HiDtectTM Rapid Identification Discs for Confirmation of Food Pathogens

Introduction: Rapid Identification of food borne pathogens especially Escherichia coli, have been considered to be a major challenge in food industries. Classical method of bacterial identification involves the use of enriched and selective medias for the growth of organisms and subsequent confirmation using series of biochemical tests, that would take 48-72 hrs for the completion. Present study describes the use of HiDtect™, a novel chromogen based paper disc technology for the rapid, qualitative detection of E. coli.

Purpose: For rapid detection and confirmation of E.coli in water and food samples.

Methods: Three sets of chromogenic discs such as DT 006, DT007 and DT008 were prepared using chromognic, fluorogenic and dual technologies. ATCC 25922 and six other isolates of E.coli were used for the inclusivity study whereas Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923) and Salmonella Typhimurium (ATCC 14028) were used for Exclusivity study. All the cultures were grown on Plate Count Agar. Fully grown cultures were replicated on the three different chromogenic discs by placing the discs over the colonies for 30 sec to 1 min. These discs after replication were incubated at 35-37°C for 1-4 hours and observed for colour change (DT006), fluorescence (DT007) and both (DT008).

Results: The incubated discs were checked for the presence of E. coli by observing the blue colouration (in DT006), fluorescence (in DT007) and both blue colouration and fluorescence (in DT008) of the replicated colonies. All the tests were performed at least in triplicates and presented as qualitative observations. Results (Table 1) obtained shows that these discs have high specificity and reproducibility in comparison with the routine biochemical methods.

Table 1: Results of various discs after replication of the colonies

Organism	DT006 Colourchange	DT007 fluorescence under UV light	DT008 Colourchange/ fluorescence under UV light
E. coli (ATCC 25922) and six isolates	blue	Positive	Positive
Pseudomonas aeruginosa (ATCC 27853)	colourless	Negative	colourless / Negative
Staphylococcus aureus (ATCC 25923)	colourless	Negative	colourless / Negative
Salmonella Typhimurium (ATCC 14028)	colourless	Negative	colourless / Negative

Significance: Chromogenic discs have advantages of saving costs, time and labour over the conventional methods for identification of E.coli.  

• Direct application without any preparations.
• Confirmed results are obtained within 1-4 hours in comparison to 48-72 hrs required by traditional methods.
• The technology is highly sensitive, that can identify even a single developed colony.
• Discs after identification can be stored for further traceability without any deterioration in colour.