published in the August issue of Open Forum Infectious Diseases.
“This was a pan-European study with many hospitals, many different clinical settings, and as far as I’m aware, it hasn’t been done before. [The new study] covers a lot of European countries and a lot of surgical specialties,” said lead author Jan Kluytmans, MD. The study also captures the current state of preventive strategies in surgery, such as changes in air flow, dress, and skin preparation, he added.
The study included 5004 patients from 33 hospitals in ten European countries, of whom 67.3% were found to be SA carriers. The median age was 65 years, and 49.8% of patients were male. Open cardiac, and knee and hip prosthesis surgeries made up the largest fraction, but there were 12 types of surgery included in the study.
There were 100 SA surgical site or blood infections. The researchers found an association between surgical site or blood infection and SA carriage at any site (adjusted hazard ratio [aHR], 4.6; 95% CI, 2.1-10.0) and nasal SA carriage (aHR, 4.2; 95% CI, 2.0-8.6). Extranasal SA carriage was not associated with an increased infection risk.
Each 1-unit increase in nasal bacteria was associated with an increase in infection risk (aHR, 1.23; 95% CI, 1.05-1.43).
A strength of the study is that it is the largest prospective study yet conducted on SA carriage in surgical patients, but the researchers were unable to do a subgroup of methicillin-resistant SA (MRSA) due to small numbers of infections.
The study confirms the value of the decolonization strategy, which the World Health Organization has endorsed with the highest level of scientific evidence that is available in preventive strategies in surgery. WHO strongly recommends decolonization for cardiothoracic and orthopedic surgery using intranasal applications of mupirocin 2% ointment with or without a combination of chlorhexidine gluconate body wash. It has a conditional recommendation for a similar procedure before other types of surgery.
However, “It is not widely practiced, and although that was not a surprise to me, I think it’s really disappointing to see that proven effective strategies are not being practiced,” said Dr. Kluytmans, professor of medical microbiology at University Medical Center Utrecht, Utrecht University, the Netherlands. “If I would come into surgery being a carrier, and not be decolonized, I would really be quite angry because it puts you at risk, which is preventable. I think that’s something we owe to our patients,” he said.
He said that some may have concerns about the potential for decolonization to contribute to antibiotic resistance, but the short-term prophylaxis — typically a few days — should not foster resistance, according to Dr. Kluytmans. “If you use it short term, just before surgery, it has been shown in many studies that resistance isn’t a big problem and it can be monitored.”
The link specifically to SA nasal carriage is a mystery, according to Dr. Kluytmans. “It puzzles me still how it gets from the nares to the wound during surgery. So that’s my million-dollar question that I would like to resolve. We would like to study it, but we haven’t quite a bright idea how to do that,” he said.
The results are compelling, according to Heather Evans, MD, who was asked for comment. “On the face of it, this looks like a no-brainer. We should be decolonizing all patients that go to the operating room, and it’s not a terribly unpleasant thing for a patient to undergo to have decolonization done. Particularly for patients who are at higher risk for having a severe complication, like someone that has an operation that’s involving an implant, for example, I think it really makes a lot of sense to do this low-cost intervention for those patients,” said Dr. Evans, professor of medicine at The Medical University of South Carolina as well as the president of the Surgical Infection Society.
She noted that many facilities test for methicillin-resistant SA, but usual not SA more broadly. “This is a very interesting and compelling study that makes us rethink that, and maybe it isn’t even worth testing to see if you have staph aureus, maybe we should just be putting Betadine in everyone’s nostrils when they come to the operating room. It just seems like it would be a pretty low-cost intervention and something that could potentially have a big impact,” said Dr. Evans.
Although she was impressed by the study, Dr. Evans noted that the researchers tested for carriage at sites unrelated to the surgical site. “It really made me wonder if it would have added even more credibility to the study if there had been a sample taken after surgical prep was done to demonstrate that there is actually no staph aureus present on the skin at the time that the wound was made,” she said.
The question ties into the recent “Trojan horse” hypothesis, which suggests that endemic carriage of bacteria is responsible for most surgical site infections, rather than the long-held belief that operating room contamination is to blame. “That would sort of fly with this study, that the patient is walking around with Staph aureus and not necessarily on their skin or at their surgical site, but it’s endemic in their body,” said Dr. Evans.
Dr. Kluytmans and Dr. Evans have no relevant financial disclosures.