An inoculation loop (also called a smear loop, inoculation wand or microstreaker) is a simple tool used mainly by microbiologists to pick up and transfer a small sample of microorganisms called inoculum from a microbial culture, e.g. for streaking on a culture plate.^[1][2] This process is called inoculation.

Inoculation loops

The tool consists of a thin handle with a loop about 5 mm wide or smaller at the end. It was originally made of twisted metal wire (such as platinum, tungsten or nichrome), but disposable molded plastic versions are now common. The size of the loop determines the volume of liquid an inoculation loop can transfer. An early report of the use of an inoculation loop as an analytical tool was by O'Sullivan et al.^[3] in a 1960 published protocol developed to improve methods for culturing urine samples. A 3mm diameter loop was used to deliver a consistent volume of urine for analysis. Loops can now be purchased to transfer volumes ranging from 1-10 microliters, though pipettes have replaced inoculation loops as more reliable tools to deliver small volumes of liquid.