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Answer by labsupport on question Observing growth on a slice of bread

Submitted by sat on 08 April 2020

Science ASSIST strongly advises against any microbiological experiments being conducted at home.

There are risks associated with growing mould on slices of bread.  These risks can be well controlled when conducted in the school science laboratory but cannot be guaranteed when conducted in the home environment.

The home environment has several limitations:

What are the hazards?

Environmental sampling

Sampling environmental surfaces and incubating on bread (or agar plates, also referred to as Petri dishes) will lead to the growth of unknown microorganisms or ‘wild’ bacterial and fungal cultures, some of which may be pathogenic (a microorganism which can cause disease). Sampling should not be conducted from areas that are likely to contain pathogens such as toilet areas, human body fluids or skin and surfaces where raw meats are handled.1

With the current COVID-19 pandemic, we advise against conducting environmental sampling. Instead, we are being encouraged by the government, to routinely clean frequently touched hard surfaces with detergent/disinfectant solution/wipe.2

Growing mould on slices of bread

In a school setting this may be conducted using good quality zip lock bags.1 However whilst the bread is placed in a sandwich bag for incubation, it is essential that bags are well sealed and never opened.

Release of mould spores:

In a home environment: we have concerns that there is an increased likelihood that the bags may be opened releasing fungal spores and possibly aerosols of any other microorganism.

Biological risk assessment

When conducting a microbiology activity, it is important to consider what microorganisms are being used and how they are being used.

Before schools embark on working with microorganisms, they should ask the following questions and perform a site-specific biological risk assessment.

Science ASSIST resources:

Science ASSIST has produced “GUIDELINES for best practice for microbiology in Australian schools” see https://assist.asta.edu.au/resource/4196/guidelines-best-practice-microb... We recommend that your school is familiar with the content of this guide.

Note: In attachment 1, There is a SOP for ‘Growing fungi on bread’ and a SOP for environmental sampling titled ‘Microbes are everywhere’, both of which have detailed instructions and safety notes.

We have also previously answered questions on the use of bread mould. See:

References

1 Science ASSIST. 2016. GUIDELINES for best practice for microbiology in Australian schools. Science ASSIST website, https://assist.asta.edu.au/resource/4196/guidelines-best-practice-microb...

2 ‘Good hygiene for coronavirus (COVID-19)’, Australian Government Department of Health website, https://www.health.gov.au/news/health-alerts/novel-coronavirus-2019-ncov... (Accessed 8 April 2020)