Friday, 28 August 2020

Modern myth #4: You need to use a Bunsen burner

Many microbiologists find that the use of pre-sterilized disposable tools to transfer media and bacterial cultures result in lower contamination rates compared with reusable inoculating loops. The latter is a process known to create aerosols that may increase potential air contaminants.

Depending on the organism handled, this can create an element of risk. Several studies have shown that particles of less than 5 um are most effective in establishing airborne infection in laboratory animals; and particles of 1 to 5 um can be deposited in the alveoli, with preferential deposition occurring with 1- to 2-um particles. Particles larger than 3.5 are most probably deposited in the upper respiratory tract. Particles in the 2.0- to 3.5- um range appear to offer equal opportunities for both upper respiratory and alveolar deposition.

Where Bunsen burners are used, it is optimal to flame a loop in the airspace underneath the burner flame.

Moreover, the idea that the Bunsen burner creates an upward draft of air to prevent contaminants in the air from settling on the work surface below does not always result in more robust practices, as sometimes airflow disruption leads to particles settling out.


Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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