CFUCalc

Instructions and Guidelines

1.CFU Calc is an App developed for Mobile phones.

2.For better results and precision, it is advised that this guide/instructions be read through till the end. If you wish to proceed with reading the material later, you have the option to download and save this as a PDF document for future reference and ease. Please click here for the same.

3.As you click on the CFU Calc App it would have automatically directed you to the Logo flash screen followed by this screen that you are viewing.

4.At the bottom of this screen you will find a button to ‘Proceed to Capture & Calculate’. This button will direct you to the ‘Main Menu’ Screen.

5.The ‘Main Menu’ Screen will show the following options, ‘Single Plate Counting’, ‘Multiple Plate (Dilution) Counting’ & ‘Your Archive’. Each of these options have defined functionalities.

6.The ‘Single Plate Counting’ option is to facilitate your colony counting procedure of individual plates. As you click on this option, you will be directed to a screen displaying the camera view with 02 options at the bottom, ‘Click Photo’ & ‘Go Back’. Allow the camera to adjust and once you have focused, just click on the ‘Capture’ button and within seconds the 3^rd option ‘see counted colonies’ will appear at the bottom. Select this option and a screen displaying the captured image, also showing the colonies counted in ‘Blue’ will appear. At the bottom of the image the value of colonies counted will be displayed.

7.The ‘Multiple Plate (Dilution) Counting’ option is to facilitate colony counting of multiple petriplates (multiple dilutions in single, duplicate or triplicate) by Pour Plate method and calculating the Colony Forming Units (CFU) per gm (in case of solid samples) or per mL (in case of liquid samples). As you click on this option, you will be directed to a screen displaying the following,

a. ‘Sample Name / Description’ – This has to be filled-in by typing (eg: Milk Code -1234)

b.‘Sample Type’ – Dropdown option (Solid or Liquid)

c.‘Dilutions (From / To)’ – Dropdown option (10^-1 to 10^-10). The user has the freedom to select, considering the experimental plan or design,from the range of dilutions.

d.‘Number of Plates per dilution’ – Dropdown option ( Single / Duplicate / Triplicate). The user has the freedom to select, considering the experimental plan or design.

Note : All columns must be filled

Once the columns are filled and the petri plates are ready in sequence (from Lower dilution to higher dilution ) the ‘Capture Image’ can be clicked. Depending on the ‘Number of Plates’ per dilution, say 10^-1 to 10^-4 in duplicates, in

the order of lower dilution to higher dilution, images will be captured by the App, prompting the user to change the

petriplate, after image capture. As you click on ‘Capture Image’, you will be directed to a screen displaying the

camera view with 02 options at the bottom, ‘Click Photo’ & ‘Go Back’.

This screen will also display the dilution factor and the plate number at the top of the camera view as ‘ Plate: 1/2 of 2 for dilution :10^-x ’. Allow the camera to adjust and once you have focused, just click on the ‘Capture’ button and

within seconds the screen will prompt for the next image to be captured (the user then should shift to the next plate

in sequence) and the cycle will proceed till the total number of plates per dilution for the selected range of dilutions

are captured and complete. After image is captured the screen will also display the ‘Last Plate Count’. Once the image

capturing session is complete the App will automatically display the CFU (CFU/gm or mL) and the Log10 value of the

CFU calculated. At this stage the entire set of raw images & colony counted images along with the values and CFU

calculated will be archived as .jpg and PDF formats in the mobile.

Please note :

# The petriplate for counting of colonies should be adjusted to be within the ‘Red circle’ frame that will be visible on the Camera view.

# Capture image of the petriplate upright, the agar at the bottom.

# The App will capture images even with the lid of the petriplate on, however, for better results it is advised to capture without the lid.

# It is also advised that markings/labels on the plate be temporarily removed and redone after image capturing. The App will inadvertently capture spots, markings and labels on the plate and will count them as colonies.

# For best results and precision, plates with agar medium that are light shaded (eg: Plate Count Agar) be placed on dark/black background for image capturing, similarly, plates with agar medium that are dark shaded (eg: Chromogenic Agar) be placed on light/white background for image capturing.

# The App is programmed to calculate the CFU/gm or mL by Pour plating method using the formula as per ISO 7218:2007(E). As per standard the App for calculating the CFU/gm or mL will consider only those plates that have a count >30 and <300 only.

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