Medical Implants Are Breeding Ground For Microbes, Bacteria, Study Finds

More than two-thirds of medical implants and the surrounding tissue tested positive for bacteria or fungus, according to the findings of a new study. 

Danish researchers looked at samples from patient implants, as well as tissue from around the implant, collected from five different hospitals in the Capital region of Denmark, indicating that a large number of microbes colonized patient implants, even when the implants were not removed because of an infection.

The findings were published earlier this month in APMIS, the Journal of Pathology, Microbiology and Immunology, with a majority of tissue and implants sampled from “clinically uninfected” implants showing evidence of bacteria, fungi or both types of microbes.

Using in-depth microbiological detection methods, researchers examined the prevalence of bacteria and fungi on 106 clinically uninfected implants from four patient groups: those who suffered aseptic loosening, healing fractures, craniofacial complications, and recently deceased patients. They compared those samples to 39 negative controls and five samples that were positive for bacteria or fungi.

According to the findings, 73% of the samples tested positive for bacteria, fungi or both. The findings indicate that 66% of samples were colonized by bacteria and 40% by fungi. Despite the high rates of colonization, none of the patients showed signs of infection.

Researchers also noted that the most common microbes present in the samples were not microbes that typically cause common implant infections. They were microbes that can cause infections, but not commonly at implant sites.

An analysis of the tissue surrounding the implants was also conducted as part of the study, to detect signs of inflammation and determine if the bacterial or fungal colonization induced an inflammatory response in the body.

More than 90% of samples from people with healed fractures and craniofacial implants had signs of mild to moderate inflammation. Roughly 45% from biopsies and aseptic loosening implants had inflammation, but researchers found no signs of inflammation from the deceased patients.

Researchers indicate the implants may offer a distinct opportunity for microbial colonization. Introducing an implant into the body allows for a new habitat for bacteria to breed.

Medical implants are an important aspect of modern medicine. They save thousands of lives, such as pacemakers, or improve mobility, like knee and hip replacements. In fact, estimates project an increase of 600% in total knee replacements by 2030 in the United States.

The likelihood of implant infections largely depends on the implant and surgical procedure; however, infection rates average roughly one to two percent.

The research suggests the presence of foreign objects in the body alters the human microbiome by providing new habitats. However, researchers are unsure whether the creation of the new habitats and colonies is beneficial or harmful, like the rest of the human microbiome which exists on the skin and in the gut. It is unclear at this point if the microbes detected are precursors to infection.