History of laboratory-acquired infections
When it comes to any discussion of laboratory-acquired infections today, many think of SARS-CoV-2 and the resulting COVID-19 pandemic. Whether it originated from a zoonotic source (an infection spread between animals and humans) or as a laboratory-generated virus that “leaked”, the origin of the SARS-CoV-2 virus remains somewhat uncertain. SARS-CoV-2 aside, over the last fifty years, there have been several documented laboratory-acquired infections, with Brucella accounting for most of those infections.
Diagnostic laboratories that process human samples for testing and research laboratories studying human diseases work with potentially infectious material. There are many sources of exposure and routes of infection. Direct contact with spills of infectious samples, improper or insufficient use of personal protective equipment (PPE), or inhalation of aerosolized material, are some of the many ways scientists, healthcare professionals, and laboratory technicians can experience a laboratory-acquired infection.
Centrifuges as an exposure source
To avoid laboratory-acquired infections, training for proper sample handling is essential. Additionally, clinicians and researchers routinely use PPE, such as gloves, masks or face shields, shoe covers, and protective garments like lab coats, coveralls, or positive pressure personnel suits (i.e., space suits), to protect themselves from infectious materials. In addition to PPE, features of commonly used lab equipment can offer an additional layer of protection.
Centrifuges are used in nearly every laboratory worldwide to separate serum from plasma in clinical settings, pellet cells for storage, isolate proteins, and purify viral particles. Thus, laboratory centrifuges are one potential source of exposure to infectious material. Because of the high speed at which a centrifuge spins, samples can become aerosolized if the sample tube or vessel is not properly sealed. Additionally, sample vessels that are cracked or not rated to withstand high enough force may fail and leak. Unbalanced rotors may cause excessive stress on sample vessels, resulting in failure. This can pose a risk for researchers and lab workers.
By preventing the escape of liquids or aerosols in the event of a spill or vessel failure, hermetically sealed centrifuge rotors can protect researchers from exposure to potentially infectious samples in clinical and research laboratories. Centrifuges may be equipped with hermetically sealed lids for the entire rotor or for individual buckets.
Many centrifuges can be purchased already configured with hermetically sealed rotors such as the HERMLE Z366 Series Universal Centrifuge configured with a 24 x 1.5/2.0ml Hermetically sealed rotor.
Alternatively, hermetically sealed rotors, like this 30 x 2.0ml Hermetically Sealed Rotor for the HERMLE Z36-HK Refrigerated Centrifuge, can be purchased to add protection to existing centrifuge equipment.
Lids can also be purchased for individual swing-out buckets, such as the Z366-250-LID, that fits Hermle universal centrifuges.
Rotors such as the Eppendorf FA-20x5 ml rotor with aerosol-tight QuickLock® rotor lid, the rotor, lid, and adapters are all autoclavable, allowing for sterilization of hazardous materials.
Safe use of laboratory centrifuges
Safe centrifuge operation can greatly reduce the likelihood of infection. Best practices include:
- Use centrifuge sample containers that are appropriate for the speed. At high speeds, centrifuge tubes or vessels can break, leaking potentially hazardous samples into the rotor and centrifuge chamber. Most manufacturers provide the maximum relative centrifugal force (RCF) rating for their centrifuge tubes.
- Balance your samples. Unbalanced rotors can cause damage to the equipment or result in exposure to hazardous materials due to a spill or breakage. In general, the greater the RCF, the more sensitive a centrifuge is to improper balancing.
- Don’t overfill sample containers. In a fixed-angle rotor, the sample will be pushed up the side of the container wall during centrifugation. Also, make sure that sample tubes are free of cracks and properly sealed prior to centrifugation.
- Use appropriate PPE. The recommended PPE will depend upon the hazards associated with your sample material, though a lab coat, gloves, and goggles are recommended for all infectious materials. Dispose of soiled PPE and wash/decontaminate reusable items before storing them.
- Clean regularly and after any spill. If there has been a spill, leave the centrifuge closed and the rotor covered for 30 minutes to reduce aerosolization of infectious or hazardous materials. Before opening the sealed rotor, decontaminate the exterior and transfer the entire rotor to a biosafety cabinet. Consider the nature of the samples being worked with and make sure to follow your specific lab’s or institution’s protocol for handling spills and exposures. Use appropriate PPE when cleaning any centrifuge, even when there has been no known spill or leak. Autoclave any autoclavable components or sterilize by other means (e.g., UV light, disinfectant).
- Regular centrifuge maintenance can reduce the risk of contamination. Manufacturer instructions regarding regular maintenance and checks should be available for most centrifuges in the owner's manual. Make sure to check that the seal does not have any tears or holes. Rotors have a recommended life span and should be replaced or at least regularly tested after that timeframe.
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