Other Possible Causes of a Well-Publicized Outbreak of Pseudomonas aeruginosa Following Arthroscopy in Texas

Background: Seven patients at a hospital in Houston, TX, were diagnosed during a two-week period in 2009 with joint space infection of pansusceptible P. aeruginosa following arthroscopic procedures of the knee or shoulder. Tosh et al. (2011), who investigated and published the principal report discussing this bacterial outbreak, conclude that its most likely cause was the improper reprocessing of certain reusable, physically-complex, heat-stable arthroscopic instruments used during these arthroscopic procedures. These reusable instruments reportedly remained contaminated with remnant tissue, despite diligent efforts by the hospital to clean their internal structures. This retained bioburden presumably shielded the outbreak’s strain of embedded P. aeruginosa from contact with the pressurized steam, reportedly resulting in ineffective sterilization of these arthroscopic instruments and bacterial transmission. Objectives: First, to clarify which specific sterilization methods, in addition to steam sterilization, Methodist Hospital employed to process its reusable arthroscopic instrumentation at the time of its outbreak, in 2009; second, to evaluate Tosh et al.’s (2011) conclusion that ineffective steam sterilization due to inadequate cleaning was the most likely cause of this hospital’s outbreak; third, to consider whether any other hitherto unrecognized factors could have plausibly contributed to this outbreak; and, fourth, to assess whether any additional recommendations might be warranted to prevent disease transmission following arthroscopic procedures. Methods: The medical literature was reviewed; some of the principles of quality assurance, engineering and a root-cause analysis were employed; and Tosh et al.’s (2011) findings and conclusions were reviewed and compared with those of other published reports that evaluated the risk of disease transmission associated with the steam sterilization of physically-complex, heat-stable, soiled surgical instruments. Results and Conclusion: Reports documenting outbreaks of P. aeruginosa or another vegetative bacterium associated with the steam sterilization of inadequately cleaned surgical or arthroscopic instruments are scant. This finding—coupled with a number of published studies demonstrating the effective steam sterilization of complex instruments contaminated with vegetative bacteria mixed with organic debris, or, in one published series of tests, with resistant bacterial endospores coated with hydraulic fluid—raises for discussion whether Methodist Hospital’s outbreak might have been due to one or more factors other than, or in addition to, that which Tosh et al. (2011) conclude was its most likely cause. An example of such a factor not ruled out by Tosh et al. (2011) findings would be the re-contamination of the implicated arthroscopic instruments after sterilization. The specific methods that Methodist Hospital employed at the time of its outbreak to sterilize some of its arthroscopic instrumentation remain unclear. A number of additional recommendations are provided to prevent disease transmission following arthroscopic procedures.