, such as Streptococcus, Staphylococcus, Bacillus and Kocuria. Sixty‐five representative isolates were further characterized in vitro regarding the potential for adhesion and egg product spoilage. A high diversity was observed from one genus to another. Kocuria and Rothia isolates showed significantly higher adhesion than the isolates of the other genera. Only the isolates belonging to the genera Bacillus and Lysinibacillus, associated with high enzymatic activities on a solid egg‐based medium, were able to induce spoilage of liquid whole egg.ConclusionsBacteria collected on stainless steel surfaces placed in egg processing industries could be associated to liquid egg product spoilage.Significance and Impact of the StudyThis study provides new insights on the bacterial contamination in egg processing companies and represents a first step for the effective control of undesirable bacteria in liquid egg products

Toxigenic potential and antimicrobial susceptibility of Bacillus cereus group bacteria isolated from Tunisian foodstuffs

International audienceBackground: Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The aim of this study was to assess the sanitary potential risks of 174 B. cereus group strains isolated from different foodstuffs by detecting and profiling virulence genes (hblA, hblB, hblC, hblD, nheA, nheB, nheC, cytK, bceT and ces), testing the isolates cytotoxic activity on Caco-2 cells and antimicrobial susceptibility towards 11 antibiotics. Results: The entertoxin genes detected among B. cereus isolates were, in decreasing order, nheA (98.9%), nheC (97.7%) and nheB (86.8%) versus hblC (54.6%), hblD (54.6%), hblA (29.9%) and hblB (14.9%), respectively encoding for Non-hemolytic enterotoxin (NHE) and Hemolysin BL (HBL). The isolates are multi-toxigenic, harbouring at least one gene of each NHE and HBL complexes associated or not to bceT, cytK-2 and ces genes. Based on the incidence of virulence genes, the strains were separated into 12 toxigenic groups. Isolates positive for cytK (37,9%) harbored the cytK-2 variant. The detection rates of bceT and ces genes were 50.6 and 4%, respectively. When bacteria were incubated in BHI-YE at 30°C for 18 h and for 5 d, 70.7 and 35% of the strains were shown to be cytotoxic to Caco-2 cells, respectively. The cytotoxicity of B. cereus strains depended on the food source of isolation. The presence of virulence factors is not always consistent with cytotoxicity. However, different combinations of enterotoxin genetic determinants are significantly associated to the cytotoxic potential of the bacteria. All strains were fully sensitive to rifampicin, chloramphenicol, ciprofloxacin, and gentamycin. The majority of the isolates were susceptible to streptomycin, kanamycin, erythromycin, vancomycin and tetracycline but showed resistance to ampicillin and novobiocin. Conclusion: Our results contribute data that are primary to facilitate risk assessments in order to prevent food poisoning due to B. cereus group

Identification of the bacteria and their metabolic activities associated with the microbial spoilage of custard cream desserts

The famous French dessert “ile flottante” consists of a sweet egg white foam floating on a vanilla custard cream,which contains highly nutritive raw materials, including milk, sugar and egg. Spoilage issues are therefore a keyconcern for the manufacturers. This study explored the bacterial diversity of 64 spoiled custard cream dessertsmanufactured by 2 French companies. B. cereus group bacteria, coagulase negative Staphylococcus, Enterococcus and Leuconostoc spp. were isolated from spoiled products. Thirty-one bacterial isolates representative of the main spoilage species were tested for their spoilage abilities. Significant growth and pH decrease were observed regardless of species. While off-odours were detected with B. cereus group and staphylococci, yoghurt odours were detected with Enterococcus spp. and Leuconostoc spp. B. cereus group bacteria produced various esters and several compounds derived from amino acid and sugar metabolism. Most Staphylococci produced phenolic compounds. Enterococcus spp. and Leuconostoc spp. isolates produced high levels of compounds derived from sugar metabolism. Each type of spoilage bacteria was associated with a specific volatile profile and lactic acid was identified as a potential marker of spoilage of custard cream-based desserts. These findings provide valuable information for manufacturers to improve food spoilage detection and prevention of chilled desserts made with milk and egg

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Use of stainless steel chips for the recovery of adhering bacteria in the pipelines of 7 french egg breaking companies

The adhesion of microorganisms to industrial surfaces is frequently observed in the food industry. Adhering bacteria can colonize the surfaces and organize into biofilms that provide cell protection against many stresses such as those due to disinfectants. Poorly controlled, they can be the source of food product contamination and/or food spoilage, and therefore may have important economical and sanitary consequences.The aim of this study was to use stainless steel chips for the identification of the type of adhering bacteria inside the pipelines of 7 French egg breaking companies.Sterile stainless steel chips were suspended inside the pipelines at two levels, before and after the pasteurizer, and at two seasons (summer and winter). After two months, the adhering flora was harvested by sonication and scrapping in tryptone salt, followed by plating onto BHI-YE and incubation for 1 to 7 day(s) at 30°C, with or without oxygen. After incubation, the colonies were identified by sequencing.The harvested cells were mainly facultative aerobic-anaerobic and Gram positive bacteria. However, a broad range of diversity was highlighted, at the location level (7 companies), at the process level (before and after pasteurization), and at the season level (summer and winter).This study, using a simple system of recovery of adhering cells, highlights the flora present on the surface of the equipments of egg breaking companies and represents the first step to better understand and control cell adhesion and biofilm development in this type of food industry

