Contribution à la lutte contre les contaminants microbiens des locaux et des collections des bibliothèques au moyen d’huiles essentielles

Abstract

Contamination of indoor environments and associated health risks remain of little concern in developing countries. Yet some of these environments such as the Central Library of the University of Yaoundé I and the Library of the French Institute of Cameroon receive a large number of people, subject to microbial contamination. As the whole world faces a health crisis (COVID-19) which has so far been responsible for more than 870.000 deaths worldwide, it is imperative to find effective and safe room disinfection solutions for the man. The purpose of this study was to formulate an essential oil-based disinfectant that is effective against microbial contaminants in libraries. Sampling was done using the sedimentation method for bioaerosols and by swabbing for surfaces. The characterization of microbial isolates was done by observing their macroscopic, microscopic and biochemical characters. Essential oils from the pericarps of Citrus sinensis, the leaves of Cymbopogon citratus, the flower buds of Eugenia caryophylla, the leaves of Mentha sp cf piperita, the flowers of Cananga odorata and the leaves of Eucalyptus globulus were obtained by hydrodistillation and analysed by Gas Chromatography and Gas Chromatography/Mass Spectrometry. Before the evaluation of the antimicrobial and antibiofilm activity of these essential oils and their combinations by aromatogram, microatmosphere and microdilution methods, the ability of bacterial isolates to form biofilms were demonstrated by Congo Red Agar and Tissus Culture Plate methods. The detection of some cellular targets of the essential oils were evaluated by Spectrophotometry. The disinfectant has been formulated based on these essential oils and, the most active combinations and their disinfecting powers have been determined. A greater proportion of fungal isolates were obtained in both libraries, with frequencies of 56 % and 68 % for Central Library of the University of Yaoundé I and that of the French Institute of Cameroon respectively. The indoor air of the Central Library of the University of Yaoundé I had a high level of pollution unlike the air of the French Institute of Cameroon which had an intermediate level of pollution. The most common bacteria in both libraries belonged to the genera Bacillus, Staphylococcus and Pseudomonas. The most represented fungal genera were Aspergillus sp and Penicillium sp. In general, essential oils showed better activity in the gas phase. The Minimal Inhibitory Concentrations of the combinations were smaller then those of the individual essential oils. All the essential oils showed a lytic effect on the wall and the plasma membrane of the tested bacteria resulting in the release of the genetic material. The disinfectant based on the most active combination showed a better disinfecting activity with a log reduction of 100 % on all microorganisms tested from 5 min of contact time. All of these results allow us to consider the use of essential oils in the disinfection of library premises. Key words: .