Disinfectant sensitivity of hospital related mycobiota

Soňa Jaďuďová 1 Elena Piecková 2

1Slovenská zdravotnícka univerzita v Bratislave, oddelenie toxikológie, Bratislava, Slovenská republika
2Medical Faculty, Slovak Medical University, Bratislava, Slovakia

Introduction/Aim: The mortality of severely immunocompromised patients with nosocomial mould infections is as high as over 20 %. The air dispersion of fungal propagules in the environment is the main route of transmission of mould deep mycoses. Airborne fungal loads in different departments even of the same hospital might vary very much, esp. in the seasons with high temperatures and humidity. To combat that successfully, effective preventive measures, incl. disinfection, must be applied according to good hygienic practice. Complex mycological analysis of airborne mycobiota in a hospital was performed, and fungal sensitivity to polyhexamethylene-guanidin (PHMG) was tested according to the adapted norm STN EN 1650 (2020) Chemical disinfectants and antiseptics.

Materials/Methods: To perform qualitative and quantitative analysis, indoor and related outdoor aeromycobiota at the different units of intensive care was sampled volumetrically and the settled one from the surfaces, incl. central air conditioning systems (HVAC), by mean of adhesive tapes during the hot summer 2019. Thirty seven cultivable fungal isolates were submitted to the antifungal testing: strains of Rhizopus and Penicillium selected from the outdoor isolates, 16 others (aspergilli, incl. sexual development stages, penicillia, fusaria, Trichoderma, Rhizopus) from indoor mycoaerosol, and 19 (aspergilli, penicillia, fusaria, Dematiaceae, Mucor) from surfaces in the hospital. A commercial PHMG disinfectant recommended for usage in health care premises was applied at the concentrations 6 and 10 % to every fungus for 30, 60, and 90 min following the procedure in the forementioned STN.

Results/Discussion: The most striking findings were related to the indoor mycobiotic quantity in some operation theaters with HVAC where the air fungal loads reached counts above 20,000 colony forming units (cfu) in m3, with presence of pathogenic Aspergillus fumigatus and highly risky Fusarium, usually refractile to any antifungal treatment. Fusarium yielded strain-dependent sensitivity results – the strains related to food at the kitchen were sensitive, while the ones from transplantology and ICUs exhibited resistance. The finding might indicate the selection of antifungal resistant strains in the most sensitive patient wards. Airborne A. fumigatus and A. terreus were sensitive to the disinfectant under all the application regimes tested. Some rooms of the intense medicine clinic were colonized with acremonia, Trichoderma – fungi with sticky spores, able to form biofilms on medical devices. Rapidly growing zygomycota was omnipresent in all the departments investigated and was disinfectant resistant, as expected. These lower fungi indicate indoor organic contamination, and were found e. g. on the trolleys for food delivery to the patients. That might be assessed as another potential route of fungal spreading in the hospital. That is alarming – zygomycoses are usually fatal as well. Surprisingly, the air fungal quantity in the hospital kitchen was only as low as 10 cfu/m3, incl. penicillia, aspergilli, melanized plants-related fungi and food processing fungi. The black fungi exhibited disinfectant resistance.

Conclusion: Effective hygienic preventive measures resulting in lowering of fungal load present in the hospital ambient should employ combination of chemically different antifungals and their regular time-course rotation to minimize its quantity and the spectrum as well.

Keywords: Nosocomial Mycoses; Fungal Bioaerosol; Polymer Antifungals; Disinfection Efficacy; ISO/EN/STN Testing