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It is common among healthcare workers and patients alike to believe that infections in hospitals stem from their exposure to superbugs in their environment. However, genetic data on bacteria tells another story: most so-called healthcare-associated infections are actually caused by bacteria that were present in the patient's body before admission to the hospital, and which are normally harmless.
Many scientists have compared bacteria that inhabit the nose, skin, and other parts of the body with bacteria that cause pneumonia, diarrhea, bloodstream infections, and surgical site infections: when the body is healthy, the bacteria are well-behaved and harmless, but when disease strikes, these microorganisms are often the culprit of serious infections.
A new study published in Science Translational Medicine further supports this view. The authors' team found that many surgical site infections that occur after spinal surgery are caused by microorganisms that are already present on the patient's skin.
Surgical infections are a long-standing problem
Among the different types of healthcare-associated infections, surgical site infections are the most problematic.
A 2013 study of the U.S. healthcare system found that surgical site infections account for the largest share of total hospital-acquired infection-related expenditure—more than 33 percent of the $9.8 billion spent annually is spent on surgical site infections. In addition, this type of infection is also an important cause of readmission or death after surgery.
The team of authors of the new study is a team of clinicians from the University of Washington's Harbourview Medical Center. They are well aware of the hospital's efforts to prevent infection: disinfecting all surgical equipment, using ultraviolet light to clean the operating room, following strict surgical gown protocols, and monitoring airflow in the operating room......
Hospitals follow strict protocols to prevent infections from being triggered by surgical procedures
Even so, about one-third of surgical cases are followed by surgical site infections, and it is often difficult to explain the cause.
As medical conditions have improved, the incidence of many other medical complications has steadily decreased, but according to the U.S. Agency for Healthcare Research and Quality (AHRQ) and the Centers for Disease Control and Prevention (CDC), the problem of surgical site infections has not changed.
In fact, postoperative infection rates are expected to increase due to the rise in antibiotic resistance worldwide.
It is you who infect yourself
According to the two lead authors of the new paper, Dustin Long and Chloe Bryson-Cahn, their team of physician-scientists with expertise in critical care, infectious diseases, experimental medicine, microbiology, pharmacy, orthopedics and neurosurgery wanted to better understand how and why patients experience postoperative infections.
Whereas previous research on surgical site infections was limited to a single bacterial species and used older genetic analysis methods, the new technology opens up avenues for studying all types of bacteria and testing their antibiotic resistance genes simultaneously.
Dr. Lang et al. focused on the risk of infection during spine surgery for three reasons:
First, the number of women and men undergoing spinal surgery for a variety of reasons is similar, which means that the findings will be broadly applicable. Second, in the United States, spine surgery occupies more health care resources than any other type of surgical procedure. In addition, the problem of infection after spine surgery is painful for patients, as it usually requires multiple surgeries and long-term antibiotic treatment to have a chance of curing the disease.
Over the past year, Dr. Lang's team has conducted preoperative bacterial samples from more than 200 patients in their nasal, skin, and feces, and followed them for 90 days to compare the samples with subsequent infections.
Staphylococcus aureus is a common cause of hospital-acquired bacterial infections
The results of the study showed that the types of bacteria that live on the skin of patients' backs vary from person to person, but they also show some common patterns -
Bacteria around the upper back, neck and shoulders are more similar to those found in the nose, and bacteria that usually live in the lower back are more similar to bacteria in the intestines and stool. In addition, the relative frequency of the occurrence of microorganisms in specific areas of the dorsal skin is closely related to the frequency with which they occur in the event of postoperative infection in that area.
In fact, up to 86% (19 out of 22 isolates) of the bacteria that cause spinal surgeries are genetically matched to bacteria (from feces, nasal passages, or intestines) that patients carry before surgery. The figure of 86 per cent is very close to the previous estimate obtained with the help of genetic techniques for Staphylococcus aureus.
On the other hand, nearly 60% of infections are resistant to prophylactic antibiotics used during surgery or/and antiseptics used to clean the skin before the incision. It turns out that the root cause of this antibiotic resistance is not in the hospital, but from resistant microorganisms that have lived with patients for a long time without being known to them.
Individualized surgical infection prevention
Dr. Lang et al. point out that now that more insights have been gained about surgical site infections, prevention and care efforts need to be adapted accordingly.
If we know in advance the condition of the patient's own microbiome, the most likely source of surgical infection, the medical team has the opportunity to carry out highly targeted preoperative prophylaxis. Current infection prevention protocols are fairly one-size-fits-all, for example, doctors use the antibiotic cefazolin for the vast majority of surgical patients. A more personalized regimen leads to better anti-infective results.
Of course, the premise of personalization is to be able to understand the microbiome of the case, and at the same time to accurately translate the microbiome information into the risk of infection, which requires us to carry out more research work to explore more scientific and accurate postoperative infection prevention and control programs.
Developing an individualized infection prevention plan for each patient will enhance the effectiveness of prevention
Currently, practice guidelines, commercial product development, hospital protocols, and certifications related to infection prevention often focus on the sterility of the physical environment. This approach is correct – the fact that most "nosocomial infections" come from hospitals is enough to justify it. On the other hand, a more patient-centric, personalized approach to infection prevention will benefit both hospitals and patients.
Sources:
Infections after surgery are more likely due to bacteria already on your skin than from microbes in the hospital − new research
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