The implantation of medical devices inside of the body can have several important health benefits including replacement of missing or dysfunctional body parts, delivery of medications, monitoring of bodily functions, or by providing support to specific organs and tissues. Some implants are made of natural tissues that come from the body such as skin or bone while others are made of metal, plastic, or ceramic materials.
Scientists have identified clinical strains of Staphylococcus epidermidis which showed a high capacity to produce biofilms as well as genes which confer resistance to commonly used antibiotics. Credit: StaphOff Biotech, Inc.
Despite the many benefits of implanted medical devices, one of the most common complications is an infection. The majority of these infections are caused by bacteria that reside on the skin at the time the surgery was performed. In many cases, an infection will be treated with antibiotics. Unfortunately, the incidence of antibiotic resistant bacteria in clinical settings has increased dramatically, causing treatment of these infections to become increasingly difficult. In severe cases where treatment fails, the implant must be removed all together in order to prevent sepsis.
In a recent study published in Frontiers in Microbiology, scientists studied 25 staphylococcal biofilm-forming clinical isolates belonging to the following species: S. aureus, S. epidermidis, S. hominis, and S. capitis. Staphylococcus are commonly found on human skin and are well-known causative agents of human disease specifically related to healthcare-associated infections including those involving implanted medical devices.
Authors reported that of the 25 isolates studied, Staphylococcus epidermidis isolates demonstrated the greatest ability to form biofilms. This is an important observation since the ability to form biofilms increases the ability of bacteria within the biofilms to pass virulence genes to one another through a process known as conjugative plasmid-mediated horizontal gene transfer. Virulence genes include those which enable the bacteria to cause disease in the host as well as genes that protect the bacteria from antibiotics (antibiotic resistance genes).
All 25 isolates in this study were found to contain antibiotic resistance genes as well as horizontal transfer genes present on mobile genetic elements known as plasmids. The plasmids were identified as pSK41 and pT181. The antibiotic resistance genes that were most prevalent among isolates conferred resistance to gentamicin, erythromycin, and tetracycline.
Authors concluded that because the clinical isolates in this study contained antibiotic resistance genes, horizontal transfer genes, as well as mobile genetic elements suggests the ability of these isolates to pass along antibiotic resistance to other bacteria. Although, authors noted that they could not be sure whether specified antibiotic resistance genes were encoded in the chromosomal DNA or plasmid DNA.
Studies such as the one discussed here help to underline the importance of collecting epidemiological data on antibiotic resistance in order to develop control strategies for the global antibiotic resistance crisis. In this particular case, therapies which target the ability of Staphylococcus species to form biofilms on medical implant devices may help reduce the transfer of antibiotic resistance genes as well as reducing the potential for complications after surgery.