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The use of direct epifluorescent microscopy (DEM) and the direct epifluorescent filter technique (DEFT) to assess microbial populations on food contact surfaces
Author(s) -
Holah J.T.,
Betts R.P.,
Thorpe R.H.
Publication year - 1988
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1988.tb01888.x
Subject(s) - total viable count , biology , bacteria , genetics
Two rapid methods, direct epifluorescent microscopy (DEM) and the direct epifluorescent filter technique (DEFT) on swab resuspension fluids, were compared with the traditional total viable count (TVC) on swab resuspension fluids for their ability to enumerate surface populations of attached bacteria. The degree of error in estimating surface populations was shown to be significantly less with DEM than DEFT followed by TVC. DEM estimated populations in the range 3 times 10 3 to 5 times 10 7 colonies/cm 2 whilst DEFT enumerated populations above 3 times 10 4 colonies/cm 2 and TVC above 3 times 10 5 colonies/cm 2 (as measured by DEM). Swabbing was shown to remove a constant proportion of organisms from the surface populations tested, although below 3 times 10 5 colonies/cm 2 most of the organisms remained in the cotton matrix and were difficult to resuspend. DEFT was more able to enumerate swab resuspension fluids obtained from surface populations below 3 times 10 5 colonies/cm 2 than was TVC.