Analytical performances of food microbiology laboratories - critical analysis of 7 years of proficiency testing results.

AIM: Based on the results of 19 food microbiology proficiency testing (PT) schemes, this study aimed to assess the laboratory performances, to highlight the main sources of unsatisfactory analytical results and to suggest areas of improvement. METHODS AND RESULTS: The 2009-2015 results of REQUASUD and IPH PT, involving a total of 48 laboratories, were analysed. On average, the laboratories failed to detect or enumerate foodborne pathogens in 3·0% of the tests. Thanks to a close collaboration with the PT participants, the causes of outliers could be identified in 74% of the cases. The main causes of erroneous PT results were either pre-analytical (handling of the samples, timing of analysis), analytical (unsuitable methods, confusion of samples, errors in colony counting or confirmation) or postanalytical mistakes (calculation and encoding of results). CONCLUSIONS: PT schemes are a privileged observation post to highlight analytical problems, which would otherwise remain unnoticed. In this perspective, this comprehensive study of PT results provides insight into the sources of systematic errors encountered during the analyses. SIGNIFICANCE AND IMPACT OF THE STUDY: This study draws the attention of the laboratories to the main causes of analytical errors and suggests practical solutions to avoid them, in an educational purpose. The observations support the hypothesis that regular participation to PT, when followed by feed-back and appropriate corrective actions, can play a key role in quality improvement and provide more confidence in the laboratory testing results.

Commutability of food microbiology proficiency testing samples.

AIM: Food microbiology proficiency testing (PT) is a useful tool to assess the analytical performances among laboratories. PT items should be close to routine samples to accurately evaluate the acceptability of the methods. However, most PT providers distribute exclusively artificial samples such as reference materials or irradiated foods. This raises the issue of the suitability of these samples because the equivalence-or 'commutability'-between results obtained on artificial vs. authentic food samples has not been demonstrated. In the clinical field, the use of noncommutable PT samples has led to erroneous evaluation of the performances when different analytical methods were used. This study aimed to provide a first assessment of the commutability of samples distributed in food microbiology PT. METHODS AND RESULTS: REQUASUD and IPH organized 13 food microbiology PTs including 10-28 participants. Three types of PT items were used: genuine food samples, sterile food samples and reference materials. The commutability of the artificial samples (reference material or sterile samples) was assessed by plotting the distribution of the results on natural and artificial PT samples. This comparison highlighted matrix-correlated issues when nonfood matrices, such as reference materials, were used. Artificially inoculated food samples, on the other hand, raised only isolated commutability issues. CONCLUSIONS: In the organization of a PT-scheme, authentic or artificially inoculated food samples are necessary to accurately evaluate the analytical performances. Reference materials, used as PT items because of their convenience, may present commutability issues leading to inaccurate penalizing conclusions for methods that would have provided accurate results on food samples. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, the commutability of food microbiology PT samples was investigated. The nature of the samples provided by the organizer turned out to be an important factor because matrix effects can impact on the analytical results.

Association between age at first calving, year and season of first calving and milk production in Holstein cows.

The effects of first calving (FC) in Holstein heifers on their first lactation, second lactation and lifetime milk production were examined from an initial database of 459 743 animals that first calved between 1 January 1990 and 31 July 2010 in Wallonia, Belgium. The FC age class (18 to 22, 22 to 26, 26 to 30, 30 to 34, 34 to 38 and 38 to 42 months), the FC season and FC year class (1990 to 1994, 1995 to 1999, 2000 to 2004 and 2005 to 2010) were considered when analysing the first and second lactation data. Lifetime data were similarly analysed, but did not include animals that calved after 2005 because many of them were still lactating. Only 24% of animals had their FC before 26 months of age. Animals that first calved between 22 and 26 months of age had more lactations and productive days during their life. They also had higher first and second lactation milk production and lifetime milk production. Summer or autumn FC improved first lactation, second lactation and lifetime milk production, as well as production per day of lactation, compared with winter or spring FC. Compared with animals that calved for the first time in 1990 to 1994, animals with a FC in 2000 to 2004 had a longer calving interval (0.5 months), fewer lactations per animal (-0.6) and fewer days in their lifetime lactation (a reduction of 144 days). As a result, the animals' lifetime production did not increase between 1990 to 1994 and 2000 to 2004, although milk production per day of lactation (22.85 v. 20.49 l/day) and per day of life (11.49 v. 10.78 l/day) improved. Milk fat content was lower in 2000 to 2004 than in 1990 to 1994, but protein content remained relatively constant, probably because of the cows' higher production level and increased dietary concentrate supplementation.

