Just How Sterile Is Your Biodebris After Autoclaving?

It’s an ugly truth—cannulated drills and reamers often get fragments of biological debris (biodebris) stuck in them that autoclaving doesn’t always remove. Such tools are critical for surgical cases and when the situation arises that a surgeon finds biodebris in the instrument, some opt for caution while others subscribe to the notion that autoclaving has sterilized the debris, but, is the sterilization process of the instrument, in fact, killing the infection-causing potential in the retained biodebris?

The US Centers for Disease Control and Prevention (CDC) states that annually, there are 722,000 health care-associated infections reported in the United States, but this number is likely higher. Of these infections, 157,500 are surgical site infections (SSI). Although there have been infection clusters related to surgery that mentioned retained biodebris, no definitive epidemiological link between orthopedic SSIs has been linked with the biodebris retained in cannulated instruments. Furthermore, manufacturers work to make instruments less vulnerable to bioburden contamination and easier to reprocess; however, there is an inherent risk with some tools even after proper sterilizing per manufacturer recommendations. Seeking to address just how much microbial life is left on biodebris in cannulated instruments following autoclaving, a research team found some fascinating results.

The research team attempted to replicate a typical orthopedic surgical scenario by creating a hole in cortical and cancellous bone and then letting the instrument set for a period of time (mimicking that of non-use during surgery) prior to cleaning and disinfection. Different wait times were used for the instrument after drilling. The team used 15 cannulated drill bits, 12 of which were exposed to a bacterial mixture for 60, 120, or 180 minutes before reprocessing. “Three of the 12 bits, designated as positive controls, were not sterilized,” the authors write. “The remaining 3 drill bits, designated as negative controls, received only sterile water. Thus, we had 5 separate groups with 3 drill bits in each group. The drill bits were autoclave sterilized and then examined for bacterial growth.”

The bacterial strains used to identify contamination included clinically relevant ones: Bacillus cereus, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus (MRSA).

After the team simulated surgery and the wait times, the drill bits were cleaned and sterilized per manufacturer recommendations (sterilization peel-pack with a chemical sterilization indicator and then autoclaved per directions).

The investigators found that all 3 of the positive control drill bits were positive for all 3 organisms. Of the experimental group, 1 of the drill bits from the 60-minute wait time grew a strain of Bacillus different than B. cereus, and the other 2 drill bits within this group were negative for microbial growth.

Of the drill bits in the 120-minute group, 2 of them had microbial growth at 48 hours, which was different than the strain used to inoculate them. In the 180-minute group, 1 drill-bit was positive for a Bacillus species, while the other 2 had negative growth.

Although this experiment scenario was one in which manual cleaning was not performed, it is widely known that, while very effective in removing microbial contamination, this act relies upon staff, and it is not completed perfectly every time.

Overall, this study was small and had some limitations (ie, lack of manual cleaning, etc.); however, it highlights the misconception that autoclaving alone will wholly sterilize biodebris that may be retained in cannulated surgical instruments such as drill bits. Further evaluation should be done for a wider range of instruments; but, this particular analysis homes in on the importance of manual cleaning and inspection of instruments prior to utilization.