Mechanisms of antimicrobial action of quarternary ammonium compounds

PhD ceremony: Ms. M. Crismaru, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Mechanisms of antimicrobial action of quarternary ammonium compounds

Promotor(s): prof. H.J. Busscher, prof. J.A. Loontjens, prof. H.C. van der Mei

Faculty: Medical Sciences

On April 6, 2012, the Dagblad van het Noorden reported that a man, 51 years old, died after his pacemaker was replaced. Shortly after his arrival at home, he returned to the hospital with a high-fever. Although he was seen by a medical practitioner and a cardiologist, he was sent home. O ne week later, the man died due to an infection, apparently caused by a “sleeping bacteria” around the pacemaker. This is a clear case of a “biomaterial-associated-infection”, representing the topic of this thesis.

Infection of biomaterial implants and devices are accompanied by high morbidity and mortality, and are extremely costly to the health-care-system. Yet, they appear more and more in an ageing society where many people rely on implants to attain a high quality of life up till old age. Treatment of infected implants frequently includes long-term antibiotic use, often without success, and mostly an infected implant has to be replaced.

Quaternary Ammonium Compounds (QAC) are highly antimicrobial when applied in solution, but also when immobilized on a surface, for example of biomedical implants or devices. Although there have been hypotheses regarding mechanisms of antimicrobial action of immobilized QACs, no clear evidence exists. In collaboration with researchers from the Zernike Institute, we explored the mechanism of antimicrobial action of immobilized QACs on biomaterial surfaces and their bacterial killing potential.

Immobilized QAC coatings have a totally different working mechanism than antimicrobials in solution, that may not easily give rise to the development of antibiotic-resistance. Most importantly, immobilized QAC molecules may assist to kill adhering bacteria and prevent deadly cases of biomaterial-associated-infections in a growing group of patients relying on biomaterial implants and devices.