The positive biological indicator signals time to take action

When a carbon monoxide detector goes off, you take action immediately.

If the levels are low enough, you may open windows and doors to try and ventilate the area. Otherwise you evacuate the area and call for help. A carbon monoxide leak is very serious and has to be corrected. If the area is safely ventilated, you may investigate potential causes on your own, or you may bring in a qualified technician to investigate. It may be a small fix on an appliance, or it could be time to replace the furnace. In any case, the cause has to be found, and fixed.

Similar to a carbon monoxide detector, a positive biological indicator (BI) tells sterile processing staff that they need to take action immediately. They need to follow their facility policy and procedures, retest the sterilizer, quarantine or retrieve any affected loads, and possibly advise OR staff and patients if any nonsterile devices have been used on patients. Then, there must be a thorough investigation of the sterilizer, as well as the department processes and systems, to find and correct the cause of the failure. The BI is a simple way to test sterilization processes, equipment and technique. A positive BI prompts you to examine whether you’re following department standards and best practices, or if the sterilization process needs to improve. Like when a carbon monoxide detector goes off, you don’t have the option of ignoring a positive BI. You can’t see microorganisms on surgical tools, and ignoring a positive BI could compromise the safety of others – and possibly the reputation of your facility. Thoroughly reviewing the cause of a positive BI ensures that your sterilization process will be better in the long run, avoiding a potential recall or a compromise in patient safety.

According to the ANSI/AAMI/ISO 14161:2009, BIs represent a microbiological challenge to a sterilization process and are a means to directly assess the microbial lethality of a sterilization cycle. The end-goal of sterilization is to kill any microorganisms on the medical devices. The BI, with its large numbers of resistant spores, presents a greater challenge to the process than the microorganisms on the devices. So, if the sterilization process kills the BI (negative BI) you can have increased confidence that it also killed the organisms on the medical devices. On the other hand, a positive BI indicates a sterilization process failure that may mean that there are still living and potentially infection-causing microorganisms on the medical devices.

Biological indicator resistance - the critical aspect of BI performance
The resistance of a biological indicator is a measure of how difficult it is to inactivate or kill the BI. The greater the BI resistance the more of a challenge the BI presents to the sterilization process. More resistant BIs will be more sensitive to equipment malfunctions or human errors that result in sterilization process failures. International performance standards for BIs define the appropriate resistance level for BIs used to monitor steam and ethylene oxide sterilizers. Right now, however, there is no standard that defines appropriate resistance for BIs used in vaporized hydrogen peroxide (VH2O2) sterilization. Because of this, BIs for monitoring VH2O2 sterilizers can have significant variation in resistance. BI manufacturers can adjust their BI resistance by how they grow and apply their spores, or by the physical design of their BI, or both. For VH202 sterilization then, it is important to select a biological indicator that has been designed and tested in conditions that relate closely to the actual sterilization cycles they will be used to monitor.

Using VH202 BIs with appropriate resistance levels to monitor sterilization loads can help sterilization departments identify some common errors made in VH202 sterilization practices. Some of the most common errors that lead to a positive BI are:

• Improper loading and organizing of packs within the sterilizer chamber;
• Overloading the sterilizer chamber;
• Use of incompatible materials;
• Over filling rigid containers; and
• Using the wrong type of packaging.

VH202 sterilization processes require close attention to manufacturer’s Instructions for Use (IFUs) for multiple items that are part of the sterilization process. IFU’s that should be reviewed include the following: the IFU of the devices that are being processed in each load, the IFU of the sterilization packaging materials and lastly, the IFU of the sterilizer doing the sterilizing. Due to the complexities involved with VH2O2 sterilization, sterile processing department teams must adhere to best practices and pay attention very closely to what is happening within their low temperature systems. Understanding and following the correct IFU for all of the various devices, machines and packaging materials can be very challenging.

Testing the effectiveness of the VH2O2 sterilizer with indicators that are provided by a manufacturer that are independent of sterilizer equipment and separate from the sterilizer manufacturer’s indicator products can provide additional, relevant and timely information to help departments make decisions. These indicators provide objective information from an independent source to help you more thoroughly evaluate the entire sterilization process. This is important as VH2O2 is a complex and technique sensitive sterilization process.

Mercy Medical Center Resolves Sterilization Failures as Indicated by a Positive BI
When Mercy Medical Center in Dubuque, Iowa, switched to a third-party monitoring company to help monitor its VH202 sterilization, it started receiving failed cycles as indicated by positive BIs, which was a very rare occurrence with the use of the sterilizer manufacturer’s BI, because these BIs were less of a challenge. Alarmed by the positive BI incident, a collaborative team of the BI manufacturer and the sterile processing department team ran a series of four BI test cycles along with a review of the sterilization process. In the end, it turned out that a few, old plastic trays and lids were over challenging the effectiveness of the sterilizer. A simple packaging change eliminated the marginal and failed sterilizer cycles. The change in packaging not only allowed Mercy to achieve negative BI results, but gave it the option to increase load output by sterilizing more devices per cycle with the new trays. The result was a win for patient safety, and a win for department efficiency.

A positive BI can truly be a positive learning experience when it makes the sterilization team:

1. Examine potential sterilization technique issues. Technique matters, particularly in the VH202 sterilization modality. If the manufacturer’s Instructions for Use aren’t followed, it can cause a positive BI. For example, presence of excess moisture is a possible occurrence and can lead to a positive BI. That positive BI requires an examination of the process, and technique errors can be caught and addressed.
2. Determine if load size and weight meet guidelines. Each container or wrap has clearly defined weight guidelines. If loads are too heavy, or are over weight restrictions, it might trigger a positive BI simply due to overloading.
3. Evaluate each cycle to determine if it’s appropriate. When an inappropriate cycle is chosen for the intended load, it could trigger a positive BI. Avoid this mistake by following your device’s Instructions for Use.

The bacterial spores might be a small part of the entire sterilization process, but it is a critical one. Appropriately resistant spores can tell you many things about your sterilization process and practices. If you should experience a positive BI – although it may cause alarm – it can also create a positive learning experience. A BI challenge should provide a way for sterilization departments to truly stop and examine their process. An “alarm” on their routine sterilization practice.

To learn more about VH202 sterilization best practices, visit

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