Objective
To provide a procedure for the operation and calibration of the Colony Counter.
Scope
This SOP covers the operation and calibration of the Colony Counter.
Responsibility
Microbiologist: Responsible for operation, calibration, and maintenance of the instrument. Maintain required records.
QA Officer/QAM: Review the records and governing the document.
Procedure
Operation
- Ensure that the instrument is visibly clean and free from dust.
- Switch ON the mains, Turn ON the instrument by pressing the reset On/Off Switch, the display will indicate some numbers.
- Reset the counter by pressing the reset switch. The counter should now read 0000.
- Place the Petri plate on the graduated Woulffhneugal glass plate provided on the top of the instrument.
- Position the magnifying lens to focus the Petri plate or clear visibility. Ensure that a sufficient margin is left between the magnifying lens and the Petri plate in order to use the marker conveniently while colony counting.
- Remove the cap of the Auto-mark and touch the marking point of the probe on the Petri Dish where a Bacteriological Colony is located. Press the probe gently. The counter will register a count, there will be a beep and an ink dot will be marked on the Petri Dish. Continue till all the colonies are thus counted.
- As a colony is marked with ink while it is being counted, missing a count or double counting is avoided. When the counting is completed note the reading on the counter.
- The COUNT push button switch (next to the RESET switch) may be used to count sparsely populated plates or for some other counting purpose also.
- If the Petri plate is not to be contaminated with the marking, then counting can be done in either of the following methods :
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- If the Petri plate is finely plated (thin layer) then it can be kept upside down, and marking can be done on the bottom side (which is on Top)
- The lid can be kept over the plate and marking may be done on the glass cover. But in this case, as there is a gap between the media and the marking, the counting should be done in one sitting without altering the view angle or moving/turning the plate or its cover.
Refilling the ink cartridge in the Auto-mark:
- Unscrew the body of the Auto-mark and remove the cartridge from the inside.
- Gently pull, and open the cap at the back of the cartridge.
- Put about five drops of ink and reverse the procedure for refitting.
- The body of the Auto-mark should be tightened in such a manner, that the gentle push on the probe would register a count.
Calibration
- Operate the instrument as per the above procedure.
- Electronic digit counts the number accurately, to be tested by using the COUNT switch by manual counting.
- Record the result in the calibration format as per given in Annexure - 1.
Routine maintenance
- Clean the instrument with dry cloth.
- Clean magnifying glass with tissue paper.
Annexure
Annexure – 1: Colony Counter Calibration Record Format
Annexure – 2: Colony counter usage log book
Abbreviation
SOP: Standard Operating Procedure
QA: Quality Assurance
QAM: Quality Assurance Manager
Revision History
Nil
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