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Colony Counter- Sorts, Precept, Working, Components, Makes use of, Examples


A colony counter is a tool that’s ceaselessly used to rely bacterial or different microorganism colonies on a plate that comprises a gelled progress medium.

Microbiologists should deal with the daunting job of counting colonies, which may often be undersized and obscured by the distinctive colour of the tradition media or the enumeration course of itself. Thus, on a regular basis routines require a greater and simpler methodology of optimizing procedures.

A colony forming unit or CFU is a exact measurement to find out what number of bacterial or mycelial cells are current in a given pattern. Thus, the colony counting method screens viable CFUs, which may nonetheless reproduce by way of a course of like binary fission below rigorously monitored settings.

Objective of colony counting

To find out the approximate variety of cells in a pattern primarily based on the cell’s propensity to proceed rising and increasing within the presence of particular components, corresponding to temperature and the standard of the dietary medium. Ideally, a single viable cell can bear large replication to turn into a completely developed colony, given the proper circumstances.

Points with colony counting

The next issues have to be addressed when making an attempt to rely all bacterial colonies which might be current in a pattern or filter:

  • The variety of colonies that don’t overlap.
  • The variety of colonies that overlap.
  • The variety of colonies that contact the perimeters.
  • To scale back the rely due to noise.
  • Colonies of assorted sizes, shapes, and colours.
  • The combination of these talked about above 5 would be the remaining rely.

Significance of Colony counting

Totally different companies, together with these within the meals and beverage industries, make use of the colony counting method. A number of the significance embrace:

  • Figuring out the colony counts helps to make make sure that the discharge of merchandise received’t ultimately trigger any hurt.
  • Professionals could also be extra knowledgeable about any well being points a affected person could also be experiencing if they’ve extra details about the focus of microorganisms of their blood. One can decide the development of a contagious illness, and even the efficacy of the person’s immune system might be monitored.

Sorts of Colony counters

There are lots of sorts of colony counters. A few of these colony counters are handbook, whereas others are automated. Whether or not handbook counting or computerized counting, triphenyl tetrazolium chloride (TTC) was included to make the colonies extra obvious. Stay micro organism convert TTC to a deep crimson coloured product such that the colorized bacterial colonies are brilliant in comparison with the background.

Colony Counter. Picture Supply: Neu-tec Group and Giles Scientific.

Handbook colony counters

Handbook and semi-automatic counters depend on a technician’s skill to tell apart between colonies and mark them on the plate’s exterior utilizing a particular pen. The gadget maintains monitor of colonies with such markings. Though this method considerably aids, it’s nonetheless time-consuming, chaotic, and susceptible to errors.

Components and their features of handbook colony counters

Auto marker probe pen: A counter pen’s stress on a colony causes a rely to be registered by an audible beep and an advance on a pc display.

Digital show: It displays the whole rely made by the counter pen.

Lens: It helps in magnification.

Gentle supply: A backlight supply is used for illumination functions.

Handbook colony counter video

Working Precept of Handbook colony counters

A Petri plate is positioned on an digital stress pad with gentle illumination, and every colony on the plate is marked by tapping the plate with an auto marker probe pen. A rely is registered within the digital show by the contact’s stress. This stress might be altered primarily based on the scenario. It facilitates avoiding the error of overlooking or counting colonies twice. The gear additionally has a graticule for Wolfheugal, a segmentation disc, and centering adapters for 50-90mm plates. Moreover, added options embrace darkening background for clear colonies, glare-free illumination that permits for optimum peripheral colony viewing, and an built-in averaging software for a number of plate counting.

Limitations of Handbook colony counters

  • Labour intensive
  • Time-consuming
  • Relative low throughput
  • Excessive danger of human error

Computerized colony counters

To successfully rely colonies, the autonomous bacterial colony counter employs picture processing strategies, together with grey scaling, thresholding, filtering, and many others.

Components and their Capabilities of computerized colony counter

  1. Tradition dish: For a spread of tradition dishes, together with the traditional plate inoculation methodology, the spiral inoculation methodology, and many others., the automated colony counter is suitable. 
  2. Gentle supply: A sturdy LED gentle supply serves because the automated colony counter’s gentle supply. There are 4 totally different gentle sources and background colour mixtures in it. Elective clever distant management multi-color gentle supply background enhancing the accuracy of the rely of assorted media colour and kind mixtures.
  3. Imaging: The traditional synthetic colony counter makes use of a 3–6 magnification lens for imaging. 
  4. Picture processing: The automated colony counting has a sturdy image processing characteristic. Background processing, colour marking, interference correction, colony growth, space calculation, and different components not seen in standard colony counts are offered within the related software program.
  5. Database: Computerized colony counters enhance knowledge storage, clever question, knowledge export, and many others., with database processing in comparison with conventional colony counters. Some may also configure operator permissions, knowledge modification permissions, and many others., to make the measured knowledge safer. Moreover, you could print and edit experiences on-line concurrently.

