A selective medium for the rapid detection by an impedance technique of Pseudomonas spp. associated with poultry meat

IS511 is an endogenous insertion sequence (IS) of the bacterium Caulobacter crescentus strain CB15 and it is the first Caulobacter IS to be characterized at the molecular level. We determined the 1266-bp nucleotide sequence of IS511 and investigated its genetic organization, relationship to other ISs, and transposition properties. IS511 belongs to a distinct branch of the IS3 family that includes ISR1, IS476, and IS1222, based on nucleotide sequence similarity. The nucleotide sequence of IS511 encodes open reading frames (orfs) designated here as orfA and orfB, and their relative organization and amino acid sequences of the predicted protein products are very similar to those of orfAs and orfBs of other IS3 family members. Nuclease S1 protection assays identified an IS511 RNA, and its 5' end maps approximately 16 nucleotides upstream of orfA and about six nucleotides downstream of a sequence that is similar to the consensus sequence of C. crescentus housekeeping promoters. Evidence is presented that IS511 is capable of precise excision from the chromosome, and transposition from the chromosome to a plasmid. Transpositional insertions of IS511 occurred within sequences with a relatively high G + C content, and they were usually, but not always, flanked by a 4-bp direct repeat that matches a sequence at the site of insertion. We also determined the nucleotide sequence flanking the four endogenous IS511 elements that reside in the chromosome of C. crescentus. Our findings demonstrate that IS511 is a transposable IS that belongs to a branch of the IS3 family.     

Effective viscoelastic behavior of short fibers composites using virtual DMA experiments

Mechanics of Time-Dependent Materials - May it be for environmental or economic reasons, mass reduction has become one of the main goals in mechanics. The short fiber thermoplastics composite is an...     

Use of a competitive exclusion product (Broilact) to prevent Salmonella colonization of newly hatched chicks.

The study described here was carried out at the request of a French company to utilize the authors' experience of 'competitive exclusion' treatment for poultry. The objective of the study was to determinate the safety and efficacy of a particular treatment product (Broilact) in protecting chicks against Salmonella infection.     

Validation of EN ISO standard methods 6888 Part 1 and Part 2: 1999--enumeration of coagulase-positive staphylococci in foods

The methods of European and International Organisations for Standardization for the enumeration of coagulase-positive staphylococci (CPS, Staphylococcus aureus and other species) described in EN ISO 6888 Part 1 and Part 2: 1999 were validated by order of the European Commission (Standards, Measurement and Testing Fourth Framework Programme Project SMT4-CT96-2098). EN ISO 6888-1 prescribes the use of Baird-Parker (BP) agar whereas EN ISO 6888-2 prescribes the use of Rabbit Plasma Fibrinogen Agar (RPFA). The objective was to determine the precision of each method in terms of repeatability (r) and reproducibility (R) using three different food types inoculated with various levels of S. aureus and a typical background flora. The results are intended for publication in the associated standards. Cheese, meat and dried egg powder were examined by 24 laboratories from 16 countries in Europe. Each participant received eight test materials per food type: blind duplicates at four inoculum levels (0, 10(3), 10(4) to 10(5), 10(5) to 10(6) cfu/g). In addition, two reference materials (RM) (capsules containing milk powder inoculated with S. aureus) were included in the study. All test materials were subjected to stringent homogeneity and stability testing before being used in the collaborative trial. Two statistical methods were used to calculate the precision parameters. Draft EN ISO 16140: 2000 method appeared more appropriate to the case of microbiological data than ISO 5725-2: 1994 method and was retained to calculate the precision data.Concerning EN ISO 6888-1, overall values for repeatability (r) when used with food test materials was r=log(10) 0.28 (expressed as an absolute difference between log(10)-transformed test results). For the reference materials, r=log(10) 0.19. Overall values for reproducibility (R) when used with food test materials were R=log(10) 0.43. For the reference materials, R=log(10) 0.39.Concerning EN ISO 6888-2, overall values for repeatability (r) when used with food test materials were r=log(10) 0.22. For the reference materials, r=log(10) 0.17. Overall values for reproducibility (R) when used with food test materials were R=log(10) 0.33. For the reference materials, R=log(10) 0.31.These results were presented to the ISO technical committee and to the Comité Européen de Normalisation (CEN). Both committees agreed to incorporate the precision data obtained with food materials as two amendments to EN ISO 6888-1 and -2, and to give an equal status to each part of the standard.     

Bibliography of food microbiology

The European and International Standard method for the detection of Listeria monocytogenes, described in EN ISO 11290 Part 1: 1997 (International Organisation for Standardisation, Geneva) was validated by order of the European Commission (Standards, Measurement and Testing Fourth Framework Programme Project SMT4-CT96-2098). Nineteen laboratories in 14 countries in Europe participated in a collaborative trial to determine the performance characteristics of the method, which are intended for publication in the corresponding standard. An additional objective of this project was to devise a new series of parameters to indicate the 'precision' of microbiological qualitative methods. The method was challenged with three food types, namely fresh cheese, minced beef and dried egg powder and a reference material. Inoculation levels ranged from 5 to 100 cfu/25 g. Each participant examined five replicates of each food type at three inoculum levels and five reference materials. Both PALCAM and Oxford media were assessed. All test materials were subjected to stringent homogeneity and stability testing before being used in the collaborative trial. The results demonstrated that the method prescribed in EN ISO 11290-1 had an overall sensitivity of 85.6% and a specificity of 97.4%. L. monocytogenes was detected in most cases after primary enrichment, although secondary enrichment often yielded further positives. However, a significant number of false-negative results were obtained with all food types when large numbers of L. innocua were present in the test materials. L. innocua tended to dominate L. monocytogenes during the selective enrichment stages and thus masked small numbers of colonies of L. monocytogenes on the isolation media. There was no evidence from this collaborative study to demonstrate a significant difference in performance between Oxford and PALCAM media. Due to the problem of false-negative results with this method as highlighted in this trial, recommendations have been made to ISO to launch a revision of the standard to improve the detection of low numbers of L. monocytogenes in foods. New statistical methods devised to advance the measurement of the performance of qualitative microbiological methods are also described.     

