Évaluation du BactoScan FC pour la numération des bactéries du lait cru

Abstract

-Evaluation of BactoScan FC for the enumeration of bacteria in raw milk. The evaluation of BactoScan FC for routine enumeration of bacteria in raw milk was carried out according to the model proposed by the International Dairy Federation. The linearity of response of BactoScan FC was verified between 6 000 and 27 000 000 pulses . mL -1 without reaching the limits of detection which have not been determined. The transmission error was estimated at 0.09% and the repeatability at 0.084 log 10 CFU . mL -1 for a 60 000 CFU . mL -1 mean level of contamination. The stability of the equipment over time was verified; in both the short term and the long term, reproducibility is in the same order of magnitude as repeatability. The relationship between BactoScan FC and the reference method is linear over the whole range analysed (700 to 26 000 000 CFU . mL -1 ), with a determination threshold estimated at under 4 000 CFU . mL -1 . The regression equation between the reference method and the BactoScan FC is: log 10 (CFU . mL -1 ) = 0.839 × log 10 (pulses . mL -1 ) + 0.095. The accuracy of estimation of the reference value, expressed by the residual standard deviation of the regression, is 0.287 log 10 CFU . mL -1 . Finally, the independence of this estimate compared to the somatic cell level of the samples was verified. BactoScan FC / bacteriological quality / raw milkRésumé -L'évaluation du BactoScan FC pour la numération en routine des bactéries du lait cru a été réalisée selon le modèle proposé par la Fédération Internationale de Laiterie. La linéarité de réponse du BactoScan FC a été vérifiée entre 6 000 et 27 000 000 impulsions . mL -1 sans toutefois atteindre les limites de détection qui restent indéterminées. L'erreur de transfert a été estimée

The application of flow cytometry in determining the bacteriological quality of raw sheep’s milk in Slovakia

“…The obtained s Rl was somewhat better for raw cow's milk than for raw sheep's milk. Still, it was in the same order of magnitude as s r or s R presented in other studies [4,11,17] and it was within desired limits [14]. The only exception was the interval between 10 IBC·µL -1 and 50 IBC·µL -1 for raw sheep's milk, but only a small data set was appraised here.…”

“…Upon routine testing it was confirmed that within-laboratory reproducibility of BSC-FC depends on IBC counts [4,11,17], no matter which milk was analysed (Tab. I).…”

“…To establish the conversion of IBC into CFU for raw sheep's milk, the model of linear regression was chosen [11,19,20]. Values in log 10 IBC·µL -1 were set as the independent variable -x and values from the anchor method in log 10 CFU·mL -1 were set as the dependent variable -y [19].…”

“…It can be achieved by following international standards [7,10]. The application of this approach in BSC-FC methodology has been described in several works [11,19,20]. Summarisation of calculated regressions was done by Suhren et al [18].…”

“…Summarisation of calculated regressions was done by Suhren et al [18]. Additionally, other aspects of the method have also been evaluated; for example, precision and accuracy [3,11,17], carry-over [4,16], measuring range and linearity [4,11,16] and effect of somatic cells on counting [3,11,16].…”