After surgical instruments undergo multiple uses and processing cycles, they can become contaminated while sustaining structural damage and collecting biofilm.

  • Researchers found that after using and decontaminating surgical instruments 20 times, neither a manual nor automated cleaning process removed all the patient secretions.
  • Some instruments need to be disassembled for cleaning.
  • Biofilm is tolerant to removal by detergent; any existing secretion or biofilm makes it easier for bacteria to attach in subsequent cleaning cycles.

Research shows that surgical instruments that undergo multiple uses and processing cycles are contaminated and sustain structural damage, black stains, and biofilm. But newer instruments with more complex designs also can harbor infectious agents.1,2

Inadequate reprocessing of reusable surgical instruments can be problematic. When surgical instruments are processed many times, biofilm still can be found at small levels, whether the cleaning is manual or includes some automation, investigators discovered.

“In our study, both manually and automatically cleaning instruments significantly reduced patient secretions to below levels considered to represent ‘clean,’ using assays that measure ATP and protein,” says Karen Vickery, BVSc, MVSc, PhD, MASM, on the faculty of medicine and health sciences, Macquarie University in Sydney, Australia.

Failed processing of surgical instruments was rated a top health technology hazard by the Emergency Care Research Institute in 2017. Part of the issue is the sheer volume of instruments cleaned. In one large U.S. hospital, there were about 40,000 reusable surgical instruments processed each day.2

“Stainless steel surgical instruments are used and processed many times over their lifetime,” Vickery notes. “However, in our study, replicating this use/decontamination process only 20 times, we found that neither the manual or automatic cleaning process was able to remove all the patient secretions.”

Biofilm could be found on the manually cleaned instruments through the use of scanning electron microscopy, Vickery says. Researchers compared manual cleaning, when instruments are scrubbed and rinsed by hand, and automatic cleaning, when instruments are cleaned by hand first and then flushed with a detergent while subjected to sonication.1

“Sonication helps break up patient secretions and biofilm, using sound waves the same way the dentist cleans a patient’s teeth,” Vickery explains. “The instruments then go into a washer disinfector machine, which automatically washes the instruments. The automatically cleaned instruments have two additional cleaning processes compared with the manually cleaned instruments.”

In a study about barriers to cleaning effectiveness, investigators found that complex designed instruments are difficult to clean.2 “In some cases, instruments need to be disassembled for cleaning; in our study, this included the depth gauge,” Vickery says. “Some instruments have lumens, which can’t be visualized.”

In Vickery’s study, this included the depth gauge plus flexible medullary reamer. “The most important part of decontaminating instruments is the manual clean as it is this clean that removes the majority of patient secretions, such as blood,” Vickery adds. “The manual clean process is highly susceptible to human error.”

Why does instrument reprocessing fail sometimes? Researchers duplicated the ways instrument processing could fall short. They contaminated instruments and left them for seven hours to mimic a worse-case scenario, Vickery says. “This gave contaminating bacteria enough time to attach to the instrument surface and form an early biofilm, and it gave patient secretions enough time to dry onto the instrument,” she says. “Dry soil is harder to remove than wet soil.”

Although researchers used brushes to clean inside lumens, this was not a perfect cleaning process. “The physics of the process dictate that the bristles don’t necessarily touch every part of the surface, leaving some microscopic areas unbrushed,” Vickery explains. “These areas, therefore, are cleaned only with the chemistry of the detergent and water pressure.”Biofilm is particularly tolerant to removal by detergent. Any patient secretion or biofilm makes it easier for bacteria to attach in subsequent cleaning cycles. “Over the 20 cycles, the uncleaned microscopic areas increased in size until they were large enough to enable biofilm to fully develop in the manually cleaned instruments,” Vickery says.


  1. Costa DM, Lopes LKO, Tipple AFV, et al. Evaluation of stainless steel surgical instruments subjected to multiple use/processing. Infect Dis Health 2018;23:3-9.
  2. Lopes LKO, Costa DM, Tipple AFV, et al. Complex design of surgical instruments as barrier for cleaning effectiveness, favouring biofilm formation. J Hosp Infect 2018; Nov 10. pii: S0195-6701(18)30587-5. doi: 10.1016/j.jhin.2018.11.001. [Epub ahead of print].