Among potentially pathogen microorganisms, Aeromonas can be present and grow in refrigerated raw milk thanks to their wide diffusion and psychrotrophic properties. In this study, quantitative determination of Aeromonas spp. in Ryan Agar, GSP Agar and Starch DNA Agar was carried out in 56 samples of raw milk from automatic vending machines in 4 Tuscan provinces, representing more than 80% of the total, both at the collecting time and after 4 days of refrigerated storage at mean temperature of 4°C. Qualitative detection of Aeromonas in the same samples at the collecting time was made and 120 strains of Aeromonas were collected and genotypically confirmed. For each sample, the presence of the mandatory data for the vending machine was verified, as well as the agreement between the display temperature of each vending machine and the effective milk temperature. Moreover, total bacterial count of each milk sample was determined. Qualitative research gave positive result in 78,6% of samples. On GSP Agar and Starch DNA Agar mean values of Aeromonas counts resulted within 2 log cfu/mL for the total of samples, both at the collecting time and after storage, and within 3 and 4 log cfu/mL, respectively, for positive samples, with maximum values of 4,65 and 5,30 log cfu/mL, at the collecting time and after 4 days, respectively. On Ryan Agar, highly aspecific, mean values for the total of samples overestimated of more than 2 log cfu/mL compared to the other culture media were obtained, as demonstrated by the results of phenotypical tests on isolated strains. The examined vending machines gave evidence of a good degree of agreement with law but milk temperature at the collecting resulted, often in discrepancy with data showed by displays, beyond the mandatory limits in 23,2% of samples. Mean value of milk total bacterial count at the collecting was 5,09 log cfu/mL. On the basis of the results obtained, the possibility of Aeromonas food disease for the consumers of mik from vending machines appears poorly probable because sufficient counts could be obtained only drinking not boiled milk, stored beyond expiry date in sufficient thermal abuse and in presence of high Aeromonas counts at the collecting time.
Presenza e sviluppo di Aeromonas spp. in latte crudo erogato da distributori automatici in Toscana
PEDONESE, FRANCESCA;TURCHI, BARBARA;TORRACCA, BEATRICE;D'ASCENZI, CARLO;NUVOLONI, ROBERTA
2012-01-01
Abstract
Among potentially pathogen microorganisms, Aeromonas can be present and grow in refrigerated raw milk thanks to their wide diffusion and psychrotrophic properties. In this study, quantitative determination of Aeromonas spp. in Ryan Agar, GSP Agar and Starch DNA Agar was carried out in 56 samples of raw milk from automatic vending machines in 4 Tuscan provinces, representing more than 80% of the total, both at the collecting time and after 4 days of refrigerated storage at mean temperature of 4°C. Qualitative detection of Aeromonas in the same samples at the collecting time was made and 120 strains of Aeromonas were collected and genotypically confirmed. For each sample, the presence of the mandatory data for the vending machine was verified, as well as the agreement between the display temperature of each vending machine and the effective milk temperature. Moreover, total bacterial count of each milk sample was determined. Qualitative research gave positive result in 78,6% of samples. On GSP Agar and Starch DNA Agar mean values of Aeromonas counts resulted within 2 log cfu/mL for the total of samples, both at the collecting time and after storage, and within 3 and 4 log cfu/mL, respectively, for positive samples, with maximum values of 4,65 and 5,30 log cfu/mL, at the collecting time and after 4 days, respectively. On Ryan Agar, highly aspecific, mean values for the total of samples overestimated of more than 2 log cfu/mL compared to the other culture media were obtained, as demonstrated by the results of phenotypical tests on isolated strains. The examined vending machines gave evidence of a good degree of agreement with law but milk temperature at the collecting resulted, often in discrepancy with data showed by displays, beyond the mandatory limits in 23,2% of samples. Mean value of milk total bacterial count at the collecting was 5,09 log cfu/mL. On the basis of the results obtained, the possibility of Aeromonas food disease for the consumers of mik from vending machines appears poorly probable because sufficient counts could be obtained only drinking not boiled milk, stored beyond expiry date in sufficient thermal abuse and in presence of high Aeromonas counts at the collecting time.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
