To the Editor:
With great interest, we followed the recent publication of Gargiulo et al.1 reporting on perioperative microbiological contamination during drug application. Bacterial contaminants were detected in 6.3% of patients and in 2.4% of sampled syringes. These numbers are alarming, suggesting a potential role of intraoperative management in postoperative infections. The study inherits an interesting design including close-to-real-life conditions. However, there remains some source of bias that is not completely addressable in this setting, and the number of contaminations may even be higher. Especially high contamination rates of propofol are a known problem related to its formulation; consequently, propofol syringes should be prepared directly before application and used propofol syringes should be disposed immediately. Although even the laboratory environment of drug preparation may inherit a, very low, bacterial contamination risk, syringe handling is a key element in this context.2 Compared to the study by Gargiulo et al.,1 other authors observed higher contamination rates of syringes,2–4 and as the study was performed unblinded, there is a high probability of a relevant Hawthorne effect. Additionally, some aspects are not completely reported in study description:
Was there any report or policy on wipe disinfection of glass ampoules or disinfection of the injection port?
How long in advance were drugs prepared before application to patients?
How long did it take from sampling to analyzing syringes and filters?
These factors may explain at least some of the observed variability between participating anesthesiologists and are modifiable factors during clinical care.
Finally, we completely agree that microbacterial contamination in the operating room is of high relevance and warrants further investigation. However, the association between contaminated syringes and injection ports and subsequent infection may be difficult to study, e.g., because of infections associated with implants that may be diagnosed only with a delay of months. Immunocompromised patients, those with prosthetic valves,4 or preterm newborns5 may be of specifically high risk in this context. Without doubt, measures to increase awareness of aseptic techniques in conjunction with antibiotic stewardship initiatives may reduce the burden of perioperative infections.6
Dr. Spies received funding from Merck Sharp and Dome GmbH (Haar, Bavaria, Germany), Astra Zeneca (Wedel, Schleswig-Holstein, Germany), Bristol-Myers Squibb GmbH (Munich, Bavaria, Germany), Pfizer (Berlin, Berlin, Germany), and Fresenius Kabi (Bad Homburg, Hessen, Germany). The other authors declare no competing interests.