Staphylococcus epidermidis is a major cause of life-threatening infections after surgery and is present on the skin of all humans. Researchers say that it is becoming increasingly dangerous due to antibiotic resistance, but is commonly overlooked by physicians and scientists (Nature Communications Nov. 23, 2018; 9(1):5034)
Investigators have identified 61 genes that permit this normally harmless skin bacterium, a close relative of MRSA, to cause life-threatening illness.
“Staphylococcus epidermidis is a deadly pathogen in plain sight . . . It has always been ignored clinically because it has frequently been assumed that it was a contaminant in lab samples or it was simply accepted as a known risk of surgery,” said study author Dr. Sam Sheppard, PhD, Director of Bioinformatics at the Milner Centre for Evolution at the University of Bath in Bath, U.K., in a press release.
In the future, identification of patients who are most at risk of infection prior to undergoing surgery may be possible as a result of the research conducted by Dr. Sheppard and his colleagues.
“Post-surgical infections can be incredibly serious and fatal. Infection accounts for almost a third of deaths in the U.K. so I believe we should be doing more to reduce the risk if we possibly can,” said Dr. Sheppard. “If we can identify who is most at risk of infection, we can target those patients with extra hygiene precautions before they undergo surgery.”
Study methods
The researchers obtained samples from patients who had infections following hip or knee joint replacement and fracture fixation operations and compared them with swab samples from the skin of healthy volunteers.
Then, the genetic variation in the whole genomes of bacteria found in samples from diseased and healthy individuals were compared. From this, the investigators identified 61 genes in the disease-causing bacteria that were not present in most of the healthy samples.
“Because the pathogen is so abundant, they can evolve very fast by swapping genes with each other,” said Dr. Sheppard.
Dr. Sam Sheppard was the team leader of the investigation.
Photo by the University of Bath press.
Notably, there was a small number of healthy individuals who were found to be carrying the more lethal form of the bacteria without knowing it.
The genes help the bacterium grow in the bloodstream, avoid the host’s immune response, make the cell surface sticky to help organisms form biofilms, and make the pathogen resistant to antibiotics.
“If we do nothing to control this, there is a risk that these disease-causing genes could spread more widely, meaning post-operative infections that are resistant to antibiotics could become even more common,” said Dr. Sheppard.
The researchers agree that more research is needed to determine how the findings can be used in practice.
“[For example,] prosthetic joint replacement surgery helps many patients live independent and pain-free lives, but can take a catastrophic course through S. epidermidis infection,” said study co-author Dr. Dietrich Mack, from the Bioscientia Institute for Medical Diagnostics GmbH in Ingelheim, Germany.
“These infections are difficult to diagnose and there is hope that disease-associated genes may help to separate harmless skin isolates from disease-causing S. epidermidis strains in the clinical laboratory.”