Cronobacter Support
06-03-2009, 04:25 PM
1st International Conference on Cronobacter Poster Abstract 56
Effect of the sample size on the detection of Cronobacter sakazakii in infant formula.
According to current legislation in Europe, is compulsory an analysis of 30 samples by lot if Enterobacteria are detected in infant formula. However, this amount of samples are very time consuming and expensive. Consequently, a number of laboratories may perform a composite of samples, increasing the amount of product, with a risk of no detection of the pathogen. The aim of our work was to compare different protocols to determine the detection level when the quantity of sample is higher than 25g, using different contamination levels. A total of 180 samples were analyzed, according to ISO-TS-22964-2006 method. Three different wild Cronobacter sakazakii strains have been used to inoculate the samples at different contamination levels. All the study has been performed by duplicates and positive and negative controls in each analysis used. Series of 30 samples has been studied according to current legislation. Our results shown equal results, when compositing of two samples (50g) is used and when only a sample is analyzed (25g). In any case, if the number of samples is higher than 5 (more than 125g), Cronobacter sakazakii is detected when the contamination level is lower than 100 ufc. However, when a composite of 5 samples was performed results are different, according to the volume of enrichment broth and the pre-enrichment inoculum. On this case, an increment in the volume of enrichment broth linked to an increase of the pre-enrichment inoculums used let us to detect all expected positive samples. All composites with a low level of contamination were not detected if the pre-enrichment volume was not equivalent to the 5 grouped samples (0,5 ml). When we make a dry or wet composite and only 0,1ml of pre-enrichment has been inoculated into enrichment medium, a group of each 5 samples has been not detected. However, if we increased level of inoculums to 0,5 ml, we obtain a detection of 100% of samples. Currently, if a composite of samples is performed, is necessary to consider a modification of the protocol to assure a nice detection of the pathogen. If the composite is higher than 2 samples, detection is not assured, if the laboratory cannot increase the volume of pre-enrichment broth in equal proportion than the recommended in the ISO protocol.
José Juan Rodriguez-Jerez, Dora Isela Salas-Vázquez, Fabián González-Rivas & Mercedes Marín De Mateo
Departamento de Ciencia Animal y de los Alimentos, Facultad de Veterinaria, Campus UAB, 08193 Bellaterra (Barcelona), Spain.
Effect of the sample size on the detection of Cronobacter sakazakii in infant formula.
According to current legislation in Europe, is compulsory an analysis of 30 samples by lot if Enterobacteria are detected in infant formula. However, this amount of samples are very time consuming and expensive. Consequently, a number of laboratories may perform a composite of samples, increasing the amount of product, with a risk of no detection of the pathogen. The aim of our work was to compare different protocols to determine the detection level when the quantity of sample is higher than 25g, using different contamination levels. A total of 180 samples were analyzed, according to ISO-TS-22964-2006 method. Three different wild Cronobacter sakazakii strains have been used to inoculate the samples at different contamination levels. All the study has been performed by duplicates and positive and negative controls in each analysis used. Series of 30 samples has been studied according to current legislation. Our results shown equal results, when compositing of two samples (50g) is used and when only a sample is analyzed (25g). In any case, if the number of samples is higher than 5 (more than 125g), Cronobacter sakazakii is detected when the contamination level is lower than 100 ufc. However, when a composite of 5 samples was performed results are different, according to the volume of enrichment broth and the pre-enrichment inoculum. On this case, an increment in the volume of enrichment broth linked to an increase of the pre-enrichment inoculums used let us to detect all expected positive samples. All composites with a low level of contamination were not detected if the pre-enrichment volume was not equivalent to the 5 grouped samples (0,5 ml). When we make a dry or wet composite and only 0,1ml of pre-enrichment has been inoculated into enrichment medium, a group of each 5 samples has been not detected. However, if we increased level of inoculums to 0,5 ml, we obtain a detection of 100% of samples. Currently, if a composite of samples is performed, is necessary to consider a modification of the protocol to assure a nice detection of the pathogen. If the composite is higher than 2 samples, detection is not assured, if the laboratory cannot increase the volume of pre-enrichment broth in equal proportion than the recommended in the ISO protocol.
José Juan Rodriguez-Jerez, Dora Isela Salas-Vázquez, Fabián González-Rivas & Mercedes Marín De Mateo
Departamento de Ciencia Animal y de los Alimentos, Facultad de Veterinaria, Campus UAB, 08193 Bellaterra (Barcelona), Spain.