Four Quadrant Streak procedure - How to properly streak a Petri plate for isolated colonies

in order to correctly treat an infection or identify a contaminant microbiologists must first isolate the target microbe from a sample or specimen that often contains other microorganisms streaking agar plates is an essential technique used in the laboratory to isolate pure individual colonies from a larger sample source before beginning it is important to

remember individual microbial cells are not visible to the naked eye avoid the tendency to over-inoculate the plate a common mistake that will cause the plate to be overloaded with colonies and result in a confluence of growth this is particularly critical for certain specimen types such as stool samples where isolation of single colonies is extremely important

also agar is similar in consistency and firmness to jello and can be prone to breaking the gel matrix the goal when inoculating plates is to streak the surface gently and not to cut tear or stab the gel matrix with the inoculating loop to prepare ensure the bench top is clean disinfected and organized

make sure the tools such as loops and labeling pins are within easy reach laboratory personnel should use good hand hygiene aseptic technique and wear appropriate clothing such as a lab coat and gloves ensure clothing is tight fitting near open flames or sterilizing equipment such as a bunsen burner or incinerator allow the plate to reach room

temperature prior to inoculation to avoid temperature shock to cells which may affect recovery always label plates on the bottom of the dish prior to use this is essential to identify the sample after incubation and to ensure the plate can be identified in the event the lid is lost dropped or accidentally switched to