Development and validation of stable reference materials for food microbiology using Bacillus cereus and Clostridium perfringens spores.

AIMS: To develop a new type of microbiological Reference Materials (RMs), displaying long-term stability at room temperature. The purpose was to produce and validate two batches of RMs for the enumeration of Bacillus cereus and Clostridium perfringens. METHODS AND RESULTS: The RMs were based on spores of B. cereus and Cl. perfringens, adsorbed on calcium carbonate pellets. Two batches of 1000 units were manufactured and validated in compliance with ISO guide 35. After verification of their homogeneity, the stability of the 'RM-B. cereus' and 'RM-Cl. perfringens' batches was proven during at least 36 and 9 months, respectively, at room temperature. The validation study was completed by international collaborative trial involving 12 laboratories, allowing the validation of the assigned values. CONCLUSIONS: The methodology developed in this work enabled to produce easy-to-handle and cost-effective RMs, displaying an unprecedented stability at room temperature, a good homogeneity and a precise and validated assigned value. SIGNIFICANCE AND IMPACT OF THE STUDY: This study revealed new paths for the development of stable microbiological RMs. Overcoming the intrinsic instability of the living cells makes it possible to produce valuable tools for the quality assurance of microbiology laboratories.

Biofilters to treat the pesticides wastes from spraying applications: results after 4 years of study.

Biofilters were developed in order to eliminate or reduce the quantity of pesticides from rinsing and cleaning waters of sprayers. Biofilters consist in 1, 2 or 3 plastic containers of 1 m3 placed in a vertical pile and containing a substrate elaborated from a homogenised mixture of local soil, chopped straw and compost able to absorb and degrade the pesticides. Biofilters are installed near the area for cleaning and rinsing the sprayer and the waste waters are pumped into the system. Since 2002, a pilot study is carried out in Belgium in order to evaluate the efficacy of these systems. Twenty pilot systems were installed since 2002 until 2004 in several farms, agricultural technical centres or schools and in a municipal maintenance service. The efficacy of the biofilters was studied for several chemical classes of herbicides (sulfonylurea, aryloxyalcanoic acids, chloroacetanilides), insecticides (pyrethroids, carbamates) and fungicides (dicarboximides, phenylamides, triazoles and strobilurines). The balance of the inputs and the outputs of the pesticides was determined by monitoring the elutes. The degradation kinetic of pesticides into the substrate was evaluated by analysing the pesticides into the substrate. The microbiological activity of the substrate was also evaluated by measuring respiration and some indirect parameters like dry matter content, Kjeldahl nitrogen content, organic carbon content and biological oxygen demand (BOD). Results obtained until now after four years of experiments have showed an overall good efficacy (retention) of pesticides by the biofilter and a high degradation rate for the majority of pesticides. Biofilters permit to reduce highly the quantity of pesticides from rinsing and cleaning waters of sprayers and contribute significantly to the reduction of the contamination of surface water. Biofilters are now registered by the Ministry of Agriculture and Environment of the Walloon Region in Belgium and are recommended to pesticides users.

[A unique case of destructive polyarthritis associated with multicentric Castleman's disease]. / Un cas particulier de polyarthrite destructrice associée à une maladie de Castleman multicentrique.

This is an original report of a 75-year-old woman suffering from multicentric Castleman's disease associated with a destructive polyarthritis, which do not correspond to any known rhumatologic disease. Cattleman's disease (angiofollicular lymph node hyperplasia) is a lymphoproliferative disorder of unknown etiology. Two forms are described: a localized and a multicentric. In the literature, associations of Cattleman's disease and connective tissue disease such as rheumatoid arthritis have been described. Association with POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M component, skin changes) and amylosis have also been described.