How clean is your incubator shaker?

Different levels of cleaning and decontamination

What cleaning agents to use 

A ‘mild cleaning agent’ such as soap or household detergent will clean greasy surfaces but may have little antimicrobial activity. It can be applied with a soft, lint-free cloth such as microfibre, although unwanted residue may be created and an additional rinse may be required. Many generic ‘quaternary ammonium compounds’ (quats) have antimicrobial properties and are widely used as disinfectants. The antimicrobial activity depends on the quats’ ability to disrupt cell walls. They are not good against some gram-negative bacteria and of little value against fungal spores and non-enveloped viruses. 

Quats can be very effective if used properly: 

• Clean the area first. 
• Use soft water, distilled or RO (reverse osmosis) water since hard water can make quats less microbicidal
  
• Apply directly to the surface, allow a short time for the quats to take effect, then wipe off.

Quats work as surfactants (more like a wetting agent). They do not corrode metal or damage plastics, unlike oxidative disinfectants and cleaners such as peroxide or bleach. They can potentially cause staining and leave a residue. However, some residue is desirable to maximise the antimicrobial effects. There are many commercial brands available which are cheap and effective hard surface cleaners for laboratory use.

When choosing a product, the following characteristics should be considered: 

• A quaternary ammonium compound with the option of additives such as corrosion inhibitors 
• Used for medical and general applications 
• Does not stain or irritate the skin 
• Has good materials compatibility with rubber, plastic, and metal without causing oxidation 
• A bactericide, viricide and fungicide (Candida), effective within 5 minutes. 

A good example of a combined cleaning agent and disinfectant for incubator shakers is Fermacidal D2 from IC Products SA or Biocidal ZF™ from WAK-Chemie Medical GmbH. 

Alternatives to Quats:

• Oxidative disinfectants such as bleaches: If these splash onto metal parts, especially bearings, they can cause corrosion. As a rule, do not use bleach in any device that contains metal components. It will damage everything from interior sheet metal to solenoid valves.
• Use of ultra-violet radiation to decontaminate the interior (some manufacturer provide as option for their incubation shakers). 
• Hydrogen peroxide: This can permanently damage humidification sensors. As this can be used to decontaminate an entire laboratory or cleanroom areas, care should be taken to prevent access to the incubator chamber if a humidification option has been fitted. If possible, the humidification sensor should be removed or covered.

Cleaning of hard surfaces inside and outside the shaker 

If a flask has broken or culture medium has escaped, clean the chamber immediately with a neutral household cleaner as a first step. Then clean with disinfectants e.g. quats, if necessary.  

Depending on your laboratory guidelines cleaning of the outside surface should be part of a general laboratory routine (SOP).  

Use a damp cloth and mild detergent to clean the touchscreen panel of the controller and the plexiglass cover protecting the lighting unit – do not apply liquid directly to the surfaces or use aggressive chemicals. Dry with a clean cloth.  

There is a risk of damage to the surfaces due to use of abrasive cleaners such as scouring pads and similar utensils. Only clean the glass door inside and outside with a soft cleaning cloth and mild detergent solution (diluted with de-ionised water). Make sure no residues are left behind by rinsing with clean water. 

Wipe the trays and their mounted parts regularly (rails, clips, adhesive matting, etc.) with a soft cloth and a mild household cleaner. If necessary, disinfect with a standard disinfectant e.g. quats.

Cleaning under the tray  

If the area under the shaking table has a hygienic design, it will have a smooth base and is deep enough to hold spills from large flasks i.e. several hundred millilitres. Ideally, there is a drain, and this will lead to a nozzle for removing contaminated culture and cleaning fluids. After disconnecting main power, an operator should be able to reach inside to access all areas under the tray.   

Depending on the shaker the parts of drive system inside the chamber range from simple counterweight to complex bearings and cog assemblies. If there is only a counterweight you can easily clean it by yourself, otherwise you will need help from a service technician for proper cleaning. Again, bleach should never be used as some of these parts can be uncoated metal in the interior of an incubated shaker.

If you encounter pieces of broken glass remove them carefully while wearing protective gloves. The culture fluid can then be wiped up with a cloth soaked in disinfectant. It is then safe to proceed to the next step.      

A typical rinse:  

• Carefully add hot water into the shaker ensuring it does not come in contact with the electrical system or fans, to avoid the risk of permanent damage 
• Pour it carefully into the base of the chamber
• Use a large beaker to pour it into the incubation chamber 
• Do not use a pressurized water hose for cleaning  
• Drain it away through a drain hole, if present. If the drain outlet nozzle is not connected to the in-house wastewater system, push a hose onto the drain nozzle and let the water run into an appropriately sized container.
• Thoroughly dry the base area with paper towels

Please note: This overview is not intended to replace advice included in the operating manuals of specific incubator shakers from individual manufacturers, and company standards should supersede recommendations provided here. Basic methods and definitions have been provided which should be applicable in almost all cases. Any relevant comments, ideas for new posts and constructive criticism are always welcome.