Rapid And Quantitative Detection Of Aerobic Plate Count And E.coli 0157:H7 And Aerobic Plate Count In Milk By Flow Cytometry

Milk is under the threat of food safety problems such as microbial contamination.The traditional bacteriology-based culture method for bacterial detection are time-consuming and invalid for meeting the needs of the market.This study is aimed at rapid and quantitative detection of aerobic plate count and E.coli 0157:H7 in milk by FCM.The results are as follows:1.For aerobic plate count in milk,Escherichia coli,Staphylococcus aureus and Bacillus subtilis were selected as the representative strains for research.The total bacteria were labeled with SYTO 9 and PI,and then detected by FCM.The accuracy and the specificity of the method were good,with the detection range of 103-108 CFU/mL in PBS.As for the detection of aerobic plate count in milk,the sensitivity is 102 CFU/mL.2.For E.coli O157:H7 in milk,the bacteria were stained by FITC-Iabeled anti-E.coli 0157 antibody and PI,and then detected by FCM.The accuracy and the specificity of the method were good,with the detection range of 10-108 CFU/mL in PBS.As for the detection of Escherichia coli 0157:H7 in milk,the sensitivity is 101 CFU/mL.3.When detecting bacteria in milk,it is necessary to eliminate the interference of impurities in the milk.As a result,the SSC of FCM can distinguish the bacteria from somatic cells in milk accurately.In addition,the purification of bacteria in milk can eliminate the proteins and lipids in milk effectively.4.The enrichment culture technique can improve the sensitivity of FCM method for bacteria detection.After 6.5 h-enrichment incubation at 37 C in NB,the concentration of E.coli 0157:H7 increased by 967 ± 143 times.After 4.5 h-enrichment incubation at 37 C in NB,the concentration of E.coli increased by 92 ± 25 times;the concentration of Staphylococcus aureus increased by 44± 9 times;concentration of Bacillus,suhtilis increased by 372 ± 67 times.5.FCM method for the detection of E.coli 0157:H7 and aerobic plate count in milk was developed.The process is:bacterial purification—enrichment incubation—fluorescence labeling—FCM detection.In conclusion,the FCM method can reduce the detection time,and accomplish rapid and quantitative detection of bacteria in milk.