Automated microbial identification system
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The document discusses an automated bacterial identification system that rapidly detects and identifies bacteria and yeasts in clinical specimens using lyophilized media in disposable cards. It highlights the system's components, including a vacuum chamber for sample processing and an incubation and analysis chamber where color changes are analyzed to identify bacteria. While the system offers advantages such as reduced human error and faster results, it has limitations including high cost and inability to analyze mixed cultures or identify viruses.
Automated microbial identification system
- 2. INTRODUCTION An automated, computerized system, the automicrobic system, has been developed for the detection, enumeration & identification of bacteria & yeasts in clinical specimens. The biological basis for the system resides in lyophilized, highly selective & specific media enclosed in wells of disposable plastic curette, or a cartridge. Introduction of a suitable specimen rehydrates & inoculates the media in the wells. An automated optical system monitors, & the
- 3. It is an instrument used for automatic computer- assisted identification of bacteria The conventional method of identification of bacteria is very lengthy
- 4. It mainly involves staining, motility test, cultural characteristics, a series of biochemical tests and finally searching the name of the bacteria in ‘Bergey’s Manual of Determinative Bacteriology’ by matching the results with those available in the manual. The automatic bacteria identification system automatically identifies the bacteria in very short time. The system uses disposable cards. One card is required for the identification of one bacteria. The system can accommodate a series of cards, which can be arranged on a cassette, thus enabling the identification of several bacteria at a time.
- 6. Mains:it is the source of electric current for the equipment runs using alternating current(AC) supplied through a three-ply cable. The 3 wires are phase(+), neutral(-) & earthing(E).the earthing helps in the safe operation in the equipment against electric shock due to any short-circuit. Plug: A three-pin plug provides non-sparkling interface b/w the equipment & the mains. Connecting cable: A three-ply cable connects the main with the equipment. Control panel: it is the panel or switchboard containing all the switches , with which the functions of the systems can be controlled. The different parameters like temperature, & time of incubation required for the operation of the system can be programmed on the
- 7. Vaccum chamber: it is the chamber, into which the cassette containing the card & the bacterial suspensions to be identified to be put. A high vaccum is created inside the chamber, which forces the bacterial suspensions to be sucked into the capillary tubes & dispensed into the wells of the cards. Incubation & analysis chamber: in this chamber, incubation & color readings takes place simultaneously. The cassette containing the cards dispensed with the bacteria suspension is put into it. After scanning the barcodes on the cards, the capillary tubes are cut & the cut ends seals automatically. Then , the cards are positioned onto a carosol(a wheel like stru), which moves in such a ways that in every 15 mins each card comes in front of the colour reader. The colour reader reads the changes in colour at three different wavelengths. The changes in the colour of the media in the wells of the each card are recorded & sent to the computer for the comparison of the results with the databaase & display of the names of the bacteria in terms of genus & species.
- 8. Waste disposal chamber: after analysis, the used cards automatically get collected in the waste disposal chamber for the further disposal to outside after sterilization. Cards: the identification of each unknown bacteria requires one disposable card . There are few types of card s each specific for a particular group of bacteria. The type of card to be used for a particular unknown bacteria is determined by a preliminary test like gram staining. wells: Each card has several rows of well. Usually there are 8rows of 8 wells each (8*8=64wells). The wells contain different dehydrated media for different microbial tests required for the identification of the bacteria.when the bacteria suspension is dispensed into alll the wells. the dehydrated media become hydrated by the suspension liquid. The hydrated media allows the bacteria to grow. The growth of the bacteria in the wells results in the change in the colour of the media in the particular way, which is characteristic for each bacteria species.
- 9. Suspension of bacteria:the unkonwn bacteria grown as isolated colony on a plate or as pure culture grown on a slant is taken . A loopful of the bacteria is transferrd aseptically into sterile saline solution in a test tube & a suspension of bacteria is made. The suspension should contain a prescribed density of bacteria as determined by a densitometer. Capillary tube: a capillary tube is fixed to each card, which sucks the suspension of bacteria& dispenses into all the wells. Cassette:it can hold a series of cards along with their respective test tubes containing bacteria suspensions. The test tubes & cards are fixed in such a way that the tips of the suction capillary tubes of the cards remain deeply submerged in the suspensions. Computer systems: the results of colour changes results by the analysis chamber to the computer, which automatically compares them with those available in its library(
- 10. ADVANTAGES Reduce human errors Safety Improve turnaround time Increase productivity Run more tests Operate with fewer instruments
- 11. DISADVANTAGES Automation is too expensive for microbiology laboratories & labs are too small to automate. Need pure culture In mixed cultures, will pick up the dominant organism Antimicrobial susceptibility not possible Viruses not identified Identifies only organisms in database
- 12. BIBLIOGRAPHY www.americanpharmaceuticalreview JOURNAL, OF CLINICAL MICROBIOLOGY, oct,1997, p.406-413
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