Comparison of two PCR methods targeting two different gene sequences for the detection of Bacillus cereus group bacteria in egg products

Bacillus cereus group bacteria are able to produce toxins and their various enzymatic activities are also recognized as causing food spoilage, even at refrigerated temperatures, when psychrotolerant strains are involved. The lack of a rapid and accurate detection method, suitable for a simple routine analysis, is currently the main hurdle for the control of these populations in the sector of egg product manufacturing.Rationale : The aim of this study was to evaluate the performances of two PCR methods for the detection of B. cereus group bacteria. Whole liquid egg products (174 samples) provided by different companies were enriched in 5 g/L lithium chloride in peptone water. After DNA extraction, the detection of B. cereus group bacteria was assayed by a classical PCR method targeting a cspF gene sequence, as described by Francis et al. (1998) and by a real-time PCR method targeting a sspE gene sequence, as described by Kim et al. (2005). Results : Our results show good correlation between both methods for 86% of the analyzed samples. Ten percent of positive samples assayed by real-time PCR, targeting the sspE gene sequence, were found negative under classical PCR detection, targeting the cspF gene sequence. Only 4% of the analyzed samples were negative under real-time PCR detection and positive under classical PCR. Conclusion : Our results show good correlation between both the PCR methods described in the literature for the detection of B. cereus group bacteria in liquid whole egg and probably in other food, by targeting two different specific gene sequences. The method using real-time PCR seems to be more sensible and presents the advantage to be faster than the classical PCR method. Depending on the availability of their laboratory material, one of these methods could be proposed to manufacturers in order to detect this food spoilage and putative pathogenic microbiota

Use of pulsed-field gel electrophoresis for the discrimination of Bacillus cereus group isolates in liquid egg products collected in french egg breaking companies

Bacteria belonging to the Bacillus cereus group are commonly found in soil, air, dust, water and in many raw and processed foods. Several strains of this group have been implicated in food-borne illness. These bacteria are also prolific enzyme producers (lipases, proteases) and are recognised as causing spoilage in several pasteurised foodstuffs. Some strains exhibit psychrotrophic properties, causing an increasing problem during refrigerated storage and distribution of perishable food products. The monitoring and control of these bacteria are then of high importance for the egg breaking industry. For a better understanding of their diversity and ecological distribution, successful molecular typing methods are needed.Among the methods described for the typing of B. cereus group strains, the pulsed-field gel electrophoresis (PFGE) has already been carried out in order to build B. cereus genetic maps, to show the genomic diversity among B. cereus and B. thuringiensis, to discriminate B. anthracis from B. cereus and B. thuringiensis, and for several epidemiologic investigations.The aim of the present study was to discriminate, by a PFGE method adapted in our laboratory from the work of Gautier et al. (1996), a collection of psychrotrophic bacteria belonging to the B. cereus group collected in 6 egg breaking companies during a period covering a warm and a cold season

The volatilome allows assigning custard cream spoilage to a specific bacterial genus

National audienceCustard cream-based desserts, made up of highly nutritive raw materials, are easily spoiled by specific microbial contaminants. Little is known about these spoilage issues. The objective of this study was to fully characterize the type of bacteria and the respective metabolic activities involved in the spoilage of custard cream-based desserts. Materials &Methods (700) The level of bacterial contamination of 64 spoiled commercial custard cream-based desserts was measured (PCA, 24h, 30°C) and colonies were identified based on their 16SrDNA sequences. Over a bacterial collection of 565 isolates, 33 isolates of the 4 dominant genera were submitted to individual challenge tests (inoculum size of 3 log CFU/mL, incubation at 10°C for 21d in sterile custard cream). Microbial growth, sensorial evaluation, and biochemical changes (acidification; hydrolysis of sugar, protein and fats; production of volatile compounds and organic acids) were measured and the set of data was subjected to a principal component analysis (R software). Results (360) The spoilage was characterised by high bacterial counts (> 6 log CFU/mL) with predominance of Gram-positive bacteria, including Bacillus cereus group cells. The metabolic activities were highly dependent on the genus. The volatilome fingerprint appeared as a specific marker allowing assigning each type of spoilage to a specific bacterial genus. Significance (125) A better understanding of custard cream spoilage issues could help manufacturers improve detection and prevention