Abstract
This research explored several alternative coliforms and E. coli detection strategies proposed for industrial
application especially low-resource settings and less advanced food manufacturers. The colony count using 2
industrial favourites (i.e., PetrifilmTM by 3M and regular pour plate techniques) were contrasted to 4 alternative lowcost
strategies. Two modified conventional protocol (i.e., pour and spread plate techniques) in standard mini Petri
dishes and two drop plate techniques in microtiter plate formats (i.e., 24 - and 96-well plate) were applied to count
industrial frozen food samples. The colony detection in all treatments was visually facilitated by low-cost digital
microscopy technique comparing colony count, the detection time and the colony area in pixels. All experiments
except for the PetrifilmTM E. coli/Coliform (EC) Plate utilized Chromocult® Coliform Agar (CCA). The inoculum
sizes were varied depending on the cell count technique used; 10 ȝl and 5 ȝl for the 24- and 96-well microtiter plates,
50 ȝl for the mini-plate (both pour and spread plate techniques), and 1000 ȝl for the full-size Petri dishes and
PetrifilmTM E. coli/Coliform (EC) Plate. The incubation temperature was fixed at 35r2qC. The number of colonies
from the conventional pour plate technique was plotted against those of the other techniques. In all treatments, the
relationship plots showed highly linearity from the lower detection limit (100 CFU/ml depending on technique used)
to the upper detection limit (10,000 CFU/ml). The slopes of all regression lines were close to unity showing very high
correlation of the values of colony counts from different techniques. All techniques were applied to evaluate actual
swap samples from the production line and returned highly consistent colony count numbers and good separation of
E. coli from coliforms. The colony counts from the ready-to-eat product samples showed similar and comparable
results to the two routine factory techniques. The results indicated that all six colony count methods were simply
interchangeable to perform colony enumeration in the low-resource industrial setting
AbstractThis research explored several alternative coliforms and E. coli detection strategies proposed for industrialapplication especially low-resource settings and less advanced food manufacturers. The colony count using 2industrial favourites (i.e., PetrifilmTM by 3M and regular pour plate techniques) were contrasted to 4 alternative lowcoststrategies. Two modified conventional protocol (i.e., pour and spread plate techniques) in standard mini Petridishes and two drop plate techniques in microtiter plate formats (i.e., 24 - and 96-well plate) were applied to countindustrial frozen food samples. The colony detection in all treatments was visually facilitated by low-cost digitalmicroscopy technique comparing colony count, the detection time and the colony area in pixels. All experimentsexcept for the PetrifilmTM E. coli/Coliform (EC) Plate utilized Chromocult® Coliform Agar (CCA). The inoculumsizes were varied depending on the cell count technique used; 10 ȝl and 5 ȝl for the 24- and 96-well microtiter plates,50 ȝl for the mini-plate (both pour and spread plate techniques), and 1000 ȝl for the full-size Petri dishes andPetrifilmTM E. coli/Coliform (EC) Plate. The incubation temperature was fixed at 35r2qC. The number of coloniesfrom the conventional pour plate technique was plotted against those of the other techniques. In all treatments, therelationship plots showed highly linearity from the lower detection limit (100 CFU/ml depending on technique used)to the upper detection limit (10,000 CFU/ml). The slopes of all regression lines were close to unity showing very highcorrelation of the values of colony counts from different techniques. All techniques were applied to evaluate actualswap samples from the production line and returned highly consistent colony count numbers and good separation ofE. coli from coliforms. The colony counts from the ready-to-eat product samples showed similar and comparableresults to the two routine factory techniques. The results indicated that all six colony count methods were simplyinterchangeable to perform colony enumeration in the low-resource industrial setting
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