Control of Multidrug Resistant Pseudomonas Aeruginosa through Hospital Construction Design and Extensive Environmental and Clinical Surveillance in an Allogeneic Transplantat Unit

Introduction: Immunocompromised patients are increasingly threatened by multidrug resistant bacterial strains. Following allogeneic stem cell transplantation (SCT), patients are especially at risk for multidrug resistant Pseudomonas aeruginosa (MRPA) which as a pathogen can be the cause of life-threatening septicemias. A possible reservoir and source of nosocomial infections are biofilms in shower drains, sinks, and toilets. For this reason, substantial targeted renovation was performed in the bathrooms of our SCT unit. We subsequently performed extensive surveillance of patients status as carriers and took numerous environmental samples.

Methods: Renovation/ conversion works of our transplant unit (2 wards with 20 HEPA filtered patients rooms, all equipped with separate shower baths) began in 2011 and included the installation of Pall-Aquasafe water filters (Pall Cooperation, Port Washington, NY) on all faucet and shower heads. Washbasins were equipped with Biorec Disinfection siphons (MoveoMed, Radebeul, Germany), which use UV and temperature together with frequent vibration and a bactericidal coating for disinfection. In addition, the toilets were replaced with rimless toilet basins and a system was developed to supply the flushing water with disinfectant at appropriate concentrations. The shower outlet drains were modified and covered by a heavy metal lid that cannot be easily removed and prevents aerosol formation. All renovation work was completed in April 2014. Cleaning and disinfection takes place once a day and the removable metal devices of the showers are sterilized once a week as well as every time a patient is discharged. In addition, extensive training of all personal in infection prevention was performed and the work of the cleaning personal was supervised closely. Environmental sampling was performed monthly in every room. Patients were screened upon admission and weekly during their treatment on the SCT unit by either anal swabs or stool cultures. Standard antibiotic prophylaxis consisted of ciprofloxacin and metronidazole for patients undergoing allogeneic SCT. Metronidazole prophylaxis was omitted in August 2013.

Results: Peri-renovation environmental sampling detected MRPA in 22,6% of swabs from the toilets and 11,8% of swabs from the shower outlets in 2012. The rate decreased to 15,1% from the toilets and 4,4% from the shower outlets in 2013 and reached 10,1% from the toilets and 0,6% from the shower outlets in the first six months of 2014. In 2012, 15 out of 197 patients (7.6%), receiving an allogeneic SCT or treatment for severe post-transplant complications (mainly GvHD) were affected by MRPA. This number decreased to 13 out of 206 (6.3%) in 2013 and 2 out of 95 (2.1%) in the first half in 2014. Overall 18 patients (3.6%) were colonized only and 12 patients (2.4%) developed bacteremia from MRPA.

Discussion: Environmental sources must be taken into consideration for the prevention of nosocomial infections. The implemented measures in our transplant unit can serve as an example for the reduction of biofilm, which can act as a reservoir for MRPA. Because of inconsistent local conformity of environmental and clinical isolates it still remains unclear whether the reason for colonisation and infection lays in environmental contamination and / or antibiotic selection in already precolonized patients. Further investigations will employ MRPA genotyping to determine genetic relationships between isolates from patients and environmental isolates.