Streak plating is an indispensable instrument in microbiology. It’s so elementary, that it’s usually ignored. Now we have compiled a listing of greatest practices that can assist you grasp your method, save time, and keep away from errors in your laboratory.
The streak plate technique depends on the precept of dilution to isolate particular person bacterial or fungal colonies. Acquiring remoted colonies is important to many downstream purposes similar to performing biochemical, genetic, or antimicrobial susceptibility testing. This method can use many sources as an inoculum, similar to Microbiologics KWIK-STIK™, a colony sub-cultured from one agar plate to a different, or a cell suspension.
1. Label first, streak second. Clearly labeling your plates to determine the microorganism solely takes just a few seconds and can assist you to keep away from a giant headache later. Listed below are some frequent and fewer frequent labels so as to add to your plate.
| Widespread Plate Labels | Uncommon/Miscellaneous Plate Labels |
| Date | The kind of media (in case you make your individual media label) |
| Organism title, catalog quantity, or lot quantity | Subculture quantity |
| Technician’s Initials | Particular environment and development situations (e.g., MA = microaerophilic, AN = anaerobic, CO2, and many others.) |
| Development period of organism (for instance, notice the expansion time if required time is longer than 24 hours) |
As a substitute of writing these frequent labels in your plate, we simplified it for you! We offer a pull-off tab on the KWIK-STIK™ gadget to label your media; the pull-off tab contains the organism’s title, catalog quantity and lot quantity.
For steering on media and incubation situations for the microorganisms you might be culturing, confer with TIB.081, Beneficial Development Necessities.
2. Preserve the agar dry. Ensure the agar plates are freed from droplets of condensed moisture. If moisture is current, depart the plates at room temperature in a single day or place them in a laminar circulation hood to dry for at the least quarter-hour.
3. Keep away from contamination. There are lots of sources of contamination to be cognizant of whereas streak plating. Contacting the sting of the plate is a standard supply of contamination; due to this fact, keep away from touching the sting of the plate with the loop whereas streaking or inoculating the agar with the swab. Respiration on media is one other frequent reason for contamination. Observe open plates at a protected distance out of your face. Though microbiologists are skilled to keep away from respiratory on media, it stays a standard reason for contamination in any laboratory. Preserve your laminar circulation hood and vents clear to keep away from contamination as nicely.
4. A bit goes a great distance. Solely a small quantity of inoculum is required. Use remoted colonies if taking an inoculum from one other plate or use solely 5 to 10µl from a suspension. Please notice that fastidious organisms (e.g., S. pneumoniae, Neisseria spp., and many others.) could require a heavier inoculum. Confer with TIB.2031, Upkeep of High quality Management Strains.
5. Keep away from gouging of agar. Streak calmly in easy, speedy actions to keep away from gouging the agar plate. Gouged agar received’t produce as many colonies (or look almost as stunning) as a rigorously streaked plate. Gouging can dehydrate the plate faster and should trigger you to select up contaminants.
6. Don’t overlook to sterilize. All the time use sterile tools to unfold the inoculum and keep away from contamination. Flame the loop or use a brand new disposable loop after you streak every quadrant. Utilizing a brand new or sterilized loop permits you to successfully dilute the inoculum on the plate and procure remoted colonies by spreading the inoculum thinner and extra evenly. If utilizing a broth, sterilize your tube opening earlier than and after use.
7. All the time begin by plating on non-selective agar. This helps make sure the organism is rising correctly. The selective and differential media could not have sufficient vitamins to assist the organism resuscitate after lyophilization or hydration. When plating on a selective agar in parallel or for downstream purposes, bear in mind to make use of high quality management organisms. Exceptions could apply, please confer with the media producer’s Directions for Use.
8. Streak for colony isolation. Utilizing a three-phase or four-phase streak will present the very best isolation. Please see under for particular directions for streak plating and the next video.
9. Incubate plates inverted. This helps keep away from accrued condensation from dripping onto colonies throughout incubation.
10. After incubation, study your plate rigorously. After colonies have grown, overview your plate to make sure colonies meet expectations for colony morphology on the certificates of study. Some strains have two or extra colony sorts that are listed on the certificates of study.
Streak Plating with KWIK-STIK
As talked about, the streak plate technique could be carried out with Microbiologics’ KWIK-STIK™. The truth is, KWIK-STIK has been praised for many years for its easy, all-inclusive design which makes life simpler for laboratory technicians whereas decreasing probabilities for errors. Every KWIK-STIK comprises a qualitative lyophilized microorganism pellet, ampoule of hydrating fluid and inoculating swab. Every part you might want to develop reference cultures for QC testing is included on this one helpful gadget. Accessible in packs of two, 6, or as a QC set, KWIK-STIKs are universally used for every type of microbiological management testing.
Please watch our Streak-Plating Greatest Practices with KWIK-STIK video to learn to use this elementary plating method with Microbiologics KWIK-STIK product. Additionally, obtain our Streak Plate Technique with KWIK-STIK illustrated directions.