Modeling the effective viscoelastic properties of PEEK matrix reinforced by arbitrary oriented short glass fibers

Mechanics of Time-Dependent Materials - The aim of this work consists in estimating and modeling the viscoelastic behavior at small strain of KetaSpire® KT-880 PEEK fiber composites reinforced...     

Validation of ISO method 11290 part 2. Enumeration of Listeria monocytogenes in foods.

The European and International Standard method for the enumeration of Listeria monocytogenes, described in EN ISO 11290 Part 2: 1998 [EN ISO 11290-2 Microbiology of Food and Animal Feedingstuffs-Horizontal Method for the Detection and Enumeration of L. monocytogenes: Part 2. Enumeration; International Organisation for Standardisation, Geneva.] was validated by order of the European Commission (Standards, Measurement and Testing Fourth Framework Programme Project SMT4-CT96-2098). The objective was to determine the precision of the method in terms of repeatability (r) and reproducibility (R) using three different food types inoculated with various levels of L. monocytogenes and a typical background flora. The results are intended for publication in the associated standards. Cheese, meat, dried egg powder and reference materials were examined by 21 laboratories in 16 countries in Europe. Each participant received eight test materials per food type: blind duplicates at four inoculum levels (0, 10(2), 10(3), 10(4) cfu/g). In addition, two reference materials containing L. monocytogenes were included in the study. All test materials were subjected to stringent homogeneity and stability testing before being used in the collaborative trial. Participants were required to use only PALCAM agar for enumeration of L. monocytogenes, as prescribed by the reference method. Statistical analyses has been performed using a newly introduced approach for food microbiology (draft standard prEN ISO 16140 [prEN ISO 16140 Microbiology of Food and Animal Feedingstuffs-Protocol for the Validation of Alternative Methods, International Organisation for Standardisation, Geneva.], the precision data being calculated using robust estimates. Overall values for repeatability (r) of EN ISO 11290-2 when used with food test materials were r = log10 0.58 (expressed as an absolute difference between log10-transformed test results) or r = 3.8 (expressed as an absolute ratio between test results on the normal scale). For the reference materials (capsules containing approximately 5000 cfu), r = log10 0.34 (expressed as an absolute difference between log10-transformed test results) or r = 2.2 (expressed as an absolute ratio between test results on the normal scale). Overall values for reproducibility (R) of EN ISO 11290-2 when used with food test materials were R = log10 0.81 (expressed as a difference between log10-transformed test results) or R = 6.5 (expressed as an absolute ratio between test results on the normal scale). For the reference materials, R = log10 0.51 (expressed as a difference between log10-transformed test results) or R = 3.2 (expressed as an absolute ratio between test results on the normal scale). Further studies have been initiated by ISO TC34/SC9 to try to enhance the isolation of L. monocytogenes from foods and improve the confirmation procedures.     

Behaviour up to rupture of woven ply laminate structures under static loading conditions

A general model based on continuum damage mechanics (CDM) and a non-local ply scale criterion were developed to describe the failure of carbon woven ply laminated structures. This non-local criterion is based on mean quantities over a fracture characteristic volume (FCV) corresponding to a cylinder with a circular area and a given ply thickness. The nonlinear behaviour and the non-local criterion were implemented in the finite element code ABAQUS. This paper presents new comparisons between the results of experimental data and simulations performed on plates with notches and saw cuts. The results show the efficiency of this approach, even for structures with very high stress gradients. A simplified approach based on the FCV and the Tsai criterion is also presented here and the results obtained with this method are then compared with the experimental data.     

A non-local criterion for modelling unbalanced woven ply laminates with stress concentrations

A non-local ply scale criterion [Hochard C, Lahellec N, Bordreuil C. A ply scale non-local fibre rupture criterion for CFRP woven ply laminated structures. Compos Struct 2007;80:321–26] was previously developed for predicting the failure of balanced woven ply structures with stress concentrations. This non-local criterion was based on the mean values determined over a Fracture Characteristic Volume (FCV) corresponding to a cylinder with a circular area and the same thickness as the ply. This non-local approach along with a ply scale continuum damage behavioural model was implemented in the ABAQUS Finite Element Code. The behavioural model was developed from a classical Continuum Damage Mechanics (CDM) model [Ladevèze P. A damage computational method for composite structures. Comput Struct 1992;44:79–87]. In the present study, this approach was extended to the case of unbalanced woven ply. The FCV approach and the CDM behavioural model are presented and comparisons are made between the experimental data and the modelling predictions obtained on plates with open holes, notches and saw cuts.