Computerized colony counter video

Precept of Computerized colony counters

A pc-based system is essentially composed of the gathering of pictures using any of the digital image-capturing gadgets corresponding to doc scanners, charge-coupled gadgets (CCD), digital cameras, webcams, or video gear. Colonies might be enumerated from pictures of plates by using software program instruments. Each plate is photographed after which analyzed. The recorded pictures are then transformed to digital recordsdata on a pc utilizing programmable image-processing software program. Single/multi-threshold segmentation methods are used to separate and determine any colonies current. The backgrounds of the objects and objects themselves can differ enormously in automated techniques. To enhance visibility and enhance precision, one of many three illumination methods can usually be chosen. They’re:

  • Transmission approach: Utilized to frequent, excessive distinction objects with largely clear backgrounds.
  • Reflection approach: Used for objects with excessive distinction and opaque backgrounds.
  • Darkfield approach: For low-contrast, largely clear objects.

Benefits of computerized colony counters

  • Precisely rely even essentially the most tough samples
  • Work with any pattern kind, even samples with little or no distinction
  • Tackle colonies of each measurement and kind
  • Deal with all noises.
  • Even in extraordinarily overlapping colonies, excessive curvature areas might be discovered.
  • Click on images of a Petri plate containing colonies in about 10 seconds, and the software program can consider it instantly.
  • The time wanted for counting is diminished.
  • Use of software program decreases handbook effort.

Utility of colony counters

  • Bacterial colony counting is utilized in microbiology labs to evaluate the filter or membrane’s capability for retention.
  • It’s essential for figuring out the efficacy of disinfectants, together with to be used in testing the protection of meals and medicines, in addition to medical examination assessments in medical services and the pharmaceutical trade.
  • Measure the density of microorganisms in liquid tradition by counting every colony on an agar plate, slide mini gel, or petri dish.
  • Ame’s testing
  • Bacterial mutation assays


a. Colony counter JL Collection (Producer: Zhejiang FUXIA Medical Know-how Co., Ltd.)


  • It’s a specific kind of digital show semi-automatic micro organism examination software.
  • A counter, a probing pen, and a counting pool make up the gadget.
  • CMOS built-in circuits are used within the design and manufacturing of the counter. 
  • The bacterial colony distinction is seen within the counting pool with a black depth background when the energy-saving ring lamp is utilized for aspect lighting. 
  • The instrument show is made as a three-digit quantity following the bacterial rely take a look at protocol. 
  • The take a look at pattern have to be diluted and repeated when the variety of bacterial colonies in a petri dish surpasses 999 to verify the rely’s accuracy.

b. Colony counter QUANTOM TxTM (Producer: Logos Biosystems)


  • The QUANTOM TxTM scans as much as 10 fields of view and generates exact single bacterial cell counts. 
  • The delicate program can think about how varied micro organism can have various sizes, shapes, and configurations.
  •  A computerized, image-based cell counter referred to as the QUANTOM TxTM Microbial Cell Counter can rapidly determine particular person bacterial cells. Even essentially the most compact clusters of micro organism could also be counted utilizing the corporate’s progressive bacteria-optimized cell detection software program.

c. Colony counter LKB 2002 (Producer: POL-EKO-APARATURA sp.j.)


  • The LKB 2002 colony counter can mechanically modify for various Petri-plate weights.
  • For plates with a diameter of lower than 120 mm, adapters are included. 
  • The colony counter has an adjustable stress power, a magnifying glass, and shock-resistant counting know-how. 
  • You’ll be able to work in opposition to a lightweight or darkish background as a result of the ring gentle illuminates the counting subject. 
  • Quite a few useful options, together with total imply worth calculation and acoustic/visible counting management, are included with the LKB 2002 colony counter.

d. Colony counter Scan® 300 (Producer: Interscience)


  • The Scan 300 is an computerized colony counter with all the mandatory elements for counting Petri dishes. It’s tailor-made to the frequent media in meals microbiology, together with PCA and MRS.
  • Languages: English, French, Japanese, Chinese language, Russian, Spanish, and German 
  • Minimal measurement of the detected colony: 0.1 mm 
  • Digital camera: 1 megapixel – magnification x 28 
  • Relying on spherical Petri dishes of roughly 55 to 90 mm


  1. Gupta, S., Kamboj, P., & Kaushik, S. (2012). Methodology for Computerized Bacterial Colony Counter.
  2. Khandpur, R.S. (2020). Compendium of Biomedical Instrumentation || Colony Counter, Automated., 491–494. doi:10.1002/9781119288190.ch95


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