Snapshot: Biomaterials that deliver antimicrobials

Hospital acquired infections are increasingly common, but new antimicrobial devices could stem the tide. To reduce the toll of hospital acquired illnesses, manufacturers are increasingly developing various 'anti-infective' devices. In this special report we examine the potential market for antimicrobial biomaterials.


In recent years, hospital acquired infections, also called nosocomial infections, have gained significant attention. According to the Center for Disease Control and Prevention (CDC), approximately 1.7 million patients in the US acquire an infection during their stay in a hospital.

Out of these, more than 99,000 patients die from complications resulting from such infections. Fortunately, according to CDC estimates, up to one-third of infections acquired in healthcare settings are preventable.

The most common healthcare-associated infections are urinary tract infections (32% of the total infections), surgical site infections (22% of total), pneumonias (15% of total) and bloodstream infections (14% of total). Moreover, these hospital infections cost nearly $6.7 billion in the US and $1.7 billion in the UK due to additional hospital stays each year. Increases in additional costs of hospital care and drugs significantly impacts upon healthcare budgets.

As a solution to device related hospital infections, medical device manufacturers are increasing their investments for the development of various 'anti-infective', 'bioactive' or 'antimicrobial' devices.

Antimicrobial therapy and resistance

"In recent years, hospital acquired infections, also called nosocomial infections, have gained significant attention."

During device implantation the bacterial contamination of a medical device acts as a source of infection. The adherence of bacteria to the surface results in colonisation, thus leading to the formation of a microbial biofilm. Biofilm formation is a natural form of growth and survival strategy of bacteria to evade the response of the host's immune system.

During the treatment of device related infections the main concern for clinicians is the magnitude of resistance possessed by the biofilm bacteria. They can be 1,000 times more resistant to antibiotics than their planktonic counterparts. This obviously presents particular difficulties in the treatment of infections associated with the existing medical devices.

In 1998, in the US, 80 million prescriptions of antibiotics for human use were filled.

Because of today's overuse of antibiotics, about 70% of the bacteria that cause infections in hospitals are resistant to at least one of the antibiotics commonly used for treatment.

According to the study conducted by CDC an alarming increase in the resistance of bacteria that cause hospital acquired infections has been documented, especially in the staphylococci and pneumococci (streptococcus pneumoniae). Study observations revealed 25% of bacterial pneumonia cases were shown to be resistant to penicillin, and an additional 25% of cases were resistant to more than one antibiotic.

In this scenario the potential for the development of resistance to antimicrobials introduced into biomaterials for clinical use is a major cause for concern. The release of 'sub inhibitory' concentrations of antimicrobials from biomaterials into surrounding tissue could induce resistance in infecting bacteria.

In order to overcome this problem, researchers or manufacturers employ more than one antibiotic within the biomaterial. This combination approach with a broad spectrum of activity yields promising results, thereby leading to more efficient elimination of the infection with reduced chance of resistance build-up.

Antimicrobial biomaterials: Device overview

In device related infections, the administration of antimicrobials by the systemic or oral routes generally fails to reach the wall of biofilm. In such a scenario the control over the infection is achieved by maintaining sufficiently high concentrations of the antimicrobials in the vicinity of the device for a site-specific activity.

The immersion of the device in the antibiotic solution and coating the device with antimicrobial agents, prior to implantation, are relatively simple preparation methods to achieve control over infection.

"More than 99,000 patients die from complications resulting from such infections."

However, the limited mass of drug that can be incorporated may be insufficient for a prolonged antimicrobial effect, and the release of the drug following implantation of the device is rapid and relatively uncontrolled.

To reduce these concerns, polymeric biomaterials are designed by directly incorporating the antimicrobial agent into the polymeric matrix of the medical devices.

The impregnation of the antibiotic happens at the polymer synthesis stage or at the device manufacturing stage.

Incorporation of Rifampicin in silicone based cerebrospinal fluid shunts, hexetidine in (polyvinyl chloride) PVC and ofloxacin-blended polylactone are a few examples of antimicrobial biomaterials.

Market drivers

Increasing incidence of implant related hospital infections

Hospital acquired infections resulting in surgical wound site infections are a major problem in healthcare facilities.

In a prevalence survey conducted in the US in 1996, the surgical wound infection accounted for 12.3% of all hospital acquired infections. In the incidence study, surgical wound infections accounted for 24% of all nosocomial infections.

In the US the overall number of hospital acquired infections are estimated to occur in 5% of all hospitalisations. The majority of infections, estimated at 11.4%, occur in the neonatal intensive care units (NICU). In the overall hospital acquired infection rates, 20% to 22% of infections are of surgical site wound infections.

The increasing incidence of hospital acquired infections in implant related infections of orthopaedic patients is also compelling surgeons to use antibiotic impregnated biomaterials as a substitute for normal polymeric implants.

Along with the increasing incidence of infections, the advantages associated with antibiotic biomaterials such as absorbable and controlled release of a drug for long periods is expected to drive the market of biomaterials that deliver antimicrobials.

Increasing incidence of arthritis and other orthopaedic diseases due to elderly population

Globally, 350 million people are suffering from arthritis and more than half of those with arthritis are less than 65 years of age. According to the US Centre of Disease Control (CDC), 47.8 million people in the US were affected by some form of arthritis during 2005.

Lifestyle changes and increasing obesity are the other major factors contributing to the increased incidence of orthopaedic diseases. The rapid urbanisation of the world and the resultant lifestyle changes, are expected to bring down the onset age for musculoskeletal disorders in the future, which will translate into a larger patient population and further drive the demand for biomaterials implants that deliver antimicrobials.

Thus, a rising incidence of arthritis and an aging population will add to the musculoskeletal disorder epidemic, which in turn will drive the antimicrobial biomaterials market.

Market restraints

Shortage of expert orthopaedic surgeons is acting as a restraint

"During device implantation the bacterial contamination of a medical device acts as a source of infection."

Globally, in the orthopaedic domain there is an imbalance between the number of surgeons performing surgeries and the demand for procedures.

According to the Association of American Medical Colleges (AAMC), from 1985 to 2006, the percentage of doctors of age 55 or over rose from 27% to 34%.

About 250,000 surgeons are expected to retire by 2020 in the US, which is one of the biggest markets for orthopaedic devices.

The decrease in surgeons is going to affect orthopaedic implant volumes. Also, the number of surgeons entering the profession is declining.

Expert orthopaedic surgeons are required to employ the antimicrobial biomaterials, as it involves skilful tactics for the implantation of biomaterial implants at the damaged bone joints. This shortage of experienced surgeons is expected to negatively affect the antimicrobial biomaterials market in future.

Lack of interoperability

No single medical device manufacturer or drug company has the organisation backup or expertise required to model, develop and launch antimicrobial biomaterial implants to the market for clinical use.

One of the biggest challenges is the difficulty between drug and device companies working together to offer the best product possible. This can be challenging because companies need to work not only through the potential cultural differences between their two countries, but also their industries: different practices and mind-sets, as well as different business strategies. Thus, non-availability of an integrated skill-set within any single organisation acts as a restraint for the antimicrobial biomaterials market.